"""Re-render mel-spectrogram PNGs from existing bg/fg_gt/fg_pred wav triplets.

Style: librosa.display.specshow with time/Hz axes + colorbar + title (matches
audioldm_train sample callback look). Reusable any time inference output exists
under <root>/{sa,frieren,...}/val_<sid>_{bg,fg_gt,fg_pred}.wav.

Usage:
    python render_specs.py                       # default: /home/dingqy/inference_demo
    python render_specs.py --root /path/to/dir   # any dir of {sa,frieren} subdirs
    python render_specs.py --subdir sa           # only one subdir
"""
import argparse, re, sys
from pathlib import Path
import numpy as np
import torch
import torchaudio
import matplotlib
matplotlib.use("Agg")
import matplotlib.pyplot as plt
import librosa.display as ld
from librosa.filters import mel as librosa_mel_fn

# Hop lengths chosen to match each model's STFT setup so time axis is honest
SUBDIR_DEFAULTS = {
    "sa":      {"sr": 44100, "n_fft": 2048, "hop_length": 512,  "n_mels": 128, "fmax": 22050},
    "frieren": {"sr": 16000, "n_fft": 1024, "hop_length": 256,  "n_mels": 80,  "fmax": 8000},
}


def log_mel(wav_ct, sr, n_fft, hop_length, n_mels, fmax):
    """[C,T] tensor → log-mel [n_mels, T_mel] (channel-mean)."""
    w = wav_ct.mean(0, keepdim=True).float() if wav_ct.dim() == 2 else wav_ct.float().unsqueeze(0)
    mb = torch.from_numpy(librosa_mel_fn(sr=sr, n_fft=n_fft, n_mels=n_mels,
                                          fmin=0, fmax=fmax)).float()
    win = torch.hann_window(n_fft)
    spec = torch.stft(w, n_fft=n_fft, hop_length=hop_length, win_length=n_fft,
                      window=win, center=True, return_complex=True).abs()
    return (mb @ spec[0]).clamp(min=1e-5).log10().numpy() * 20.0  # → dB scale


def render_panels(panels, title, out_path, sr, hop_length, fmax):
    """panels: list of (label, mel) tuples. Renders one row per panel with
    shared vmin/vmax + colorbar."""
    n = len(panels)
    fig, axes = plt.subplots(n, 1, figsize=(10, 2.5 * n), dpi=110, sharex=True)
    if n == 1:
        axes = [axes]
    vmin = min(m.min() for _, m in panels)
    vmax = max(m.max() for _, m in panels)
    last_img = None
    for ax, (label, m) in zip(axes, panels):
        last_img = ld.specshow(m, x_axis="time", y_axis="mel",
                               sr=sr, hop_length=hop_length, fmax=fmax,
                               cmap="magma", ax=ax, vmin=vmin, vmax=vmax)
        ax.set_ylabel(f"{label}\nmel (Hz)", fontsize=9)
    axes[0].set_title(title, fontsize=11)
    axes[-1].set_xlabel("time (s)")
    fig.colorbar(last_img, ax=axes, format="%+.1f", label="log-mel (dB)",
                 shrink=0.9, pad=0.02)
    fig.savefig(out_path, bbox_inches="tight")
    plt.close(fig)


# Back-compat shim — older callers may still call render_triplet().
def render_triplet(bg_mel, fg_gt_mel, fg_pred_mel, title, out_path,
                   sr, hop_length, fmax):
    render_panels([("bg", bg_mel), ("fg_gt", fg_gt_mel), ("fg_pred", fg_pred_mel)],
                  title, out_path, sr, hop_length, fmax)


# Panel kinds discovered, in render order. mixture / fg_gt are optional.
PANEL_ORDER = ["bg", "fg_gt", "fg_pred", "mixture"]


def discover_pairs(subdir):
    """Find {sample_id: {kind: path}} for each val_<sid>_<kind>.wav under subdir.
    Always require bg + fg_pred; fg_gt and mixture are optional."""
    found = {}
    pat = re.compile(r"^val_(.+)_(bg|fg_gt|fg_pred|mixture)\.wav$")
    for p in Path(subdir).iterdir():
        m = pat.match(p.name)
        if not m: continue
        sid, kind = m.group(1), m.group(2)
        found.setdefault(sid, {})[kind] = p
    out = []
    for sid, d in sorted(found.items()):
        if "bg" in d and "fg_pred" in d:
            out.append((sid, d))
    return out


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--root", default="/home/dingqy/inference_demo",
                    help="dir containing model subdirs (e.g., sa/, frieren/)")
    ap.add_argument("--subdir", action="append",
                    help="restrict to specific subdir(s) (default: all known)")
    args = ap.parse_args()

    root = Path(args.root)
    if not root.exists():
        sys.exit(f"root not found: {root}")
    subdirs = args.subdir if args.subdir else list(SUBDIR_DEFAULTS.keys())

    for sub in subdirs:
        d = root / sub
        if not d.exists():
            print(f"[skip] {d} does not exist")
            continue
        cfg = SUBDIR_DEFAULTS.get(sub)
        if cfg is None:
            print(f"[skip] {sub}: unknown subdir; add an entry to SUBDIR_DEFAULTS")
            continue
        pairs = discover_pairs(d)
        print(f"[{sub}] {len(pairs)} val groups under {d}")
        for sid, kind_to_path in pairs:
            panels = []
            for kind in PANEL_ORDER:
                if kind not in kind_to_path: continue
                w, sr_w = torchaudio.load(str(kind_to_path[kind]))
                if sr_w != cfg["sr"]:
                    w = torchaudio.functional.resample(w, sr_w, cfg["sr"])
                m = log_mel(w, cfg["sr"], cfg["n_fft"], cfg["hop_length"],
                            cfg["n_mels"], cfg["fmax"])
                panels.append((kind, m))
            out_path = d / f"val_{sid}_spec.png"
            render_panels(panels,
                          title=f"[{sub}] {sid}",
                          out_path=str(out_path),
                          sr=cfg["sr"], hop_length=cfg["hop_length"],
                          fmax=cfg["fmax"])
            kinds = [k for k, _ in panels]
            print(f"  rendered {out_path.name}  ({'+'.join(kinds)})")


if __name__ == "__main__":
    main()