caery_lib/

lib.rs

#![doc = include_str!("../README.md")]

use std::ffi::OsString;
use std::fmt;
use std::io::{BufRead, BufReader, Read};
use std::path::{Path, PathBuf};
use std::process::{Child, Command, Stdio};
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::mpsc::{self, Receiver, Sender};
use std::sync::Arc;
use std::thread;
use std::time::{Duration, Instant};

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ConversionMode {
    ExtractAudio,
    TranscodeVideo,
    TranscodeAudio,
}

impl ConversionMode {
    pub const ALL: [ConversionMode; 3] = [
        ConversionMode::ExtractAudio,
        ConversionMode::TranscodeVideo,
        ConversionMode::TranscodeAudio,
    ];

    pub fn title(self) -> &'static str {
        match self {
            ConversionMode::ExtractAudio => "Video -> Audio",
            ConversionMode::TranscodeVideo => "Video -> Video",
            ConversionMode::TranscodeAudio => "Audio -> Audio",
        }
    }

    pub fn description(self) -> &'static str {
        match self {
            ConversionMode::ExtractAudio => "Strip video and encode the audio track only.",
            ConversionMode::TranscodeVideo => "Re-encode video into another container/codec route.",
            ConversionMode::TranscodeAudio => "Convert one audio file into another audio format.",
        }
    }

    pub fn source_label(self) -> &'static str {
        match self {
            ConversionMode::ExtractAudio | ConversionMode::TranscodeVideo => "VIDEO SOURCE",
            ConversionMode::TranscodeAudio => "AUDIO SOURCE",
        }
    }

    pub fn note_text(self) -> &'static str {
        match self {
            ConversionMode::ExtractAudio => {
                "EXTRACT ROUTE // SOURCE VIDEO -> AUDIO CODEC -> OUTPUT CONTAINER"
            }
            ConversionMode::TranscodeVideo => {
                "VIDEO ROUTE // SOURCE STREAMS -> TRANSCODE MATRIX -> OUTPUT CONTAINER"
            }
            ConversionMode::TranscodeAudio => {
                "AUDIO ROUTE // SOURCE AUDIO -> CODEC CONVERSION -> OUTPUT FILE"
            }
        }
    }

    pub fn expects_video_input(self) -> bool {
        matches!(
            self,
            ConversionMode::ExtractAudio | ConversionMode::TranscodeVideo
        )
    }

    pub fn output_extension(self, audio: AudioFormat, video: VideoFormat) -> &'static str {
        match self {
            ConversionMode::ExtractAudio | ConversionMode::TranscodeAudio => audio.extension(),
            ConversionMode::TranscodeVideo => video.extension(),
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum AudioFormat {
    Mp3,
    M4a,
    Flac,
    Wav,
    Ogg,
    Opus,
}

impl AudioFormat {
    pub const ALL: [AudioFormat; 6] = [
        AudioFormat::Mp3,
        AudioFormat::M4a,
        AudioFormat::Flac,
        AudioFormat::Wav,
        AudioFormat::Ogg,
        AudioFormat::Opus,
    ];

    pub fn label(self) -> &'static str {
        match self {
            AudioFormat::Mp3 => "MP3",
            AudioFormat::M4a => "M4A/AAC",
            AudioFormat::Flac => "FLAC",
            AudioFormat::Wav => "WAV",
            AudioFormat::Ogg => "OGG",
            AudioFormat::Opus => "OPUS",
        }
    }

    pub fn extension(self) -> &'static str {
        match self {
            AudioFormat::Mp3 => "mp3",
            AudioFormat::M4a => "m4a",
            AudioFormat::Flac => "flac",
            AudioFormat::Wav => "wav",
            AudioFormat::Ogg => "ogg",
            AudioFormat::Opus => "opus",
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum VideoFormat {
    Mp4,
    Mkv,
    Webm,
    Mov,
}

impl VideoFormat {
    pub const ALL: [VideoFormat; 4] = [
        VideoFormat::Mp4,
        VideoFormat::Mkv,
        VideoFormat::Webm,
        VideoFormat::Mov,
    ];

    pub fn label(self) -> &'static str {
        match self {
            VideoFormat::Mp4 => "MP4",
            VideoFormat::Mkv => "MKV",
            VideoFormat::Webm => "WEBM",
            VideoFormat::Mov => "MOV",
        }
    }

    pub fn extension(self) -> &'static str {
        match self {
            VideoFormat::Mp4 => "mp4",
            VideoFormat::Mkv => "mkv",
            VideoFormat::Webm => "webm",
            VideoFormat::Mov => "mov",
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum QualityPreset {
    Compact,
    Balanced,
    Archive,
}

impl QualityPreset {
    pub const ALL: [QualityPreset; 3] = [
        QualityPreset::Compact,
        QualityPreset::Balanced,
        QualityPreset::Archive,
    ];

    pub fn label(self) -> &'static str {
        match self {
            QualityPreset::Compact => "Compact",
            QualityPreset::Balanced => "Balanced",
            QualityPreset::Archive => "Archive",
        }
    }

    pub fn description(self) -> &'static str {
        match self {
            QualityPreset::Compact => "smaller file",
            QualityPreset::Balanced => "general use",
            QualityPreset::Archive => "higher fidelity",
        }
    }

    fn x264_crf(self) -> &'static str {
        match self {
            QualityPreset::Compact => "28",
            QualityPreset::Balanced => "23",
            QualityPreset::Archive => "18",
        }
    }

    fn vp9_crf(self) -> &'static str {
        match self {
            QualityPreset::Compact => "38",
            QualityPreset::Balanced => "32",
            QualityPreset::Archive => "24",
        }
    }

    fn audio_bitrate(self) -> &'static str {
        match self {
            QualityPreset::Compact => "128k",
            QualityPreset::Balanced => "192k",
            QualityPreset::Archive => "256k",
        }
    }

    fn vorbis_quality(self) -> &'static str {
        match self {
            QualityPreset::Compact => "3",
            QualityPreset::Balanced => "5",
            QualityPreset::Archive => "8",
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ConversionRequest {
    pub mode: ConversionMode,
    pub input_path: PathBuf,
    pub output_path: PathBuf,
    pub audio_format: AudioFormat,
    pub video_format: VideoFormat,
    pub quality: QualityPreset,
    pub overwrite: bool,
}

/// A conversion route inferred from input and output file extensions.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[non_exhaustive]
pub enum ConversionRoute {
    ExtractAudio(AudioFormat),
    TranscodeVideo(VideoFormat),
    TranscodeAudio(AudioFormat),
}

impl ConversionRoute {
    pub fn mode(self) -> ConversionMode {
        match self {
            ConversionRoute::ExtractAudio(_) => ConversionMode::ExtractAudio,
            ConversionRoute::TranscodeVideo(_) => ConversionMode::TranscodeVideo,
            ConversionRoute::TranscodeAudio(_) => ConversionMode::TranscodeAudio,
        }
    }

    pub fn audio_format(self) -> Option<AudioFormat> {
        match self {
            ConversionRoute::ExtractAudio(format) | ConversionRoute::TranscodeAudio(format) => {
                Some(format)
            }
            ConversionRoute::TranscodeVideo(_) => None,
        }
    }

    pub fn video_format(self) -> Option<VideoFormat> {
        match self {
            ConversionRoute::TranscodeVideo(format) => Some(format),
            ConversionRoute::ExtractAudio(_) | ConversionRoute::TranscodeAudio(_) => None,
        }
    }

    pub fn output_extension(self) -> &'static str {
        match self {
            ConversionRoute::ExtractAudio(format) | ConversionRoute::TranscodeAudio(format) => {
                format.extension()
            }
            ConversionRoute::TranscodeVideo(format) => format.extension(),
        }
    }
}

/// An error produced while inferring a conversion from file extensions.
#[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]
#[non_exhaustive]
pub enum RouteInferenceError {
    #[error("unsupported input extension for {0}")]
    UnsupportedInput(PathBuf),
    #[error("unsupported output extension for {0}")]
    UnsupportedOutput(PathBuf),
    #[error("audio input cannot be converted into a video output")]
    AudioToVideo,
}

/// Infers a supported route from two paths without accessing the filesystem.
pub fn infer_route(input: &Path, output: &Path) -> Result<ConversionRoute, RouteInferenceError> {
    let input_is_audio = supported_audio_extension(input);
    let input_is_video = supported_video_extension(input);

    if !input_is_audio && !input_is_video {
        return Err(RouteInferenceError::UnsupportedInput(input.to_path_buf()));
    }

    if let Some(format) = audio_format_from_path(output) {
        return if input_is_audio {
            Ok(ConversionRoute::TranscodeAudio(format))
        } else {
            Ok(ConversionRoute::ExtractAudio(format))
        };
    }

    if let Some(format) = video_format_from_path(output) {
        return if input_is_audio {
            Err(RouteInferenceError::AudioToVideo)
        } else {
            Ok(ConversionRoute::TranscodeVideo(format))
        };
    }

    Err(RouteInferenceError::UnsupportedOutput(output.to_path_buf()))
}

/// Creates a balanced, no-overwrite request inferred from two paths.
///
/// The paths do not need to exist until the request is validated or started.
pub fn request_from_paths(
    input: impl AsRef<Path>,
    output: impl AsRef<Path>,
) -> Result<ConversionRequest, RouteInferenceError> {
    let input = input.as_ref();
    let output = output.as_ref();
    let route = infer_route(input, output)?;
    let (audio_format, video_format) = match route {
        ConversionRoute::ExtractAudio(format) | ConversionRoute::TranscodeAudio(format) => {
            (format, VideoFormat::Mp4)
        }
        ConversionRoute::TranscodeVideo(format) => (AudioFormat::Mp3, format),
    };

    Ok(ConversionRequest {
        mode: route.mode(),
        input_path: input.to_path_buf(),
        output_path: output.to_path_buf(),
        audio_format,
        video_format,
        quality: QualityPreset::Balanced,
        overwrite: false,
    })
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct CommandSpec {
    pub program: String,
    pub args: Vec<String>,
}

impl fmt::Display for CommandSpec {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(formatter, "{}", self.program)?;
        for arg in &self.args {
            write!(formatter, " {}", shell_quote(arg))?;
        }
        Ok(())
    }
}

#[derive(Debug, thiserror::Error)]
pub enum ConversionError {
    #[error("select a source media file first")]
    MissingInput,
    #[error("source file does not exist: {0}")]
    MissingInputFile(String),
    #[error("source path must be a regular file: {0}")]
    InputNotFile(String),
    #[error("selected route expects a video source: {0}")]
    ExpectedVideoInput(String),
    #[error("selected route expects an audio source: {0}")]
    ExpectedAudioInput(String),
    #[error("choose an output file path first")]
    MissingOutput,
    #[error("output parent folder does not exist: {0}")]
    MissingOutputFolder(String),
    #[error("output cannot be the same file as the source")]
    SameInputOutput,
    #[error("output extension should be .{expected} for the selected route")]
    OutputExtensionMismatch { expected: &'static str },
    #[error("output already exists; enable overwrite or choose another path: {0}")]
    OutputExists(String),
}

pub fn build_command(request: &ConversionRequest) -> Result<CommandSpec, ConversionError> {
    validate_request(request)?;

    let args = ffmpeg_arguments(request)
        .into_iter()
        .map(|arg| arg.to_string_lossy().into_owned())
        .collect();

    Ok(CommandSpec {
        program: "ffmpeg".to_owned(),
        args,
    })
}

fn ffmpeg_arguments(request: &ConversionRequest) -> Vec<OsString> {
    let mut args = [
        "-hide_banner",
        "-nostdin",
        "-progress",
        "pipe:1",
        "-nostats",
        if request.overwrite { "-y" } else { "-n" },
        "-i",
    ]
    .into_iter()
    .map(OsString::from)
    .collect::<Vec<_>>();
    args.push(request.input_path.as_os_str().to_owned());

    match request.mode {
        ConversionMode::ExtractAudio | ConversionMode::TranscodeAudio => {
            push_args(&mut args, ["-map", "0:a:0", "-vn"]);
            apply_audio_args(&mut args, request.audio_format, request.quality);
        }
        ConversionMode::TranscodeVideo => {
            push_args(&mut args, ["-map", "0:v:0", "-map", "0:a?", "-sn"]);
            apply_video_args(&mut args, request.video_format, request.quality);
        }
    }

    args.push(request.output_path.as_os_str().to_owned());
    args
}

pub fn validate_request(request: &ConversionRequest) -> Result<(), ConversionError> {
    if request.input_path.as_os_str().is_empty() {
        return Err(ConversionError::MissingInput);
    }

    let input_display = request.input_path.display().to_string();
    let metadata = std::fs::metadata(&request.input_path)
        .map_err(|_| ConversionError::MissingInputFile(input_display.clone()))?;
    if !metadata.is_file() {
        return Err(ConversionError::InputNotFile(input_display));
    }

    if request.mode.expects_video_input() && !supported_video_extension(&request.input_path) {
        return Err(ConversionError::ExpectedVideoInput(
            request.input_path.display().to_string(),
        ));
    }
    if matches!(request.mode, ConversionMode::TranscodeAudio)
        && !supported_audio_extension(&request.input_path)
    {
        return Err(ConversionError::ExpectedAudioInput(
            request.input_path.display().to_string(),
        ));
    }

    if request.output_path.as_os_str().is_empty() {
        return Err(ConversionError::MissingOutput);
    }

    if request.input_path == request.output_path
        || canonical_match(&request.input_path, &request.output_path)
    {
        return Err(ConversionError::SameInputOutput);
    }

    if let Some(parent) = request.output_path.parent() {
        if !parent.as_os_str().is_empty() && !parent.is_dir() {
            return Err(ConversionError::MissingOutputFolder(
                parent.display().to_string(),
            ));
        }
    }

    let expected = request
        .mode
        .output_extension(request.audio_format, request.video_format);
    if path_extension_lower(&request.output_path).as_deref() != Some(expected) {
        return Err(ConversionError::OutputExtensionMismatch { expected });
    }

    if request.output_path.exists() && !request.overwrite {
        return Err(ConversionError::OutputExists(
            request.output_path.display().to_string(),
        ));
    }

    Ok(())
}

fn canonical_match(left: &Path, right: &Path) -> bool {
    match (std::fs::canonicalize(left), std::fs::canonicalize(right)) {
        (Ok(left), Ok(right)) => left == right,
        _ => false,
    }
}

fn apply_audio_args(args: &mut Vec<OsString>, format: AudioFormat, quality: QualityPreset) {
    match format {
        AudioFormat::Mp3 => {
            push_args(
                args,
                ["-c:a", "libmp3lame", "-b:a", quality.audio_bitrate()],
            );
        }
        AudioFormat::M4a => {
            push_args(args, ["-c:a", "aac", "-b:a", quality.audio_bitrate()]);
            push_args(args, ["-movflags", "+faststart"]);
        }
        AudioFormat::Flac => push_args(args, ["-c:a", "flac"]),
        AudioFormat::Wav => push_args(args, ["-c:a", "pcm_s16le"]),
        AudioFormat::Ogg => {
            push_args(
                args,
                ["-c:a", "libvorbis", "-q:a", quality.vorbis_quality()],
            );
        }
        AudioFormat::Opus => {
            push_args(args, ["-c:a", "libopus", "-b:a", quality.audio_bitrate()]);
        }
    }
}

fn apply_video_args(args: &mut Vec<OsString>, format: VideoFormat, quality: QualityPreset) {
    match format {
        VideoFormat::Mp4 | VideoFormat::Mkv | VideoFormat::Mov => {
            push_args(
                args,
                [
                    "-c:v",
                    "libx264",
                    "-preset",
                    "medium",
                    "-crf",
                    quality.x264_crf(),
                    "-pix_fmt",
                    "yuv420p",
                    "-c:a",
                    "aac",
                    "-b:a",
                    quality.audio_bitrate(),
                ],
            );
            if matches!(format, VideoFormat::Mp4 | VideoFormat::Mov) {
                push_args(args, ["-movflags", "+faststart"]);
            }
        }
        VideoFormat::Webm => {
            push_args(
                args,
                [
                    "-c:v",
                    "libvpx-vp9",
                    "-b:v",
                    "0",
                    "-crf",
                    quality.vp9_crf(),
                    "-c:a",
                    "libopus",
                    "-b:a",
                    quality.audio_bitrate(),
                ],
            );
        }
    }
}

fn push_args<const N: usize>(args: &mut Vec<OsString>, values: [&str; N]) {
    args.extend(values.into_iter().map(OsString::from));
}

pub fn probe_duration(path: &Path) -> Option<f64> {
    let output = Command::new("ffprobe")
        .args([
            "-v",
            "error",
            "-show_entries",
            "format=duration",
            "-of",
            "default=noprint_wrappers=1:nokey=1",
        ])
        .arg(path)
        .output()
        .ok()?;

    if !output.status.success() {
        return None;
    }

    let text = String::from_utf8_lossy(&output.stdout);
    text.lines()
        .find_map(|line| line.trim().parse::<f64>().ok())
        .filter(|duration| *duration > 0.0 && duration.is_finite())
}

#[derive(Debug, Clone, PartialEq)]
pub enum OperationEvent {
    Started(String),
    Log(String),
    Progress {
        current_seconds: f64,
        total_seconds: f64,
    },
    Finished(Result<(), String>),
}

pub fn start_operation(
    command: CommandSpec,
    expected_duration: Option<f64>,
) -> Receiver<OperationEvent> {
    let (tx, rx) = mpsc::channel();
    thread::spawn(move || run_operation(command, expected_duration, tx));
    rx
}

/// Validates a request and starts its conversion on a background thread.
///
/// Process startup and ffmpeg failures are reported through the returned event
/// stream as [`OperationEvent::Finished`].
pub fn start_conversion(
    request: &ConversionRequest,
) -> Result<Receiver<OperationEvent>, ConversionError> {
    let command = build_command(request)?;
    let expected_duration = probe_duration(&request.input_path);
    Ok(start_operation(command, expected_duration))
}

const DEFAULT_TOOL_CHECK_TIMEOUT: Duration = Duration::from_secs(2);
const DEFAULT_PROBE_TIMEOUT: Duration = Duration::from_secs(10);
const PROCESS_POLL_INTERVAL: Duration = Duration::from_millis(20);

/// Configures the executables and timeouts used by embedded conversions.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Converter {
    ffmpeg_path: PathBuf,
    ffprobe_path: PathBuf,
    tool_check_timeout: Duration,
    probe_timeout: Duration,
}

impl Default for Converter {
    fn default() -> Self {
        Self {
            ffmpeg_path: PathBuf::from("ffmpeg"),
            ffprobe_path: PathBuf::from("ffprobe"),
            tool_check_timeout: DEFAULT_TOOL_CHECK_TIMEOUT,
            probe_timeout: DEFAULT_PROBE_TIMEOUT,
        }
    }
}

impl Converter {
    /// Uses `ffmpeg` and `ffprobe` from `PATH`.
    pub fn new() -> Self {
        Self::default()
    }

    /// Uses explicit ffmpeg and ffprobe executable paths.
    pub fn with_programs(
        ffmpeg_path: impl Into<PathBuf>,
        ffprobe_path: impl Into<PathBuf>,
    ) -> Self {
        Self {
            ffmpeg_path: ffmpeg_path.into(),
            ffprobe_path: ffprobe_path.into(),
            ..Self::default()
        }
    }

    /// Sets the maximum time allowed for each executable availability check.
    pub fn with_tool_check_timeout(mut self, timeout: Duration) -> Self {
        self.tool_check_timeout = timeout;
        self
    }

    /// Sets the maximum duration probe time before conversion continues without a total.
    pub fn with_probe_timeout(mut self, timeout: Duration) -> Self {
        self.probe_timeout = timeout;
        self
    }

    pub fn ffmpeg_path(&self) -> &Path {
        &self.ffmpeg_path
    }

    pub fn ffprobe_path(&self) -> &Path {
        &self.ffprobe_path
    }

    /// Checks both executables synchronously using their `-version` option.
    ///
    /// Run this outside a UI render loop. Each check is bounded by the
    /// configured tool-check timeout.
    pub fn check_tools(&self) -> ToolAvailability {
        ToolAvailability {
            ffmpeg: check_tool(&self.ffmpeg_path, self.tool_check_timeout),
            ffprobe: check_tool(&self.ffprobe_path, self.tool_check_timeout),
        }
    }

    /// Starts a conversion worker and returns immediately.
    ///
    /// Validation, probing, and process startup happen on the worker thread.
    pub fn spawn(&self, request: ConversionRequest) -> ConversionJob {
        let (tx, events) = mpsc::channel();
        let cancellation = Arc::new(AtomicBool::new(false));
        let worker_cancellation = Arc::clone(&cancellation);
        let converter = self.clone();
        let input_path = request.input_path.clone();
        let output_path = request.output_path.clone();
        thread::spawn(move || {
            run_conversion_job(converter, request, worker_cancellation, tx);
        });

        ConversionJob {
            events,
            cancellation,
            input_path,
            output_path,
        }
    }
}

/// The result of checking one external executable.
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub enum ToolStatus {
    Available,
    Unavailable(String),
    TimedOut,
}

impl ToolStatus {
    pub fn is_available(&self) -> bool {
        matches!(self, ToolStatus::Available)
    }
}

impl fmt::Display for ToolStatus {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            ToolStatus::Available => formatter.write_str("available"),
            ToolStatus::Unavailable(error) => write!(formatter, "unavailable: {error}"),
            ToolStatus::TimedOut => formatter.write_str("timed out"),
        }
    }
}

/// Availability information for the external tools used by Caery.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ToolAvailability {
    ffmpeg: ToolStatus,
    ffprobe: ToolStatus,
}

impl ToolAvailability {
    pub fn ffmpeg(&self) -> &ToolStatus {
        &self.ffmpeg
    }

    pub fn ffprobe(&self) -> &ToolStatus {
        &self.ffprobe
    }

    /// Whether conversion can be attempted. ffprobe is optional for progress totals.
    pub fn conversion_ready(&self) -> bool {
        self.ffmpeg.is_available()
    }

    pub fn duration_progress_available(&self) -> bool {
        self.ffprobe.is_available()
    }
}

/// Checks `ffmpeg` and `ffprobe` from `PATH` synchronously.
pub fn check_tools() -> ToolAvailability {
    Converter::new().check_tools()
}

fn check_tool(program: &Path, timeout: Duration) -> ToolStatus {
    let mut command = Command::new(program);
    command
        .arg("-version")
        .stdin(Stdio::null())
        .stdout(Stdio::null())
        .stderr(Stdio::null());
    configure_process_group(&mut command);
    let mut child = match command.spawn() {
        Ok(child) => child,
        Err(error) => return ToolStatus::Unavailable(error.to_string()),
    };
    let started = Instant::now();

    loop {
        match child.try_wait() {
            Ok(Some(status)) if status.success() => return ToolStatus::Available,
            Ok(Some(status)) => return ToolStatus::Unavailable(format!("exited with {status}")),
            Ok(None) if started.elapsed() >= timeout => {
                terminate_child(&mut child);
                return ToolStatus::TimedOut;
            }
            Ok(None) => thread::sleep(PROCESS_POLL_INTERVAL),
            Err(error) => {
                terminate_child(&mut child);
                return ToolStatus::Unavailable(error.to_string());
            }
        }
    }
}

fn configure_process_group(command: &mut Command) {
    #[cfg(unix)]
    {
        use std::os::unix::process::CommandExt;

        command.process_group(0);
    }
}

fn terminate_child(child: &mut Child) {
    #[cfg(unix)]
    if let Ok(process_group) = i32::try_from(child.id()) {
        // Worker processes are group leaders, so this also terminates wrappers and descendants.
        unsafe {
            libc::kill(-process_group, libc::SIGKILL);
        }
    }

    let _ = child.kill();
    let _ = child.wait();
}

/// The terminal result of an embedded conversion job.
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub enum ConversionOutcome {
    Succeeded,
    Cancelled,
    Failed(String),
}

impl ConversionOutcome {
    pub fn is_success(&self) -> bool {
        matches!(self, ConversionOutcome::Succeeded)
    }

    pub fn is_cancelled(&self) -> bool {
        matches!(self, ConversionOutcome::Cancelled)
    }
}

/// Events emitted by a cancellable embedded conversion job.
#[derive(Debug, Clone, PartialEq)]
#[non_exhaustive]
pub enum ConversionEvent {
    Started(String),
    Log(String),
    #[non_exhaustive]
    Progress {
        current_seconds: f64,
        total_seconds: Option<f64>,
    },
    Finished(ConversionOutcome),
}

/// A non-blocking conversion with event polling and cancellation.
#[must_use = "dropping a conversion job requests cancellation"]
pub struct ConversionJob {
    events: Receiver<ConversionEvent>,
    cancellation: Arc<AtomicBool>,
    input_path: PathBuf,
    output_path: PathBuf,
}

impl ConversionJob {
    pub fn input_path(&self) -> &Path {
        &self.input_path
    }

    pub fn output_path(&self) -> &Path {
        &self.output_path
    }

    pub fn try_recv(&self) -> Result<ConversionEvent, mpsc::TryRecvError> {
        self.events.try_recv()
    }

    pub fn recv(&self) -> Result<ConversionEvent, mpsc::RecvError> {
        self.events.recv()
    }

    pub fn recv_timeout(
        &self,
        timeout: Duration,
    ) -> Result<ConversionEvent, mpsc::RecvTimeoutError> {
        self.events.recv_timeout(timeout)
    }

    /// Idempotently asks the worker to stop probing or terminate ffmpeg.
    pub fn cancel(&self) {
        self.cancellation.store(true, Ordering::Release);
    }

    pub fn cancellation_requested(&self) -> bool {
        self.cancellation.load(Ordering::Acquire)
    }
}

impl Drop for ConversionJob {
    fn drop(&mut self) {
        self.cancel();
    }
}

/// Starts a cancellable conversion using `ffmpeg` and `ffprobe` from `PATH`.
pub fn spawn_conversion(request: ConversionRequest) -> ConversionJob {
    Converter::new().spawn(request)
}

fn run_conversion_job(
    converter: Converter,
    request: ConversionRequest,
    cancellation: Arc<AtomicBool>,
    tx: Sender<ConversionEvent>,
) {
    if cancellation.load(Ordering::Acquire) {
        let _ = tx.send(ConversionEvent::Finished(ConversionOutcome::Cancelled));
        return;
    }

    if let Err(error) = validate_request(&request) {
        let outcome = if cancellation.load(Ordering::Acquire) {
            ConversionOutcome::Cancelled
        } else {
            ConversionOutcome::Failed(error.to_string())
        };
        let _ = tx.send(ConversionEvent::Finished(outcome));
        return;
    }

    let expected_duration = match probe_duration_for_job(
        &converter.ffprobe_path,
        &request.input_path,
        converter.probe_timeout,
        &cancellation,
    ) {
        ProbeOutcome::Duration(duration) => duration,
        ProbeOutcome::Cancelled => {
            let _ = tx.send(ConversionEvent::Finished(ConversionOutcome::Cancelled));
            return;
        }
    };

    if cancellation.load(Ordering::Acquire) {
        let _ = tx.send(ConversionEvent::Finished(ConversionOutcome::Cancelled));
        return;
    }

    run_job_operation(
        &converter.ffmpeg_path,
        ffmpeg_arguments(&request),
        expected_duration,
        cancellation,
        tx,
    );
}

enum ProbeOutcome {
    Duration(Option<f64>),
    Cancelled,
}

fn probe_duration_for_job(
    program: &Path,
    path: &Path,
    timeout: Duration,
    cancellation: &AtomicBool,
) -> ProbeOutcome {
    if cancellation.load(Ordering::Acquire) {
        return ProbeOutcome::Cancelled;
    }

    let mut command = Command::new(program);
    command
        .args([
            "-v",
            "error",
            "-show_entries",
            "format=duration",
            "-of",
            "default=noprint_wrappers=1:nokey=1",
        ])
        .arg(path)
        .stdin(Stdio::null())
        .stdout(Stdio::piped())
        .stderr(Stdio::null());
    configure_process_group(&mut command);
    let mut child = match command.spawn() {
        Ok(child) => child,
        Err(_) => return ProbeOutcome::Duration(None),
    };
    let started = Instant::now();

    let status = loop {
        match child.try_wait() {
            Ok(Some(status)) => break Some(status),
            Ok(None) if cancellation.load(Ordering::Acquire) => {
                terminate_child(&mut child);
                return ProbeOutcome::Cancelled;
            }
            Ok(None) if started.elapsed() >= timeout => {
                terminate_child(&mut child);
                break None;
            }
            Ok(None) => thread::sleep(PROCESS_POLL_INTERVAL),
            Err(_) => {
                terminate_child(&mut child);
                break None;
            }
        }
    };

    if !matches!(status, Some(status) if status.success()) {
        return ProbeOutcome::Duration(None);
    }
    let mut stdout = String::new();
    let duration = child
        .stdout
        .take()
        .and_then(|mut stream| stream.read_to_string(&mut stdout).ok())
        .and_then(|_| {
            stdout
                .lines()
                .find_map(|line| line.trim().parse::<f64>().ok())
        })
        .filter(|duration| *duration > 0.0 && duration.is_finite());
    ProbeOutcome::Duration(duration)
}

fn run_job_operation(
    program: &Path,
    args: Vec<OsString>,
    expected_duration: Option<f64>,
    cancellation: Arc<AtomicBool>,
    tx: Sender<ConversionEvent>,
) {
    if cancellation.load(Ordering::Acquire) {
        let _ = tx.send(ConversionEvent::Finished(ConversionOutcome::Cancelled));
        return;
    }

    let mut command = Command::new(program);
    command
        .args(&args)
        .stdin(Stdio::null())
        .stdout(Stdio::piped())
        .stderr(Stdio::piped());
    configure_process_group(&mut command);
    let mut child = match command.spawn() {
        Ok(child) => child,
        Err(error) => {
            let _ = tx.send(ConversionEvent::Finished(ConversionOutcome::Failed(
                format!("failed to start ffmpeg: {error}"),
            )));
            return;
        }
    };
    if cancellation.load(Ordering::Acquire) {
        terminate_child(&mut child);
        let _ = tx.send(ConversionEvent::Finished(ConversionOutcome::Cancelled));
        return;
    }
    let _ = tx.send(ConversionEvent::Started(display_os_command(program, &args)));

    let stdout = child.stdout.take();
    let stderr = child.stderr.take();
    let stdout_thread =
        stdout.map(|stream| forward_conversion_stream(stream, tx.clone(), expected_duration));
    let stderr_thread =
        stderr.map(|stream| forward_conversion_stream(stream, tx.clone(), expected_duration));

    let outcome = loop {
        match child.try_wait() {
            Ok(Some(status)) if status.success() => break ConversionOutcome::Succeeded,
            Ok(Some(status)) => {
                break ConversionOutcome::Failed(format!("ffmpeg exited with status {status}"));
            }
            Ok(None) if cancellation.load(Ordering::Acquire) => {
                terminate_child(&mut child);
                break ConversionOutcome::Cancelled;
            }
            Ok(None) => thread::sleep(PROCESS_POLL_INTERVAL),
            Err(error) => {
                terminate_child(&mut child);
                break ConversionOutcome::Failed(format!("failed to wait for ffmpeg: {error}"));
            }
        }
    };

    if let Some(thread) = stdout_thread {
        let _ = thread.join();
    }
    if let Some(thread) = stderr_thread {
        let _ = thread.join();
    }

    let _ = tx.send(ConversionEvent::Finished(outcome));
}

fn display_os_command(program: &Path, args: &[OsString]) -> String {
    let command = CommandSpec {
        program: program.display().to_string(),
        args: args
            .iter()
            .map(|arg| arg.to_string_lossy().into_owned())
            .collect(),
    };
    command.to_string()
}

fn forward_conversion_stream<R>(
    stream: R,
    tx: Sender<ConversionEvent>,
    expected_duration: Option<f64>,
) -> thread::JoinHandle<()>
where
    R: Read + Send + 'static,
{
    thread::spawn(move || {
        let reader = BufReader::new(stream);
        for line in reader.lines() {
            let line = match line {
                Ok(line) => line.trim().to_owned(),
                Err(error) => {
                    let _ = tx.send(ConversionEvent::Log(format!("stream read failed: {error}")));
                    break;
                }
            };

            if line.is_empty() {
                continue;
            }

            if let Some(current_seconds) = parse_ffmpeg_progress_seconds(&line) {
                let current_seconds = expected_duration
                    .map(|total| current_seconds.min(total))
                    .unwrap_or(current_seconds);
                let _ = tx.send(ConversionEvent::Progress {
                    current_seconds,
                    total_seconds: expected_duration,
                });
                continue;
            }

            if is_ffmpeg_progress_metadata(&line) {
                continue;
            }

            let _ = tx.send(ConversionEvent::Log(line));
        }
    })
}

fn run_operation(command: CommandSpec, expected_duration: Option<f64>, tx: Sender<OperationEvent>) {
    let _ = tx.send(OperationEvent::Started(command.to_string()));

    let mut child = match Command::new(&command.program)
        .args(&command.args)
        .stdout(Stdio::piped())
        .stderr(Stdio::piped())
        .spawn()
    {
        Ok(child) => child,
        Err(error) => {
            let _ = tx.send(OperationEvent::Finished(Err(format!(
                "failed to start ffmpeg: {error}"
            ))));
            return;
        }
    };

    let stdout = child.stdout.take();
    let stderr = child.stderr.take();
    let stdout_thread = stdout.map(|stream| forward_stream(stream, tx.clone(), expected_duration));
    let stderr_thread = stderr.map(|stream| forward_stream(stream, tx.clone(), expected_duration));

    let result = match child.wait() {
        Ok(status) if status.success() => Ok(()),
        Ok(status) => Err(format!("ffmpeg exited with status {status}")),
        Err(error) => Err(format!("failed to wait for ffmpeg: {error}")),
    };

    if let Some(thread) = stdout_thread {
        let _ = thread.join();
    }
    if let Some(thread) = stderr_thread {
        let _ = thread.join();
    }

    let _ = tx.send(OperationEvent::Finished(result));
}

fn forward_stream<R>(
    stream: R,
    tx: Sender<OperationEvent>,
    expected_duration: Option<f64>,
) -> thread::JoinHandle<()>
where
    R: Read + Send + 'static,
{
    thread::spawn(move || {
        let reader = BufReader::new(stream);
        for line in reader.lines() {
            let line = match line {
                Ok(line) => line.trim().to_owned(),
                Err(error) => {
                    let _ = tx.send(OperationEvent::Log(format!("stream read failed: {error}")));
                    break;
                }
            };

            if line.is_empty() {
                continue;
            }

            if let Some(current_seconds) = parse_ffmpeg_progress_seconds(&line) {
                if let Some(total_seconds) = expected_duration {
                    let _ = tx.send(OperationEvent::Progress {
                        current_seconds: current_seconds.min(total_seconds),
                        total_seconds,
                    });
                }
                continue;
            }

            if is_ffmpeg_progress_metadata(&line) {
                continue;
            }

            let _ = tx.send(OperationEvent::Log(line));
        }
    })
}

pub fn parse_ffmpeg_progress_seconds(line: &str) -> Option<f64> {
    let (key, value) = line.trim().split_once('=')?;
    match key {
        "out_time_us" | "out_time_ms" => value
            .trim()
            .parse::<f64>()
            .ok()
            .map(|microseconds| microseconds / 1_000_000.0),
        "out_time" => parse_ffmpeg_timestamp(value.trim()),
        _ => None,
    }
}

fn parse_ffmpeg_timestamp(value: &str) -> Option<f64> {
    let mut parts = value.split(':');
    let hours = parts.next()?.parse::<f64>().ok()?;
    let minutes = parts.next()?.parse::<f64>().ok()?;
    let seconds = parts.next()?.parse::<f64>().ok()?;
    if parts.next().is_some() {
        return None;
    }
    Some(hours * 3600.0 + minutes * 60.0 + seconds)
}

fn is_ffmpeg_progress_metadata(line: &str) -> bool {
    let Some((key, _)) = line.split_once('=') else {
        return false;
    };

    matches!(
        key,
        "bitrate"
            | "drop_frames"
            | "dup_frames"
            | "fps"
            | "frame"
            | "progress"
            | "speed"
            | "stream_0_0_q"
            | "total_size"
    )
}

pub fn duration_progress_label(current_seconds: f64, total_seconds: f64) -> String {
    let percent = if total_seconds <= 0.0 {
        0.0
    } else {
        current_seconds / total_seconds * 100.0
    }
    .clamp(0.0, 100.0);

    format!(
        "{} / {} ({percent:.1}%)",
        format_duration(current_seconds),
        format_duration(total_seconds)
    )
}

pub fn format_duration(seconds: f64) -> String {
    let seconds = seconds.max(0.0).round() as u64;
    let hours = seconds / 3600;
    let minutes = (seconds % 3600) / 60;
    let seconds = seconds % 60;

    if hours > 0 {
        format!("{hours}:{minutes:02}:{seconds:02}")
    } else {
        format!("{minutes}:{seconds:02}")
    }
}

pub fn suggest_output_path(
    input_path: &Path,
    mode: ConversionMode,
    audio_format: AudioFormat,
    video_format: VideoFormat,
) -> Option<PathBuf> {
    if input_path.as_os_str().is_empty() {
        return None;
    }

    let mut filename = input_path.file_stem()?.to_os_string();
    let extension = mode.output_extension(audio_format, video_format);
    filename.push("-caery.");
    filename.push(extension);
    let mut output = input_path.parent().map(PathBuf::from).unwrap_or_default();
    output.push(filename);
    Some(output)
}

pub fn supported_media_extension(path: &Path) -> bool {
    supported_audio_extension(path) || supported_video_extension(path)
}

/// Returns the selectable audio output format represented by a path.
pub fn audio_format_from_path(path: &Path) -> Option<AudioFormat> {
    match path_extension_lower(path).as_deref()? {
        "mp3" => Some(AudioFormat::Mp3),
        "m4a" => Some(AudioFormat::M4a),
        "flac" => Some(AudioFormat::Flac),
        "wav" => Some(AudioFormat::Wav),
        "ogg" => Some(AudioFormat::Ogg),
        "opus" => Some(AudioFormat::Opus),
        _ => None,
    }
}

/// Returns the selectable video output format represented by a path.
pub fn video_format_from_path(path: &Path) -> Option<VideoFormat> {
    match path_extension_lower(path).as_deref()? {
        "mp4" => Some(VideoFormat::Mp4),
        "mkv" => Some(VideoFormat::Mkv),
        "webm" => Some(VideoFormat::Webm),
        "mov" => Some(VideoFormat::Mov),
        _ => None,
    }
}

pub fn supported_audio_extension(path: &Path) -> bool {
    matches!(
        path_extension_lower(path).as_deref(),
        Some(
            "aac"
                | "aif"
                | "aiff"
                | "alac"
                | "flac"
                | "m4a"
                | "mp3"
                | "oga"
                | "ogg"
                | "opus"
                | "wav"
                | "wma"
        )
    )
}

pub fn supported_video_extension(path: &Path) -> bool {
    matches!(
        path_extension_lower(path).as_deref(),
        Some(
            "3gp"
                | "avi"
                | "flv"
                | "m2ts"
                | "m4v"
                | "mkv"
                | "mov"
                | "mp4"
                | "mpeg"
                | "mpg"
                | "ogv"
                | "ts"
                | "webm"
                | "wmv"
        )
    )
}

pub fn media_kind_label(path: &Path) -> &'static str {
    if supported_video_extension(path) {
        "VIDEO"
    } else if supported_audio_extension(path) {
        "AUDIO"
    } else {
        "FILE"
    }
}

pub fn path_extension_lower(path: &Path) -> Option<String> {
    path.extension()
        .and_then(|extension| extension.to_str())
        .map(|extension| extension.to_ascii_lowercase())
}

pub fn human_size(bytes: u64) -> String {
    const UNITS: [&str; 5] = ["B", "KiB", "MiB", "GiB", "TiB"];
    let mut value = bytes as f64;
    let mut unit = 0;

    while value >= 1024.0 && unit < UNITS.len() - 1 {
        value /= 1024.0;
        unit += 1;
    }

    if unit == 0 {
        format!("{} {}", bytes, UNITS[unit])
    } else {
        format!("{value:.1} {}", UNITS[unit])
    }
}

pub fn shell_quote(value: &str) -> String {
    if value.is_empty() {
        return "''".to_owned();
    }

    format!("'{}'", value.replace('\'', "'\"'\"'"))
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::fs;
    use std::io::Write;
    use tempfile::{tempdir, NamedTempFile};

    fn request(input: &Path, output: &Path, mode: ConversionMode) -> ConversionRequest {
        ConversionRequest {
            mode,
            input_path: input.to_path_buf(),
            output_path: output.to_path_buf(),
            audio_format: AudioFormat::Mp3,
            video_format: VideoFormat::Mp4,
            quality: QualityPreset::Balanced,
            overwrite: true,
        }
    }

    #[cfg(unix)]
    fn executable_script(directory: &Path, name: &str, body: &str) -> PathBuf {
        use std::os::unix::fs::PermissionsExt;

        let path = directory.join(name);
        fs::write(&path, format!("#!/bin/sh\n{body}\n")).expect("write script");
        let mut permissions = fs::metadata(&path).expect("script metadata").permissions();
        permissions.set_mode(0o755);
        fs::set_permissions(&path, permissions).expect("make script executable");
        path
    }

    fn terminal_outcome(job: &ConversionJob) -> ConversionOutcome {
        loop {
            let event = job
                .recv_timeout(Duration::from_secs(2))
                .expect("conversion event");
            if let ConversionEvent::Finished(outcome) = event {
                return outcome;
            }
        }
    }

    #[test]
    fn infers_routes_without_accessing_the_filesystem() {
        assert_eq!(
            infer_route(Path::new("song.WAV"), Path::new("song.flac")),
            Ok(ConversionRoute::TranscodeAudio(AudioFormat::Flac))
        );
        assert_eq!(
            infer_route(Path::new("clip.mp4"), Path::new("clip.opus")),
            Ok(ConversionRoute::ExtractAudio(AudioFormat::Opus))
        );
        assert_eq!(
            infer_route(Path::new("clip.mkv"), Path::new("clip.WEBM")),
            Ok(ConversionRoute::TranscodeVideo(VideoFormat::Webm))
        );
    }

    #[test]
    fn infers_every_selectable_output_format() {
        for format in AudioFormat::ALL {
            let output = PathBuf::from(format!("output.{}", format.extension()));
            assert_eq!(
                infer_route(Path::new("song.wav"), &output),
                Ok(ConversionRoute::TranscodeAudio(format))
            );
            assert_eq!(
                infer_route(Path::new("clip.mp4"), &output),
                Ok(ConversionRoute::ExtractAudio(format))
            );
        }

        for format in VideoFormat::ALL {
            let output = PathBuf::from(format!("output.{}", format.extension()));
            assert_eq!(
                infer_route(Path::new("clip.mp4"), &output),
                Ok(ConversionRoute::TranscodeVideo(format))
            );
        }
    }

    #[test]
    fn route_inference_rejects_unsupported_pairs_and_extensions() {
        assert_eq!(
            infer_route(Path::new("song.wav"), Path::new("song.mp4")),
            Err(RouteInferenceError::AudioToVideo)
        );
        assert!(matches!(
            infer_route(Path::new("notes.txt"), Path::new("notes.mp3")),
            Err(RouteInferenceError::UnsupportedInput(_))
        ));
        assert!(matches!(
            infer_route(Path::new("song.wav"), Path::new("song.aac")),
            Err(RouteInferenceError::UnsupportedOutput(_))
        ));
    }

    #[test]
    fn inferred_request_uses_embedding_defaults() {
        let request = request_from_paths("clip.mp4", "clip.flac").expect("infer request");

        assert_eq!(request.mode, ConversionMode::ExtractAudio);
        assert_eq!(request.audio_format, AudioFormat::Flac);
        assert_eq!(request.video_format, VideoFormat::Mp4);
        assert_eq!(request.quality, QualityPreset::Balanced);
        assert!(!request.overwrite);
    }

    #[cfg(unix)]
    #[test]
    fn tool_checks_report_available_missing_and_timed_out_programs() {
        let directory = tempdir().expect("temp dir");
        let available = executable_script(directory.path(), "available", "exit 0");
        let slow = executable_script(directory.path(), "slow", "sleep 5");
        let missing = directory.path().join("missing");

        let available_tools = Converter::with_programs(&available, &available).check_tools();
        assert!(available_tools.conversion_ready());
        assert!(available_tools.duration_progress_available());

        let unavailable_tools = Converter::with_programs(&missing, &slow)
            .with_tool_check_timeout(Duration::from_millis(100))
            .check_tools();
        assert!(matches!(
            unavailable_tools.ffmpeg(),
            ToolStatus::Unavailable(_)
        ));
        assert_eq!(unavailable_tools.ffprobe(), &ToolStatus::TimedOut);
    }

    #[cfg(unix)]
    #[test]
    fn spawned_conversion_returns_immediately_and_cancels_during_probe() {
        let directory = tempdir().expect("temp dir");
        let input = directory.path().join("clip.mp4");
        let output = directory.path().join("clip.mp3");
        fs::write(&input, "fake video").expect("write input");
        let ffmpeg = executable_script(directory.path(), "ffmpeg", "exit 0");
        let ffprobe = executable_script(directory.path(), "ffprobe", "sleep 5");
        let request = request(&input, &output, ConversionMode::ExtractAudio);
        let converter =
            Converter::with_programs(ffmpeg, ffprobe).with_probe_timeout(Duration::from_secs(5));

        let started = Instant::now();
        let job = converter.spawn(request);
        assert!(started.elapsed() < Duration::from_millis(250));
        assert_eq!(job.input_path(), input);
        assert_eq!(job.output_path(), output);
        thread::sleep(Duration::from_millis(80));
        job.cancel();

        assert_eq!(terminal_outcome(&job), ConversionOutcome::Cancelled);
    }

    #[cfg(unix)]
    #[test]
    fn spawned_conversion_cancels_running_ffmpeg() {
        let directory = tempdir().expect("temp dir");
        let input = directory.path().join("clip.mp4");
        let output = directory.path().join("clip.mp3");
        fs::write(&input, "fake video").expect("write input");
        let ffprobe = executable_script(directory.path(), "ffprobe", "printf '10.0\\n'");
        let ffmpeg = executable_script(
            directory.path(),
            "ffmpeg",
            "printf 'out_time_us=1000000\\n'\nsleep 5",
        );
        let request = request(&input, &output, ConversionMode::ExtractAudio);
        let job = Converter::with_programs(ffmpeg, ffprobe).spawn(request);

        loop {
            if matches!(
                job.recv_timeout(Duration::from_secs(2))
                    .expect("conversion event"),
                ConversionEvent::Started(_)
            ) {
                break;
            }
        }
        job.cancel();

        assert_eq!(terminal_outcome(&job), ConversionOutcome::Cancelled);
    }

    #[cfg(unix)]
    #[test]
    fn missing_ffprobe_still_reports_timestamp_progress() {
        let directory = tempdir().expect("temp dir");
        let input = directory.path().join("clip.mp4");
        let output = directory.path().join("clip.mp3");
        fs::write(&input, "fake video").expect("write input");
        let ffmpeg = executable_script(
            directory.path(),
            "ffmpeg",
            "printf 'out_time_us=1250000\\n'",
        );
        let request = request(&input, &output, ConversionMode::ExtractAudio);
        let job = Converter::with_programs(ffmpeg, directory.path().join("missing")).spawn(request);
        let mut progress = None;

        loop {
            match job
                .recv_timeout(Duration::from_secs(2))
                .expect("conversion event")
            {
                ConversionEvent::Progress {
                    current_seconds,
                    total_seconds,
                } => progress = Some((current_seconds, total_seconds)),
                ConversionEvent::Finished(outcome) => {
                    assert_eq!(outcome, ConversionOutcome::Succeeded);
                    break;
                }
                _ => {}
            }
        }

        assert_eq!(progress, Some((1.25, None)));
    }

    #[cfg(unix)]
    #[test]
    fn embedded_runner_preserves_non_utf8_paths() {
        use std::os::unix::ffi::OsStringExt;

        let directory = tempdir().expect("temp dir");
        let input = directory
            .path()
            .join(OsString::from_vec(b"clip-\xff.mp4".to_vec()));
        let output = directory
            .path()
            .join(OsString::from_vec(b"clip-\xfe.mp3".to_vec()));
        fs::write(&input, "fake video").expect("write input");
        let ffmpeg = executable_script(
            directory.path(),
            "ffmpeg",
            "for arg in \"$@\"; do last=$arg; done\nprintf converted > \"$last\"",
        );
        let request = request(&input, &output, ConversionMode::ExtractAudio);
        let job = Converter::with_programs(ffmpeg, directory.path().join("missing")).spawn(request);

        assert_eq!(terminal_outcome(&job), ConversionOutcome::Succeeded);
        assert_eq!(
            fs::read_to_string(output).expect("read output"),
            "converted"
        );
    }

    #[test]
    fn quotes_shell_values_safely() {
        assert_eq!(shell_quote(""), "''");
        assert_eq!(shell_quote("clip.mp4"), "'clip.mp4'");
        assert_eq!(
            shell_quote("artist's clip.mp4"),
            "'artist'\"'\"'s clip.mp4'"
        );
    }

    #[test]
    fn suggests_caery_output_name() {
        let path = Path::new("/tmp/source.video.mp4");

        let output = suggest_output_path(
            path,
            ConversionMode::ExtractAudio,
            AudioFormat::Flac,
            VideoFormat::Mp4,
        )
        .expect("suggest output");

        assert_eq!(output, PathBuf::from("/tmp/source.video-caery.flac"));
    }

    #[test]
    fn builds_audio_extraction_command() {
        let mut input = NamedTempFile::with_suffix(".mp4").expect("temp video");
        writeln!(input, "fake video").expect("write temp video");
        let output = input.path().with_file_name("clip-caery.mp3");
        let request = request(input.path(), &output, ConversionMode::ExtractAudio);

        let command = build_command(&request).expect("build command");

        assert_eq!(command.program, "ffmpeg");
        assert!(command.args.contains(&"-vn".to_owned()));
        assert!(command.args.contains(&"libmp3lame".to_owned()));
        assert!(command.args.contains(&output.display().to_string()));
    }

    #[test]
    fn builds_webm_transcode_command() {
        let mut input = NamedTempFile::with_suffix(".mkv").expect("temp video");
        writeln!(input, "fake video").expect("write temp video");
        let output = input.path().with_file_name("clip-caery.webm");
        let mut request = request(input.path(), &output, ConversionMode::TranscodeVideo);
        request.video_format = VideoFormat::Webm;

        let command = build_command(&request).expect("build command");

        assert!(command.args.contains(&"libvpx-vp9".to_owned()));
        assert!(command.args.contains(&"libopus".to_owned()));
        assert!(command.args.contains(&"0:a?".to_owned()));
    }

    #[test]
    fn high_level_conversion_rejects_invalid_requests_before_spawning() {
        let request = ConversionRequest {
            mode: ConversionMode::ExtractAudio,
            input_path: PathBuf::new(),
            output_path: PathBuf::from("output.mp3"),
            audio_format: AudioFormat::Mp3,
            video_format: VideoFormat::Mp4,
            quality: QualityPreset::Balanced,
            overwrite: false,
        };

        let error = start_conversion(&request).expect_err("reject invalid request");

        assert!(matches!(error, ConversionError::MissingInput));
    }

    #[test]
    fn rejects_existing_output_without_overwrite() {
        let mut input = NamedTempFile::with_suffix(".wav").expect("temp audio");
        writeln!(input, "fake audio").expect("write temp audio");
        let output = NamedTempFile::with_suffix(".mp3").expect("temp output");
        let mut request = request(input.path(), output.path(), ConversionMode::TranscodeAudio);
        request.overwrite = false;

        let error = validate_request(&request).expect_err("reject existing output");

        assert!(matches!(error, ConversionError::OutputExists(_)));
    }

    #[test]
    fn parses_ffmpeg_progress_lines() {
        assert_eq!(
            parse_ffmpeg_progress_seconds("out_time_us=1250000"),
            Some(1.25)
        );
        assert_eq!(
            parse_ffmpeg_progress_seconds("out_time_ms=2500000"),
            Some(2.5)
        );
        assert_eq!(
            parse_ffmpeg_progress_seconds("out_time=00:01:02.500000"),
            Some(62.5)
        );
        assert_eq!(parse_ffmpeg_progress_seconds("frame=20"), None);
    }

    #[test]
    fn labels_duration_progress() {
        assert_eq!(duration_progress_label(30.0, 120.0), "0:30 / 2:00 (25.0%)");
    }

    #[test]
    fn formats_human_sizes() {
        assert_eq!(human_size(0), "0 B");
        assert_eq!(human_size(1024), "1.0 KiB");
        assert_eq!(human_size(4 * 1024 * 1024 * 1024), "4.0 GiB");
    }
}