"""Measure audio with ffmpeg: RMS and peak per 50 ms window. The checker and the assembler both use this."""
import math
import os
import re
import subprocess
import tempfile


def ffmpeg(args):
    r = subprocess.run(["ffmpeg", "-nostdin", "-hide_banner", "-loglevel", "error", "-y"] + args, capture_output=True, text=True)
    if r.returncode != 0:
        raise RuntimeError("ffmpeg failed: " + r.stderr.strip()[-500:])


def probe(path):
    out = subprocess.run(["ffprobe", "-v", "error", "-select_streams", "a:0", "-show_entries",
                          "stream=codec_name,sample_rate,channels,bit_rate:format=duration", "-of", "default=nw=1", path],
                         capture_output=True, text=True, check=True).stdout
    return dict(line.split("=", 1) for line in out.strip().splitlines())


def windows(path):
    """[(rms_db, peak_db)] for consecutive 50 ms windows of the decoded file."""
    sr = int(probe(path)["sample_rate"])
    n = sr // 20
    with tempfile.TemporaryDirectory() as tmp:
        rms_file, peak_file = os.path.join(tmp, "rms.txt"), os.path.join(tmp, "peak.txt")
        af = ("asetnsamples=n=%d:p=0,astats=metadata=1:reset=1,"
              "ametadata=print:key=lavfi.astats.Overall.RMS_level:file=%s,"
              "ametadata=print:key=lavfi.astats.Overall.Peak_level:file=%s" % (n, rms_file, peak_file))
        r = subprocess.run(["ffmpeg", "-nostdin", "-hide_banner", "-loglevel", "error", "-i", path, "-af", af, "-f", "null", "-"],
                           capture_output=True, text=True)
        if r.returncode != 0:
            raise RuntimeError("ffmpeg failed: " + r.stderr.strip()[-500:])
        read = lambda p, key: [float(v) for v in re.findall(key + r"=(-?[\d.]+|-inf|inf)", open(p).read())]
        rms, peak = read(rms_file, "RMS_level"), read(peak_file, "Peak_level")
    return list(zip(rms, peak))


def db_mean_power(values):
    """Overall level in dB of equal-length windows given as dB RMS."""
    if not values:
        return float("-inf")
    p = sum(10 ** (v / 10) for v in values) / len(values)
    return 10 * math.log10(p) if p > 0 else float("-inf")


def overall(path):
    """(rms_db, peak_db) of the whole file."""
    w = windows(path)
    return db_mean_power([r for r, _ in w]), max(p for _, p in w)