//! Silence operations: insert silence at a position or remove a range of silence.

use crate::error::CoreError;

/// Insert silence (zeros) at the given frame position for the specified duration.
///
/// Operates on interleaved sample data. Positions are in frame units.
pub fn apply_insert_silence(
    samples: &mut Vec<f32>,
    channels: u16,
    start_frame: usize,
    duration_frames: usize,
) -> Result<(), CoreError> {
    let ch = channels as usize;
    if ch == 0 {
        return Err(CoreError::Internal("insert_silence: channels must be > 0".to_string()));
    }
    let total_frames = samples.len() / ch;

    if start_frame > total_frames {
        return Err(CoreError::Internal(format!(
            "insert_silence: start_frame ({start_frame}) exceeds total frames ({total_frames})"
        )));
    }
    if duration_frames == 0 {
        return Ok(());
    }

    let insert_at = start_frame * ch;
    let insert_count = duration_frames * ch;
    samples.splice(insert_at..insert_at, std::iter::repeat_n(0.0f32, insert_count));
    Ok(())
}

/// Remove a range of samples (typically silence) between two frame positions.
///
/// Operates on interleaved sample data. `start_frame` inclusive, `end_frame` exclusive.
pub fn apply_remove_range(
    samples: &mut Vec<f32>,
    channels: u16,
    start_frame: usize,
    end_frame: usize,
) -> Result<(), CoreError> {
    let ch = channels as usize;
    if ch == 0 {
        return Err(CoreError::Internal("remove_range: channels must be > 0".to_string()));
    }
    let total_frames = samples.len() / ch;

    if start_frame >= end_frame {
        return Err(CoreError::Internal(
            "remove_range: start_frame must be less than end_frame".to_string(),
        ));
    }
    if end_frame > total_frames {
        return Err(CoreError::Internal(format!(
            "remove_range: end_frame ({end_frame}) exceeds total frames ({total_frames})"
        )));
    }

    let start_sample = start_frame * ch;
    let end_sample = end_frame * ch;
    samples.drain(start_sample..end_sample);
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn insert_silence_mono_middle() {
        let mut samples = vec![1.0, 2.0, 3.0];
        apply_insert_silence(&mut samples, 1, 1, 2).unwrap();
        assert_eq!(samples, vec![1.0, 0.0, 0.0, 2.0, 3.0]);
    }

    #[test]
    fn insert_silence_stereo_start() {
        let mut samples = vec![1.0, 2.0, 3.0, 4.0]; // 2 frames stereo
        apply_insert_silence(&mut samples, 2, 0, 1).unwrap();
        assert_eq!(samples, vec![0.0, 0.0, 1.0, 2.0, 3.0, 4.0]);
    }

    #[test]
    fn insert_silence_at_end() {
        let mut samples = vec![1.0, 2.0, 3.0];
        apply_insert_silence(&mut samples, 1, 3, 2).unwrap();
        assert_eq!(samples, vec![1.0, 2.0, 3.0, 0.0, 0.0]);
    }

    #[test]
    fn insert_silence_zero_duration_noop() {
        let mut samples = vec![1.0, 2.0, 3.0];
        apply_insert_silence(&mut samples, 1, 1, 0).unwrap();
        assert_eq!(samples, vec![1.0, 2.0, 3.0]);
    }

    #[test]
    fn insert_silence_out_of_bounds() {
        let mut samples = vec![1.0, 2.0, 3.0];
        assert!(apply_insert_silence(&mut samples, 1, 10, 1).is_err());
    }

    #[test]
    fn remove_range_mono() {
        let mut samples = vec![1.0, 0.0, 0.0, 2.0, 3.0];
        apply_remove_range(&mut samples, 1, 1, 3).unwrap();
        assert_eq!(samples, vec![1.0, 2.0, 3.0]);
    }

    #[test]
    fn remove_range_stereo() {
        let mut samples = vec![1.0, 2.0, 0.0, 0.0, 3.0, 4.0]; // 3 stereo frames
        apply_remove_range(&mut samples, 2, 1, 2).unwrap();
        assert_eq!(samples, vec![1.0, 2.0, 3.0, 4.0]);
    }

    #[test]
    fn remove_range_invalid() {
        let mut samples = vec![1.0, 2.0, 3.0];
        assert!(apply_remove_range(&mut samples, 1, 2, 1).is_err());
    }

    #[test]
    fn remove_range_out_of_bounds() {
        let mut samples = vec![1.0, 2.0, 3.0];
        assert!(apply_remove_range(&mut samples, 1, 0, 10).is_err());
    }
}