use crate::prelude::*;

/// Menu Plugin; empty struct for Plugin impl
pub(crate) struct SavePlugin;

impl Plugin for SavePlugin {
    fn build(&self, app: &mut App) {
        app.init_asset::<SaveEntity>()
            .init_asset_loader::<SaveEntityLoader>()
            .add_systems(Startup, test_save_entity)
            .add_systems(
                Update,
                check_loaded_entity_assets.run_if(on_event::<AssetEvent<SaveEntity>>()),
            );
    }
}

#[derive(Asset, TypePath, Debug, Default)]
pub(crate) struct SaveEntity {
    transform: Option<Transform>,
    name: Option<Name>,
    uuid: Option<EntityUuid>,
    model: Option<(Handle<Gltf>, String)>,
    // TODO: Option<bool> feels like an antipattern as this is either Some(true) or None and never Some(false).
    // Either encode more Camera data in this or replace it with Option<()> or just bool.
    camera: Option<bool>,
}

impl SaveEntity {
    fn parse(
        text: &str,
        load_context: &mut LoadContext,
    ) -> Result<SaveEntity, parse::SaveEntityParseError> {
        let lines = text.split('\n');
        let mut entity = SaveEntity { ..default() };
        lines.into_iter().for_each(|line| {
            if let Ok(name) = parse::parse_save_name(line) {
                entity.name = Some(name);
            } else if let Ok(transform) = parse::parse_save_transform(line) {
                entity.transform = Some(transform);
            } else if let Ok(uuid) = parse::parse_save_uuid(line) {
                entity.uuid = Some(EntityUuid(uuid));
            } else if let Ok((gltf_path, scene_name)) = parse::parse_save_model(line) {
                let handle = load_context.load(gltf_path);
                entity.model = Some((handle, scene_name));
            } else if let Ok(true) = parse::parse_save_camera(line) {
                entity.camera = Some(true);
            }
        });
        Ok(entity)
    }
}

#[derive(Component, Clone, Debug)]
struct EntityUuid(Uuid);

mod parse {
    use super::*;

    #[derive(Error, Debug)]
    pub(crate) enum SaveEntityParseError {
        #[error("Failed to parse Uuid: {0}")]
        Uuid(#[from] uuid::Error),
        #[error("Failed to parse name")]
        Name,
        #[error("Failed to parse Transform")]
        Transform,
        #[error("Failed to parse Entity")]
        Nom(nom::Err<nom::error::Error<Box<str>>>),
    }

    // Convert Nom error to parse error
    // https://stackoverflow.com/a/77974858/3096574
    impl From<nom::Err<nom::error::Error<&str>>> for SaveEntityParseError {
        fn from(err: nom::Err<nom::error::Error<&str>>) -> Self {
            SaveEntityParseError::Nom(err.map_input(|input| input.into()))
        }
    }

    fn parse_word<'a>(w: &'a str) -> impl Fn(&'a str) -> IResult<&'a str, &'a str> {
        move |i: &'a str| {
            tag(w)(i)
        }
    }

    fn parse_xyz(i: &str) -> IResult<&str, (f32, f32, f32)> {
        tuple((float, space1, float, space1, float))(i)
            .map(|(s, (x, _, y, _, z))| (s, (x, y, z)))
    }

    fn parse_wxyz(i: &str) -> IResult<&str, (f32, f32, f32, f32)> {
        tuple((
            float,
            space1,
            float,
            space1,
            float,
            space1,
            float,
        ))(i)
        .map(|(s, (w, _, x, _, y, _, z))| (s, (w, x, y, z)))
    }

    fn parse_string(i: &str) -> IResult<&str, &str> {
        let (rem, (_, out, _)) = tuple((tag("\""), take_until1("\""), tag("\"")))(i)?;
        Ok((rem, out))
    }

    ///
    /// ```
    /// let parsed = parse_save_transform("transform translation 1.0 2.0 3.0 rotation 1.0 0.0 0.0 0.0 scale 1.0 1.0 1.0").unwrap();
    /// let expected = Transform { translation: Vec3::new(1.0, 1.0, 1.0), rotation: Quat::from_xzyw(1.0, 0.0, 0.0, 0.0), scale: Vec3::ONE };
    ///
    /// assert_eq!(parsed, expected);
    /// ```
    ///
    pub(crate) fn parse_save_transform(line: &str) -> Result<Transform, SaveEntityParseError> {
        let (rem, _) = tag("transform")(line)?;

        let mut transform = Transform::default();

        let mut curr = rem.trim_start();
        for _ in 0..3 {
            println!("Curr: {:?}", curr);
            if let Ok((rem, (_, _, (x, y, z)))) = tuple((parse_word("translation"), space1, parse_xyz))(curr.trim_start()) {
                transform.translation = Vec3::new(x, y, z);
                curr = rem.trim_start();
            } else if let Ok((rem, (_, _, (x, y, z, w)))) = tuple((parse_word("rotation"), space1, parse_wxyz))(curr.trim_start()) {
                transform.rotation = Quat::from_xyzw(x, y, z, w);
                curr = rem.trim_start();
            } else if let Ok((rem, (_, _, (x, y, z)))) = tuple((parse_word("scale"), space1, parse_xyz))(curr.trim_start()) {
                transform.scale = Vec3::new(x, y, z);
                curr = rem.trim_start();
            } else {
                return Err(SaveEntityParseError::Transform);
            }
        }

        // Assert there are no trailing characters on the line
        debug_assert_eq!(curr, "");

        Ok(transform)
    }

    #[test]
    fn test_parse_transform() {
        let line = "transform translation 1.0 2.0 3.0 rotation 0.1 0.2 0.3 1.0 scale 1.1 1.2 1.3";
        let parsed = parse_save_transform(line).unwrap();
        let expected = Transform {
            translation: Vec3::new(1.0, 2.0, 3.0),
            rotation: Quat::from_xyzw(0.1, 0.2, 0.3, 1.0),
            scale: Vec3::new(1.1, 1.2, 1.3),
        };

        assert_eq!(parsed, expected);
    }

    ///
    /// ```
    /// let parsed = parse_save_name("name asfd").unwrap();
    /// let expected = Name::new("asdf");
    ///
    /// assert_eq!(parsed, expected);
    /// ```
    ///
    pub(crate) fn parse_save_name(line: &str) -> Result<Name, SaveEntityParseError> {
        let (remainder, _) = tag("name")(line)?;
        let n = remainder.trim().to_string();
        if n.is_empty() {
            Err(SaveEntityParseError::Name)
        } else {
            let name = Name::new(n);
            Ok(name)
        }
    }

    #[test]
    fn test_parse_name() {
        {
            let line = "name Van";
            let parsed = parse_save_name(line).unwrap();
            let expected = Name::new("Van");

            assert_eq!(parsed, expected);
        }
        {
            let line = "name Big Mike";
            let parsed = parse_save_name(line).unwrap();
            let expected = Name::new("Big Mike");

            assert_eq!(parsed, expected);
        }
    }

    ///
    /// ```
    /// let parsed = parse_save_uuid("uuid 339dd18f-761a-4997-b515-ef57f4dc2447").unwrap();
    /// let expected = Uuid::parse_str("339dd18f-761a-4997-b515-ef57f4dc2447").unwrap();
    ///
    /// assert_eq!(parsed, expected);
    /// ```
    ///
    pub(crate) fn parse_save_uuid(line: &str) -> Result<Uuid, SaveEntityParseError> {
        let (remainder, _) = tag("uuid")(line)?;
        let uuid = Uuid::try_parse(remainder.trim())?;
        Ok(uuid)
    }

    #[test]
    fn test_parse_uuid() {
        let line = "uuid 1c16ab9a-5f79-4340-8469-4086f69c64f2";
        let parsed = parse_save_uuid(line).unwrap();
        let expected = Uuid::parse_str("1c16ab9a-5f79-4340-8469-4086f69c64f2").unwrap();

        assert_eq!(parsed, expected);
    }

    pub(crate) fn parse_save_model(line: &str) -> Result<(String, String), SaveEntityParseError> {
        let (rem, (_, _, gltf_name, _, scene_name)) = tuple((
            tag("model"),
            space1,
            parse_string,
            space1,
            parse_string,
        ))(line)?;

        debug_assert_eq!(rem, "");

        Ok((String::from(gltf_name), String::from(scene_name)))
    }

    #[test]
    fn test_parse_model() {
        let line = "model \"models/foo.glb\" \"My Scene\"";
        let parsed = parse_save_model(line).unwrap();
        let expected = (String::from("models/foo.glb"), String::from("My Scene"));

        assert_eq!(parsed, expected);
    }

    pub(crate) fn parse_save_camera(line: &str) -> Result<bool, SaveEntityParseError> {
        let (_rem, cam) = tag("camera")(line)?;
        Ok(!cam.is_empty())
    }

    #[test]
    fn test_parse_camera() {
        {
            let line = "camera";
            let parsed = parse_save_camera(line).unwrap();
            let expected = true;
            assert_eq!(parsed, expected);
        }
        {
            let line = "notcamera";
            let parsed = parse_save_camera(line);
            assert!(parsed.is_err());
        }
    }
}

#[derive(Default)]
struct SaveEntityLoader;

#[derive(Error, Debug)]
enum SaveEntityLoaderError {
    #[error("Could not load asset: {0}")]
    Io(#[from] std::io::Error),
    #[error("Could not parse entity: {0}")]
    Parse(#[from] parse::SaveEntityParseError),
}

impl AssetLoader for SaveEntityLoader {
    type Asset = SaveEntity;
    type Settings = ();
    type Error = SaveEntityLoaderError;

    async fn load<'a>(
        &'a self,
        reader: &'a mut Reader<'_>,
        _settings: &'a (),
        load_context: &'a mut LoadContext<'_>,
    ) -> Result<Self::Asset, Self::Error> {
        let mut bytes = Vec::new();
        reader.read_to_end(&mut bytes).await?;

        let s = std::str::from_utf8(bytes.as_slice()).unwrap();
        let save_entity = SaveEntity::parse(s, load_context)?;
        Ok(save_entity)
    }

    fn extensions(&self) -> &[&str] {
        &["entity"]
    }
}

fn test_save_entity(loader: Res<AssetServer>, mut commands: Commands) {
    let handle: Handle<SaveEntity> = loader.load("levels/00/entities/van.entity");
    commands.spawn((
        SpatialBundle { ..default() },
        handle,
    ));
}

fn check_loaded_entity_assets(
    query: Query<(Entity, &Handle<SaveEntity>)>,
    mut events: EventReader<AssetEvent<SaveEntity>>,
    save_entities: Res<Assets<SaveEntity>>,
    mut commands: Commands,
    gltfs: Res<Assets<Gltf>>,
) {
    events.read().for_each(|event| {
        if let AssetEvent::LoadedWithDependencies { id } = event {
            query
                .iter()
                .filter(|(_, handle)| handle.id() == *id)
                .for_each(|(entity, _handle)| {
                    let saved = save_entities.get(*id).unwrap();
                    debug!(
                        "Updating entity {:?} ({:?}) because asset changed",
                        saved.name, saved.uuid
                    );

                    let mut e = commands.entity(entity);
                    // Apply camera
                    // Should be applied early to avoid clobbering transform
                    if let Some(is_camera) = &saved.camera {
                        if *is_camera {
                            e.insert(Camera3dBundle { ..default() });
                        }
                    } else {
                        e.remove::<(Camera, Camera3d)>();
                    }
                    // Apply transform
                    if let Some(transform) = &saved.transform {
                        // TODO: Only update if different
                        e.insert(*transform);
                    } else {
                        e.remove::<Transform>();
                    }
                    // Apply Name
                    if let Some(name) = &saved.name {
                        // TODO: Only update if different
                        e.insert(name.clone());
                    } else {
                        e.remove::<Name>();
                    }
                    // Apply Uuid
                    if let Some(uuid) = &saved.uuid {
                        // TODO: Only update if different
                        e.insert(uuid.clone());
                    } else {
                        e.remove::<EntityUuid>();
                    }
                    // Apply Model 
                    if let Some((gltf_handle, scene_name)) = &saved.model {
                        // Find scene and update
                        let gltf = gltfs.get(gltf_handle).unwrap();
                        let scene_handle = gltf.named_scenes.get(scene_name.as_str().into()).unwrap();
                        e.insert(scene_handle.clone());
                    } else {
                        e.remove::<Handle<Scene>>();
                    }
                });
        }
    })
}