//! Management of async loaders

use crate::avm1::{Object, TObject};
use crate::display_object::{DisplayObject, MorphShape, TDisplayObject};
use crate::player::Player;
use crate::tag_utils::SwfMovie;
use gc_arena::{Collect, CollectionContext};
use generational_arena::{Arena, Index};
use std::future::Future;
use std::pin::Pin;
use std::sync::{Arc, Mutex, Weak};
use url::form_urlencoded;

pub type Handle = Index;

type Error = Box<dyn std::error::Error>;

/// Holds all in-progress loads for the player.
pub struct LoadManager<'gc>(Arena<Loader<'gc>>);

unsafe impl<'gc> Collect for LoadManager<'gc> {
    fn trace(&self, cc: CollectionContext) {
        for (_, loader) in self.0.iter() {
            loader.trace(cc)
        }
    }
}

impl<'gc> LoadManager<'gc> {
    /// Construct a new `LoadManager`.
    pub fn new() -> Self {
        Self(Arena::new())
    }

    /// Add a new loader to the `LoadManager`.
    ///
    /// This function returns the loader handle for later inspection. A loader
    /// handle is valid for as long as the load operation. Once the load
    /// finishes, the handle will be invalidated (and the underlying loader
    /// deleted).
    pub fn add_loader(&mut self, loader: Loader<'gc>) -> Handle {
        let handle = self.0.insert(loader);
        self.0
            .get_mut(handle)
            .unwrap()
            .introduce_loader_handle(handle);

        handle
    }

    /// Retrieve a loader by handle.
    pub fn get_loader(&self, handle: Handle) -> Option<&Loader<'gc>> {
        self.0.get(handle)
    }

    /// Retrieve a loader by handle for mutation.
    pub fn get_loader_mut(&mut self, handle: Handle) -> Option<&mut Loader<'gc>> {
        self.0.get_mut(handle)
    }

    /// Kick off a movie clip load.
    ///
    /// Returns the loader's async process, which you will need to spawn.
    pub fn load_movie_into_clip(
        &mut self,
        player: Weak<Mutex<Player>>,
        target_clip: DisplayObject<'gc>,
        fetch: Pin<Box<dyn Future<Output = Result<Vec<u8>, Error>>>>,
    ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + 'static>> {
        let loader = Loader::Movie {
            self_handle: None,
            target_clip,
        };
        let handle = self.add_loader(loader);

        let loader = self.get_loader_mut(handle).unwrap();
        loader.introduce_loader_handle(handle);

        loader.movie_loader(player, fetch)
    }

    /// Kick off a form data load into an AVM1 object.
    ///
    /// Returns the loader's async process, which you will need to spawn.
    pub fn load_form_into_object(
        &mut self,
        player: Weak<Mutex<Player>>,
        target_object: Object<'gc>,
        fetch: Pin<Box<dyn Future<Output = Result<Vec<u8>, Error>>>>,
    ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + 'static>> {
        let loader = Loader::Form {
            self_handle: None,
            target_object,
        };
        let handle = self.add_loader(loader);

        let loader = self.get_loader_mut(handle).unwrap();
        loader.introduce_loader_handle(handle);

        loader.form_loader(player, fetch)
    }
}

impl<'gc> Default for LoadManager<'gc> {
    fn default() -> Self {
        Self::new()
    }
}

/// A struct that holds garbage-collected pointers for asynchronous code.
pub enum Loader<'gc> {
    /// Loader that is loading a new movie into a movieclip.
    Movie {
        /// The handle to refer to this loader instance.
        self_handle: Option<Handle>,

        /// The target movie clip to load the movie into.
        target_clip: DisplayObject<'gc>,
    },

    /// Loader that is loading form data into an AVM1 object scope.
    Form {
        /// The handle to refer to this loader instance.
        self_handle: Option<Handle>,

        /// The target AVM1 object to load form data into.
        target_object: Object<'gc>,
    },
}

unsafe impl<'gc> Collect for Loader<'gc> {
    fn trace(&self, cc: CollectionContext) {
        match self {
            Loader::Movie { target_clip, .. } => target_clip.trace(cc),
            Loader::Form { target_object, .. } => target_object.trace(cc),
        }
    }
}

impl<'gc> Loader<'gc> {
    /// Set the loader handle for this loader.
    ///
    /// An active loader handle is required before asynchronous loader code can
    /// run.
    pub fn introduce_loader_handle(&mut self, handle: Handle) {
        match self {
            Loader::Movie { self_handle, .. } => *self_handle = Some(handle),
            Loader::Form { self_handle, .. } => *self_handle = Some(handle),
        }
    }

    /// Construct a future for the given movie loader.
    ///
    /// The given future should be passed immediately to an executor; it will
    /// take responsibility for running the loader to completion.
    ///
    /// If the loader is not a movie then the returned future will yield an
    /// error immediately once spawned.
    pub fn movie_loader(
        &mut self,
        player: Weak<Mutex<Player>>,
        fetch: Pin<Box<dyn Future<Output = Result<Vec<u8>, Error>>>>,
    ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + 'static>> {
        let handle = match self {
            Loader::Movie { self_handle, .. } => self_handle.expect("Loader not self-introduced"),
            _ => return Box::pin(async { Err("Non-movie loader spawned as movie loader".into()) }),
        };

        let player = player
            .upgrade()
            .expect("Could not upgrade weak reference to player");

        Box::pin(async move {
            let data = fetch.await?;
            let movie = Arc::new(SwfMovie::from_data(&data));

            player
                .lock()
                .expect("Could not lock player!!")
                .update(|avm, uc| {
                    let loader = uc.load_manager.get_loader(handle);
                    let that = match loader {
                        Some(Loader::Movie { target_clip, .. }) => target_clip,
                        None => return Err("Loader expired during loading".into()),
                        _ => return Err("Non-movie loader spawned as movie loader".into()),
                    };
                    let mut mc = that
                        .as_movie_clip()
                        .expect("Attempted to load movie into not movie clip");

                    mc.replace_with_movie(uc.gc_context, movie.clone());
                    mc.post_instantiation(uc.gc_context, *that, avm.prototypes().movie_clip);

                    let mut morph_shapes = fnv::FnvHashMap::default();
                    mc.preload(uc, &mut morph_shapes);

                    // Finalize morph shapes.
                    for (id, static_data) in morph_shapes {
                        let morph_shape = MorphShape::new(uc.gc_context, static_data);
                        uc.library
                            .library_for_movie_mut(movie.clone())
                            .register_character(
                                id,
                                crate::character::Character::MorphShape(morph_shape),
                            );
                    }

                    Ok(())
                })
        })
    }

    pub fn form_loader(
        &mut self,
        player: Weak<Mutex<Player>>,
        fetch: Pin<Box<dyn Future<Output = Result<Vec<u8>, Error>>>>,
    ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + 'static>> {
        let handle = match self {
            Loader::Form { self_handle, .. } => self_handle.expect("Loader not self-introduced"),
            _ => return Box::pin(async { Err("Non-form loader spawned as form loader".into()) }),
        };

        let player = player
            .upgrade()
            .expect("Could not upgrade weak reference to player");

        Box::pin(async move {
            let data = fetch.await?;

            player.lock().unwrap().update(|avm, uc| {
                let loader = uc.load_manager.get_loader(handle);
                let that = match loader {
                    Some(Loader::Form { target_object, .. }) => *target_object,
                    None => return Err("Loader expired during loading".into()),
                    _ => return Err("Non-movie loader spawned as movie loader".into()),
                };

                for (k, v) in form_urlencoded::parse(&data) {
                    that.set(&k, v.into_owned().into(), avm, uc)?;
                }

                Ok(())
            })
        })
    }
}