From 003751847250083fdd749a21f47a04f058b1a108 Mon Sep 17 00:00:00 2001
From: Manuel Schmidbauer <development@manu.software>
Date: Sun, 27 Feb 2022 14:30:31 +0100
Subject: [PATCH] Impl #1357: Agent chase abort

- Adds util funcs to calculate benefit of continue pursue vs letting
target escape
- Hooks util funcs into agent's hostile tree
---
 CHANGELOG.md                 |  1 +
 server/src/sys/agent.rs      | 27 ++++++++++++++++++++--
 server/src/sys/agent/util.rs | 44 +++++++++++++++++++++++++++++++++++-
 3 files changed, 69 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c12d5a7fee..1de1daf941 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Waypoints saved between sessions and shared with group members.
 - New rocks
 - Weapon trails
+- Hostile agent will now abort pursuing their target based on multiple metrics
 
 ### Changed
 
diff --git a/server/src/sys/agent.rs b/server/src/sys/agent.rs
index d339e87fb7..9f54c7b96f 100644
--- a/server/src/sys/agent.rs
+++ b/server/src/sys/agent.rs
@@ -15,7 +15,7 @@ use crate::{
         data::{AgentData, AttackData, Path, ReadData, Tactic, TargetData},
         util::{
             aim_projectile, can_see_tgt, get_entity_by_id, is_dead, is_dead_or_invulnerable,
-            is_invulnerable, try_owner_alignment,
+            is_invulnerable, stop_pursuing, try_owner_alignment,
         },
     },
 };
@@ -613,6 +613,20 @@ impl<'a> AgentData<'a> {
 
             if let Some(tgt_pos) = read_data.positions.get(target) {
                 let dist_sqrd = self.pos.0.distance_squared(tgt_pos.0);
+                let origin_dist_sqrd = match agent.patrol_origin {
+                    Some(pos) => pos.distance_squared(self.pos.0),
+                    None => 1.0,
+                };
+
+                let own_health_fraction = match self.health {
+                    Some(val) => val.fraction(),
+                    None => 1.0,
+                };
+                let target_health_fraction = match read_data.healths.get(target) {
+                    Some(val) => val.fraction(),
+                    None => 1.0,
+                };
+
                 let in_aggro_range = agent
                     .psyche
                     .aggro_dist
@@ -645,7 +659,16 @@ impl<'a> AgentData<'a> {
                     self.exclaim_relief_about_enemy_dead(agent, event_emitter);
                     agent.target = None;
                     self.idle(agent, controller, read_data, rng);
-                } else if is_invulnerable(target, read_data) {
+                } else if is_invulnerable(target, read_data)
+                    || stop_pursuing(
+                        dist_sqrd,
+                        origin_dist_sqrd,
+                        own_health_fraction,
+                        target_health_fraction,
+                        read_data.time.0 - selected_at,
+                        &agent.psyche,
+                    )
+                {
                     agent.target = None;
                     self.idle(agent, controller, read_data, rng);
                 } else {
diff --git a/server/src/sys/agent/util.rs b/server/src/sys/agent/util.rs
index ac17813ffb..fe999526fe 100644
--- a/server/src/sys/agent/util.rs
+++ b/server/src/sys/agent/util.rs
@@ -1,6 +1,6 @@
 use crate::sys::agent::{AgentData, ReadData};
 use common::{
-    comp::{buff::BuffKind, Alignment, Pos},
+    comp::{agent::Psyche, buff::BuffKind, Alignment, Pos},
     consts::GRAVITY,
     terrain::{Block, TerrainGrid},
     util::Dir,
@@ -79,3 +79,45 @@ impl<'a> AgentData<'a> {
             .map_or(false, |b| b.kinds.contains_key(&buff))
     }
 }
+
+/// Calculates whether the agent should continue chase or let the target escape.
+///
+/// Will return true when score of letting target escape is higher then the
+/// score of continuing the pursue, false otherwise.
+pub fn stop_pursuing(
+    dist_to_target_sqrd: f32,
+    dist_to_home_sqrd: f32,
+    own_health_fraction: f32,
+    target_health_fraction: f32,
+    dur_since_last_attacked: f64,
+    psyche: &Psyche,
+) -> bool {
+    should_let_target_escape(
+        dist_to_home_sqrd,
+        dur_since_last_attacked,
+        own_health_fraction,
+    ) > should_continue_to_pursue(dist_to_target_sqrd, psyche, target_health_fraction)
+}
+
+/// Scores the benefit of continuing the pursue in value from 0 to infinity.
+fn should_continue_to_pursue(
+    dist_to_target_sqrd: f32,
+    psyche: &Psyche,
+    target_health_fraction: f32,
+) -> f32 {
+    let aggression_score = (1.0 / psyche.flee_health.max(0.25))
+        * psyche.aggro_dist.unwrap_or(psyche.sight_dist)
+        * psyche.sight_dist;
+
+    (100.0 * aggression_score) / (dist_to_target_sqrd * target_health_fraction)
+}
+
+/// Scores the benefit of letting the target escape in a value from 0 to
+/// infinity.
+fn should_let_target_escape(
+    dist_to_home_sqrd: f32,
+    dur_since_last_attacked: f64,
+    own_health_fraction: f32,
+) -> f32 {
+    (dist_to_home_sqrd / own_health_fraction) * dur_since_last_attacked as f32 * 0.005
+}