package com.carvalab;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.WritableByteChannel;
import java.util.Date;

import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.StreamingOutput;

import spark.Request;
import spark.Response;

import static spark.Spark.*;

public class App {

    static int chunk_size = 1024 * 1024; // 1MB chunks
    private static File audio;

    public static void main(String[] args) {
        // serve media from file system
        URL url = ClassLoader.getSystemClassLoader().getResource("music.mp3");
        audio = new File(url.getFile());

        head("/music", (req, resp) -> {
            System.out.println("Requesting header support...");
            return acceptRangeHeaders(resp);
        });

        get("/music", (req, resp) -> {
            System.out.println("Get stream chunk...");
            return streamAudio(req, resp);
        });

        get("/", (req, resp) -> {
            return "Online.";
        });
    }

    public static StreamingOutput streamAudio(Request req, Response resp){
        //Read range parameter
        String range = req.headers("Range");

        try {
            return buildStream(resp, audio, range);
        } catch (Exception e) {
            e.printStackTrace();
        }

        System.out.println("Failed!");
        resp.type("text/html");
        resp.status(404);
        resp.body("WTF");
        return null;
    }

    public static Response acceptRangeHeaders(Response resp){
        resp.type("audio/mp3");
        resp.status(206);
        resp.header(HttpHeaders.CONTENT_LENGTH, String.valueOf(audio.length()));
        return resp;
    }

    private static StreamingOutput buildStream(Response resp, final File asset, final String range) throws Exception {
        resp.type("audio/mp3");

        // range not requested : Firefox, Opera, IE do not send range headers
        if (range == null) {
            StreamingOutput streamer = output -> {
                try (FileChannel inputChannel = new FileInputStream(asset).getChannel(); WritableByteChannel outputChannel = Channels.newChannel(output)) {
                    inputChannel.transferTo(0, inputChannel.size(), outputChannel);
                }
            };
            resp.status(200);
            resp.header(HttpHeaders.CONTENT_LENGTH, String.valueOf(asset.length()));
            return streamer;
        }

        String[] ranges = range.split("=")[1].split("-");
        final int from = Integer.parseInt(ranges[0]);
        /**
         * Chunk media if the range upper bound is unspecified. Chrome sends "bytes=0-"
         */
        int to = chunk_size + from;
        if (to >= asset.length()) {
            to = (int) (asset.length() - 1);
        }
        if (ranges.length == 2) {
            to = Integer.parseInt(ranges[1]);
        }

        final String responseRange = String.format("bytes %d-%d/%d", from, to, asset.length());
        final RandomAccessFile raf = new RandomAccessFile(asset, "r");
        raf.seek(from);

        final int len = to - from + 1;
        final MediaStreamer streamer = new MediaStreamer(len, raf);
        resp.status(206);
        resp.header("Accept-Ranges", "bytes");
        resp.header("Content-Range", responseRange);
        resp.header(HttpHeaders.CONTENT_LENGTH, ""+streamer.getLength());
        resp.header(HttpHeaders.LAST_MODIFIED, new Date(asset.lastModified()).toString());

        return streamer;
    }
}