import os
import shutil
import sys

def sync_media_from_b_to_a(dir_a, dir_b, dry_run=False, dry_run_file="sync_dry_run.txt", error_file="sync_errors.txt"):
    """
    For each subdirectory in A, use its name to search B for a media file (.mkv or .mp4) with the same base name.
    If found, move all files from that B subdirectory into the corresponding A subdirectory.
    If dry_run is True, only print and save what would be moved.
    Also record directories where no match or exceptions occur.
    """
    media_exts = ('.mkv', '.mp4')
    dry_run_lines = []
    error_lines = []
    for subdir_a in os.listdir(dir_a):
        path_a = os.path.join(dir_a, subdir_a)
        if not os.path.isdir(path_a):
            continue
        base_name = subdir_a
        found = False
        try:
            for root_b, dirs_b, files_b in os.walk(dir_b):
                for file_b in files_b:
                    name_b, ext_b = os.path.splitext(file_b)
                    if ext_b.lower() in media_exts and name_b == base_name:
                        found = True
                        msg = f"Found match for '{base_name}' in '{root_b}'."
                        print(msg)
                        dry_run_lines.append(msg)
                        for src_file in os.listdir(root_b):
                            src_file_path = os.path.join(root_b, src_file)
                            dest_file_path = os.path.join(path_a, src_file)
                            if dry_run:
                                line = f"[DRY-RUN] Would move: {src_file_path} -> {dest_file_path}"
                                print(line)
                                dry_run_lines.append(line)
                            else:
                                shutil.move(src_file_path, dest_file_path)
                                print(f"Moved: {src_file_path} -> {dest_file_path}")
                        break
                if found:
                    break
            if not found:
                msg = f"No match found in B for '{base_name}' in '{path_a}'."
                print(msg)
                error_lines.append(msg)
        except Exception as e:
            msg = f"Exception for '{base_name}' in '{path_a}': {e}"
            print(msg)
            error_lines.append(msg)
    # Save dry run and error logs if dry_run
    if dry_run:
        with open(dry_run_file, "w", encoding="utf-8") as f:
            for line in dry_run_lines:
                f.write(line + "\n")
        print(f"Dry run output saved to {dry_run_file}")
    if error_lines:
        with open(error_file, "w", encoding="utf-8") as f:
            for line in error_lines:
                f.write(line + "\n")
        print(f"Errors/unmatched directories saved to {error_file}")

if __name__ == "__main__":
    # python3 sync_media.py <dir_A> <dir_B> [--dry-run]
    if len(sys.argv) < 3:
        print("Usage: python sync_media.py <dir_A> <dir_B> [--dry-run]")
    else:
        dry_run = "--dry-run" in sys.argv
        sync_media_from_b_to_a(
            sys.argv[1],
            sys.argv[2],
            dry_run=dry_run,
            dry_run_file="sync_dry_run.txt",
            error_file="sync_errors.txt"
        )