import subprocess

import numpy as np

from core.paths import _bin


def x_to_t(x: float, width: float, view_start: float, view_dur: float) -> float:
    """Map a pixel x in [0,width] to a time in [view_start, view_start+view_dur]."""
    if width <= 0 or view_dur <= 0:
        return view_start
    return view_start + (x / width) * view_dur


def t_to_x(t: float, width: float, view_start: float, view_dur: float) -> int:
    """Map a time to a pixel x in [0,width] (rounded)."""
    if width <= 0 or view_dur <= 0:
        return 0
    return int(round((t - view_start) / view_dur * width))


def peaks(samples, buckets: int = 128) -> list[float]:
    """Reduce a 1-D sample array to *buckets* normalized peak magnitudes (0..1)."""
    if samples is None or len(samples) == 0:
        return [0.0] * buckets
    a = np.abs(np.asarray(samples, dtype="float32"))
    idx = np.linspace(0, len(a), buckets + 1).astype(int)
    out = [float(a[idx[i]:idx[i + 1]].max()) if idx[i + 1] > idx[i] else 0.0
           for i in range(buckets)]
    m = max(out) or 1.0
    return [v / m for v in out]


def load_region_samples(path: str, start: float, duration: float,
                        sr: int = 8000) -> np.ndarray:
    """Decode a [start, start+duration] mono slice via ffmpeg for waveform
    preview (low sample rate). Returns a float32 numpy array, empty on failure."""
    cmd = [
        _bin("ffmpeg"), "-ss", str(start), "-i", path, "-t", str(duration),
        "-vn", "-ac", "1", "-ar", str(sr), "-f", "f32le",
        "-loglevel", "error", "pipe:1",
    ]
    try:
        proc = subprocess.run(cmd, capture_output=True, timeout=60)
    except Exception:
        return np.zeros(0, dtype="float32")
    if proc.returncode != 0 or not proc.stdout:
        return np.zeros(0, dtype="float32")
    buf = proc.stdout
    buf = buf[: len(buf) - (len(buf) % 4)]
    return np.frombuffer(buf, dtype="float32")