# processors/page_normalizer.py

import os
import re

from core.constants import IMAGE_EXTENSIONS
from core.result import StepResult


def _natural_sort_key(name: str):
    parts = re.split(r"(\d+)", name)
    return [int(p) if p.isdigit() else p.lower() for p in parts]


def preview_normalize_pages(work_dir: str) -> list[tuple[str, str]]:
    """Devuelve lista de (nombre_actual, nombre_final) sin modificar nada."""
    images = []
    for root, _, files in os.walk(work_dir):
        for f in files:
            ext = os.path.splitext(f)[1].lower()
            if ext in IMAGE_EXTENSIONS:
                images.append(os.path.join(root, f))

    images.sort(key=lambda p: _natural_sort_key(os.path.splitext(os.path.basename(p))[0]))
    total = len(images)
    if total == 0:
        return []

    width = len(str(total))
    result = []
    for i, src in enumerate(images):
        ext = os.path.splitext(src)[1].lower()
        original_name = os.path.basename(src)
        final_name = f"{str(i + 1).zfill(width)}{ext}"
        if original_name != final_name:
            result.append((original_name, final_name))

    return result


def normalize_pages(work_dir: str) -> StepResult:
    """
    Renombra las imágenes del cómic a una numeración secuencial con zero-padding.
    Fase 1: renombra a nombres temporales para evitar colisiones.
    Fase 2: renombra a 001.ext, 002.ext… con ancho = len(str(total)).
    """
    # Recopilar imágenes con natural sort
    images = []
    for root, _, files in os.walk(work_dir):
        for f in files:
            ext = os.path.splitext(f)[1].lower()
            if ext in IMAGE_EXTENSIONS:
                images.append(os.path.join(root, f))

    images.sort(key=lambda p: _natural_sort_key(os.path.splitext(os.path.basename(p))[0]))
    total = len(images)
    if total == 0:
        return StepResult(step="normalize_pages", changed=False)

    width = len(str(total))

    # Fase 1: renombrar a temporales para evitar colisiones intermedias
    temp_paths = []
    for i, src in enumerate(images):
        ext = os.path.splitext(src)[1].lower()
        tmp = os.path.join(os.path.dirname(src), f".tmp_rename_{i}{ext}")
        os.rename(src, tmp)
        temp_paths.append(tmp)

    # Fase 2: renombrar a nombre final
    changed = False
    details = []
    for i, tmp in enumerate(temp_paths):
        ext = os.path.splitext(tmp)[1].lower()
        final_name = f"{str(i + 1).zfill(width)}{ext}"
        final_path = os.path.join(os.path.dirname(tmp), final_name)
        os.rename(tmp, final_path)
        original_name = os.path.basename(images[i])
        if original_name != final_name:
            details.append(f"{original_name} → {final_name}")
            changed = True

    return StepResult(step="normalize_pages", changed=changed, details=details)