import subprocess
import json
import os
import glob

def run_ffmpeg_cmd(cmd):
    result = subprocess.run(cmd, check=True, capture_output=True, text=True)
    return result.stdout.strip()

# 1. Ask for directory
input_dir = input("Enter the directory containing your .m4b files: ").strip()

# Collect and sort files
input_files = sorted(glob.glob(os.path.join(input_dir, "*.m4b")))
if not input_files:
    raise SystemExit("❌ No .m4b files found in that directory.")

# 2. List files with numbering
print("\nAvailable files:")
for i, f in enumerate(input_files, 1):
    print(f"[{i}] {os.path.basename(f)}")

# 3. Ask user for start-end range
user_range = input("\nEnter the range of files to merge (e.g. 1-10): ").strip()
try:
    start, end = map(int, user_range.split("-"))
    selected_files = input_files[start-1:end]
except Exception:
    raise SystemExit("❌ Invalid range format. Use start-end (e.g. 1-5).")

# 4. Ask for output name
output_name = input("\nEnter the final audiobook name (without extension): ").strip()
final_output = f"{output_name}.m4b"

# 5. Extract metadata (for chapters & global tags)
chapters = []
current_start = 0
global_tags = None

for f in selected_files:
    probe = subprocess.check_output([
        "ffprobe", "-v", "quiet", "-print_format", "json",
        "-show_format", "-show_streams", f
    ])
    meta = json.loads(probe)

    # Duration
    duration = float(meta["format"]["duration"])

    # Title for chapter name (falls back to filename)
    title = meta["format"]["tags"].get("title") if "tags" in meta["format"] else None
    if not title:
        title = os.path.splitext(os.path.basename(f))[0]

    chapters.append({
        "start": current_start,
        "end": current_start + duration,
        "title": title
    })
    current_start += duration

    # Save global tags from the first file
    if global_tags is None and "tags" in meta["format"]:
        global_tags = meta["format"]["tags"]

# 6. Write FFmetadata chapters file
with open("chapters.txt", "w", encoding="utf-8") as f:
    f.write(";FFMETADATA1\n")
    if global_tags:
        # Copy album/author/etc. from first file
        for key, value in global_tags.items():
            if key.lower() not in ["title", "name"]:  # don’t overwrite audiobook title
                f.write(f"{key}={value}\n")

    for ch in chapters:
        f.write("\n[CHAPTER]\n")
        f.write("TIMEBASE=1/1000\n")
        f.write(f"START={int(ch['start']*1000)}\n")
        f.write(f"END={int(ch['end']*1000)}\n")
        f.write(f"title={ch['title']}\n")

# 7. Create file list for ffmpeg concatenation
with open("file_list.txt", "w", encoding="utf-8") as f:
    for fpath in selected_files:
        f.write(f"file '{os.path.abspath(fpath)}'\n")

# 8. Concatenate into merged.m4b
run_ffmpeg_cmd([
    "ffmpeg", "-f", "concat", "-safe", "0", "-i", "file_list.txt",
    "-c", "copy", "merged.m4b"
])

# 9. Add chapter metadata + final output name
run_ffmpeg_cmd([
    "ffmpeg", "-i", "merged.m4b", "-i", "chapters.txt",
    "-map_metadata", "1", "-c", "copy", final_output
])

print(f"\n✅ Done! Created '{final_output}' with {len(chapters)} chapters.")