//! Load assets (images or voxel data) from files

use dot_vox::DotVoxData;
use image::DynamicImage;
use lazy_static::lazy_static;
use std::{
    borrow::Cow,
    fs, io,
    path::{Path, PathBuf},
    sync::Arc,
};

pub use assets_manager::{
    asset::Ron,
    loader::{
        self, BincodeLoader, BytesLoader, JsonLoader, LoadFrom, Loader, RonLoader, StringLoader,
    },
    source, Asset, AssetCache, BoxedError, Compound, Error,
};

lazy_static! {
    /// The HashMap where all loaded assets are stored in.
    static ref ASSETS: AssetCache =
        AssetCache::new(&*ASSETS_PATH).unwrap();
}

pub fn start_hot_reloading() { ASSETS.enhance_hot_reloading(); }

pub type AssetHandle<T> = assets_manager::Handle<'static, T>;
pub type AssetGuard<T> = assets_manager::AssetGuard<'static, T>;
pub type AssetDir<T> = assets_manager::DirReader<'static, T, source::FileSystem>;

/// The Asset trait, which is implemented by all structures that have their data
/// stored in the filesystem.
pub trait AssetExt: Sized + Send + Sync + 'static {
    /// Function used to load assets from the filesystem or the cache.
    /// Example usage:
    /// ```no_run
    /// use veloren_common_assets::{AssetExt, Image};
    ///
    /// let my_image = Image::load("core.ui.backgrounds.city").unwrap();
    /// ```
    fn load(specifier: &str) -> Result<AssetHandle<Self>, Error>;

    /// Function used to load assets from the filesystem or the cache and return
    /// a clone.
    fn load_cloned(specifier: &str) -> Result<Self, Error>
    where
        Self: Clone,
    {
        Self::load(specifier).map(AssetHandle::cloned)
    }

    /// Function used to load essential assets from the filesystem or the cache.
    /// It will panic if the asset is not found. Example usage:
    /// ```no_run
    /// use veloren_common_assets::{AssetExt, Image};
    ///
    /// let my_image = Image::load_expect("core.ui.backgrounds.city");
    /// ```
    #[track_caller]
    fn load_expect(specifier: &str) -> AssetHandle<Self> {
        Self::load(specifier).unwrap_or_else(|err| {
            panic!(
                "Failed loading essential asset: {} (error={:?})",
                specifier, err
            )
        })
    }

    /// Function used to load essential assets from the filesystem or the cache
    /// and return a clone. It will panic if the asset is not found.
    #[track_caller]
    fn load_expect_cloned(specifier: &str) -> Self
    where
        Self: Clone,
    {
        Self::load_expect(specifier).cloned()
    }

    fn load_owned(specifier: &str) -> Result<Self, Error>;
}

pub fn load_dir<T: Asset>(specifier: &str) -> Result<AssetDir<T>, Error> {
    Ok(ASSETS.load_dir(specifier)?)
}

impl<T: Compound> AssetExt for T {
    fn load(specifier: &str) -> Result<AssetHandle<Self>, Error> { ASSETS.load(specifier) }

    fn load_owned(specifier: &str) -> Result<Self, Error> { ASSETS.load_owned(specifier) }
}

pub struct Image(pub Arc<DynamicImage>);

impl Image {
    pub fn to_image(&self) -> Arc<DynamicImage> { Arc::clone(&self.0) }
}

pub struct PngLoader;
impl Loader<Image> for PngLoader {
    fn load(content: Cow<[u8]>, _: &str) -> Result<Image, BoxedError> {
        let format = image::ImageFormat::Png;
        let image = image::load_from_memory_with_format(&content, format)?;
        Ok(Image(Arc::new(image)))
    }
}

impl Asset for Image {
    type Loader = PngLoader;

    const EXTENSION: &'static str = "png";
}

pub struct DotVoxAsset(pub DotVoxData);

pub struct DotVoxLoader;
impl Loader<DotVoxAsset> for DotVoxLoader {
    fn load(content: std::borrow::Cow<[u8]>, _: &str) -> Result<DotVoxAsset, BoxedError> {
        let data = dot_vox::load_bytes(&content).map_err(|err| err.to_owned())?;
        Ok(DotVoxAsset(data))
    }
}

impl Asset for DotVoxAsset {
    type Loader = DotVoxLoader;

    const EXTENSION: &'static str = "vox";
}

lazy_static! {
    /// Lazy static to find and cache where the asset directory is.
    /// Cases we need to account for:
    /// 1. Running through airshipper (`assets` next to binary)
    /// 2. Install with package manager and run (assets probably in `/usr/share/veloren/assets` while binary in `/usr/bin/`)
    /// 3. Download & hopefully extract zip (`assets` next to binary)
    /// 4. Running through cargo (`assets` in workspace root but not always in cwd incase you `cd voxygen && cargo r`)
    /// 5. Running executable in the target dir (`assets` in workspace)
    /// 6. Running tests (`assets` in workspace root)
    pub static ref ASSETS_PATH: PathBuf = {
        let mut paths = Vec::new();

        // Note: Ordering matters here!

        // 1. VELOREN_ASSETS environment variable
        if let Ok(var) = std::env::var("VELOREN_ASSETS") {
            paths.push(var.into());
        }

        // 2. Executable path
        if let Ok(mut path) = std::env::current_exe() {
            path.pop();
            paths.push(path);
        }

        // 3. Root of the repository
        if let Ok(path) = std::env::current_dir() {
            // If we are in the root, push path
            if path.join(".git").is_dir() {
                paths.push(path);
            } else {
                // Search .git directory in parent directries
                for ancestor in path.ancestors().take(10) {
                    if ancestor.join(".git").is_dir() {
                        paths.push(ancestor.to_path_buf());
                        break;
                    }
                }
            }
        }

        // 4. System paths
        #[cfg(all(unix, not(target_os = "macos"), not(target_os = "ios"), not(target_os = "android")))]
        {
            if let Ok(result) = std::env::var("XDG_DATA_HOME") {
                paths.push(format!("{}/veloren/", result).into());
            } else if let Ok(result) = std::env::var("HOME") {
                paths.push(format!("{}/.local/share/veloren/", result).into());
            }

            if let Ok(result) = std::env::var("XDG_DATA_DIRS") {
                result.split(':').for_each(|x| paths.push(format!("{}/veloren/", x).into()));
            } else {
                // Fallback
                let fallback_paths = vec!["/usr/local/share", "/usr/share"];
                for fallback_path in fallback_paths {
                    paths.push(format!("{}/veloren/", fallback_path).into());
                }
            }
        }

        tracing::trace!("Possible asset locations paths={:?}", paths);

        for mut path in paths.clone() {
            if !path.ends_with("assets") {
                path = path.join("assets");
            }

            if path.is_dir() {
                tracing::info!("Assets found path={}", path.display());
                return path;
            }
        }

        panic!(
            "Asset directory not found. In attempting to find it, we searched:\n{})",
            paths.iter().fold(String::new(), |mut a, path| {
                a += &path.to_string_lossy();
                a += "\n";
                a
            }),
        );
    };
}

/// Returns the actual path of the specifier with the extension.
///
/// For directories, give `""` as extension.
pub fn path_of(specifier: &str, ext: &str) -> PathBuf { ASSETS.source().path_of(specifier, ext) }

fn get_dir_files(files: &mut Vec<String>, path: &Path, specifier: &str) -> io::Result<()> {
    for entry in (fs::read_dir(path)?).flatten() {
        let path = entry.path();
        let maybe_stem = path.file_stem().and_then(|stem| stem.to_str());

        if let Some(stem) = maybe_stem {
            let specifier = format!("{}.{}", specifier, stem);

            if path.is_dir() {
                get_dir_files(files, &path, &specifier)?;
            } else {
                files.push(specifier);
            }
        }
    }

    Ok(())
}

pub struct Directory(Vec<String>);

impl Directory {
    pub fn iter(&self) -> impl Iterator<Item = &String> { self.0.iter() }
}

impl Compound for Directory {
    fn load<S: source::Source>(_: &AssetCache<S>, specifier: &str) -> Result<Self, Error> {
        let specifier = specifier.strip_suffix(".*").unwrap_or(specifier);
        let root = ASSETS.source().path_of(specifier, "");
        let mut files = Vec::new();

        get_dir_files(&mut files, &root, specifier)?;

        Ok(Directory(files))
    }
}

pub mod asset_tweak {
    use super::{Asset, AssetExt, RonLoader};
    use serde::{de::DeserializeOwned, Deserialize};

    #[derive(Clone, Deserialize)]
    struct AssetTweakWrapper<T>(T);

    impl<T> Asset for AssetTweakWrapper<T>
    where
        T: Clone + Sized + Send + Sync + 'static + DeserializeOwned,
    {
        type Loader = RonLoader;

        const EXTENSION: &'static str = "ron";
    }

    /// NOTE: Don't use it in code, it's debug only
    pub fn tweak_expect<T>(path: &str) -> T
    where
        T: Clone + Sized + Send + Sync + 'static + DeserializeOwned,
    {
        tracing::warn!("AssetTweaker used in release build!");
        let handle = <AssetTweakWrapper<T> as AssetExt>::load_expect(path);
        let AssetTweakWrapper(value) = handle.read().clone();
        value
    }
}

#[cfg(test)]
mod tests {
    use super::asset_tweak::tweak;
    use std::{
        convert::AsRef,
        fmt::Debug,
        fs::{self, File},
        io::Write,
        path::{Path, PathBuf},
    };

    // Return path to repository by searching 10 directories back
    fn find_root() -> Option<PathBuf> {
        std::env::current_dir().map_or(None, |path| {
            // If we are in the root, push path
            if path.join(".git").is_dir() {
                return Some(path);
            }
            // Search .git directory in parent directries
            for ancestor in path.ancestors().take(10) {
                if ancestor.join(".git").is_dir() {
                    return Some(ancestor.to_path_buf());
                }
            }
            None
        })
    }

    struct DirectoryGuard<P>
    where
        P: AsRef<Path>,
    {
        dir: P,
    }

    impl<P> DirectoryGuard<P>
    where
        P: AsRef<Path>,
    {
        fn create(dir: P) -> Self {
            fs::create_dir_all(&dir).expect("failed to create directory");
            Self { dir }
        }
    }

    impl<P> Drop for DirectoryGuard<P>
    where
        P: AsRef<Path>,
    {
        fn drop(&mut self) { fs::remove_dir(&self.dir).expect("failed to remove directory"); }
    }

    struct FileGuard<P>
    where
        P: AsRef<Path> + Debug,
    {
        file: P,
    }

    impl<P> FileGuard<P>
    where
        P: AsRef<Path> + Debug,
    {
        fn create(file: P) -> (Self, File) {
            let f =
                File::create(&file).unwrap_or_else(|_| panic!("failed to create file {:?}", &file));
            (Self { file }, f)
        }
    }

    impl<P> Drop for FileGuard<P>
    where
        P: AsRef<Path> + Debug,
    {
        fn drop(&mut self) {
            fs::remove_file(&self.file)
                .unwrap_or_else(|_| panic!("failed to create file {:?}", &self.file));
        }
    }

    #[test]
    fn test_tweaked_string() {
        let root = find_root().expect("failed to discover repository_root");
        let tweak_dir = root.join("assets/common/tweak/");
        let _dir_guard = DirectoryGuard::create(tweak_dir.clone());

        // define test files
        let from_int = tweak_dir.clone().join("int_tweak.ron");
        let from_string = tweak_dir.clone().join("string_tweak.ron");
        let from_map = tweak_dir.clone().join("map_tweak.ron");

        // setup fs guards
        let (_file_guard1, mut file1) = FileGuard::create(from_int);
        let (_file_guard2, mut file2) = FileGuard::create(from_string);
        let (_file_guard3, mut file3) = FileGuard::create(from_map);

        // write to file and check result
        file1.write(b"(5)").expect("failed to write to the file");
        let x = tweak::<i32>("common.tweak.int_tweak");
        assert_eq!(x, 5);

        // write to file and check result
        file2
            .write(br#"("Hello Zest")"#)
            .expect("failed to write to the file");
        let x = tweak::<String>("common.tweak.string_tweak");
        assert_eq!(x, "Hello Zest".to_owned());

        // write to file and check result
        file3
            .write(
                br#"
        ({
            "wow": 4,
            "such": 5,
        })
        "#,
            )
            .expect("failed to write to the file");
        let x: std::collections::HashMap<String, i32> = tweak("common.tweak.map_tweak");
        let mut map = std::collections::HashMap::new();
        map.insert("wow".to_owned(), 4);
        map.insert("such".to_owned(), 5);
        assert_eq!(x, map);
    }
}