Psychotoxical-psysonic/src-tauri/src/audio/decode.rs

//! Symphonia `SizedDecoder`, gapless trim, and `build_source` / `build_streaming_source`.
use std::io::{Cursor, Read, Seek};
use std::sync::atomic::{AtomicBool, AtomicU32, AtomicU64};
use std::sync::Arc;
use std::time::Duration;

use rodio::source::UniformSourceIterator;
use rodio::Source;
use symphonia::core::{
    audio::{AudioBufferRef, SampleBuffer, SignalSpec},
    codecs::{DecoderOptions, CODEC_TYPE_NULL},
    formats::{FormatOptions, FormatReader, SeekMode, SeekTo},
    io::{MediaSource, MediaSourceStream, MediaSourceStreamOptions},
    meta::MetadataOptions,
    probe::Hint,
    units::{self, Time},
};

use super::codec::{psysonic_codec_registry, try_make_radio_decoder};
use super::sources::*;

// ─── SizedCursorSource — correct byte_len for seekable in-memory sources ──────
//
// rodio's internal ReadSeekSource wraps Cursor<Vec<u8>> but hardcodes
// byte_len() → None.  This tells symphonia "stream length unknown", which
// prevents the FLAC demuxer from seeking (it validates seek offsets against
// the total stream length from byte_len).  MP3 is unaffected because its
// demuxer uses Xing/LAME headers instead.
//
// This wrapper provides the actual byte length, fixing seek for all formats.

pub(crate) struct SizedCursorSource {
    inner: Cursor<Vec<u8>>,
    len: u64,
}

impl Read for SizedCursorSource {
    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
        self.inner.read(buf)
    }
}

impl Seek for SizedCursorSource {
    fn seek(&mut self, pos: std::io::SeekFrom) -> std::io::Result<u64> {
        self.inner.seek(pos)
    }
}

impl MediaSource for SizedCursorSource {
    fn is_seekable(&self) -> bool { true }
    fn byte_len(&self) -> Option<u64> { Some(self.len) }
}

// ─── SizedDecoder — symphonia decoder with correct byte_len ───────────────────
//
// Replaces rodio::Decoder::new() which wraps the source in ReadSeekSource
// (byte_len = None).  This constructs the symphonia pipeline directly,
// providing the correct byte_len via SizedCursorSource.
//
// Implements Iterator<Item = i16> + Source — identical interface to
// rodio::Decoder, so the rest of the source chain is unchanged.

/// Debug logging: codec parameters in human-readable form to verify whether
/// playback is genuinely lossless.
pub(crate) fn log_codec_resolution(
    tag: &str,
    params: &symphonia::core::codecs::CodecParameters,
    container_hint: Option<&str>,
) {
    let codec_name = symphonia::default::get_codecs()
        .get_codec(params.codec)
        .map(|d| d.short_name)
        .unwrap_or("?");
    let rate = params.sample_rate.map(|r| format!("{} Hz", r)).unwrap_or_else(|| "? Hz".into());
    let bits = params.bits_per_sample
        .or(params.bits_per_coded_sample)
        .map(|b| format!("{}-bit", b))
        .unwrap_or_else(|| "?-bit".into());
    let ch = params.channels
        .map(|c| format!("{}ch", c.count()))
        .unwrap_or_else(|| "?ch".into());
    let lossless = codec_name.starts_with("pcm")
        || matches!(
            codec_name,
            "flac" | "alac" | "wavpack" | "monkeys-audio" | "tta" | "shorten"
        );
    let kind = if lossless { "LOSSLESS" } else { "lossy" };
    crate::app_deprintln!(
        "[stream] {tag}: codec={codec_name} ({kind}) {bits} {rate} {ch} container={}",
        container_hint.unwrap_or("?")
    );
}

/// Max retries for IO/packet-read errors (fatal — network drop, truncated file).
const DECODE_MAX_RETRIES: usize = 3;
/// Max *consecutive* DecodeErrors before giving up on a file.
/// Non-fatal errors like "invalid main_data offset" are silently dropped up to
/// this limit so a handful of corrupt MP3 frames never aborts an otherwise
/// playable track (VLC-style frame dropping).
const MAX_CONSECUTIVE_DECODE_ERRORS: usize = 100;

pub(crate) struct SizedDecoder {
    decoder: Box<dyn symphonia::core::codecs::Decoder>,
    current_frame_offset: usize,
    format: Box<dyn FormatReader>,
    total_duration: Option<Time>,
    buffer: SampleBuffer<i16>,
    spec: SignalSpec,
    /// Counts consecutive DecodeErrors in the hot-path. Reset to 0 on every
    /// successfully decoded frame. Used to detect fully undecodable streams.
    consecutive_decode_errors: usize,
}

impl SizedDecoder {
    pub(crate) fn new(data: Vec<u8>, format_hint: Option<&str>, hi_res: bool) -> Result<Self, String> {
        let data_len = data.len() as u64;
        let source = SizedCursorSource {
            inner: Cursor::new(data),
            len: data_len,
        };
        // Hi-Res: 4 MB read-ahead so Symphonia demuxes fewer Read calls for
        // high-bitrate files (88.2 kHz/24-bit FLAC ≈ 1800 kbps).
        // Standard: 512 KB is plenty for MP3/AAC — larger buffers waste allocation
        // and compete with the playback thread at track start.
        let buf_len = if hi_res { 4 * 1024 * 1024 } else { 512 * 1024 };
        let mss = MediaSourceStream::new(
            Box::new(source) as Box<dyn MediaSource>,
            MediaSourceStreamOptions { buffer_len: buf_len },
        );

        let mut hint = Hint::new();
        if let Some(ext) = format_hint {
            hint.with_extension(ext);
        }
        let format_opts = FormatOptions {
            // Disable gapless parsing — Symphonia 0.5.5 crashes on `edts` atoms
            // present in older iTunes-purchased M4A files.
            enable_gapless: false,
            ..Default::default()
        };

        let meta_opts = symphonia::core::meta::MetadataOptions {
            // Cap embedded cover art at 8 MiB so oversized MJPEG images in
            // iTunes M4A files don't choke the parser.
            limit_visual_bytes: symphonia::core::meta::Limit::Maximum(8 * 1024 * 1024),
            ..Default::default()
        };

        let probed = symphonia::default::get_probe()
            .format(&hint, mss, &format_opts, &meta_opts)
            .map_err(|e| {
                let hint_str = format_hint.unwrap_or("unknown");
                // Always print the raw Symphonia error to the terminal for diagnosis.
                crate::app_eprintln!("[psysonic] probe failed (hint={hint_str}): {e}");
                if e.to_string().to_lowercase().contains("unsupported") {
                    format!("unsupported format: .{hint_str} files cannot be played (no demuxer)")
                } else {
                    format!("could not open audio stream (.{hint_str}): {e}")
                }
            })?;

        let track = probed.format
            .tracks()
            .iter()
            // Explicitly select only audio tracks: must have a valid codec and a
            // sample_rate. This skips MJPEG cover-art streams that iTunes M4A
            // files embed as a secondary video track.
            .find(|t| {
                t.codec_params.codec != CODEC_TYPE_NULL
                    && t.codec_params.sample_rate.is_some()
            })
            .ok_or_else(|| {
                crate::app_eprintln!("[psysonic] no audio track found among {} tracks", probed.format.tracks().len());
                "no playable audio track found in file".to_string()
            })?;

        let track_id = track.id;
        let total_duration = track.codec_params.time_base
            .zip(track.codec_params.n_frames)
            .map(|(base, frames)| base.calc_time(frames));

        log_codec_resolution("bytes", &track.codec_params, format_hint);

        let mut decoder = psysonic_codec_registry()
            .make(&track.codec_params, &DecoderOptions::default())
            .map_err(|e| {
                crate::app_eprintln!("[psysonic] codec init failed: {e}");
                if e.to_string().to_lowercase().contains("unsupported") {
                    "unsupported codec: no decoder available for this audio format".to_string()
                } else {
                    format!("failed to initialise audio decoder: {e}")
                }
            })?;

        let mut format = probed.format;

        // Decode the first packet to initialise spec + buffer.
        // DecodeErrors (e.g. "invalid main_data offset") are non-fatal: drop the
        // frame and try the next packet up to MAX_CONSECUTIVE_DECODE_ERRORS times.
        let mut decode_errors: usize = 0;
        let decoded = loop {
            let packet = match format.next_packet() {
                Ok(p) => p,
                Err(symphonia::core::errors::Error::IoError(_)) => {
                    break decoder.last_decoded();
                }
                Err(e) => {
                    crate::app_eprintln!("[psysonic] next_packet error: {e}");
                    return Err(format!("could not read audio data: {e}"));
                }
            };
            if packet.track_id() != track_id {
                crate::app_eprintln!("[psysonic] skipping packet for track {} (want {})", packet.track_id(), track_id);
                continue;
            }
            match decoder.decode(&packet) {
                Ok(decoded) => break decoded,
                Err(symphonia::core::errors::Error::DecodeError(ref msg)) => {
                    decode_errors += 1;
                    crate::app_eprintln!("[psysonic] init: dropped corrupt frame #{decode_errors}: {msg}");
                    if decode_errors >= MAX_CONSECUTIVE_DECODE_ERRORS {
                        return Err("too many consecutive decode errors during init — file may be corrupt".into());
                    }
                }
                Err(e) => {
                    crate::app_eprintln!("[psysonic] fatal decode error: {e}");
                    return Err(format!("audio decode error: {e}"));
                }
            }
        };

        let spec = decoded.spec().to_owned();
        let buffer = Self::make_buffer(decoded, &spec);

        Ok(SizedDecoder {
            decoder,
            current_frame_offset: 0,
            format,
            total_duration,
            buffer,
            spec,
            consecutive_decode_errors: 0,
        })
    }

    /// Build a decoder from any `MediaSource` (e.g. track-stream or radio).
    /// Uses `enable_gapless: false` — live streams are not seekable; gapless
    /// trimming requires seeking to read the LAME/iTunSMPB end-padding info.
    pub(crate) fn new_streaming(
        media: Box<dyn MediaSource>,
        format_hint: Option<&str>,
        source_tag: &str,
    ) -> Result<Self, String> {
        // Larger read-ahead buffer for the live streaming SPSC consumer — reduces
        // read() call frequency into the ring buffer, easing I/O spikes.
        let mss = MediaSourceStream::new(media, MediaSourceStreamOptions { buffer_len: 512 * 1024 });
        let mut hint = Hint::new();
        if let Some(ext) = format_hint { hint.with_extension(ext); }
        let format_opts = FormatOptions { enable_gapless: false, ..Default::default() };
        let probed = symphonia::default::get_probe()
            .format(&hint, mss, &format_opts, &MetadataOptions::default())
            .map_err(|e| format!("{source_tag}: format probe failed: {e}"))?;

        let track = probed.format.tracks().iter()
            .find(|t| t.codec_params.codec != CODEC_TYPE_NULL)
            .ok_or_else(|| format!("{source_tag}: no audio track found"))?;
        let track_id = track.id;
        log_codec_resolution(source_tag, &track.codec_params, format_hint);
        // Live streams have no known total frame count → total_duration = None.
        let total_duration = None;
        let mut decoder = try_make_radio_decoder(&track.codec_params, &DecoderOptions::default())
            .map_err(|e| format!("{source_tag}: codec init failed: {e}"))?;
        let mut format = probed.format;

        let mut errors = 0usize;
        let decoded = loop {
            let packet = match format.next_packet() {
                Ok(p) => p,
                Err(_) => break decoder.last_decoded(),
            };
            if packet.track_id() != track_id { continue; }
            match decoder.decode(&packet) {
                Ok(d) => break d,
                Err(symphonia::core::errors::Error::DecodeError(ref msg)) => {
                    errors += 1;
                    crate::app_eprintln!("[psysonic] {source_tag} init: dropped corrupt frame #{errors}: {msg}");
                    if errors >= MAX_CONSECUTIVE_DECODE_ERRORS {
                        return Err(format!("{source_tag}: too many consecutive decode errors"));
                    }
                }
                Err(e) => return Err(format!("{source_tag}: decode error: {e}")),
            }
        };
        let spec = decoded.spec().to_owned();
        let buffer = Self::make_buffer(decoded, &spec);
        Ok(SizedDecoder { decoder, current_frame_offset: 0, format, total_duration, buffer, spec, consecutive_decode_errors: 0 })
    }

    #[inline]
    fn make_buffer(decoded: AudioBufferRef, spec: &SignalSpec) -> SampleBuffer<i16> {
        let duration = units::Duration::from(decoded.capacity() as u64);
        let mut buffer = SampleBuffer::<i16>::new(duration, *spec);
        buffer.copy_interleaved_ref(decoded);
        buffer
    }

    /// Refine position after a coarse seek — decode packets until we reach the
    /// exact requested timestamp.
    fn refine_position(
        &mut self,
        seek_res: symphonia::core::formats::SeekedTo,
    ) -> Result<(), String> {
        let mut samples_to_pass = seek_res.required_ts - seek_res.actual_ts;
        let packet = loop {
            let candidate = self.format.next_packet()
                .map_err(|e| format!("refine seek: {e}"))?;
            if candidate.dur() > samples_to_pass {
                break candidate;
            }
            samples_to_pass -= candidate.dur();
        };

        let mut decoded = self.decoder.decode(&packet);
        for _ in 0..DECODE_MAX_RETRIES {
            if decoded.is_err() {
                let p = self.format.next_packet()
                    .map_err(|e| format!("refine retry: {e}"))?;
                decoded = self.decoder.decode(&p);
            }
        }

        let decoded = decoded.map_err(|e| format!("refine decode: {e}"))?;
        decoded.spec().clone_into(&mut self.spec);
        self.buffer = Self::make_buffer(decoded, &self.spec);
        self.current_frame_offset = samples_to_pass as usize * self.spec.channels.count();
        Ok(())
    }
}

impl Iterator for SizedDecoder {
    type Item = i16;

    #[inline]
    fn next(&mut self) -> Option<i16> {
        if self.current_frame_offset >= self.buffer.len() {
            // Loop until a decodable packet is found or the stream ends.
            // DecodeErrors (e.g. MP3 "invalid main_data offset") are non-fatal:
            // drop the frame and advance to the next packet. IO errors and a
            // clean end-of-stream both terminate the iterator normally.
            loop {
                let packet = self.format.next_packet().ok()?;
                match self.decoder.decode(&packet) {
                    Ok(decoded) => {
                        self.consecutive_decode_errors = 0;
                        decoded.spec().clone_into(&mut self.spec);
                        self.buffer = Self::make_buffer(decoded, &self.spec);
                        self.current_frame_offset = 0;
                        break;
                    }
                    Err(symphonia::core::errors::Error::DecodeError(ref msg)) => {
                        #[cfg(not(debug_assertions))]
                        let _ = msg;
                        self.consecutive_decode_errors += 1;
                        // Log sparingly: first drop, then every 10th to avoid spam.
                        if self.consecutive_decode_errors == 1
                            || self.consecutive_decode_errors % 10 == 0
                        {
                            crate::app_deprintln!(
                                "[psysonic] dropped corrupt frame #{}: {msg}",
                                self.consecutive_decode_errors
                            );
                        }
                        if self.consecutive_decode_errors >= MAX_CONSECUTIVE_DECODE_ERRORS {
                            crate::app_deprintln!(
                                "[psysonic] {MAX_CONSECUTIVE_DECODE_ERRORS} consecutive decode \
                                 failures — stream appears unrecoverable, stopping"
                            );
                            return None;
                        }
                        // continue → fetch next packet
                    }
                    Err(_) => return None, // IO error or fatal codec error → end of stream
                }
            }
        }

        let sample = *self.buffer.samples().get(self.current_frame_offset)?;
        self.current_frame_offset += 1;
        Some(sample)
    }
}

impl Source for SizedDecoder {
    #[inline]
    fn current_frame_len(&self) -> Option<usize> {
        Some(self.buffer.samples().len())
    }

    #[inline]
    fn channels(&self) -> u16 {
        self.spec.channels.count() as u16
    }

    #[inline]
    fn sample_rate(&self) -> u32 {
        self.spec.rate
    }

    #[inline]
    fn total_duration(&self) -> Option<Duration> {
        self.total_duration.map(|Time { seconds, frac }| {
            Duration::new(seconds, (frac * 1_000_000_000.0) as u32)
        })
    }

    fn try_seek(&mut self, pos: Duration) -> Result<(), rodio::source::SeekError> {
        let seek_beyond_end = self
            .total_duration()
            .is_some_and(|dur| dur.saturating_sub(pos).as_millis() < 1);

        let time: Time = if seek_beyond_end {
            let t = self.total_duration.unwrap_or(pos.as_secs_f64().into());
            // Step back a tiny bit — some demuxers can't seek to the exact end.
            let mut secs = t.seconds;
            let mut frac = t.frac - 0.0001;
            if frac < 0.0 {
                secs = secs.saturating_sub(1);
                frac = 1.0 - frac;
            }
            Time { seconds: secs, frac }
        } else {
            pos.as_secs_f64().into()
        };

        let to_skip = self.current_frame_offset % self.channels() as usize;

        let seek_res = self
            .format
            .seek(SeekMode::Accurate, SeekTo::Time { time, track_id: None })
            .map_err(|e| rodio::source::SeekError::Other(
                Box::new(std::io::Error::new(std::io::ErrorKind::Other, e.to_string()))
            ))?;

        self.refine_position(seek_res)
            .map_err(|e| rodio::source::SeekError::Other(
                Box::new(std::io::Error::new(std::io::ErrorKind::Other, e))
            ))?;

        self.current_frame_offset += to_skip;
        Ok(())
    }
}

// ─── Encoder-gap trimming (iTunSMPB) ─────────────────────────────────────────
//
// MP3/AAC encoders prepend an "encoder delay" (typically 576–2112 silent
// samples for LAME) and append end-padding to fill the final frame.
// iTunes embeds the exact counts in an ID3v2 COMM frame with description
// "iTunSMPB". Format: " 00000000 DELAY PADDING TOTAL ..."  (space-separated hex)
//
// Parsing strategy: scan raw bytes for the ASCII marker, then extract the
// first whitespace-separated hex tokens after it.

pub(crate) struct GaplessInfo {
    delay_samples: u64,
    total_valid_samples: Option<u64>,
}

impl Default for GaplessInfo {
    fn default() -> Self {
        Self { delay_samples: 0, total_valid_samples: None }
    }
}

pub(crate) fn find_subsequence(data: &[u8], needle: &[u8]) -> Option<usize> {
    data.windows(needle.len()).position(|w| w == needle)
}

pub(crate) fn parse_gapless_info(data: &[u8]) -> GaplessInfo {
    let pos = match find_subsequence(data, b"iTunSMPB") {
        Some(p) => p,
        None => return GaplessInfo::default(),
    };

    // In M4A/iTunes files the key is followed by a binary 'data' atom header
    // (16 bytes: size[4] + "data"[4] + type_flags[4] + locale[4]) before the
    // actual value string. Search for the " 00000000 " sentinel that every
    // iTunSMPB value starts with to locate the true start of the text.
    let search_end = data.len().min(pos + 8 + 128);
    let search_window = &data[pos + 8..search_end];
    let value_start = find_subsequence(search_window, b" 00000000 ")
        .map(|off| pos + 8 + off)
        .unwrap_or(pos + 8);

    let tail = &data[value_start..data.len().min(value_start + 256)];
    let text: String = tail.iter()
        .map(|&b| b as char)
        .filter(|c| c.is_ascii_hexdigit() || *c == ' ')
        .collect();

    let parts: Vec<&str> = text.split_whitespace().collect();
    // parts[0] = "00000000", parts[1] = delay, parts[2] = padding, parts[3] = total
    if parts.len() < 3 {
        return GaplessInfo::default();
    }
    let delay = u64::from_str_radix(parts.get(1).unwrap_or(&"0"), 16).unwrap_or(0);
    let padding = u64::from_str_radix(parts.get(2).unwrap_or(&"0"), 16).unwrap_or(0);
    let total_raw = parts.get(3).and_then(|s| u64::from_str_radix(s, 16).ok());

    let total_valid = total_raw.map(|t| t).filter(|&t| t > 0).or_else(|| {
        // Derive from delay + padding if total not available:
        // Not possible without knowing total encoded samples, so just use None.
        let _ = padding;
        None
    });

    GaplessInfo { delay_samples: delay, total_valid_samples: total_valid }
}

/// Result of build_source: the fully-wrapped source plus metadata and control Arcs.
pub(crate) struct BuiltSource {
    pub(crate) source: PriorityBoostSource<CountingSource<NotifyingSource<TriggeredFadeOut<EqualPowerFadeIn<EqSource<DynSource>>>>>>,
    pub(crate) duration_secs: f64,
    pub(crate) output_rate: u32,
    pub(crate) output_channels: u16,
    /// Trigger for the sample-level crossfade fade-out.
    pub(crate) fadeout_trigger: Arc<AtomicBool>,
    /// Total samples for the fade-out (set before triggering).
    pub(crate) fadeout_samples: Arc<AtomicU64>,
}

/// Build a fully-prepared playback source:
///   decode → trim → resample → EQ → fade-in → triggered-fade-out → notify → count
///
/// `fade_in_dur`:
///   • `Duration::ZERO`          — unity gain; used for gapless chain (no click)
///   • `Duration::from_millis(5)` — micro-fade; used for hard cuts (anti-click)
///   • `Duration::from_secs_f32(cf)` — full equal-power fade-in for crossfade
///
/// `sample_counter`: atomic counter incremented per sample for drift-free position.
/// `target_rate`: canonical output sample rate for resampling (0 = no resampling).
/// `format_hint`: optional file extension (e.g. "flac", "mp3") to help symphonia probe.
pub(crate) fn build_source(
    data: Vec<u8>,
    duration_hint: f64,
    eq_gains: Arc<[AtomicU32; 10]>,
    eq_enabled: Arc<AtomicBool>,
    eq_pre_gain: Arc<AtomicU32>,
    done_flag: Arc<AtomicBool>,
    fade_in_dur: Duration,
    sample_counter: Arc<AtomicU64>,
    target_rate: u32,
    format_hint: Option<&str>,
    hi_res: bool,
) -> Result<BuiltSource, String> {
    let gapless = parse_gapless_info(&data);

    let decoder = SizedDecoder::new(data, format_hint, hi_res)?;
    let sample_rate = decoder.sample_rate();
    let channels = decoder.channels();

    // Determine effective duration.
    // Prefer hint from Subsonic API (reliable) over decoder (unreliable for VBR MP3).
    let effective_dur = if duration_hint > 1.0 {
        duration_hint
    } else {
        decoder.total_duration()
            .map(|d| d.as_secs_f64())
            .unwrap_or(duration_hint)
    };

    // Apply encoder-delay trim and optional end-padding trim,
    // then resample to the canonical target rate if needed.
    let dyn_src: DynSource = if gapless.delay_samples > 0 || gapless.total_valid_samples.is_some() {
        let delay_dur = Duration::from_secs_f64(
            gapless.delay_samples as f64 / sample_rate as f64
        );
        let base = decoder.convert_samples::<f32>().skip_duration(delay_dur);

        if let Some(total) = gapless.total_valid_samples {
            let valid_dur = Duration::from_secs_f64(total as f64 / sample_rate as f64);
            let trimmed = base.take_duration(valid_dur);
            if target_rate > 0 && sample_rate != target_rate {
                DynSource::new(UniformSourceIterator::new(trimmed, channels, target_rate))
            } else {
                DynSource::new(trimmed)
            }
        } else {
            if target_rate > 0 && sample_rate != target_rate {
                DynSource::new(UniformSourceIterator::new(base, channels, target_rate))
            } else {
                DynSource::new(base)
            }
        }
    } else {
        let converted = decoder.convert_samples::<f32>();
        if target_rate > 0 && sample_rate != target_rate {
            DynSource::new(UniformSourceIterator::new(converted, channels, target_rate))
        } else {
            DynSource::new(converted)
        }
    };

    let output_rate = if target_rate > 0 && sample_rate != target_rate { target_rate } else { sample_rate };

    let fadeout_trigger = Arc::new(AtomicBool::new(false));
    let fadeout_samples = Arc::new(AtomicU64::new(0));

    let eq_src = EqSource::new(dyn_src, eq_gains, eq_enabled, eq_pre_gain);
    let fade_in = EqualPowerFadeIn::new(eq_src, fade_in_dur);
    let fade_out = TriggeredFadeOut::new(fade_in, fadeout_trigger.clone(), fadeout_samples.clone());
    let notifying = NotifyingSource::new(fade_out, done_flag);
    let counting = CountingSource::new(notifying, sample_counter);
    let boosted = PriorityBoostSource::new(counting);

    Ok(BuiltSource {
        source: boosted,
        duration_secs: effective_dur,
        output_rate,
        output_channels: channels,
        fadeout_trigger,
        fadeout_samples,
    })
}

/// Streaming variant of `build_source`: uses a live `SizedDecoder` source
/// (non-seekable) and skips iTunSMPB parsing, but preserves the same EQ/fade/
/// counting wrappers and output metadata.
pub(crate) fn build_streaming_source(
    decoder: SizedDecoder,
    duration_hint: f64,
    eq_gains: Arc<[AtomicU32; 10]>,
    eq_enabled: Arc<AtomicBool>,
    eq_pre_gain: Arc<AtomicU32>,
    done_flag: Arc<AtomicBool>,
    fade_in_dur: Duration,
    sample_counter: Arc<AtomicU64>,
    target_rate: u32,
) -> Result<BuiltSource, String> {
    let sample_rate = decoder.sample_rate();
    let channels = decoder.channels();

    // For streaming starts prefer server-provided duration when available.
    let effective_dur = if duration_hint > 1.0 {
        duration_hint
    } else {
        decoder
            .total_duration()
            .map(|d| d.as_secs_f64())
            .unwrap_or(duration_hint)
    };

    let converted = decoder.convert_samples::<f32>();
    let dyn_src: DynSource = if target_rate > 0 && sample_rate != target_rate {
        DynSource::new(UniformSourceIterator::new(converted, channels, target_rate))
    } else {
        DynSource::new(converted)
    };

    let output_rate = if target_rate > 0 && sample_rate != target_rate {
        target_rate
    } else {
        sample_rate
    };

    let fadeout_trigger = Arc::new(AtomicBool::new(false));
    let fadeout_samples = Arc::new(AtomicU64::new(0));

    let eq_src = EqSource::new(dyn_src, eq_gains, eq_enabled, eq_pre_gain);
    let fade_in = EqualPowerFadeIn::new(eq_src, fade_in_dur);
    let fade_out = TriggeredFadeOut::new(fade_in, fadeout_trigger.clone(), fadeout_samples.clone());
    let notifying = NotifyingSource::new(fade_out, done_flag);
    let counting = CountingSource::new(notifying, sample_counter);
    let boosted = PriorityBoostSource::new(counting);

    Ok(BuiltSource {
        source: boosted,
        duration_secs: effective_dur,
        output_rate,
        output_channels: channels,
        fadeout_trigger,
        fadeout_samples,
    })
}