package org.fox.ttrss.util;

import java.io.*;
import java.util.*;

import android.content.Context;
import android.os.*;

import com.bumptech.glide.*;
import com.bumptech.glide.integration.okhttp3.OkHttpUrlLoader;
import com.bumptech.glide.load.model.GlideUrl;
import com.bumptech.glide.module.GlideModule;

import okhttp3.*;
import okio.*;

public class OkHttpProgressGlideModule implements GlideModule {
    @Override public void applyOptions(Context context, GlideBuilder builder) {

    }
    @Override public void registerComponents(Context context, Glide glide) {
        OkHttpClient client = new OkHttpClient.Builder()
                .addNetworkInterceptor(createInterceptor(new DispatchingProgressListener()))
                .build();
        glide.register(GlideUrl.class, InputStream.class, new OkHttpUrlLoader.Factory(client));
    }

    private static Interceptor createInterceptor(final ResponseProgressListener listener) {
        return new Interceptor() {
            @Override public Response intercept(Chain chain) throws IOException {
                Request request = chain.request();
                Response response = chain.proceed(request);
                return response.newBuilder()
                        .body(new OkHttpProgressResponseBody(request.url(), response.body(), listener))
                        .build();
            }
        };
    }

    public interface UIProgressListener {
        void onProgress(long bytesRead, long expectedLength);
        /**
         * Control how often the listener needs an update. 0% and 100% will always be dispatched.
         * @return in percentage (0.2 = call {@link #onProgress} around every 0.2 percent of progress)
         */
        float getGranualityPercentage();
    }

    public static void forget(String url) {
        DispatchingProgressListener.forget(url);
    }
    public static void expect(String url, UIProgressListener listener) {
        DispatchingProgressListener.expect(url, listener);
    }

    private interface ResponseProgressListener {
        void update(HttpUrl url, long bytesRead, long contentLength);
    }

    private static class DispatchingProgressListener implements ResponseProgressListener {
        private static final Map<String, UIProgressListener> LISTENERS = new HashMap<>();
        private static final Map<String, Long> PROGRESSES = new HashMap<>();

        private final Handler handler;
        DispatchingProgressListener() {
            this.handler = new Handler(Looper.getMainLooper());
        }

        static void forget(String url) {
            LISTENERS.remove(url);
            PROGRESSES.remove(url);
        }
        static void expect(String url, UIProgressListener listener) {
            LISTENERS.put(url, listener);
        }

        @Override public void update(HttpUrl url, final long bytesRead, final long contentLength) {
            //System.out.printf("%s: %d/%d = %.2f%%%n", url, bytesRead, contentLength, (100f * bytesRead) / contentLength);

            String key = url.toString();
            final UIProgressListener listener = LISTENERS.get(key);

            if (listener == null) {
                return;
            }
            if (contentLength <= bytesRead) {
                forget(key);
            }
            if (needsDispatch(key, bytesRead, contentLength, listener.getGranualityPercentage())) {
                handler.post(new Runnable() {
                    @Override public void run() {
                        listener.onProgress(bytesRead, contentLength);
                    }
                });
            }
        }

        private boolean needsDispatch(String key, long current, long total, float granularity) {
            if (granularity == 0 || current == 0 || total == current) {
                return true;
            }
            float percent = 100f * current / total;
            long currentProgress = (long)(percent / granularity);
            Long lastProgress = PROGRESSES.get(key);
            if (lastProgress == null || currentProgress != lastProgress) {
                PROGRESSES.put(key, currentProgress);
                return true;
            } else {
                return false;
            }
        }
    }

    private static class OkHttpProgressResponseBody extends ResponseBody {
        private final HttpUrl url;
        private final ResponseBody responseBody;
        private final ResponseProgressListener progressListener;
        private BufferedSource bufferedSource;

        OkHttpProgressResponseBody(HttpUrl url, ResponseBody responseBody,
                                   ResponseProgressListener progressListener) {

            this.url = url;
            this.responseBody = responseBody;
            this.progressListener = progressListener;
        }

        @Override public MediaType contentType() {
            return responseBody.contentType();
        }

        @Override public long contentLength() {
            return responseBody.contentLength();
        }

        @Override public BufferedSource source() {
            if (bufferedSource == null) {
                bufferedSource = Okio.buffer(source(responseBody.source()));
            }
            return bufferedSource;
        }

        private Source source(Source source) {
            return new ForwardingSource(source) {
                long totalBytesRead = 0L;
                @Override public long read(Buffer sink, long byteCount) throws IOException {
                    long bytesRead = super.read(sink, byteCount);
                    long fullLength = responseBody.contentLength();
                    if (bytesRead == -1) { // this source is exhausted
                        totalBytesRead = fullLength;
                    } else {
                        totalBytesRead += bytesRead;
                    }
                    progressListener.update(url, totalBytesRead, fullLength);
                    return bytesRead;
                }
            };
        }
    }
}