t-rec 0.9.0-preview2

use std::fs::File;
use std::io::Write;
use std::process::Command;

use anyhow::{Context, Result};
use tempfile::TempDir;

use crate::core::utils::{file_name_for, IMG_EXT};

const FFMPEG_BINARY: &str = "ffmpeg";

#[cfg(target_os = "macos")]
const INST_CMD: &str = "brew install ffmpeg";
#[cfg(target_os = "windows")]
const INST_CMD: &str = "winget install ffmpeg";
#[cfg(not(any(target_os = "macos", target_os = "windows")))]
const INST_CMD: &str = "apt-get install ffmpeg";

/// checks if ffmpeg is available
pub fn check_for_ffmpeg() -> Result<()> {
    let out = Command::new(FFMPEG_BINARY)
        .arg("-version")
        .output()
        .with_context(|| {
            format!("There is an issue with '{FFMPEG_BINARY}', please install: `{INST_CMD}`")
        })?;

    if !String::from_utf8(out.stdout.to_vec())
        .with_context(|| format!("Unable to parse the `{FFMPEG_BINARY} -version`"))?
        .contains("--enable-libx264")
    {
        anyhow::bail!("ffmpeg does not support codec 'libx264', please reinstall with the option '--enable-libx264'")
    }

    Ok(())
}

/// generating the final mp4 with help of ffmpeg
///
/// Uses the concat demuxer rather than `-pattern_type glob` because glob is
/// not compiled into the default Windows ffmpeg builds.
///
/// See https://hamelot.io/visualization/using-ffmpeg-to-convert-a-set-of-images-into-a-video/
pub fn generate_mp4_with_ffmpeg(
    time_codes: &[u128],
    tempdir: &TempDir,
    target: &str,
    fps: u8,
) -> Result<()> {
    println!("🎬 🎉 🚀 Generating {target}");

    let concat_file_path = tempdir.path().join("ffmpeg_concat.txt");
    let mut concat_file =
        File::create(&concat_file_path).context("Failed to create concat file for ffmpeg")?;

    // ffmpeg's concat demuxer wants UTF-8 string paths; fail early rather than
    // silently lossy-converting (the replacement chars would surface later as
    // a confusing "file not found" from ffmpeg).
    let temp_path = tempdir
        .path()
        .to_str()
        .with_context(|| format!("Temp dir path is not valid UTF-8: {:?}", tempdir.path()))?
        .replace('\\', "/");
    for tc in time_codes {
        let frame_name = file_name_for(tc, IMG_EXT);
        let frame_path = format!("{temp_path}/{frame_name}");
        writeln!(concat_file, "file '{}'", frame_path).context("Failed to write to concat file")?;
    }
    concat_file.flush().context("Failed to flush concat file")?;
    drop(concat_file);

    let concat_file_str = concat_file_path
        .to_str()
        .with_context(|| {
            format!(
                "Concat file path is not valid UTF-8: {:?}",
                concat_file_path
            )
        })?
        .replace('\\', "/");

    let output = Command::new(FFMPEG_BINARY)
        .arg("-y")
        .arg("-r")
        .arg(fps.to_string())
        .arg("-f")
        .arg("concat")
        .arg("-safe")
        .arg("0")
        .arg("-i")
        .arg(&concat_file_str)
        .arg("-vcodec")
        .arg("libx264")
        .arg("-pix_fmt")
        .arg("yuv420p")
        // fixes: [libx264 @ 0x7fc216019000] height not divisible by 2 (650x477)
        .arg("-vf")
        .arg("pad='width=ceil(iw/2)*2:height=ceil(ih/2)*2'")
        .arg(target)
        .output()
        .with_context(|| format!("Cannot start '{FFMPEG_BINARY}' to generate the final video"))?;

    if !output.status.success() {
        anyhow::bail!(
            "ffmpeg failed with exit code {:?}\nStderr: {}",
            output.status.code(),
            String::from_utf8_lossy(&output.stderr)
        );
    }

    Ok(())
}