/*
 * Copyright 2019 Hippo Seven
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.hippo.ehviewer.gallery;

import androidx.annotation.NonNull;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

class Pipe {

    private final int capacity;
    private final byte[] buffer;

    private int head = 0;
    private int tail = 0;
    private boolean full = false;

    private boolean inClosed = false;
    private boolean outClosed = false;

    private final InputStream inputStream = new InputStream() {
        @Override
        public int read() throws IOException {
            synchronized (Pipe.this) {
                byte[] bytes = new byte[1];
                if (read(bytes, 0, 1) != -1) {
                    return bytes[0];
                } else {
                    return -1;
                }
            }
        }

        @Override
        public int read(@NonNull byte[] b, int off, int len) throws IOException {
            synchronized (Pipe.this) {
                for (; ; ) {
                    if (inClosed) {
                        throw new IOException("The InputStream is closed");
                    }
                    if (len == 0) {
                        return 0;
                    }

                    if (head == tail && !full) {
                        if (outClosed) {
                            // No bytes available and the OutputStream is closed. So it's the end.
                            return -1;
                        } else {
                            // Wait for OutputStream write bytes
                            try {
                                Pipe.this.wait();
                            } catch (InterruptedException e) {
                                throw new IOException("The thread interrupted", e);
                            }
                        }
                    } else {
                        int read = Math.min(len, (head < tail ? tail : capacity) - head);
                        System.arraycopy(buffer, head, b, off, read);
                        head += read;
                        if (head == capacity) {
                            head = 0;
                        }
                        full = false;
                        Pipe.this.notifyAll();
                        return read;
                    }
                }
            }
        }

        @Override
        public void close() {
            synchronized (Pipe.this) {
                inClosed = true;
                Pipe.this.notifyAll();
            }
        }
    };

    private final OutputStream outputStream = new OutputStream() {
        @Override
        public void write(int b) throws IOException {
            synchronized (Pipe.this) {
                byte[] bytes = new byte[]{(byte) b};
                write(bytes, 0, 1);
            }
        }

        @Override
        public void write(@NonNull byte[] b, int off, int len) throws IOException {
            synchronized (Pipe.this) {
                while (len != 0) {
                    if (head == tail && full) {
                        // The buffer is full, wait for InputStream read bytes
                        try {
                            Pipe.this.wait();
                        } catch (InterruptedException e) {
                            throw new IOException("The thread interrupted", e);
                        }
                    } else {
                        int write = Math.min(len, (head <= tail ? capacity : head) - tail);
                        System.arraycopy(b, off, buffer, tail, write);
                        off += write;
                        len -= write;
                        tail += write;
                        if (tail == capacity) {
                            tail = 0;
                        }
                        if (head == tail) {
                            full = true;
                        }
                        Pipe.this.notifyAll();
                    }
                }
            }
        }

        @Override
        public void close() {
            synchronized (Pipe.this) {
                outClosed = true;
                Pipe.this.notifyAll();
            }
        }
    };

    Pipe(int capacity) {
        this.capacity = capacity;
        this.buffer = new byte[capacity];
    }

    InputStream getInputStream() {
        return inputStream;
    }

    OutputStream getOutputStream() {
        return outputStream;
    }
}