use std::process::Command;

/// Options that ffmpeg supports but ffprobe does not.
const FFMPEG_ONLY_OPTIONS: &[&str] = &["-stream_loop", "-t"];

const ALPHA_FMTS: &[&str] = &[
    "pal8",
    "argb",
    "rgba",
    "abgr",
    "bgra",
    "yuva420p",
    "ya8",
    "yuva422p",
    "yuva444p",
    "yuva420p9be",
    "yuva420p9le",
    "yuva422p9be",
    "yuva422p9le",
    "yuva444p9be",
    "yuva444p9le",
    "yuva420p10be",
    "yuva420p10le",
    "yuva422p10be",
    "yuva422p10le",
    "yuva444p10be",
    "yuva444p10le",
    "yuva420p16be",
    "yuva420p16le",
    "yuva422p16be",
    "yuva422p16le",
    "yuva444p16be",
    "yuva444p16le",
    "rgba64be",
    "rgba64le",
    "bgra64be",
    "bgra64le",
    "ya16be",
    "ya16le",
    "gbrap",
    "gbrap16be",
    "gbrap16le",
    "ayuv64le",
    "ayuv64be",
    "gbrap12be",
    "gbrap12le",
    "gbrap10be",
    "gbrap10le",
    "gbrapf32be",
    "gbrapf32le",
    "yuva422p12be",
    "yuva422p12le",
    "yuva444p12be",
    "yuva444p12le",
    "vuya",
    "rgbaf16be",
    "rgbaf16le",
    "rgbaf32be",
    "rgbaf32le",
    "gbrap14be",
    "gbrap14le",
    "ayuv",
    "uyva",
    "rgba128be",
    "rgba128le",
    "gbrapf16be",
    "gbrapf16le",
    "yaf32be",
    "yaf32le",
    "yaf16be",
    "yaf16le",
    "gbrap32be",
    "gbrap32le",
];

fn filter_probe_args(ff_args: &[String]) -> Vec<String> {
    let mut out = Vec::new();
    let mut skip_next = false;
    for arg in ff_args {
        if skip_next {
            skip_next = false;
            continue;
        }
        if FFMPEG_ONLY_OPTIONS.contains(&arg.as_str()) {
            skip_next = true;
            continue;
        }
        out.push(arg.clone());
    }
    out
}

pub struct VideoInfo {
    pub width: u32,
    pub height: u32,
    pub num_frames: Option<u32>,
    pub fps: f64,
    pub alpha: bool,
    pub codec_tag: String,
}

pub fn probe_video(ff_args: &[String], max_frames: Option<u32>) -> VideoInfo {
    let probe_args = filter_probe_args(ff_args);
    let output = Command::new("ffprobe")
        .args(["-v", "error"])
        .args(["-select_streams", "v:0"])
        .args([
            "-show_entries",
            "stream=codec_tag_string,width,height,pix_fmt,r_frame_rate,nb_frames",
        ])
        .args(["-of", "csv=p=0"])
        .args(&probe_args)
        .output()
        .expect("failed to run ffprobe");

    if !output.status.success() {
        let stderr = String::from_utf8_lossy(&output.stderr);
        panic!("ffprobe failed: {stderr}");
    }

    let stdout = String::from_utf8_lossy(&output.stdout);
    let line = stdout.trim();
    let parts: Vec<&str> = line.split(',').collect();
    if parts.len() != 6 {
        panic!("unexpected ffprobe output: {line}");
    }

    let codec_tag = parts[0].to_string();
    let width: u32 = parts[1].parse().expect("parse width");
    let height: u32 = parts[2].parse().expect("parse height");
    let alpha = ALPHA_FMTS.contains(&parts[3]);

    let fps: f64 = if let Some((num, den)) = parts[4].split_once('/') {
        let n: f64 = num.parse().expect("parse fps numerator");
        let d: f64 = den.parse().expect("parse fps denominator");
        n / d
    } else {
        parts[4].parse().expect("parse fps")
    };
    let num_frames = parts[5].parse().ok().or(max_frames);

    VideoInfo {
        width,
        height,
        num_frames,
        fps,
        alpha,
        codec_tag,
    }
}