Improved AI code structure, added docs

rtsim/src/ai/mod.rs

@@ -0,0 +1,583 @@
+use crate::{
+    data::npc::{Controller, Npc, NpcId},
+    RtState,
+};
+use common::resources::{Time, TimeOfDay};
+use std::{any::Any, marker::PhantomData, ops::ControlFlow};
+use world::{IndexRef, World};
+
+/// The context provided to an [`Action`] while it is being performed. It should
+/// be possible to access any and all important information about the game world
+/// through this struct.
+pub struct NpcCtx<'a> {
+    pub state: &'a RtState,
+    pub world: &'a World,
+    pub index: IndexRef<'a>,
+
+    pub time_of_day: TimeOfDay,
+    pub time: Time,
+
+    pub npc_id: NpcId,
+    pub npc: &'a Npc,
+    pub controller: &'a mut Controller,
+}
+
+/// A trait that describes 'actions': long-running tasks performed by rtsim
+/// NPCs. These can be as simple as walking in a straight line between two
+/// locations or as complex as taking part in an adventure with players or
+/// performing an entire daily work schedule.
+///
+/// Actions are built up from smaller sub-actions via the combinator methods
+/// defined on this trait, and with the standalone functions in this module.
+/// Using these combinators, in a similar manner to using the [`Iterator`] API,
+/// it is possible to construct arbitrarily complex actions including behaviour
+/// trees (see [`choose`] and [`watch`]) and other forms of moment-by-moment
+/// decision-making.
+///
+/// On completion, actions may produce a value, denoted by the type parameter
+/// `R`. For example, an action may communicate whether it was successful or
+/// unsuccessful through this completion value.
+///
+/// You should not need to implement this trait yourself when writing AI code.
+/// If you find yourself wanting to implement it, please discuss with the core
+/// dev team first.
+pub trait Action<R = ()>: Any + Send + Sync {
+    /// Returns `true` if the action should be considered the 'same' (i.e:
+    /// achieving the same objective) as another. In general, the AI system
+    /// will try to avoid switching (and therefore restarting) tasks when the
+    /// new task is the 'same' as the old one.
+    // TODO: Figure out a way to compare actions based on their 'intention': i.e:
+    // two pathing actions should be considered equivalent if their destination
+    // is the same regardless of the progress they've each made.
+    fn is_same(&self, other: &Self) -> bool
+    where
+        Self: Sized;
+
+    /// Like [`Action::is_same`], but allows for dynamic dispatch.
+    fn dyn_is_same_sized(&self, other: &dyn Action<R>) -> bool
+    where
+        Self: Sized,
+    {
+        match (other as &dyn Any).downcast_ref::<Self>() {
+            Some(other) => self.is_same(other),
+            None => false,
+        }
+    }
+
+    /// Like [`Action::is_same`], but allows for dynamic dispatch.
+    fn dyn_is_same(&self, other: &dyn Action<R>) -> bool;
+
+    /// Reset the action to its initial state such that it can be repeated.
+    fn reset(&mut self);
+
+    /// Perform the action for the current tick.
+    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R>;
+
+    /// Create an action that chains together two sub-actions, one after the
+    /// other.
+    ///
+    /// # Example
+    ///
+    /// ```ignore
+    /// // Walk toward an enemy NPC and, once done, attack the enemy NPC
+    /// goto(enemy_npc).then(attack(enemy_npc))
+    /// ```
+    fn then<A1: Action<R1>, R1>(self, other: A1) -> Then<Self, A1, R>
+    where
+        Self: Sized,
+    {
+        Then {
+            a0: self,
+            a0_finished: false,
+            a1: other,
+            phantom: PhantomData,
+        }
+    }
+
+    /// Create an action that repeats a sub-action indefinitely.
+    ///
+    /// # Example
+    ///
+    /// ```ignore
+    /// // Endlessly collect flax from the environment
+    /// find_and_collect(ChunkResource::Flax).repeat()
+    /// ```
+    fn repeat<R1>(self) -> Repeat<Self, R1>
+    where
+        Self: Sized,
+    {
+        Repeat(self, PhantomData)
+    }
+
+    /// Stop the sub-action suddenly if a condition is reached.
+    ///
+    /// # Example
+    ///
+    /// ```ignore
+    /// // Keep going on adventures until your 111th birthday
+    /// go_on_an_adventure().repeat().stop_if(|ctx| ctx.npc.age > 111.0)
+    /// ```
+    fn stop_if<F: FnMut(&mut NpcCtx) -> bool>(self, f: F) -> StopIf<Self, F>
+    where
+        Self: Sized,
+    {
+        StopIf(self, f)
+    }
+
+    /// Map the completion value of this action to something else.
+    fn map<F: FnMut(R) -> R1, R1>(self, f: F) -> Map<Self, F, R>
+    where
+        Self: Sized,
+    {
+        Map(self, f, PhantomData)
+    }
+
+    /// Box the action. Often used to perform type erasure, such as when you
+    /// want to return one of many actions (each with different types) from
+    /// the same function.
+    ///
+    /// # Example
+    ///
+    /// ```ignore
+    /// // Error! Type mismatch between branches
+    /// if npc.is_too_tired() {
+    ///     goto(npc.home)
+    /// } else {
+    ///     go_on_an_adventure()
+    /// }
+    ///
+    /// // All fine
+    /// if npc.is_too_tired() {
+    ///     goto(npc.home).boxed()
+    /// } else {
+    ///     go_on_an_adventure().boxed()
+    /// }
+    /// ```
+    fn boxed(self) -> Box<dyn Action<R>>
+    where
+        Self: Sized,
+    {
+        Box::new(self)
+    }
+}
+
+impl<R: 'static> Action<R> for Box<dyn Action<R>> {
+    fn is_same(&self, other: &Self) -> bool { (**self).dyn_is_same(other) }
+
+    fn dyn_is_same(&self, other: &dyn Action<R>) -> bool {
+        match (other as &dyn Any).downcast_ref::<Self>() {
+            Some(other) => self.is_same(other),
+            None => false,
+        }
+    }
+
+    fn reset(&mut self) { (**self).reset(); }
+
+    // TODO: Reset closure state?
+    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R> { (**self).tick(ctx) }
+}
+
+// Now
+
+/// See [`now`].
+#[derive(Copy, Clone)]
+pub struct Now<F, A>(F, Option<A>);
+
+impl<R: Send + Sync + 'static, F: FnMut(&mut NpcCtx) -> A + Send + Sync + 'static, A: Action<R>>
+    Action<R> for Now<F, A>
+{
+    // TODO: This doesn't compare?!
+    fn is_same(&self, other: &Self) -> bool { true }
+
+    fn dyn_is_same(&self, other: &dyn Action<R>) -> bool { self.dyn_is_same_sized(other) }
+
+    fn reset(&mut self) { self.1 = None; }
+
+    // TODO: Reset closure state?
+    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R> {
+        (self.1.get_or_insert_with(|| (self.0)(ctx))).tick(ctx)
+    }
+}
+
+/// Start a new action based on the state of the world (`ctx`) at the moment the
+/// action is started.
+///
+/// If you're in a situation where you suddenly find yourself needing `ctx`, you
+/// probably want to use this.
+///
+/// # Example
+///
+/// ```ignore
+/// // An action that makes an NPC immediately travel to its *current* home
+/// now(|ctx| goto(ctx.npc.home))
+/// ```
+pub fn now<F, A>(f: F) -> Now<F, A>
+where
+    F: FnMut(&mut NpcCtx) -> A,
+{
+    Now(f, None)
+}
+
+// Just
+
+/// See [`just`].
+#[derive(Copy, Clone)]
+pub struct Just<F, R = ()>(F, PhantomData<R>);
+
+impl<R: Send + Sync + 'static, F: FnMut(&mut NpcCtx) -> R + Send + Sync + 'static> Action<R>
+    for Just<F, R>
+{
+    fn is_same(&self, other: &Self) -> bool { true }
+
+    fn dyn_is_same(&self, other: &dyn Action<R>) -> bool { self.dyn_is_same_sized(other) }
+
+    fn reset(&mut self) {}
+
+    // TODO: Reset closure state?
+    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R> { ControlFlow::Break((self.0)(ctx)) }
+}
+
+/// An action that executes some code just once when performed.
+///
+/// If you want to execute this code on every tick, consider combining it with
+/// [`Action::repeat`].
+///
+/// # Example
+///
+/// ```ignore
+/// // Make the current NPC say 'Hello, world!' exactly once
+/// just(|ctx| ctx.controller.say("Hello, world!"))
+/// ```
+pub fn just<F, R: Send + Sync + 'static>(mut f: F) -> Just<F, R>
+where
+    F: FnMut(&mut NpcCtx) -> R + Send + Sync + 'static,
+{
+    Just(f, PhantomData)
+}
+
+// Finish
+
+/// See [`finish`].
+#[derive(Copy, Clone)]
+pub struct Finish;
+
+impl Action<()> for Finish {
+    fn is_same(&self, other: &Self) -> bool { true }
+
+    fn dyn_is_same(&self, other: &dyn Action<()>) -> bool { self.dyn_is_same_sized(other) }
+
+    fn reset(&mut self) {}
+
+    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<()> { ControlFlow::Break(()) }
+}
+
+/// An action that immediately finishes without doing anything.
+///
+/// This action is useless by itself, but becomes useful when combined with
+/// actions that make decisions.
+///
+/// # Example
+///
+/// ```ignore
+/// now(|ctx| {
+///     if ctx.npc.is_tired() {
+///         sleep().boxed() // If we're tired, sleep
+///     } else if ctx.npc.is_hungry() {
+///         eat().boxed() // If we're hungry, eat
+///     } else {
+///         finish().boxed() // Otherwise, do nothing
+///     }
+/// })
+/// ```
+pub fn finish() -> Finish { Finish }
+
+// Tree
+
+pub type Priority = usize;
+
+pub const URGENT: Priority = 0;
+pub const IMPORTANT: Priority = 1;
+pub const CASUAL: Priority = 2;
+
+pub struct Node<R>(Box<dyn Action<R>>, Priority);
+
+/// Perform an action with [`URGENT`] priority (see [`choose`]).
+pub fn urgent<A: Action<R>, R>(a: A) -> Node<R> { Node(Box::new(a), URGENT) }
+
+/// Perform an action with [`IMPORTANT`] priority (see [`choose`]).
+pub fn important<A: Action<R>, R>(a: A) -> Node<R> { Node(Box::new(a), IMPORTANT) }
+
+/// Perform an action with [`CASUAL`] priority (see [`choose`]).
+pub fn casual<A: Action<R>, R>(a: A) -> Node<R> { Node(Box::new(a), CASUAL) }
+
+/// See [`choose`] and [`watch`].
+pub struct Tree<F, R> {
+    next: F,
+    prev: Option<Node<R>>,
+    interrupt: bool,
+}
+
+impl<F: FnMut(&mut NpcCtx) -> Node<R> + Send + Sync + 'static, R: 'static> Action<R>
+    for Tree<F, R>
+{
+    fn is_same(&self, other: &Self) -> bool { true }
+
+    fn dyn_is_same(&self, other: &dyn Action<R>) -> bool { self.dyn_is_same_sized(other) }
+
+    fn reset(&mut self) { self.prev = None; }
+
+    // TODO: Reset `next` too?
+    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R> {
+        let new = (self.next)(ctx);
+
+        let prev = match &mut self.prev {
+            Some(prev) if prev.1 <= new.1 && (prev.0.dyn_is_same(&*new.0) || !self.interrupt) => {
+                prev
+            },
+            _ => self.prev.insert(new),
+        };
+
+        match prev.0.tick(ctx) {
+            ControlFlow::Continue(()) => return ControlFlow::Continue(()),
+            ControlFlow::Break(r) => {
+                self.prev = None;
+                ControlFlow::Break(r)
+            },
+        }
+    }
+}
+
+/// An action that allows implementing a decision tree, with action
+/// prioritisation.
+///
+/// The inner function will be run every tick to decide on an action. When an
+/// action is chosen, it will be performed until completed *UNLESS* an action
+/// with a more urgent priority is chosen in a subsequent tick. [`choose`] tries
+/// to commit to actions when it can: only more urgent actions will interrupt an
+/// action that's currently being performed. If you want something that's more
+/// eager to switch actions, see [`watch`].
+///
+/// # Example
+///
+/// ```ignore
+/// choose(|ctx| {
+///     if ctx.npc.is_being_attacked() {
+///         urgent(combat()) // If we're in danger, do something!
+///     } else if ctx.npc.is_hungry() {
+///         important(eat()) // If we're hungry, eat
+///     } else {
+///         casual(idle()) // Otherwise, do nothing
+///     }
+/// })
+/// ```
+pub fn choose<R: 'static, F>(f: F) -> impl Action<R>
+where
+    F: FnMut(&mut NpcCtx) -> Node<R> + Send + Sync + 'static,
+{
+    Tree {
+        next: f,
+        prev: None,
+        interrupt: false,
+    }
+}
+
+/// An action that allows implementing a decision tree, with action
+/// prioritisation.
+///
+/// The inner function will be run every tick to decide on an action. When an
+/// action is chosen, it will be performed until completed unless a different
+/// action is chosen in a subsequent tick. [`watch`] is very unfocussed and will
+/// happily switch between actions rapidly between ticks if conditions change.
+/// If you want something that tends to commit to actions until they are
+/// completed, see [`choose`].
+///
+/// # Example
+///
+/// ```ignore
+/// choose(|ctx| {
+///     if ctx.npc.is_being_attacked() {
+///         urgent(combat()) // If we're in danger, do something!
+///     } else if ctx.npc.is_hungry() {
+///         important(eat()) // If we're hungry, eat
+///     } else {
+///         casual(idle()) // Otherwise, do nothing
+///     }
+/// })
+/// ```
+pub fn watch<R: 'static, F>(f: F) -> impl Action<R>
+where
+    F: FnMut(&mut NpcCtx) -> Node<R> + Send + Sync + 'static,
+{
+    Tree {
+        next: f,
+        prev: None,
+        interrupt: true,
+    }
+}
+
+// Then
+
+/// See [`Action::then`].
+#[derive(Copy, Clone)]
+pub struct Then<A0, A1, R0> {
+    a0: A0,
+    a0_finished: bool,
+    a1: A1,
+    phantom: PhantomData<R0>,
+}
+
+impl<A0: Action<R0>, A1: Action<R1>, R0: Send + Sync + 'static, R1: Send + Sync + 'static>
+    Action<R1> for Then<A0, A1, R0>
+{
+    fn is_same(&self, other: &Self) -> bool {
+        self.a0.is_same(&other.a0) && self.a1.is_same(&other.a1)
+    }
+
+    fn dyn_is_same(&self, other: &dyn Action<R1>) -> bool { self.dyn_is_same_sized(other) }
+
+    fn reset(&mut self) {
+        self.a0.reset();
+        self.a0_finished = false;
+        self.a1.reset();
+    }
+
+    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R1> {
+        if !self.a0_finished {
+            match self.a0.tick(ctx) {
+                ControlFlow::Continue(()) => return ControlFlow::Continue(()),
+                ControlFlow::Break(_) => self.a0_finished = true,
+            }
+        }
+        self.a1.tick(ctx)
+    }
+}
+
+// Repeat
+
+/// See [`Action::repeat`].
+#[derive(Copy, Clone)]
+pub struct Repeat<A, R = ()>(A, PhantomData<R>);
+
+impl<R: Send + Sync + 'static, A: Action<R>> Action<!> for Repeat<A, R> {
+    fn is_same(&self, other: &Self) -> bool { self.0.is_same(&other.0) }
+
+    fn dyn_is_same(&self, other: &dyn Action<!>) -> bool { self.dyn_is_same_sized(other) }
+
+    fn reset(&mut self) { self.0.reset(); }
+
+    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<!> {
+        match self.0.tick(ctx) {
+            ControlFlow::Continue(()) => ControlFlow::Continue(()),
+            ControlFlow::Break(_) => {
+                self.0.reset();
+                ControlFlow::Continue(())
+            },
+        }
+    }
+}
+
+// Sequence
+
+/// See [`seq`].
+#[derive(Copy, Clone)]
+pub struct Sequence<I, A, R = ()>(I, I, Option<A>, PhantomData<R>);
+
+impl<R: Send + Sync + 'static, I: Iterator<Item = A> + Clone + Send + Sync + 'static, A: Action<R>>
+    Action<()> for Sequence<I, A, R>
+{
+    fn is_same(&self, other: &Self) -> bool { true }
+
+    fn dyn_is_same(&self, other: &dyn Action<()>) -> bool { self.dyn_is_same_sized(other) }
+
+    fn reset(&mut self) {
+        self.0 = self.1.clone();
+        self.2 = None;
+    }
+
+    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<()> {
+        let item = if let Some(prev) = &mut self.2 {
+            prev
+        } else {
+            match self.0.next() {
+                Some(next) => self.2.insert(next),
+                None => return ControlFlow::Break(()),
+            }
+        };
+
+        if let ControlFlow::Break(_) = item.tick(ctx) {
+            self.2 = None;
+        }
+
+        ControlFlow::Continue(())
+    }
+}
+
+/// An action that consumes and performs an iterator of actions in sequence, one
+/// after another.
+///
+/// # Example
+///
+/// ```ignore
+/// // A list of enemies we should attack in turn
+/// let enemies = vec![
+///     ugly_goblin,
+///     stinky_troll,
+///     rude_dwarf,
+/// ];
+///
+/// // Attack each enemy, one after another
+/// seq(enemies
+///     .into_iter()
+///     .map(|enemy| attack(enemy)))
+/// ```
+pub fn seq<I, A, R>(iter: I) -> Sequence<I, A, R>
+where
+    I: Iterator<Item = A> + Clone,
+    A: Action<R>,
+{
+    Sequence(iter.clone(), iter, None, PhantomData)
+}
+
+// StopIf
+
+/// See [`Action::stop_if`].
+#[derive(Copy, Clone)]
+pub struct StopIf<A, F>(A, F);
+
+impl<A: Action<R>, F: FnMut(&mut NpcCtx) -> bool + Send + Sync + 'static, R> Action<Option<R>>
+    for StopIf<A, F>
+{
+    fn is_same(&self, other: &Self) -> bool { self.0.is_same(&other.0) }
+
+    fn dyn_is_same(&self, other: &dyn Action<Option<R>>) -> bool { self.dyn_is_same_sized(other) }
+
+    fn reset(&mut self) { self.0.reset(); }
+
+    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<Option<R>> {
+        if (self.1)(ctx) {
+            ControlFlow::Break(None)
+        } else {
+            self.0.tick(ctx).map_break(Some)
+        }
+    }
+}
+
+// Map
+
+/// See [`Action::map`].
+#[derive(Copy, Clone)]
+pub struct Map<A, F, R>(A, F, PhantomData<R>);
+
+impl<A: Action<R>, F: FnMut(R) -> R1 + Send + Sync + 'static, R: Send + Sync + 'static, R1>
+    Action<R1> for Map<A, F, R>
+{
+    fn is_same(&self, other: &Self) -> bool { self.0.is_same(&other.0) }
+
+    fn dyn_is_same(&self, other: &dyn Action<R1>) -> bool { self.dyn_is_same_sized(other) }
+
+    fn reset(&mut self) { self.0.reset(); }
+
+    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R1> {
+        self.0.tick(ctx).map_break(&mut self.1)
+    }
+}

rtsim/src/data/npc.rs

@@ -1,4 +1,4 @@
-use crate::rule::npc_ai::NpcCtx;
+use crate::ai::{Action, NpcCtx};
 pub use common::rtsim::{NpcId, Profession};
 use common::{
     comp,
@@ -11,10 +11,8 @@ use rand::prelude::*;
 use serde::{Deserialize, Serialize};
 use slotmap::HopSlotMap;
 use std::{
-    any::{Any, TypeId},
     collections::VecDeque,
-    marker::PhantomData,
-    ops::{ControlFlow, Deref, DerefMut, Generator, GeneratorState},
+    ops::{Deref, DerefMut, Generator, GeneratorState},
     pin::Pin,
     sync::{
         atomic::{AtomicPtr, Ordering},
@@ -54,369 +52,6 @@ impl Controller {
     pub fn idle() -> Self { Self { goto: None } }
 }
 
-pub trait Action<R = ()>: Any + Send + Sync {
-    /// Returns `true` if the action should be considered the 'same' (i.e:
-    /// achieving the same objective) as another. In general, the AI system
-    /// will try to avoid switching (and therefore restarting) tasks when the
-    /// new task is the 'same' as the old one.
-    // TODO: Figure out a way to compare actions based on their 'intention': i.e:
-    // two pathing actions should be considered equivalent if their destination
-    // is the same regardless of the progress they've each made.
-    fn is_same(&self, other: &Self) -> bool
-    where
-        Self: Sized;
-    fn dyn_is_same_sized(&self, other: &dyn Action<R>) -> bool
-    where
-        Self: Sized,
-    {
-        match (other as &dyn Any).downcast_ref::<Self>() {
-            Some(other) => self.is_same(other),
-            None => false,
-        }
-    }
-    fn dyn_is_same(&self, other: &dyn Action<R>) -> bool;
-    // Reset the action to its initial state so it can be restarted
-    fn reset(&mut self);
-
-    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R>;
-
-    fn then<A1: Action<R1>, R1>(self, other: A1) -> Then<Self, A1, R>
-    where
-        Self: Sized,
-    {
-        Then {
-            a0: self,
-            a0_finished: false,
-            a1: other,
-            phantom: PhantomData,
-        }
-    }
-    fn repeat<R1>(self) -> Repeat<Self, R1>
-    where
-        Self: Sized,
-    {
-        Repeat(self, PhantomData)
-    }
-    fn stop_if<F: FnMut(&mut NpcCtx) -> bool>(self, f: F) -> StopIf<Self, F>
-    where
-        Self: Sized,
-    {
-        StopIf(self, f)
-    }
-    fn map<F: FnMut(R) -> R1, R1>(self, f: F) -> Map<Self, F, R>
-    where
-        Self: Sized,
-    {
-        Map(self, f, PhantomData)
-    }
-    fn boxed(self) -> Box<dyn Action<R>>
-    where
-        Self: Sized,
-    {
-        Box::new(self)
-    }
-}
-
-impl<R: 'static> Action<R> for Box<dyn Action<R>> {
-    fn is_same(&self, other: &Self) -> bool { (**self).dyn_is_same(other) }
-
-    fn dyn_is_same(&self, other: &dyn Action<R>) -> bool {
-        match (other as &dyn Any).downcast_ref::<Self>() {
-            Some(other) => self.is_same(other),
-            None => false,
-        }
-    }
-
-    fn reset(&mut self) { (**self).reset(); }
-
-    // TODO: Reset closure state?
-    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R> { (**self).tick(ctx) }
-}
-
-// Now
-
-#[derive(Copy, Clone)]
-pub struct Now<F, A>(F, Option<A>);
-
-impl<R: Send + Sync + 'static, F: FnMut(&mut NpcCtx) -> A + Send + Sync + 'static, A: Action<R>>
-    Action<R> for Now<F, A>
-{
-    // TODO: This doesn't compare?!
-    fn is_same(&self, other: &Self) -> bool { true }
-
-    fn dyn_is_same(&self, other: &dyn Action<R>) -> bool { self.dyn_is_same_sized(other) }
-
-    fn reset(&mut self) { self.1 = None; }
-
-    // TODO: Reset closure state?
-    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R> {
-        (self.1.get_or_insert_with(|| (self.0)(ctx))).tick(ctx)
-    }
-}
-
-pub fn now<F, A>(f: F) -> Now<F, A>
-where
-    F: FnMut(&mut NpcCtx) -> A,
-{
-    Now(f, None)
-}
-
-// Just
-
-#[derive(Copy, Clone)]
-pub struct Just<F, R = ()>(F, PhantomData<R>);
-
-impl<R: Send + Sync + 'static, F: FnMut(&mut NpcCtx) -> R + Send + Sync + 'static> Action<R>
-    for Just<F, R>
-{
-    fn is_same(&self, other: &Self) -> bool { true }
-
-    fn dyn_is_same(&self, other: &dyn Action<R>) -> bool { self.dyn_is_same_sized(other) }
-
-    fn reset(&mut self) {}
-
-    // TODO: Reset closure state?
-    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R> { ControlFlow::Break((self.0)(ctx)) }
-}
-
-pub fn just<F, R: Send + Sync + 'static>(mut f: F) -> Just<F, R>
-where
-    F: FnMut(&mut NpcCtx) -> R + Send + Sync + 'static,
-{
-    Just(f, PhantomData)
-}
-
-// Finish
-
-#[derive(Copy, Clone)]
-pub struct Finish;
-
-impl Action<()> for Finish {
-    fn is_same(&self, other: &Self) -> bool { true }
-
-    fn dyn_is_same(&self, other: &dyn Action<()>) -> bool { self.dyn_is_same_sized(other) }
-
-    fn reset(&mut self) {}
-
-    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<()> { ControlFlow::Break(()) }
-}
-
-pub fn finish() -> Finish { Finish }
-
-// Tree
-
-pub type Priority = usize;
-
-const URGENT: Priority = 0;
-const CASUAL: Priority = 1;
-
-pub struct Node<R>(Box<dyn Action<R>>, Priority);
-
-pub fn urgent<A: Action<R>, R>(a: A) -> Node<R> { Node(Box::new(a), URGENT) }
-pub fn casual<A: Action<R>, R>(a: A) -> Node<R> { Node(Box::new(a), CASUAL) }
-
-pub struct Tree<F, R> {
-    next: F,
-    prev: Option<Node<R>>,
-    interrupt: bool,
-}
-
-impl<F: FnMut(&mut NpcCtx) -> Node<R> + Send + Sync + 'static, R: 'static> Action<R>
-    for Tree<F, R>
-{
-    fn is_same(&self, other: &Self) -> bool { true }
-
-    fn dyn_is_same(&self, other: &dyn Action<R>) -> bool { self.dyn_is_same_sized(other) }
-
-    fn reset(&mut self) { self.prev = None; }
-
-    // TODO: Reset `next` too?
-    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R> {
-        let new = (self.next)(ctx);
-
-        let prev = match &mut self.prev {
-            Some(prev) if prev.1 <= new.1 && (prev.0.dyn_is_same(&*new.0) || !self.interrupt) => {
-                prev
-            },
-            _ => self.prev.insert(new),
-        };
-
-        match prev.0.tick(ctx) {
-            ControlFlow::Continue(()) => return ControlFlow::Continue(()),
-            ControlFlow::Break(r) => {
-                self.prev = None;
-                ControlFlow::Break(r)
-            },
-        }
-    }
-}
-
-pub fn choose<R: 'static, F>(f: F) -> impl Action<R>
-where
-    F: FnMut(&mut NpcCtx) -> Node<R> + Send + Sync + 'static,
-{
-    Tree {
-        next: f,
-        prev: None,
-        interrupt: false,
-    }
-}
-
-pub fn watch<R: 'static, F>(f: F) -> impl Action<R>
-where
-    F: FnMut(&mut NpcCtx) -> Node<R> + Send + Sync + 'static,
-{
-    Tree {
-        next: f,
-        prev: None,
-        interrupt: true,
-    }
-}
-
-// Then
-
-#[derive(Copy, Clone)]
-pub struct Then<A0, A1, R0> {
-    a0: A0,
-    a0_finished: bool,
-    a1: A1,
-    phantom: PhantomData<R0>,
-}
-
-impl<A0: Action<R0>, A1: Action<R1>, R0: Send + Sync + 'static, R1: Send + Sync + 'static>
-    Action<R1> for Then<A0, A1, R0>
-{
-    fn is_same(&self, other: &Self) -> bool {
-        self.a0.is_same(&other.a0) && self.a1.is_same(&other.a1)
-    }
-
-    fn dyn_is_same(&self, other: &dyn Action<R1>) -> bool { self.dyn_is_same_sized(other) }
-
-    fn reset(&mut self) {
-        self.a0.reset();
-        self.a0_finished = false;
-        self.a1.reset();
-    }
-
-    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R1> {
-        if !self.a0_finished {
-            match self.a0.tick(ctx) {
-                ControlFlow::Continue(()) => return ControlFlow::Continue(()),
-                ControlFlow::Break(_) => self.a0_finished = true,
-            }
-        }
-        self.a1.tick(ctx)
-    }
-}
-
-// Repeat
-
-#[derive(Copy, Clone)]
-pub struct Repeat<A, R = ()>(A, PhantomData<R>);
-
-impl<R: Send + Sync + 'static, A: Action<R>> Action<!> for Repeat<A, R> {
-    fn is_same(&self, other: &Self) -> bool { self.0.is_same(&other.0) }
-
-    fn dyn_is_same(&self, other: &dyn Action<!>) -> bool { self.dyn_is_same_sized(other) }
-
-    fn reset(&mut self) { self.0.reset(); }
-
-    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<!> {
-        match self.0.tick(ctx) {
-            ControlFlow::Continue(()) => ControlFlow::Continue(()),
-            ControlFlow::Break(_) => {
-                self.0.reset();
-                ControlFlow::Continue(())
-            },
-        }
-    }
-}
-
-// Sequence
-
-#[derive(Copy, Clone)]
-pub struct Sequence<I, A, R = ()>(I, I, Option<A>, PhantomData<R>);
-
-impl<R: Send + Sync + 'static, I: Iterator<Item = A> + Clone + Send + Sync + 'static, A: Action<R>>
-    Action<()> for Sequence<I, A, R>
-{
-    fn is_same(&self, other: &Self) -> bool { true }
-
-    fn dyn_is_same(&self, other: &dyn Action<()>) -> bool { self.dyn_is_same_sized(other) }
-
-    fn reset(&mut self) {
-        self.0 = self.1.clone();
-        self.2 = None;
-    }
-
-    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<()> {
-        let item = if let Some(prev) = &mut self.2 {
-            prev
-        } else {
-            match self.0.next() {
-                Some(next) => self.2.insert(next),
-                None => return ControlFlow::Break(()),
-            }
-        };
-
-        if let ControlFlow::Break(_) = item.tick(ctx) {
-            self.2 = None;
-        }
-
-        ControlFlow::Continue(())
-    }
-}
-
-pub fn seq<I, A, R>(iter: I) -> Sequence<I, A, R>
-where
-    I: Iterator<Item = A> + Clone,
-    A: Action<R>,
-{
-    Sequence(iter.clone(), iter, None, PhantomData)
-}
-
-// StopIf
-
-#[derive(Copy, Clone)]
-pub struct StopIf<A, F>(A, F);
-
-impl<A: Action<R>, F: FnMut(&mut NpcCtx) -> bool + Send + Sync + 'static, R> Action<Option<R>>
-    for StopIf<A, F>
-{
-    fn is_same(&self, other: &Self) -> bool { self.0.is_same(&other.0) }
-
-    fn dyn_is_same(&self, other: &dyn Action<Option<R>>) -> bool { self.dyn_is_same_sized(other) }
-
-    fn reset(&mut self) { self.0.reset(); }
-
-    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<Option<R>> {
-        if (self.1)(ctx) {
-            ControlFlow::Break(None)
-        } else {
-            self.0.tick(ctx).map_break(Some)
-        }
-    }
-}
-
-// Map
-
-#[derive(Copy, Clone)]
-pub struct Map<A, F, R>(A, F, PhantomData<R>);
-
-impl<A: Action<R>, F: FnMut(R) -> R1 + Send + Sync + 'static, R: Send + Sync + 'static, R1>
-    Action<R1> for Map<A, F, R>
-{
-    fn is_same(&self, other: &Self) -> bool { self.0.is_same(&other.0) }
-
-    fn dyn_is_same(&self, other: &dyn Action<R1>) -> bool { self.dyn_is_same_sized(other) }
-
-    fn reset(&mut self) { self.0.reset(); }
-
-    fn tick(&mut self, ctx: &mut NpcCtx) -> ControlFlow<R1> {
-        self.0.tick(ctx).map_break(&mut self.1)
-    }
-}
-
 pub struct Brain {
     pub(crate) action: Box<dyn Action<!>>,
 }

rtsim/src/lib.rs

@@ -10,6 +10,7 @@
     let_chains
 )]
 
+pub mod ai;
 pub mod data;
 pub mod event;
 pub mod gen;

rtsim/src/rule/npc_ai.rs

@@ -1,11 +1,9 @@
 use std::{collections::VecDeque, hash::BuildHasherDefault};
 
 use crate::{
+    ai::{casual, choose, finish, just, now, seq, urgent, watch, Action, NpcCtx},
     data::{
-        npc::{
-            casual, choose, finish, just, now, seq, urgent, watch, Action, Brain, Controller, Npc,
-            NpcId, PathData, PathingMemory,
-        },
+        npc::{Brain, Controller, Npc, NpcId, PathData, PathingMemory},
         Sites,
     },
     event::OnTick,
@@ -254,7 +252,11 @@ impl Rule for NpcAi {
                     let mut controller = Controller { goto: npc.goto };
 
                     brain.action.tick(&mut NpcCtx {
-                        ctx: &ctx,
+                        state: ctx.state,
+                        world: ctx.world,
+                        index: ctx.index,
+                        time_of_day: ctx.event.time_of_day,
+                        time: ctx.event.time,
                         npc,
                         npc_id,
                         controller: &mut controller,
@@ -262,93 +264,46 @@ impl Rule for NpcAi {
 
                     /*
                     let action: ControlFlow<()> = try {
-                        if matches!(npc.profession, Some(Profession::Adventurer(_))) {
-                            if let Some(home) = npc.home {
-                                // Travel between random nearby sites
-                                let task = generate(
-                                    move |(_, npc, ctx): &(NpcId, &Npc, &EventCtx<_, _>)| {
-                                        // Choose a random site that's fairly close by
-                                        let tgt_site = ctx
-                                            .state
-                                            .data()
-                                            .sites
-                                            .iter()
-                                            .filter(|(site_id, site)| {
-                                                site.faction.is_some()
-                                                    && npc
-                                                        .current_site
-                                                        .map_or(true, |cs| *site_id != cs)
-                                                    && thread_rng().gen_bool(0.25)
-                                            })
-                                            .min_by_key(|(_, site)| {
-                                                site.wpos.as_().distance(npc.wpos.xy()) as i32
-                                            })
-                                            .map(|(site_id, _)| site_id)
-                                            .unwrap_or(home);
+                        brain.tick(&mut NpcData {
+                            ctx: &ctx,
+                            npc,
+                            npc_id,
+                            controller: &mut controller,
+                        });
+                        /*
+                        // // Choose a random plaza in the npcs home site (which should be the
+                        // // current here) to go to.
+                        let task =
+                            generate(move |(_, npc, ctx): &(NpcId, &Npc, &EventCtx<_, _>)| {
+                                let data = ctx.state.data();
+                                let site2 =
+                                    npc.home.and_then(|home| data.sites.get(home)).and_then(
+                                        |home| match &ctx.index.sites.get(home.world_site?).kind
+                                        {
+                                            SiteKind::Refactor(site2)
+                                            | SiteKind::CliffTown(site2)
+                                            | SiteKind::DesertCity(site2) => Some(site2),
+                                            _ => None,
+                                        },
+                                    );
 
-                                        let wpos = ctx
-                                            .state
-                                            .data()
-                                            .sites
-                                            .get(tgt_site)
-                                            .map_or(npc.wpos.xy(), |site| site.wpos.as_());
+                                let wpos = site2
+                                    .and_then(|site2| {
+                                        let plaza = &site2.plots
+                                            [site2.plazas().choose(&mut thread_rng())?];
+                                        Some(site2.tile_center_wpos(plaza.root_tile()).as_())
+                                    })
+                                    .unwrap_or(npc.wpos.xy());
 
-                                        TravelTo {
-                                            wpos,
-                                            use_paths: true,
-                                        }
-                                    },
-                                )
-                                .repeat();
+                                TravelTo {
+                                    wpos,
+                                    use_paths: true,
+                                }
+                            })
+                            .repeat();
 
-                                task_state.perform(
-                                    task,
-                                    &(npc_id, &*npc, &ctx),
-                                    &mut controller,
-                                )?;
-                            }
-                        } else {
-                            brain.tick(&mut NpcData {
-                                ctx: &ctx,
-                                npc,
-                                npc_id,
-                                controller: &mut controller,
-                            });
-                            /*
-                            // // Choose a random plaza in the npcs home site (which should be the
-                            // // current here) to go to.
-                            let task =
-                                generate(move |(_, npc, ctx): &(NpcId, &Npc, &EventCtx<_, _>)| {
-                                    let data = ctx.state.data();
-                                    let site2 =
-                                        npc.home.and_then(|home| data.sites.get(home)).and_then(
-                                            |home| match &ctx.index.sites.get(home.world_site?).kind
-                                            {
-                                                SiteKind::Refactor(site2)
-                                                | SiteKind::CliffTown(site2)
-                                                | SiteKind::DesertCity(site2) => Some(site2),
-                                                _ => None,
-                                            },
-                                        );
-
-                                    let wpos = site2
-                                        .and_then(|site2| {
-                                            let plaza = &site2.plots
-                                                [site2.plazas().choose(&mut thread_rng())?];
-                                            Some(site2.tile_center_wpos(plaza.root_tile()).as_())
-                                        })
-                                        .unwrap_or(npc.wpos.xy());
-
-                                    TravelTo {
-                                        wpos,
-                                        use_paths: true,
-                                    }
-                                })
-                                .repeat();
-
-                            task_state.perform(task, &(npc_id, &*npc, &ctx), &mut controller)?;
-                            */
-                        }
+                        task_state.perform(task, &(npc_id, &*npc, &ctx), &mut controller)?;
+                        */
                     };
                     */
 
@@ -364,23 +319,13 @@ impl Rule for NpcAi {
     }
 }
 
-pub struct NpcCtx<'a> {
-    ctx: &'a EventCtx<'a, NpcAi, OnTick>,
-    npc_id: NpcId,
-    npc: &'a Npc,
-    controller: &'a mut Controller,
-}
+fn idle() -> impl Action { just(|ctx| *ctx.controller = Controller::idle()) }
 
-fn pass() -> impl Action { just(|ctx| {}) }
-
-fn idle_wait() -> impl Action {
-    just(|ctx| *ctx.controller = Controller::idle())
-        .repeat()
-        .map(|_| ())
-}
-
-fn move_toward(wpos: Vec3<f32>, speed_factor: f32) -> impl Action {
+/// Try to walk toward a 3D position without caring for obstacles.
+fn goto(wpos: Vec3<f32>, speed_factor: f32) -> impl Action {
     const STEP_DIST: f32 = 16.0;
+    const GOAL_DIST: f32 = 2.0;
+
     just(move |ctx| {
         let rpos = wpos - ctx.npc.wpos;
         let len = rpos.magnitude();
@@ -389,76 +334,78 @@ fn move_toward(wpos: Vec3<f32>, speed_factor: f32) -> impl Action {
             speed_factor,
         ));
     })
+    .repeat()
+    .stop_if(move |ctx| ctx.npc.wpos.xy().distance_squared(wpos.xy()) < GOAL_DIST.powi(2))
+    .map(|_| {})
 }
 
-fn goto(wpos: Vec3<f32>, speed_factor: f32) -> impl Action {
-    const MIN_DIST: f32 = 2.0;
-
-    move_toward(wpos, speed_factor)
-        .repeat()
-        .stop_if(move |ctx| ctx.npc.wpos.xy().distance_squared(wpos.xy()) < MIN_DIST.powi(2))
-        .map(|_| {})
-}
-
+/// Try to walk toward a 2D position on the terrain without caring for
+/// obstacles.
 fn goto_2d(wpos2d: Vec2<f32>, speed_factor: f32) -> impl Action {
     const MIN_DIST: f32 = 2.0;
 
     now(move |ctx| {
-        let wpos = wpos2d.with_z(
-            ctx.ctx
-                .world
-                .sim()
-                .get_alt_approx(wpos2d.as_())
-                .unwrap_or(0.0),
-        );
+        let wpos = wpos2d.with_z(ctx.world.sim().get_alt_approx(wpos2d.as_()).unwrap_or(0.0));
         goto(wpos, speed_factor)
     })
 }
 
-fn path_to_site(tgt_site: SiteId) -> impl Action {
+/// Try to travel to a site. Where practical, paths will be taken.
+fn travel_to_site(tgt_site: SiteId) -> impl Action {
     now(move |ctx| {
-        let sites = &ctx.ctx.state.data().sites;
+        let sites = &ctx.state.data().sites;
 
-        // If we can, try to find a path to the site via tracks
+        // If we're currently in a site, try to find a path to the target site via
+        // tracks
         if let Some(current_site) = ctx.npc.current_site
-            && let Some((mut tracks, _)) = path_towns(current_site, tgt_site, sites, ctx.ctx.world)
+            && let Some((mut tracks, _)) = path_towns(current_site, tgt_site, sites, ctx.world)
         {
+            // For every track in the path we discovered between the sites...
             seq(tracks
                 .path
                 .into_iter()
+                // ...traverse the nodes of that path.
                 .map(|(track_id, reversed)| now(move |ctx| {
-                    let track_len = ctx.ctx.world.civs().tracks.get(track_id).path().len();
+                    let track_len = ctx.world.civs().tracks.get(track_id).path().len();
+                    // Tracks can be traversed backward (i.e: from end to beginning). Account for this.
                     seq(if reversed {
                         itertools::Either::Left((0..track_len).rev())
                     } else {
                         itertools::Either::Right(0..track_len)
                     }
                         .map(move |node_idx| now(move |ctx| {
-                            let track = ctx.ctx.world.civs().tracks.get(track_id);
-                            let next_node = track.path().nodes[node_idx];
+                            // Find the centre of the track node's chunk
+                            let node_chunk_wpos = TerrainChunkSize::center_wpos(ctx.world
+                                .civs()
+                                .tracks
+                                .get(track_id)
+                                .path()
+                                .nodes[node_idx]);
 
-                            let chunk_wpos = TerrainChunkSize::center_wpos(next_node);
-                            let path_wpos2d = ctx.ctx.world.sim()
-                                .get_nearest_path(chunk_wpos)
-                                .map_or(chunk_wpos, |(_, wpos, _, _)| wpos.as_());
+                            // Refine the node position a bit more based on local path information
+                            let node_wpos = ctx.world.sim()
+                                .get_nearest_path(node_chunk_wpos)
+                                .map_or(node_chunk_wpos, |(_, wpos, _, _)| wpos.as_());
 
-                            goto_2d(path_wpos2d.as_(), 1.0)
+                            // Walk toward the node
+                            goto_2d(node_wpos.as_(), 1.0)
                         })))
                 })))
                 .boxed()
         } else if let Some(site) = sites.get(tgt_site) {
-            // If all else fails, just walk toward the site in a straight line
+            // If all else fails, just walk toward the target site in a straight line
             goto_2d(site.wpos.map(|e| e as f32 + 0.5), 1.0).boxed()
         } else {
-            pass().boxed()
+            // If we can't find a way to get to the site at all, there's nothing more to be done
+            finish().boxed()
         }
     })
 }
 
 // Seconds
 fn timeout(ctx: &NpcCtx, time: f64) -> impl FnMut(&mut NpcCtx) -> bool + Clone + Send + Sync {
-    let end = ctx.ctx.event.time.0 + time;
-    move |ctx| ctx.ctx.event.time.0 > end
+    let end = ctx.time.0 + time;
+    move |ctx| ctx.time.0 > end
 }
 
 fn think() -> impl Action {
@@ -466,12 +413,13 @@ fn think() -> impl Action {
         if matches!(ctx.npc.profession, Some(Profession::Adventurer(_))) {
             // Choose a random site that's fairly close by
             if let Some(tgt_site) = ctx
-                .ctx
                 .state
                 .data()
                 .sites
                 .iter()
                 .filter(|(site_id, site)| {
+                    // TODO: faction.is_some() is used as a proxy for whether the site likely has
+                    // paths, don't do this
                     site.faction.is_some()
                         && ctx.npc.current_site.map_or(true, |cs| *site_id != cs)
                         && thread_rng().gen_bool(0.25)
@@ -479,429 +427,36 @@ fn think() -> impl Action {
                 .min_by_key(|(_, site)| site.wpos.as_().distance(ctx.npc.wpos.xy()) as i32)
                 .map(|(site_id, _)| site_id)
             {
-                casual(path_to_site(tgt_site))
+                casual(travel_to_site(tgt_site))
             } else {
-                casual(pass())
+                casual(finish())
             }
         } else if matches!(ctx.npc.profession, Some(Profession::Blacksmith)) {
-            casual(idle_wait())
+            casual(idle())
         } else {
             casual(
                 now(|ctx| goto(ctx.npc.wpos + Vec3::unit_x() * 10.0, 1.0))
                     .then(now(|ctx| goto(ctx.npc.wpos - Vec3::unit_x() * 10.0, 1.0)))
                     .repeat()
                     .stop_if(timeout(ctx, 10.0))
-                    .then(now(|ctx| idle_wait().stop_if(timeout(ctx, 5.0))))
+                    .then(now(|ctx| idle().repeat().stop_if(timeout(ctx, 5.0))))
                     .map(|_| {}),
             )
         }
     })
 }
 
-/*
-#[derive(Clone)]
-pub struct Generate<F, T>(F, PhantomData<T>);
-
-impl<F, T> PartialEq for Generate<F, T> {
-    fn eq(&self, _: &Self) -> bool { true }
-}
-
-pub fn generate<F, T>(f: F) -> Generate<F, T> { Generate(f, PhantomData) }
-
-impl<F, T: Task> Task for Generate<F, T>
-where
-    F: Clone + Send + Sync + 'static + for<'a> Fn(&T::Ctx<'a>) -> T,
-{
-    type Ctx<'a> = T::Ctx<'a>;
-    type State = (T::State, T);
-
-    fn begin<'a>(&self, ctx: &Self::Ctx<'a>) -> Self::State {
-        let task = (self.0)(ctx);
-        (task.begin(ctx), task)
-    }
-
-    fn run<'a>(
-        &self,
-        (state, task): &mut Self::State,
-        ctx: &Self::Ctx<'a>,
-        controller: &mut Controller,
-    ) -> ControlFlow<()> {
-        task.run(state, ctx, controller)
-    }
-}
-
-#[derive(Clone, PartialEq)]
-pub struct Goto {
-    wpos: Vec2<f32>,
-    speed_factor: f32,
-    finish_dist: f32,
-}
-
-pub fn goto(wpos: Vec2<f32>) -> Goto {
-    Goto {
-        wpos,
-        speed_factor: 1.0,
-        finish_dist: 1.0,
-    }
-}
-
-impl Task for Goto {
-    type Ctx<'a> = (&'a Npc, &'a EventCtx<'a, NpcAi, OnTick>);
-    type State = ();
-
-    fn begin<'a>(&self, (_npc, _ctx): &Self::Ctx<'a>) -> Self::State {}
-
-    fn run<'a>(
-        &self,
-        (): &mut Self::State,
-        (npc, ctx): &Self::Ctx<'a>,
-        controller: &mut Controller,
-    ) -> ControlFlow<()> {
-        if npc.wpos.xy().distance_squared(self.wpos) < self.finish_dist.powi(2) {
-            controller.goto = None;
-            FINISH
-        } else {
-            let dist = npc.wpos.xy().distance(self.wpos);
-            let step = dist.min(32.0);
-            let next_tgt = npc.wpos.xy() + (self.wpos - npc.wpos.xy()) / dist * step;
-
-            if npc.goto.map_or(true, |(tgt, _)| {
-                tgt.xy().distance_squared(next_tgt) > (step * 0.5).powi(2)
-            }) || npc.wpos.xy().distance_squared(next_tgt) < (step * 0.5).powi(2)
-            {
-                controller.goto = Some((
-                    next_tgt.with_z(
-                        ctx.world
-                            .sim()
-                            .get_alt_approx(next_tgt.map(|e| e as i32))
-                            .unwrap_or(0.0),
-                    ),
-                    self.speed_factor,
-                ));
-            }
-            CONTINUE
-        }
-    }
-}
-
-#[derive(Clone, PartialEq)]
-pub struct TravelTo {
-    wpos: Vec2<f32>,
-    use_paths: bool,
-}
-
-pub enum TravelStage {
-    Goto(Vec2<f32>),
-    SiteToSite {
-        path: PathData<(Id<Track>, bool), SiteId>,
-        progress: usize,
-    },
-    IntraSite {
-        path: PathData<Vec2<i32>, Vec2<i32>>,
-        site: Id<WorldSite>,
-    },
-}
-
-impl Task for TravelTo {
-    type Ctx<'a> = (NpcId, &'a Npc, &'a EventCtx<'a, NpcAi, OnTick>);
-    type State = (VecDeque<TravelStage>, TaskState);
-
-    fn begin<'a>(&self, (_npc_id, npc, ctx): &Self::Ctx<'a>) -> Self::State {
-        if self.use_paths {
-            let a = npc.wpos.xy();
-            let b = self.wpos;
-
-            let data = ctx.state.data();
-            let nearest_in_dir = |wpos: Vec2<f32>, end: Vec2<f32>| {
-                let dist = wpos.distance(end);
-                data.sites
-                    .iter()
-                    // TODO: faction.is_some() is currently used as a proxy for whether the site likely has paths, don't do this
-                    .filter(|(site_id, site)| site.faction.is_some() && end.distance(site.wpos.as_()) < dist * 1.2)
-                    .min_by_key(|(_, site)| site.wpos.as_().distance(wpos) as i32)
-            };
-            if let Some((site_a, site_b)) = nearest_in_dir(a, b).zip(nearest_in_dir(b, a)) {
-                if site_a.0 != site_b.0 {
-                    if let Some((path, progress)) =
-                        path_towns(site_a.0, site_b.0, &ctx.state.data().sites, ctx.world)
-                    {
-                        return (
-                            [
-                                TravelStage::Goto(site_a.1.wpos.as_()),
-                                TravelStage::SiteToSite { path, progress },
-                                TravelStage::Goto(b),
-                            ]
-                            .into_iter()
-                            .collect(),
-                            TaskState::default(),
-                        );
-                    }
-                }
-            }
-        }
-        (
-            [TravelStage::Goto(self.wpos)].into_iter().collect(),
-            TaskState::default(),
-        )
-    }
-
-    fn run<'a>(
-        &self,
-        (stages, task_state): &mut Self::State,
-        (npc_id, npc, ctx): &Self::Ctx<'a>,
-        controller: &mut Controller,
-    ) -> ControlFlow<()> {
-        let get_site2 = |site| match &ctx.index.sites.get(site).kind {
-            SiteKind::Refactor(site2)
-            | SiteKind::CliffTown(site2)
-            | SiteKind::DesertCity(site2) => Some(site2),
-            _ => None,
-        };
-
-        if let Some(stage) = stages.front_mut() {
-            match stage {
-                TravelStage::Goto(wpos) => {
-                    task_state.perform(goto(*wpos), &(npc, ctx), controller)?;
-                    stages.pop_front();
-                },
-                TravelStage::IntraSite { path, site } => {
-                    if npc
-                        .current_site
-                        .and_then(|site| ctx.state.data().sites.get(site)?.world_site)
-                        == Some(*site)
-                    {
-                        if let Some(next_tile) = path.path.front() {
-                            task_state.perform(
-                                Goto {
-                                    wpos: get_site2(*site)
-                                        .expect(
-                                            "intrasite path should only be started on a site2 site",
-                                        )
-                                        .tile_center_wpos(*next_tile)
-                                        .as_()
-                                        + 0.5,
-                                    speed_factor: 0.6,
-                                    finish_dist: 1.0,
-                                },
-                                &(npc, ctx),
-                                controller,
-                            )?;
-                            path.path.pop_front();
-                            return CONTINUE;
-                        }
-                    }
-                    task_state.perform(goto(self.wpos), &(npc, ctx), controller)?;
-                    stages.pop_front();
-                },
-                TravelStage::SiteToSite { path, progress } => {
-                    if let Some((track_id, reversed)) = path.path.front() {
-                        let track = ctx.world.civs().tracks.get(*track_id);
-                        if *progress >= track.path().len() {
-                            // We finished this track section, move to the next one
-                            path.path.pop_front();
-                            *progress = 0;
-                        } else {
-                            let next_node_idx = if *reversed {
-                                track.path().len().saturating_sub(*progress + 1)
-                            } else {
-                                *progress
-                            };
-                            let next_node = track.path().nodes[next_node_idx];
-
-                            let transform_path_pos = |chunk_pos| {
-                                let chunk_wpos = TerrainChunkSize::center_wpos(chunk_pos);
-                                if let Some(pathdata) = ctx.world.sim().get_nearest_path(chunk_wpos)
-                                {
-                                    pathdata.1.map(|e| e as i32)
-                                } else {
-                                    chunk_wpos
-                                }
-                            };
-
-                            task_state.perform(
-                                Goto {
-                                    wpos: transform_path_pos(next_node).as_() + 0.5,
-                                    speed_factor: 1.0,
-                                    finish_dist: 10.0,
-                                },
-                                &(npc, ctx),
-                                controller,
-                            )?;
-                            *progress += 1;
-                        }
-                    } else {
-                        stages.pop_front();
-                    }
-                },
-            }
-
-            if !matches!(stages.front(), Some(TravelStage::IntraSite { .. })) {
-                let data = ctx.state.data();
-                if let Some((site2, site)) = npc
-                    .current_site
-                    .and_then(|current_site| data.sites.get(current_site))
-                    .and_then(|site| site.world_site)
-                    .and_then(|site| Some((get_site2(site)?, site)))
-                {
-                    let end = site2.wpos_tile_pos(self.wpos.as_());
-                    if let Some(path) = path_town(npc.wpos, site, ctx.index, |_| Some(end)) {
-                        stages.push_front(TravelStage::IntraSite { path, site });
-                    }
-                }
-            }
-
-            CONTINUE
-        } else {
-            FINISH
-        }
-    }
-}
-
-/*
-let data = ctx.state.data();
-let site2 =
-    npc.home.and_then(|home| data.sites.get(home)).and_then(
-        |home| match &ctx.index.sites.get(home.world_site?).kind
-        {
-            SiteKind::Refactor(site2)
-            | SiteKind::CliffTown(site2)
-            | SiteKind::DesertCity(site2) => Some(site2),
-            _ => None,
-        },
-    );
-
-let wpos = site2
-    .and_then(|site2| {
-        let plaza = &site2.plots
-            [site2.plazas().choose(&mut thread_rng())?];
-        Some(site2.tile_center_wpos(plaza.root_tile()).as_())
-    })
-    .unwrap_or(npc.wpos.xy());
-
-TravelTo {
-    wpos,
-    use_paths: true,
-}
-*/
-
-trait IsTask =
-    core::ops::Generator<Data<NpcData<'static>>, Yield = (), Return = ()> + Any + Send + Sync;
-
-pub struct NpcData<'a> {
-    ctx: &'a EventCtx<'a, NpcAi, OnTick>,
-    npc_id: NpcId,
-    npc: &'a Npc,
-    controller: &'a mut Controller,
-}
-
-unsafe impl Context for NpcData<'static> {
-    type Ty<'a> = NpcData<'a>;
-}
-
-pub fn brain() -> Brain<NpcData<'static>> {
-    Brain::new(|mut data: Data<NpcData>| {
-        let mut task = TaskBox::<_, ()>::new(data.clone());
-
-        loop {
-            println!("Started");
-            while let ControlFlow::Break(end) = task.finish(0) {
-                yield end;
-            }
-
-            // Choose a new plaza in the NPC's home site to path towards
-            let path = data.with(|d| {
-                let data = d.ctx.state.data();
-
-                let current_site = data.sites.get(d.npc.current_site?)?;
-                let site2 = match &d.ctx.index.sites.get(current_site.world_site?).kind {
-                    SiteKind::Refactor(site2)
-                    | SiteKind::CliffTown(site2)
-                    | SiteKind::DesertCity(site2) => Some(site2),
-                    _ => None,
-                }?;
-
-                let plaza = &site2.plots[site2.plazas().choose(&mut thread_rng())?];
-                let end_wpos = site2.tile_center_wpos(plaza.root_tile());
-
-                if end_wpos.as_::<f32>().distance(d.npc.wpos.xy()) < 32.0 {
-                    return None;
-                }
-
-                let start = site2.wpos_tile_pos(d.npc.wpos.xy().as_());
-                let end = site2.wpos_tile_pos(plaza.root_tile());
-
-                let path = match path_in_site(start, end, site2) {
-                    PathResult::Path(path) => path,
-                    _ => return None,
-                };
-                println!(
-                    "CHOSE PATH, len = {}, start = {:?}, end = {:?}\nnpc = {:?}",
-                    path.len(),
-                    start,
-                    end,
-                    d.npc_id
-                );
-                Some((current_site.world_site?, path))
-            });
-
-            if let Some((site, path)) = path {
-                println!("Begin path");
-                task.perform(0, walk_path(site, path));
-            } else {
-                println!("No path, waiting...");
-                for _ in 0..100 {
-                    yield ();
-                }
-                println!("Waited.");
-            }
-        }
-    })
-}
-
-fn walk_path(site: Id<WorldSite>, path: Path<Vec2<i32>>) -> impl IsTask {
-    move |mut data: Data<NpcData>| {
-        for tile in path {
-            println!("TILE");
-            let wpos = data.with(|d| {
-                match &d.ctx.index.sites.get(site).kind {
-                    SiteKind::Refactor(site2)
-                    | SiteKind::CliffTown(site2)
-                    | SiteKind::DesertCity(site2) => Some(site2),
-                    _ => None,
-                }
-                .expect("intrasite path should only be started on a site2 site")
-                .tile_center_wpos(tile)
-                .as_()
-                    + 0.5
-            });
-
-            println!(
-                "Walking to next tile... tile wpos = {:?} npc wpos = {:?}",
-                wpos,
-                data.with(|d| d.npc.wpos)
-            );
-            while data.with(|d| d.npc.wpos.xy().distance_squared(wpos) > 2.0) {
-                data.with(|d| {
-                    d.controller.goto = Some((
-                        wpos.with_z(
-                            d.ctx
-                                .world
-                                .sim()
-                                .get_alt_approx(wpos.map(|e| e as i32))
-                                .unwrap_or(0.0),
-                        ),
-                        1.0,
-                    ))
-                });
-                yield ();
-            }
-        }
-
-        println!("Waiting..");
-        for _ in 0..100 {
-            yield ();
-        }
-        println!("Waited.");
-    }
-}
-*/
+// if !matches!(stages.front(), Some(TravelStage::IntraSite { .. })) {
+//     let data = ctx.state.data();
+//     if let Some((site2, site)) = npc
+//         .current_site
+//         .and_then(|current_site| data.sites.get(current_site))
+//         .and_then(|site| site.world_site)
+//         .and_then(|site| Some((get_site2(site)?, site)))
+//     {
+//         let end = site2.wpos_tile_pos(self.wpos.as_());
+//         if let Some(path) = path_town(npc.wpos, site, ctx.index, |_|
+// Some(end)) {             stages.push_front(TravelStage::IntraSite { path,
+// site });         }
+//     }
+// }