// Copyright 2020-2023 Tauri Programme within The Commons Conservancy
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT

use std::{
  io::{Read, Seek, SeekFrom, Write},
  path::PathBuf,
};

use http::{header, StatusCode};
use http_range::HttpRange;
use tao::{
  event::{Event, WindowEvent},
  event_loop::{ControlFlow, EventLoop},
  window::WindowBuilder,
};
use wry::{
  http::{header::*, Request, Response},
  WebViewBuilder,
};

fn main() -> wry::Result<()> {
  let event_loop = EventLoop::new();
  let window = WindowBuilder::new().build(&event_loop).unwrap();

  let builder = WebViewBuilder::new()
    .with_custom_protocol(
      "wry".into(),
      move |_webview_id, request| match wry_protocol(request) {
        Ok(r) => r.map(Into::into),
        Err(e) => http::Response::builder()
          .header(CONTENT_TYPE, "text/plain")
          .status(500)
          .body(e.to_string().as_bytes().to_vec())
          .unwrap()
          .map(Into::into),
      },
    )
    .with_custom_protocol(
      "stream".into(),
      move |_webview_id, request| match stream_protocol(request) {
        Ok(r) => r.map(Into::into),
        Err(e) => http::Response::builder()
          .header(CONTENT_TYPE, "text/plain")
          .status(500)
          .body(e.to_string().as_bytes().to_vec())
          .unwrap()
          .map(Into::into),
      },
    )
    // tell the webview to load the custom protocol
    .with_url("wry://localhost");

  #[cfg(any(
    target_os = "windows",
    target_os = "macos",
    target_os = "ios",
    target_os = "android"
  ))]
  let _webview = builder.build(&window)?;
  #[cfg(not(any(
    target_os = "windows",
    target_os = "macos",
    target_os = "ios",
    target_os = "android"
  )))]
  let _webview = {
    use tao::platform::unix::WindowExtUnix;
    use wry::WebViewBuilderExtUnix;
    let vbox = window.default_vbox().unwrap();
    builder.build_gtk(vbox)?
  };

  event_loop.run(move |event, _, control_flow| {
    *control_flow = ControlFlow::Wait;

    if let Event::WindowEvent {
      event: WindowEvent::CloseRequested,
      ..
    } = event
    {
      *control_flow = ControlFlow::Exit
    }
  });
}

fn wry_protocol(
  request: Request<Vec<u8>>,
) -> Result<http::Response<Vec<u8>>, Box<dyn std::error::Error>> {
  let path = request.uri().path();
  // Read the file content from file path
  let root = PathBuf::from("examples/streaming");
  let path = if path == "/" {
    "index.html"
  } else {
    //  removing leading slash
    &path[1..]
  };
  let content = std::fs::read(std::fs::canonicalize(root.join(path))?)?;

  // Return asset contents and mime types based on file extentions
  // If you don't want to do this manually, there are some crates for you.
  // Such as `infer` and `mime_guess`.
  let mimetype = if path.ends_with(".html") || path == "/" {
    "text/html"
  } else if path.ends_with(".js") {
    "text/javascript"
  } else {
    unimplemented!();
  };

  Response::builder()
    .header(CONTENT_TYPE, mimetype)
    .body(content)
    .map_err(Into::into)
}

fn stream_protocol(
  request: http::Request<Vec<u8>>,
) -> Result<http::Response<Vec<u8>>, Box<dyn std::error::Error>> {
  // skip leading `/`
  let path = percent_encoding::percent_decode(request.uri().path()[1..].as_bytes())
    .decode_utf8_lossy()
    .to_string();

  let mut file = std::fs::File::open(path)?;

  // get file length
  let len = {
    let old_pos = file.stream_position()?;
    let len = file.seek(SeekFrom::End(0))?;
    file.seek(SeekFrom::Start(old_pos))?;
    len
  };

  let mut resp = Response::builder().header(CONTENT_TYPE, "video/mp4");

  // if the webview sent a range header, we need to send a 206 in return
  // Actually only macOS and Windows are supported. Linux will ALWAYS return empty headers.
  let http_response = if let Some(range_header) = request.headers().get("range") {
    let not_satisfiable = || {
      Response::builder()
        .status(StatusCode::RANGE_NOT_SATISFIABLE)
        .header(header::CONTENT_RANGE, format!("bytes */{len}"))
        .body(vec![])
    };

    // parse range header
    let ranges = if let Ok(ranges) = HttpRange::parse(range_header.to_str()?, len) {
      ranges
        .iter()
        // map the output back to spec range <start-end>, example: 0-499
        .map(|r| (r.start, r.start + r.length - 1))
        .collect::<Vec<_>>()
    } else {
      return Ok(not_satisfiable()?);
    };

    /// The Maximum bytes we send in one range
    const MAX_LEN: u64 = 1000 * 1024;

    if ranges.len() == 1 {
      let &(start, mut end) = ranges.first().unwrap();

      // check if a range is not satisfiable
      //
      // this should be already taken care of by HttpRange::parse
      // but checking here again for extra assurance
      if start >= len || end >= len || end < start {
        return Ok(not_satisfiable()?);
      }

      // adjust end byte for MAX_LEN
      end = start + (end - start).min(len - start).min(MAX_LEN - 1);

      // calculate number of bytes needed to be read
      let bytes_to_read = end + 1 - start;

      // allocate a buf with a suitable capacity
      let mut buf = Vec::with_capacity(bytes_to_read as usize);
      // seek the file to the starting byte
      file.seek(SeekFrom::Start(start))?;
      // read the needed bytes
      file.take(bytes_to_read).read_to_end(&mut buf)?;

      resp = resp.header(CONTENT_RANGE, format!("bytes {start}-{end}/{len}"));
      resp = resp.header(CONTENT_LENGTH, end + 1 - start);
      resp = resp.status(StatusCode::PARTIAL_CONTENT);
      resp.body(buf)
    } else {
      let mut buf = Vec::new();
      let ranges = ranges
        .iter()
        .filter_map(|&(start, mut end)| {
          // filter out unsatisfiable ranges
          //
          // this should be already taken care of by HttpRange::parse
          // but checking here again for extra assurance
          if start >= len || end >= len || end < start {
            None
          } else {
            // adjust end byte for MAX_LEN
            end = start + (end - start).min(len - start).min(MAX_LEN - 1);
            Some((start, end))
          }
        })
        .collect::<Vec<_>>();

      let boundary = random_boundary();
      let boundary_sep = format!("\r\n--{boundary}\r\n");
      let boundary_closer = format!("\r\n--{boundary}\r\n");

      resp = resp.header(
        CONTENT_TYPE,
        format!("multipart/byteranges; boundary={boundary}"),
      );

      for (end, start) in ranges {
        // a new range is being written, write the range boundary
        buf.write_all(boundary_sep.as_bytes())?;

        // write the needed headers `Content-Type` and `Content-Range`
        buf.write_all(format!("{CONTENT_TYPE}: video/mp4\r\n").as_bytes())?;
        buf.write_all(format!("{CONTENT_RANGE}: bytes {start}-{end}/{len}\r\n").as_bytes())?;

        // write the separator to indicate the start of the range body
        buf.write_all("\r\n".as_bytes())?;

        // calculate number of bytes needed to be read
        let bytes_to_read = end + 1 - start;

        let mut local_buf = vec![0_u8; bytes_to_read as usize];
        file.seek(SeekFrom::Start(start))?;
        file.read_exact(&mut local_buf)?;
        buf.extend_from_slice(&local_buf);
      }
      // all ranges have been written, write the closing boundary
      buf.write_all(boundary_closer.as_bytes())?;

      resp.body(buf)
    }
  } else {
    resp = resp.header(CONTENT_LENGTH, len);
    let mut buf = Vec::with_capacity(len as usize);
    file.read_to_end(&mut buf)?;
    resp.body(buf)
  };

  http_response.map_err(Into::into)
}

fn random_boundary() -> String {
  let mut x = [0_u8; 30];
  getrandom::getrandom(&mut x).expect("failed to get random bytes");
  (x[..])
    .iter()
    .map(|&x| format!("{x:x}"))
    .fold(String::new(), |mut a, x| {
      a.push_str(x.as_str());
      a
    })
}
