from __future__ import annotations

import base64
import hashlib
from pathlib import Path
import random
import re

from PIL import Image, ImageDraw, ImageFilter

from publication_meta import CATEGORIES

WIDTH = 1200
HEIGHT = 630
MAX_BYTES = 5 * 1024 * 1024
SLUG_RE = re.compile(r"^[a-z0-9]+(?:-[a-z0-9]+)*$")

_PALETTES = {
    "وكلاء": ((17, 25, 48), (82, 214, 186)),
    "نماذج": ((20, 22, 48), (129, 140, 248)),
    "استرجاع": ((13, 31, 43), (56, 189, 248)),
    "سلامة": ((37, 21, 35), (244, 114, 182)),
    "أدوات": ((16, 30, 35), (245, 174, 65)),
    "أعمال": ((31, 24, 20), (249, 115, 80)),
}


def _art(slug: str, category: str) -> Image.Image:
    seed = int.from_bytes(hashlib.sha256(f"{slug}|{category}".encode()).digest()[:8], "big")
    rng = random.Random(seed)
    background, accent = _PALETTES[category]
    image = Image.new("RGB", (WIDTH, HEIGHT), background)

    glow = Image.new("RGBA", image.size, (0, 0, 0, 0))
    glow_draw = ImageDraw.Draw(glow, "RGBA")
    for _ in range(5):
        x = rng.randint(80, WIDTH - 80)
        y = rng.randint(60, HEIGHT - 60)
        radius = rng.randint(130, 320)
        glow_draw.ellipse(
            (x - radius, y - radius, x + radius, y + radius),
            fill=(*accent, rng.randint(18, 42)),
        )
    glow = glow.filter(ImageFilter.GaussianBlur(70))
    image = Image.alpha_composite(image.convert("RGBA"), glow)

    overlay = Image.new("RGBA", image.size, (0, 0, 0, 0))
    draw = ImageDraw.Draw(overlay, "RGBA")
    points = [(rng.randint(110, WIDTH - 110), rng.randint(90, HEIGHT - 90)) for _ in range(12)]
    for index, start in enumerate(points):
        end = points[(index * 5 + 3) % len(points)]
        draw.line((start, end), fill=(*accent, 95), width=3)
    for index, (x, y) in enumerate(points):
        radius = 8 + (index % 4) * 4
        draw.ellipse(
            (x - radius, y - radius, x + radius, y + radius),
            fill=(*accent, 220),
            outline=(235, 241, 247, 180),
            width=2,
        )

    left = 68
    top = 54
    right = WIDTH - 68
    bottom = HEIGHT - 54
    draw.rounded_rectangle((left, top, right, bottom), radius=32, outline=(*accent, 120), width=3)
    draw.line((left + 35, bottom - 55, right - 35, bottom - 55), fill=(*accent, 155), width=4)
    return Image.alpha_composite(image, overlay).convert("RGB")


def generate_cover(slug: str, category: str, output_dir: Path) -> dict:
    if not SLUG_RE.fullmatch(slug):
        raise ValueError("slug must be lowercase ASCII kebab-case")
    if category not in CATEGORIES:
        raise ValueError("category is invalid")

    output_dir.mkdir(parents=True, exist_ok=True)
    output = output_dir / f"{slug}.jpg"
    temporary = output.with_suffix(".jpg.tmp")
    image = _art(slug, category)
    image.save(temporary, format="JPEG", quality=91, optimize=True, progressive=True)

    if temporary.stat().st_size > MAX_BYTES:
        temporary.unlink(missing_ok=True)
        raise ValueError("generated cover exceeds 5MB")
    with Image.open(temporary) as check:
        if check.size != (WIDTH, HEIGHT) or check.format != "JPEG" or check.mode != "RGB":
            temporary.unlink(missing_ok=True)
            raise ValueError("generated cover failed validation")
    temporary.replace(output)

    encoded = base64.b64encode(output.read_bytes()).decode("ascii")
    return {
        "path": output,
        "coverImage": {"filename": output.name, "dataBase64": encoded},
    }