Research-Stack/5-Applications/audio-dsp/src/io/flac_input.rs

use crate::io::{Input, Timestamp, Result, SurfaceError};
use std::fs::File;
use std::path::Path;

pub struct FlacInput {
    // Simplified implementation - would use symphonia in production
    file: File,
    sample_rate: u32,
    channels: usize,
    current_time_us: u64,
    samples_per_us: f64,
    buffer: Vec<f32>,
    buffer_pos: usize,
}

impl FlacInput {
    pub fn open(path: &Path) -> Result<Self> {
        let file = File::open(path)?;

        // In production, use symphonia to read headers
        // For archive, stub with default values
        let sample_rate = 48000;
        let channels = 2;

        Ok(Self {
            file,
            sample_rate,
            channels,
            current_time_us: 0,
            samples_per_us: sample_rate as f64 / 1_000_000.0,
            buffer: Vec::new(),
            buffer_pos: 0,
        })
    }
}

impl Input for FlacInput {
    fn next_chunk(&mut self, buf: &mut [f32]) -> Result<Option<(usize, Timestamp)>> {
        // Production implementation would:
        // 1. Use symphonia to decode FLAC packets
        // 2. Convert i32 samples to f32
        // 3. Handle interleaved channels
        // 4. Manage buffering

        // Stub implementation for compilation
        if self.buffer_pos >= self.buffer.len() {
            // Would read next packet here
            return Ok(None);
        }

        let n = (self.buffer.len() - self.buffer_pos).min(buf.len());
        buf[..n].copy_from_slice(&self.buffer[self.buffer_pos..self.buffer_pos + n]);
        self.buffer_pos += n;

        let timestamp = self.current_time_us;
        self.current_time_us += (n as f64 / self.samples_per_us) as u64;

        Ok(Some((n, timestamp)))
    }

    fn sample_rate(&self) -> f32 { self.sample_rate as f32 }
    fn channels(&self) -> usize { self.channels }
}