import os
import glob
import json
import struct
import subprocess
from pathlib import Path
import time

def get_ogg_opus_duration(filepath):
    with open(filepath, 'rb') as f:
        f.seek(0, 2)
        file_size = f.tell()
        
        chunk_size = min(65536, file_size)
        f.seek(file_size - chunk_size)
        data = f.read(chunk_size)
        
        last_oggs_idx = data.rfind(b'OggS')
        if last_oggs_idx == -1:
            return 0
        
        granule_bytes = data[last_oggs_idx+6 : last_oggs_idx+14]
        granule_position = struct.unpack('<q', granule_bytes)[0]
        
        return int((granule_position / 48000.0) * 1000)

def test_concat():
    reciter_dir = Path("banna")
    surah_str = "001"
    surah_path = reciter_dir / surah_str
    
    all_opus = sorted(list(surah_path.glob(f"{surah_str}*.opus")))
    verse_opus_files = [f for f in all_opus if len(f.stem) > 3]
    
    concat_txt_path = surah_path / f"concat_{surah_str}.txt"
    target_opus = surah_path / f"{surah_str}_test.opus"
    
    cumulative_offset = 0
    with open(concat_txt_path, 'w') as f_out:
        for opus_f in verse_opus_files:
            f_out.write(f"file '{opus_f.name}'\n")
            dur = get_ogg_opus_duration(opus_f)
            cumulative_offset += dur
            print(f"{opus_f.name} dur: {dur} ms")
            
    print(f"Total cumulative: {cumulative_offset} ms")
    
    subprocess.run([
        "ffmpeg", "-y", "-hide_banner", "-loglevel", "error",
        "-f", "concat", "-safe", "0",
        "-i", str(concat_txt_path),
        "-c", "copy",
        str(target_opus)
    ], check=True)
    
    combined_dur = get_ogg_opus_duration(target_opus)
    print(f"Combined opus duration: {combined_dur} ms")
    
if __name__ == '__main__':
    test_concat()