#!/usr/bin/env python3

import sys
import re
from pathlib import Path

EP_REGEX = re.compile(r'(E)(\d{4})(.*)')

def main():
    args = sys.argv[1:]

    dry_run = False
    if args and args[0] in ("--dry-run", "-n"):
        dry_run = True
        args = args[1:]

    if len(args) != 3:
        print("Usage: script.py [--dry-run|-n] <directory> <threshold> <subtract>")
        sys.exit(1)

    directory = Path(args[0])
    threshold = int(args[1])
    subtract = int(args[2])

    if not directory.is_dir():
        print(f"Error: '{directory}' is not a directory.")
        sys.exit(1)

    # Step 1: build array of original filenames and parsed numbers
    old_array = []
    for f in sorted(directory.iterdir()):
        if not f.is_file():
            continue
        m = EP_REGEX.match(f.name)
        if m:
            prefix, num_str, rest = m.groups()
            num = int(num_str)
            old_array.append([prefix, num, rest])

    # Step 2: compute new filenames
    new_array = []
    for prefix, num, rest in old_array:
        if num >= threshold:
            new_num = num - subtract
        else:
            new_num = num
        if new_num < 0 or new_num > 9999:
            raise ValueError(f"Invalid resulting number for file: {prefix}{num:04d}{rest}")
        new_array.append([prefix, new_num, rest])

    if subtract < 0:
        new_array.reverse()
        old_array.reverse()

    # Step 3: sequential rename simulation / real rename
    for i in range(len(old_array)):
        old_name = f"{old_array[i][0]}{old_array[i][1]:04d}{old_array[i][2]}"
        new_name = f"{new_array[i][0]}{new_array[i][1]:04d}{new_array[i][2]}"

        for j in range(i):
            if old_array[j][0] == new_array[i][0] and old_array[j][1] == new_array[i][1] and old_array[j][2] == new_array[i][2]:
                raise RuntimeError(
                    f"Rename conflict in simulation:\n  Source: {old_name}\n  Target: {new_name}\n  Conflicts with: {old_array[j][0]}{old_array[j][1]:04d}{old_array[j][2]}"
                )
            if old_array[j][1] > new_array[i][1]:
                break

        print(f"\"{old_name}\" -> \"{new_name}\"", end=" ")      

        if old_name == new_name:
            print("Skipped")
            continue
        else:
            print()

        # Update simulated old_array to reflect that this file has been "renamed"
        old_array[i][1] = new_array[i][1]

        # Actually rename unless dry-run
        if not dry_run:
            target_path = directory / new_name
            if target_path.exists():
                raise RuntimeError(f"Rename would overwrite existing file on disk:\n  Source: {old_name}\n  Target: {new_name}")
            (directory / old_name).rename(target_path)

    if dry_run:
        print("Dry-run complete. No files were renamed.")
    else:
        print("Done.")

if __name__ == "__main__":
    import subprocess
    subprocess.run(["python", "/home/honney/.bin/tracker.py", "add", "substract_episode_num"])
    main()