package com.tcm.training.admin.upload;

import org.junit.jupiter.api.Test;

import java.io.ByteArrayOutputStream;
import java.nio.charset.StandardCharsets;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;

/**
 * 远程视频时长识别服务测试。
 */
class RemoteVideoDurationServiceTest {

    private final RemoteVideoDurationService remoteVideoDurationService = new RemoteVideoDurationService();

    /**
     * 应支持解析 mvhd version 0 的 MP4 时长。
     */
    @Test
    void parseDurationSecondsShouldSupportVersionZeroMovieHeader() {
        byte[] mvhdPayload = new byte[20];
        mvhdPayload[12] = 0x00;
        mvhdPayload[13] = 0x00;
        mvhdPayload[14] = 0x03;
        mvhdPayload[15] = (byte) 0xE8;
        mvhdPayload[16] = 0x00;
        mvhdPayload[17] = 0x00;
        mvhdPayload[18] = 0x1D;
        mvhdPayload[19] = 0x4C;

        byte[] mp4Bytes = wrapMoovBox(wrapBox("mvhd", mvhdPayload));

        assertEquals(8, remoteVideoDurationService.parseDurationSeconds(mp4Bytes));
    }

    /**
     * 应支持解析 mvhd version 1 的 MP4 时长。
     */
    @Test
    void parseDurationSecondsShouldSupportVersionOneMovieHeader() {
        byte[] mvhdPayload = new byte[32];
        mvhdPayload[0] = 0x01;
        mvhdPayload[20] = 0x00;
        mvhdPayload[21] = 0x00;
        mvhdPayload[22] = 0x03;
        mvhdPayload[23] = (byte) 0xE8;
        mvhdPayload[24] = 0x00;
        mvhdPayload[25] = 0x00;
        mvhdPayload[26] = 0x00;
        mvhdPayload[27] = 0x00;
        mvhdPayload[28] = 0x00;
        mvhdPayload[29] = 0x00;
        mvhdPayload[30] = 0x1D;
        mvhdPayload[31] = 0x4C;

        byte[] mp4Bytes = wrapMoovBox(wrapBox("mvhd", mvhdPayload));

        assertEquals(8, remoteVideoDurationService.parseDurationSeconds(mp4Bytes));
    }

    /**
     * 缺少 mvhd 盒子时应返回统一失败。
     */
    @Test
    void parseDurationSecondsShouldFailWhenMovieHeaderMissing() {
        byte[] mp4Bytes = wrapMoovBox(wrapBox("trak", new byte[12]));

        assertThrows(IllegalArgumentException.class, () -> remoteVideoDurationService.parseDurationSeconds(mp4Bytes));
    }

    /**
     * 尾部分段中 moov 不在起始位置时也应可识别时长。
     */
    @Test
    void parseDurationSecondsFromTailChunkShouldSupportOffsetMoovBox() {
        byte[] mvhdPayload = new byte[20];
        mvhdPayload[12] = 0x00;
        mvhdPayload[13] = 0x00;
        mvhdPayload[14] = 0x03;
        mvhdPayload[15] = (byte) 0xE8;
        mvhdPayload[16] = 0x00;
        mvhdPayload[17] = 0x00;
        mvhdPayload[18] = 0x1D;
        mvhdPayload[19] = 0x4C;
        byte[] moovBytes = wrapMoovBox(wrapBox("mvhd", mvhdPayload));
        byte[] chunkBytes = concatBytes(new byte[27], moovBytes);

        assertEquals(8, remoteVideoDurationService.parseDurationSecondsFromTailChunk(chunkBytes));
    }

    /**
     * 尾部分段中缺少完整 moov 盒子时应返回失败标记。
     */
    @Test
    void parseDurationSecondsFromTailChunkShouldFailWhenMoovBoxIncomplete() {
        byte[] truncatedChunk = new byte[]{0x00, 0x00, 0x00, 0x20, 'm', 'o', 'o', 'v', 0x00, 0x00};

        assertEquals(-1, remoteVideoDurationService.parseDurationSecondsFromTailChunk(truncatedChunk));
    }

    /**
     * 应可从尾部分段中解析普通 size 的 moov 绝对范围。
     */
    @Test
    void resolveMoovRangeFromTailChunkShouldReturnSizedRange() {
        byte[] moovBytes = wrapMoovBox(new byte[24]);
        byte[] tailChunk = concatBytes(new byte[13], moovBytes);
        long chunkStart = 1000L;
        long totalLength = chunkStart + tailChunk.length;

        RemoteVideoDurationService.ByteRange moovRange = remoteVideoDurationService.resolveMoovRangeFromTailChunk(
                tailChunk,
                chunkStart,
                totalLength
        );

        assertEquals(chunkStart + 13L, moovRange.getStart());
        assertEquals(chunkStart + 13L + moovBytes.length - 1L, moovRange.getEnd());
    }

    /**
     * 应可解析 size=0 的 moov 范围，并将结束位置定位到文件末尾。
     */
    @Test
    void resolveMoovRangeFromTailChunkShouldSupportOpenEndedMoov() {
        byte[] openEndedMoov = new byte[]{0x00, 0x00, 0x00, 0x00, 'm', 'o', 'o', 'v', 0x00, 0x00};
        byte[] tailChunk = concatBytes(new byte[9], openEndedMoov);
        long chunkStart = 2048L;
        long totalLength = chunkStart + tailChunk.length + 321L;

        RemoteVideoDurationService.ByteRange moovRange = remoteVideoDurationService.resolveMoovRangeFromTailChunk(
                tailChunk,
                chunkStart,
                totalLength
        );

        assertEquals(chunkStart + 9L, moovRange.getStart());
        assertEquals(totalLength - 1L, moovRange.getEnd());
    }

    /**
     * 包装 moov 盒子。
     */
    private byte[] wrapMoovBox(byte[] childBytes) {
        return wrapBox("moov", childBytes);
    }

    /**
     * 构造一个标准 MP4 盒子。
     */
    private byte[] wrapBox(String type, byte[] payload) {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        int boxSize = 8 + payload.length;
        outputStream.write((byte) (boxSize >> 24));
        outputStream.write((byte) (boxSize >> 16));
        outputStream.write((byte) (boxSize >> 8));
        outputStream.write((byte) boxSize);
        outputStream.write(type.getBytes(StandardCharsets.US_ASCII), 0, 4);
        outputStream.write(payload, 0, payload.length);
        return outputStream.toByteArray();
    }

    /**
     * 拼接多段字节数组。
     */
    private byte[] concatBytes(byte[] left, byte[] right) {
        byte[] merged = new byte[left.length + right.length];
        System.arraycopy(left, 0, merged, 0, left.length);
        System.arraycopy(right, 0, merged, left.length, right.length);
        return merged;
    }
}