"""ta_batch_rename.py - batch-rename texture files to a naming convention.

The finished artifact from The Technical Artist's "First Pipeline Script"
tutorial:  https://thetechnicalartist.example/python/first-pipeline-script.html

Usage:
    python ta_batch_rename.py D:/textures            # dry run (prints the plan)
    python ta_batch_rename.py D:/textures --apply    # actually rename
    python ta_batch_rename.py D:/textures --prefix T_ --apply

What it does:
    old:  "rock albedo 2.png"      new:  "T_Rock_Albedo_02.png"
    - lowercases-then-titlecases words, joins with underscores
    - zero-pads trailing numbers to two digits
    - adds the texture prefix if missing
    - refuses to run if two files would collide on the same new name
    - writes a rename log next to the folder so every run is reversible

No dependencies beyond the standard library. Python 3.8+.
"""

import argparse
import datetime
import re
import sys
from pathlib import Path


def convention(name: str, prefix: str = "T_") -> str:
    """Convert an arbitrary filename (no extension) to the convention."""
    # split on spaces, dashes, underscores, and camelCase boundaries
    words = re.split(r"[\s\-_]+", re.sub(r"(?<=[a-z0-9])(?=[A-Z])", " ", name))
    words = [w for w in words if w]

    # zero-pad a trailing number to two digits
    if words and words[-1].isdigit():
        words[-1] = f"{int(words[-1]):02d}"

    new = "_".join(w if w.isdigit() else w.title() for w in words)
    if not new.startswith(prefix):
        new = prefix + new
    return new


def plan_renames(folder: Path, prefix: str):
    """Build (old, new) pairs. Raises if two files would collide."""
    pairs = []
    for f in sorted(folder.iterdir()):
        if not f.is_file():
            continue
        new_name = convention(f.stem, prefix) + f.suffix.lower()
        if new_name != f.name:
            pairs.append((f, f.with_name(new_name)))

    targets = [b.name for _, b in pairs]
    dupes = {t for t in targets if targets.count(t) > 1}
    if dupes:
        raise SystemExit(f"COLLISION: multiple files map to {sorted(dupes)} - fix by hand first.")
    return pairs


def main() -> int:
    ap = argparse.ArgumentParser(description="Batch-rename textures to the studio convention.")
    ap.add_argument("folder", type=Path, help="folder of textures to rename")
    ap.add_argument("--prefix", default="T_", help="type prefix (default: T_)")
    ap.add_argument("--apply", action="store_true", help="actually rename (default is a dry run)")
    args = ap.parse_args()

    if not args.folder.is_dir():
        print(f"error: {args.folder} is not a folder", file=sys.stderr)
        return 2

    pairs = plan_renames(args.folder, args.prefix)
    if not pairs:
        print("nothing to do - everything already matches the convention.")
        return 0

    for old, new in pairs:
        print(f"{old.name:<40} ->  {new.name}")

    if not args.apply:
        print(f"\n{len(pairs)} file(s) would be renamed. Re-run with --apply to do it.")
        return 0

    log = args.folder / f"_rename_log_{datetime.date.today()}.txt"
    with log.open("a", encoding="utf-8") as fh:
        for old, new in pairs:
            old.rename(new)
            fh.write(f"{old.name} -> {new.name}\n")
    print(f"\nrenamed {len(pairs)} file(s). Log: {log}")
    return 0


if __name__ == "__main__":
    sys.exit(main())