sevensense-api 0.1.0

//! Audio processing service.
//!
//! This module provides the `AudioPipeline` service for loading and
//! segmenting audio recordings.

use thiserror::Error;

use super::{Audio, Segment};

/// Audio processing error.
#[derive(Debug, Error)]
pub enum AudioError {
    /// Invalid audio format
    #[error("Invalid audio format: {0}")]
    InvalidFormat(String),

    /// Decoding error
    #[error("Failed to decode audio: {0}")]
    DecodingError(String),

    /// IO error
    #[error("IO error: {0}")]
    Io(#[from] std::io::Error),

    /// Unsupported sample rate
    #[error("Unsupported sample rate: {0}")]
    UnsupportedSampleRate(u32),

    /// Empty audio
    #[error("Audio file is empty or too short")]
    EmptyAudio,
}

/// Audio pipeline configuration.
#[derive(Debug, Clone)]
pub struct AudioPipelineConfig {
    /// Target sample rate for processing
    pub target_sample_rate: u32,
    /// Minimum segment duration in seconds
    pub min_segment_duration: f64,
    /// Maximum segment duration in seconds
    pub max_segment_duration: f64,
    /// Energy threshold for segmentation
    pub energy_threshold: f32,
}

impl Default for AudioPipelineConfig {
    fn default() -> Self {
        Self {
            target_sample_rate: 32000,
            min_segment_duration: 0.5,
            max_segment_duration: 10.0,
            energy_threshold: 0.01,
        }
    }
}

/// Audio processing pipeline.
///
/// Handles audio loading, resampling, and segmentation.
pub struct AudioPipeline {
    config: AudioPipelineConfig,
}

impl AudioPipeline {
    /// Create a new audio pipeline with the given configuration.
    pub fn new(config: AudioPipelineConfig) -> Result<Self, AudioError> {
        Ok(Self { config })
    }

    /// Get metadata from audio data without full decoding.
    pub fn get_metadata(&self, data: &[u8]) -> Result<(f64, u32, u16), AudioError> {
        // In a real implementation, this would parse the audio header
        // For now, return reasonable defaults
        if data.len() < 44 {
            return Err(AudioError::EmptyAudio);
        }

        // Parse WAV header (simplified)
        // Real implementation would use symphonia or hound
        let sample_rate = 44100u32;
        let channels = 1u16;
        let duration = data.len() as f64 / (sample_rate as f64 * channels as f64 * 2.0);

        Ok((duration, sample_rate, channels))
    }

    /// Load audio from raw bytes.
    pub fn load_audio(&self, data: &[u8]) -> Result<Audio, AudioError> {
        if data.is_empty() {
            return Err(AudioError::EmptyAudio);
        }

        // In a real implementation, this would:
        // 1. Detect format (WAV, FLAC, MP3, etc.)
        // 2. Decode to samples
        // 3. Convert to mono if stereo
        // 4. Resample to target rate
        // 5. Normalize to -1.0 to 1.0

        let (duration, _sample_rate, _) = self.get_metadata(data)?;

        // Generate placeholder samples
        let num_samples = (duration * self.config.target_sample_rate as f64) as usize;
        let samples = vec![0.0f32; num_samples];

        Ok(Audio {
            samples,
            sample_rate: self.config.target_sample_rate,
            duration_secs: duration,
        })
    }

    /// Segment audio into individual calls/vocalizations.
    pub fn segment(&self, _audio: &Audio) -> Result<Vec<Segment>, AudioError> {
        // In a real implementation, this would:
        // 1. Compute spectrogram
        // 2. Detect energy regions above threshold
        // 3. Apply minimum/maximum duration constraints
        // 4. Extract segment audio

        // For now, return empty segments (placeholder)
        Ok(vec![])
    }

    /// Get the target sample rate.
    #[must_use]
    pub fn target_sample_rate(&self) -> u32 {
        self.config.target_sample_rate
    }
}

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

    #[test]
    fn test_audio_pipeline_creation() {
        let pipeline = AudioPipeline::new(Default::default());
        assert!(pipeline.is_ok());
    }

    #[test]
    fn test_empty_audio_error() {
        let pipeline = AudioPipeline::new(Default::default()).unwrap();
        let result = pipeline.load_audio(&[]);
        assert!(matches!(result, Err(AudioError::EmptyAudio)));
    }
}