"""Writes a Recipe Bundle: a zip with bundle.json and downscaled photos (see docs/recipe-bundle-format.md)."""

from __future__ import annotations

import io
import json
import zipfile
from datetime import datetime, timezone

from PIL import Image, ImageOps, UnidentifiedImageError

FORMAT = "cookit.recipe-bundle"
VERSION = 1
MAX_PHOTO_EDGE = 1600
JPEG_QUALITY = 82


def downscale(data: bytes) -> bytes | None:
    """JPEG no larger than MAX_PHOTO_EDGE on its long side, or None if the picture can't be read."""
    try:
        img = Image.open(io.BytesIO(data))
        img = ImageOps.exif_transpose(img)
    except (UnidentifiedImageError, OSError, ValueError):
        return None
    if img.mode in ("RGBA", "LA", "P"):
        img = img.convert("RGBA")
        background = Image.new("RGB", img.size, "white")
        background.paste(img, mask=img.getchannel("A"))
        img = background
    elif img.mode != "RGB":
        img = img.convert("RGB")
    img.thumbnail((MAX_PHOTO_EDGE, MAX_PHOTO_EDGE), Image.Resampling.LANCZOS)
    out = io.BytesIO()
    img.save(out, "JPEG", quality=JPEG_QUALITY, optimize=True)
    return out.getvalue()


def write_bundle(path: str, recipes: list[tuple[dict, list[bytes]]]) -> None:
    """recipes: (recipe dict, raw photo bytes in display order)."""
    with zipfile.ZipFile(path, "w", zipfile.ZIP_DEFLATED) as z:
        entries = []
        for recipe, photos in recipes:
            recipe["photos"] = []
            for raw in photos:
                jpeg = downscale(raw)
                if jpeg is None:
                    continue
                name = f"photos/{recipe['id']}-{len(recipe['photos']) + 1}.jpg"
                z.writestr(zipfile.ZipInfo(name, date_time=(2026, 1, 1, 0, 0, 0)), jpeg, zipfile.ZIP_STORED)
                recipe["photos"].append(name)
            entries.append(recipe)
        manifest = {
            "format": FORMAT,
            "version": VERSION,
            "createdAt": datetime.now(timezone.utc).replace(microsecond=0).isoformat().replace("+00:00", "Z"),
            "recipes": entries,
        }
        z.writestr("bundle.json", json.dumps(manifest, ensure_ascii=False, indent=2))