LibreMediaConverter/app/src/androidTest/java/org/libremediaconverter/ffmpeg/FFmpegEngineTest.kt

package org.libremediaconverter.ffmpeg

import android.media.MediaExtractor
import android.media.MediaFormat
import androidx.test.ext.junit.runners.AndroidJUnit4
import androidx.test.platform.app.InstrumentationRegistry
import kotlinx.coroutines.runBlocking
import org.junit.After
import org.junit.Assert.assertEquals
import org.junit.Assert.assertTrue
import org.junit.Before
import org.junit.Test
import org.junit.runner.RunWith
import org.libremediaconverter.model.ConversionRequest
import org.libremediaconverter.model.OutputFormat
import org.libremediaconverter.model.QualityTier
import java.io.File

/**
 * Exercises the bundled FFmpeg on-device.
 *
 * These are the formats the app exists for that Media3 structurally cannot produce, so
 * they are also the ones with no other coverage. Each test asserts against the produced
 * file rather than the exit code, because FFmpeg will happily report success after
 * writing something unplayable if the arguments are wrong.
 */
@RunWith(AndroidJUnit4::class)
class FFmpegEngineTest {

    private val context = InstrumentationRegistry.getInstrumentation().targetContext
    private val engine: org.libremediaconverter.convert.SoftwareTranscoder = FFmpegEngine()
    private lateinit var input: File
    private val outputs = mutableListOf<File>()

    @Before
    fun setUp() {
        input = File(context.cacheDir, "ffmpeg_sample.mp4")
        InstrumentationRegistry.getInstrumentation().context.assets
            .open("sample_h264.mp4")
            .use { asset -> input.outputStream().use { asset.copyTo(it) } }
    }

    @After
    fun tearDown() {
        input.delete()
        outputs.forEach { it.delete() }
    }

    private fun outputFor(name: String) = File(context.cacheDir, name).also {
        it.delete()
        outputs += it
    }

    private fun convert(format: OutputFormat, quality: QualityTier = QualityTier.BEST): File {
        val out = outputFor("out_${format.name.lowercase()}.${format.extension}")
        runBlocking {
            engine.run(
                request = ConversionRequest(spec = format.spec, quality = quality),
                inputPath = input.absolutePath,
                output = out,
                durationMs = 3_000,
            )
        }
        return out
    }

    private fun trackMimes(file: File): List<String> {
        val extractor = MediaExtractor()
        return try {
            extractor.setDataSource(file.absolutePath)
            (0 until extractor.trackCount).map {
                extractor.getTrackFormat(it).getString(MediaFormat.KEY_MIME).orEmpty()
            }
        } finally {
            extractor.release()
        }
    }

    // --- the formats that justify bundling FFmpeg at all -------------------

    @Test
    fun encodesMp3WhichAndroidCannotDoAtAnyApiLevel() {
        val out = convert(OutputFormat.MP3)
        assertTrue("no MP3 produced", out.exists() && out.length() > 0)
        assertTrue(
            "expected an mpeg audio track, got ${trackMimes(out)}",
            trackMimes(out).any { it.contains("mp") && it.startsWith("audio/") },
        )
    }

    @Test
    fun encodesGifWithAGeneratedPalette() {
        val out = convert(OutputFormat.GIF)
        assertTrue("no GIF produced", out.exists() && out.length() > 0)
        // GIF87a / GIF89a magic. Proves a real GIF rather than a mislabelled file.
        val magic = out.inputStream().use { String(it.readNBytes(6)) }
        assertTrue("not a GIF: $magic", magic.startsWith("GIF"))
    }

    @Test
    fun encodesMatroskaWhichMedia3CannotMux() {
        val out = convert(OutputFormat.MKV_H264)
        assertTrue("no MKV produced", out.exists() && out.length() > 0)
        // EBML magic, the Matroska container header.
        val magic = out.inputStream().use { it.readNBytes(4) }
        assertEquals(0x1A.toByte(), magic[0])
        assertEquals(0x45.toByte(), magic[1])
        assertEquals(0xDF.toByte(), magic[2])
        assertEquals(0xA3.toByte(), magic[3])
    }

    @Test
    fun encodesFlacLosslessAudio() {
        val out = convert(OutputFormat.FLAC)
        assertTrue("no FLAC produced", out.exists() && out.length() > 0)
    }

    @Test
    fun encodesWav() {
        val out = convert(OutputFormat.WAV)
        assertTrue("no WAV produced", out.exists() && out.length() > 0)
        val magic = out.inputStream().use { String(it.readNBytes(4)) }
        assertEquals("RIFF", magic)
    }

    @Test
    fun encodesOpus() {
        val out = convert(OutputFormat.OPUS)
        assertTrue("no Opus produced", out.exists() && out.length() > 0)
    }

    // --- the quality tier the GPL licence was taken for --------------------

    @Test
    fun bestQualityProducesAPlayableH264File() {
        val out = convert(OutputFormat.MP4_H264, QualityTier.BEST)
        assertTrue("no MP4 produced", out.exists() && out.length() > 0)
        assertTrue(
            "expected an AVC track, got ${trackMimes(out)}",
            trackMimes(out).any { it == MediaFormat.MIMETYPE_VIDEO_AVC },
        )
    }

    @Test
    fun bestQualityProducesAPlayableH265File() {
        val out = convert(OutputFormat.MP4_H265, QualityTier.BEST)
        assertTrue("no MP4 produced", out.exists() && out.length() > 0)
        assertTrue(
            "expected an HEVC track, got ${trackMimes(out)}",
            trackMimes(out).any { it == MediaFormat.MIMETYPE_VIDEO_HEVC },
        )
    }

    @Test
    fun failureSurfacesAsAnExceptionRatherThanASilentEmptyFile() {
        val out = outputFor("nope.mp4")
        val failure = runCatching {
            runBlocking {
                engine.run(
                    request = ConversionRequest(spec = OutputFormat.MP4_H264.spec),
                    inputPath = "/does/not/exist.mp4",
                    output = out,
                    durationMs = 1_000,
                )
            }
        }.exceptionOrNull()
        assertTrue("expected an FFmpegException, got $failure", failure is FFmpegEngine.FFmpegException)
    }
}