use fnv::FnvHashMap;
use generational_arena::Arena;
use ruffle_core::backend::audio::decoders::{AdpcmDecoder, Mp3Decoder};
use ruffle_core::backend::audio::swf::{self, AudioCompression};
use ruffle_core::backend::audio::{AudioBackend, AudioStreamHandle, SoundHandle};
use std::cell::{Cell, RefCell};
use std::rc::Rc;
use wasm_bindgen::{closure::Closure, JsCast};
use web_sys::AudioContext;

pub struct WebAudioBackend {
    context: AudioContext,
    sounds: Arena<Sound>,
    stream_data: FnvHashMap<swf::CharacterId, StreamData>,
    id_to_sound: FnvHashMap<swf::CharacterId, SoundHandle>,
    left_samples: Vec<f32>,
    right_samples: Vec<f32>,
}

thread_local! {
    static STREAMS: RefCell<Arena<AudioStream>> = RefCell::new(Arena::new());
    static NUM_SOUNDS_LOADING: Cell<u32> = Cell::new(0);
}

struct StreamData {
    format: swf::SoundFormat,
    audio_data: Vec<u8>,
    num_sample_frames: u32,
    samples_per_block: u32,
}

type AudioBufferPtr = Rc<RefCell<web_sys::AudioBuffer>>;

// A sound can be either as a JS AudioBuffer and as a on--the-fly decoded stream using a ScriptProcessorNode.
#[allow(dead_code)]
enum SoundSource {
    // Pre-decoded audio buffer.
    AudioBuffer(AudioBufferPtr),

    // Decode the audio data on the fly from a byte stream.
    Decoder(Vec<u8>),
}

struct Sound {
    format: swf::SoundFormat,
    source: SoundSource,
}

type Decoder = Box<dyn Iterator<Item = i16>>;

#[allow(dead_code)]
enum AudioStream {
    Decoder {
        decoder: Decoder,
        is_stereo: bool,
    }, // closure: Option<Closure<Box<FnMut(web_sys::AudioProcessingEvent)>>> } ,
    AudioBuffer {
        node: web_sys::AudioBufferSourceNode,
    },
}

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

impl WebAudioBackend {
    pub fn new() -> Result<Self, Error> {
        let context = AudioContext::new().map_err(|_| "Unable to create AudioContext")?;
        Ok(Self {
            context,
            sounds: Arena::new(),
            stream_data: FnvHashMap::default(),
            id_to_sound: FnvHashMap::default(),
            left_samples: vec![],
            right_samples: vec![],
        })
    }

    fn play_sound_internal(&mut self, handle: SoundHandle) -> SoundHandle {
        let sound = self.sounds.get(handle).unwrap();
        match &sound.source {
            SoundSource::AudioBuffer(audio_buffer) => {
                let audio_buffer = audio_buffer.borrow();
                let node = self.context.create_buffer_source().unwrap();
                node.set_buffer(Some(&*audio_buffer));
                node.connect_with_audio_node(&self.context.destination())
                    .unwrap();
                node.start().unwrap();

                let audio_stream = AudioStream::AudioBuffer { node };
                STREAMS.with(|streams| {
                    let mut streams = streams.borrow_mut();
                    streams.insert(audio_stream)
                })
            }
            SoundSource::Decoder(audio_data) => {
                let decoder: Decoder = match sound.format.compression {
                    AudioCompression::Adpcm => Box::new(
                        AdpcmDecoder::new(
                            std::io::Cursor::new(audio_data.to_vec()),
                            sound.format.is_stereo,
                            sound.format.sample_rate,
                        )
                        .unwrap(),
                    ),
                    AudioCompression::Mp3 => Box::new(Mp3Decoder::new(
                        if sound.format.is_stereo { 2 } else { 1 },
                        sound.format.sample_rate.into(),
                        std::io::Cursor::new(audio_data.to_vec()), //&sound.data[..]
                    )),
                    _ => unimplemented!(),
                };

                let decoder: Decoder =
                    if sound.format.sample_rate != self.context.sample_rate() as u16 {
                        Box::new(resample(
                            decoder,
                            sound.format.sample_rate,
                            self.context.sample_rate() as u16,
                            sound.format.is_stereo,
                        ))
                    } else {
                        decoder
                    };

                let audio_stream = AudioStream::Decoder {
                    decoder,
                    is_stereo: sound.format.is_stereo,
                    //closure: None,
                };
                STREAMS.with(|streams| {
                    let mut streams = streams.borrow_mut();
                    let stream_handle = streams.insert(audio_stream);
                    let script_processor_node = self.context.create_script_processor_with_buffer_size_and_number_of_input_channels_and_number_of_output_channels(4096, 0, if sound.format.is_stereo { 2 } else { 1 }).unwrap();
                    let script_node = script_processor_node.clone();
                    let closure = Closure::wrap(Box::new(move |event| {
                            STREAMS.with(|streams| {
                                let mut streams = streams.borrow_mut();
                                let audio_stream = streams.get_mut(stream_handle).unwrap();
                                let complete = WebAudioBackend::update_script_processor(audio_stream, event);
                                if complete {
                                    streams.remove(stream_handle);
                                    script_node.disconnect().unwrap();
                                }
                            })
                        }) as Box<dyn FnMut(web_sys::AudioProcessingEvent)>);
                        script_processor_node.set_onaudioprocess(Some(closure.as_ref().unchecked_ref()));
                        // TODO: This will leak memory per playing sound. Remember and properly drop the closure.
                        closure.forget();

                    stream_handle
                })
            }
        }
    }

    fn decompress_to_audio_buffer(
        &mut self,
        format: &swf::SoundFormat,
        audio_data: &[u8],
        num_sample_frames: u32,
    ) -> AudioBufferPtr {
        if format.compression == AudioCompression::Mp3 {
            return self.decompress_mp3_to_audio_buffer(format, audio_data, num_sample_frames);
        }

        // This sucks. Firefox doesn't like 5512Hz sample rate, so manually double up the samples.
        // 5512Hz should be relatively rare.
        let audio_buffer = if format.sample_rate > 5512 {
            self.context
                .create_buffer(
                    if format.is_stereo { 2 } else { 1 },
                    num_sample_frames,
                    f32::from(format.sample_rate),
                )
                .unwrap()
        } else {
            self.context
                .create_buffer(
                    if format.is_stereo { 2 } else { 1 },
                    num_sample_frames * 2,
                    11025.0,
                )
                .unwrap()
        };

        match format.compression {
            AudioCompression::Uncompressed => {
                // TODO: Check for is_16_bit.
                self.left_samples = audio_data
                    .iter()
                    .step_by(2)
                    .cloned()
                    .map(|n| f32::from(n) / 32767.0)
                    .collect();
                if format.is_stereo {
                    self.right_samples = audio_data
                        .iter()
                        .skip(1)
                        .step_by(2)
                        .cloned()
                        .map(|n| f32::from(n) / 32767.0)
                        .collect();
                }
            }
            AudioCompression::Adpcm => {
                let mut decoder =
                    AdpcmDecoder::new(audio_data, format.is_stereo, format.sample_rate).unwrap();
                if format.is_stereo {
                    while let (Some(l), Some(r)) = (decoder.next(), decoder.next()) {
                        self.left_samples.push(f32::from(l) / 32767.0);
                        self.right_samples.push(f32::from(r) / 32767.0);
                    }
                } else {
                    self.left_samples = decoder.map(|n| f32::from(n) / 32767.0).collect();
                }
            }
            _ => unimplemented!(),
        }

        // Double up samples for 5512Hz audio to satisfy Firefox.
        if format.sample_rate == 5512 {
            let mut samples = Vec::with_capacity(self.left_samples.len() * 2);
            for sample in &self.left_samples {
                samples.push(*sample);
                samples.push(*sample);
            }
            self.left_samples = samples;

            if format.is_stereo {
                let mut samples = Vec::with_capacity(self.right_samples.len() * 2);
                for sample in &self.right_samples {
                    samples.push(*sample);
                    samples.push(*sample);
                }
                self.right_samples = samples;
            }
        }

        audio_buffer
            .copy_to_channel(&mut self.left_samples, 0)
            .unwrap();
        if format.is_stereo {
            audio_buffer
                .copy_to_channel(&mut self.right_samples, 1)
                .unwrap();
        }

        Rc::new(RefCell::new(audio_buffer))
    }

    fn decompress_mp3_to_audio_buffer(
        &mut self,
        format: &swf::SoundFormat,
        audio_data: &[u8],
        _num_sample_frames: u32,
    ) -> AudioBufferPtr {
        // We use the Web decodeAudioData API to decode MP3 data.
        // TODO: Is it possible we finish loading before the MP3 is decoding?
        let audio_buffer = self
            .context
            .create_buffer(1, 1, self.context.sample_rate())
            .unwrap();
        let audio_buffer = Rc::new(RefCell::new(audio_buffer));

        let data_array = unsafe { js_sys::Uint8Array::view(&audio_data[..]) };
        let array_buffer = data_array.buffer().slice_with_end(
            data_array.byte_offset(),
            data_array.byte_offset() + data_array.byte_length(),
        );

        NUM_SOUNDS_LOADING.with(|n| n.set(n.get() + 1));

        let _num_channels = if format.is_stereo { 2 } else { 1 };
        let buffer_ptr = Rc::clone(&audio_buffer);
        let success_closure = Closure::wrap(Box::new(move |buffer: web_sys::AudioBuffer| {
            *buffer_ptr.borrow_mut() = buffer;
            NUM_SOUNDS_LOADING.with(|n| n.set(n.get() - 1));
        }) as Box<dyn FnMut(web_sys::AudioBuffer)>);
        let error_closure = Closure::wrap(Box::new(move || {
            log::info!("Error decoding MP3 audio");
            NUM_SOUNDS_LOADING.with(|n| n.set(n.get() - 1));
        }) as Box<dyn FnMut()>);
        self.context
            .decode_audio_data_with_success_callback_and_error_callback(
                &array_buffer,
                success_closure.as_ref().unchecked_ref(),
                error_closure.as_ref().unchecked_ref(),
            )
            .unwrap();

        // TODO: This will leak memory (once per decompressed MP3).
        // Not a huge deal as there are probably not many MP3s in an SWF.
        success_closure.forget();
        error_closure.forget();

        audio_buffer
    }

    fn update_script_processor(
        audio_stream: &mut AudioStream,
        event: web_sys::AudioProcessingEvent,
    ) -> bool {
        let mut complete = false;
        let mut left_samples = vec![];
        let mut right_samples = vec![];
        if let AudioStream::Decoder {
            decoder, is_stereo, ..
        } = audio_stream
        {
            let output_buffer = event.output_buffer().unwrap();
            let num_frames = output_buffer.length() as usize;

            for _ in 0..num_frames {
                if let (Some(l), Some(r)) = (decoder.next(), decoder.next()) {
                    left_samples.push(f32::from(l) / 32767.0);
                    if *is_stereo {
                        right_samples.push(f32::from(r) / 32767.0);
                    }
                } else {
                    complete = true;
                    break;
                }
            }
            output_buffer
                .copy_to_channel(&mut left_samples[..], 0)
                .unwrap();
            if *is_stereo {
                output_buffer
                    .copy_to_channel(&mut right_samples[..], 1)
                    .unwrap();
            }
        }

        complete
    }
}

impl AudioBackend for WebAudioBackend {
    fn register_sound(&mut self, sound: &swf::Sound) -> Result<SoundHandle, Error> {
        // Slice off latency seek for MP3 data.
        let data = if sound.format.compression == AudioCompression::Mp3 {
            &sound.data[2..]
        } else {
            &sound.data[..]
        };

        let sound = Sound {
            format: sound.format.clone(),
            source: SoundSource::AudioBuffer(self.decompress_to_audio_buffer(
                &sound.format,
                data,
                sound.num_samples,
            )),
        };
        Ok(self.sounds.insert(sound))
    }

    fn preload_sound_stream_head(
        &mut self,
        clip_id: swf::CharacterId,
        stream_info: &swf::SoundStreamHead,
    ) {
        self.stream_data
            .entry(clip_id)
            .or_insert_with(|| StreamData {
                format: stream_info.stream_format.clone(),
                audio_data: vec![],
                num_sample_frames: 0,
                samples_per_block: stream_info.num_samples_per_block.into(),
            });
    }

    fn preload_sound_stream_block(&mut self, clip_id: swf::CharacterId, audio_data: &[u8]) {
        if let Some(stream) = self.stream_data.get_mut(&clip_id) {
            match stream.format.compression {
                AudioCompression::Uncompressed | AudioCompression::UncompressedUnknownEndian => {
                    let frame_len = if stream.format.is_stereo { 2 } else { 1 }
                        * if stream.format.is_16_bit { 2 } else { 1 };
                    stream.num_sample_frames += (audio_data.len() as u32) / frame_len;
                    stream.audio_data.extend_from_slice(audio_data);
                }
                AudioCompression::Mp3 => {
                    let num_sample_frames =
                        (u32::from(audio_data[2]) << 8) | u32::from(audio_data[3]);
                    stream.num_sample_frames += num_sample_frames;
                    // MP3 streaming data:
                    // First two bytes = number of samples
                    // Second two bytes = 'latency seek' (amount to skip when seeking to this frame)
                    stream.audio_data.extend_from_slice(&audio_data[4..]);
                }
                _ => {
                    // TODO: This is a guess and will vary slightly from block to block!
                    stream.num_sample_frames += stream.samples_per_block;
                }
            }
        }
    }

    fn preload_sound_stream_end(&mut self, clip_id: swf::CharacterId) {
        if let Some(stream) = self.stream_data.remove(&clip_id) {
            if !stream.audio_data.is_empty() {
                let audio_buffer = self.decompress_to_audio_buffer(
                    &stream.format,
                    &stream.audio_data[..],
                    stream.num_sample_frames,
                );
                let handle = self.sounds.insert(Sound {
                    format: stream.format,
                    source: SoundSource::AudioBuffer(audio_buffer),
                });
                self.id_to_sound.insert(clip_id, handle);
            }
        }
    }

    fn play_sound(&mut self, sound: SoundHandle) {
        self.play_sound_internal(sound);
    }

    fn start_stream(
        &mut self,
        clip_id: swf::CharacterId,
        _clip_data: ruffle_core::tag_utils::SwfSlice,
        _stream_info: &swf::SoundStreamHead,
    ) -> AudioStreamHandle {
        if let Some(&handle) = self.id_to_sound.get(&clip_id) {
            self.play_sound_internal(handle)
        } else {
            log::error!("Missing stream for clip {}", clip_id);
            // TODO: Return dummy sound.
            panic!();
        }
    }

    fn is_loading_complete(&self) -> bool {
        NUM_SOUNDS_LOADING.with(|n| n.get() == 0)
    }

    fn prime_audio(&mut self) {
        // Allow audio to start playing after a user gesture.
        let _ = self.context.resume();
    }
}

// Janky resmapling code.
// TODO: Clean this up.
fn resample(
    mut input: impl Iterator<Item = i16>,
    input_sample_rate: u16,
    output_sample_rate: u16,
    is_stereo: bool,
) -> impl Iterator<Item = i16> {
    let (mut left0, mut right0) = if is_stereo {
        (input.next(), input.next())
    } else {
        let sample = input.next();
        (sample, sample)
    };
    let (mut left1, mut right1) = if is_stereo {
        (input.next(), input.next())
    } else {
        let sample = input.next();
        (sample, sample)
    };
    let (mut left, mut right) = (left0.unwrap(), right0.unwrap());
    let dt_input = 1.0 / f64::from(input_sample_rate);
    let dt_output = 1.0 / f64::from(output_sample_rate);
    let mut t = 0.0;
    let mut cur_channel = 0;
    std::iter::from_fn(move || {
        if cur_channel == 1 {
            cur_channel = 0;
            return Some(right);
        }
        if let (Some(l0), Some(r0), Some(l1), Some(r1)) = (left0, right0, left1, right1) {
            let a = t / dt_input;
            let l0 = f64::from(l0);
            let l1 = f64::from(l1);
            let r0 = f64::from(r0);
            let r1 = f64::from(r1);
            left = (l0 + (l1 - l0) * a) as i16;
            right = (r0 + (r1 - r0) * a) as i16;
            t += dt_output;
            while t >= dt_input {
                t -= dt_input;
                left0 = left1;
                right0 = right1;
                left1 = input.next();
                if is_stereo {
                    right1 = input.next();
                } else {
                    right1 = left1;
                }
            }
            cur_channel = 1;
            Some(left)
        } else {
            None
        }
    })
}