rust_highlight/src/lib.rs

use pyo3::prelude::*;
use std::process::Command;
use std::path::Path;

#[pyfunction]
fn render_video(
    id: usize,
    image_path: String,
    audio_path: String,
    duration: f64,
    words: Vec<(String, (u32, u32, u32, u32))>,
    output_dir: String,
) -> PyResult<String> {
    // Validate paths
    if !Path::new(&image_path).exists() {
        return Err(pyo3::exceptions::PyFileNotFoundError::new_err(format!(
            "Image not found: {}",
            image_path
        )));
    }
    if !Path::new(&audio_path).exists() {
        return Err(pyo3::exceptions::PyFileNotFoundError::new_err(format!(
            "Audio not found: {}",
            audio_path
        )));
    }

    let output_path = format!("{}/clip{}.mp4", output_dir, id);
    let duration_str = duration.to_string();
    let n_words = words.len() as f64;
    let highlight_duration = duration / n_words;

    // Build filter graph
    let mut filters = vec![];
    for (i, (_, (x, y, w, h))) in words.iter().enumerate() {
        let start = i as f64 * highlight_duration;
        let end = start + highlight_duration;
        filters.push(format!(
            "drawbox=x={x}:y={y}:w={w}:h={h}:color=yellow@0.5:t=fill:enable='between(t,{start:.2},{end:.2})'"
        ));
    }

    let filter_chain = filters.join(",");

    // FFmpeg command
    let status = Command::new("ffmpeg")
        .args(&[
            "-y",
            "-loop", "1",
            "-i", &image_path,
            "-i", &audio_path,
            "-vf", &filter_chain,
            "-c:v", "libx264",
            "-preset", "fast",
            "-crf", "18",
            "-pix_fmt", "yuv420p",
            "-movflags", "+faststart",
            "-c:a", "aac",
            "-b:a", "192k",
            "-r", "60",
            "-fps_mode", "vfr",  // Replaces deprecated -vsync
            "-t", &duration_str,
            &output_path,
        ])
        .status();

    match status {
        Ok(exit_status) if exit_status.success() => Ok(output_path),
        Ok(_) => Err(pyo3::exceptions::PyRuntimeError::new_err(
            "FFmpeg command failed. Check filter syntax.",
        )),
        Err(e) => Err(pyo3::exceptions::PyRuntimeError::new_err(format!(
            "Failed to execute FFmpeg: {}",
            e
        ))),
    }
}

#[pymodule]
fn rust_highlight(_py: Python, m: &PyModule) -> PyResult<()> {
    m.add_function(wrap_pyfunction!(render_video, m)?)?;
    Ok(())
}