audioview/src/agents/audio_agent.rs

use js_sys::Uint8Array;
use wasm_bindgen::JsValue;
use wasm_bindgen_futures::JsFuture;
use web_sys::{AudioContext, File};
use yew::services::reader::{FileChunk, ReaderTask};
use yew::services::{ConsoleService, ReaderService};
use yew::worker::*;
use yewtil::future::LinkFuture;

const FILE_LOAD_CHUNK_SIZE: usize = 4096;

pub struct AudioAgent {
    link: AgentLink<Self>,
    reader_service: ReaderService,
    reader_task: Option<ReaderTask>,
    audio_context: AudioContext,
    bytes_buffer: Vec<u8>,
}

pub enum Request {
    LoadSamplesFromFile(File),
}

pub enum Msg {
    FileProgress(Option<FileChunk>),
    AudioDecoded(JsValue),
    AudioDecodingFailed(JsValue),
}

impl From<Result<JsValue, JsValue>> for Msg {
    fn from(item: Result<JsValue, JsValue>) -> Self {
        match item {
            Ok(samples) => Msg::AudioDecoded(samples),
            Err(e) => Msg::AudioDecodingFailed(e),
        }
    }
}

impl Agent for AudioAgent {
    type Reach = Context<Self>;
    type Message = Msg;
    type Input = Request;
    type Output = ();

    fn create(link: AgentLink<Self>) -> Self {
        // TODO: where should the AudioContext be initialized and stored?
        Self {
            link,
            reader_service: ReaderService::new(),
            reader_task: None,
            audio_context: AudioContext::new().unwrap(),
            bytes_buffer: vec![],
        }
    }

    fn update(&mut self, msg: Self::Message) {
        match msg {
            Msg::FileProgress(Some(FileChunk::DataChunk { data, progress })) => {
                self.handle_file_progress(data, progress)
            }
            Msg::FileProgress(Some(FileChunk::Finished)) => {
                if let Err(e) = self.handle_file_loaded() {
                    ConsoleService::error(&e);
                }
            }
            Msg::AudioDecoded(samples) => {
                let audio_buffer = web_sys::AudioBuffer::from(samples);
                let data = audio_buffer.get_channel_data(0).unwrap(); // TODO: error handling
                let vec: Vec<f32> = data.to_vec();
                ConsoleService::log(&format!("Success decoding: {:?}", vec));
            }
            Msg::AudioDecodingFailed(err) => {
                ConsoleService::error(&format!("Error decoding: {:?}", err));
            }
            _ => (),
        };
    }

    fn handle_input(&mut self, input: Self::Input, _: HandlerId) {
        match input {
            Request::LoadSamplesFromFile(file) => self.load_samples_from_file(file),
        };
    }
}

impl AudioAgent {
    fn load_samples_from_file(&mut self, file: File) -> Result<(), String> {
        self.bytes_buffer = Vec::with_capacity(file.size() as usize);
        let cb = self.link.callback(Msg::FileProgress);

        let task = self
            .reader_service
            .read_file_by_chunks(file, cb, FILE_LOAD_CHUNK_SIZE)
            .map_err(|e| e.to_string())?;

        self.reader_task = Some(task);

        Ok(())
    }

    fn handle_file_progress(&mut self, mut data: Vec<u8>, _progress: f32) {
        self.bytes_buffer.append(&mut data);
    }

    fn handle_file_loaded(&self) -> Result<(), String> {
        let audio_data = Uint8Array::from(&self.bytes_buffer[..]);
        match self.audio_context.decode_audio_data(&audio_data.buffer()) {
            Ok(promise) => {
                self.link.send_future(JsFuture::from(promise));
                Ok(())
            }
            Err(e) => Err(format!("Error from decode_audio_data: {:?}", e)),
        }
    }
}