# users/signals.py
import io
import random
from PIL import Image, ImageDraw, ImageFont

from django.conf import settings
from django.core.files.base import ContentFile
from django.db.models.signals import post_save
from django.dispatch import receiver

from .models import User

PALETTE = ["#34344A", "#845A6D", "#D47386", "#C89B7B", "#32746D"]

def initials_for(user: User) -> str:
    if getattr(user, "initials", None):
        return user.initials[:2].upper()

    first = (user.first_name or "").strip()
    last = (user.last_name or "").strip()

    if first and last:
        return (first[0] + last[0]).upper()
    if first:
        return first[:2].upper()
    # fallback: email
    return (user.email or "U")[:2].upper()

def generate_avatar_png(text: str, bg_hex: str, size: int = 256) -> bytes:
    img = Image.new("RGBA", (size, size), bg_hex)
    draw = ImageDraw.Draw(img)

    font_path = getattr(settings, "AVATAR_FONT_PATH", None)
    if font_path:
        font = ImageFont.truetype(font_path, int(size * 0.42))
    else:
        font = ImageFont.load_default()

    bbox = draw.textbbox((0, 0), text, font=font)
    tw, th = bbox[2] - bbox[0], bbox[3] - bbox[1]
    x = (size - tw) / 2
    y = (size - th) / 2 - (size * 0.05)

    draw.text((x, y), text, font=font, fill="white")

    out = io.BytesIO()
    img.save(out, format="PNG", optimize=True)
    return out.getvalue()

@receiver(post_save, sender=User)
def set_default_avatar(sender, instance: User, created: bool, **kwargs):
    if not created:
        return
    if instance.image:
        return

    text = initials_for(instance)
    bg = random.choice(PALETTE)

    png_bytes = generate_avatar_png(text=text, bg_hex=bg, size=256)
    filename = f"user_{instance.pk}_avatar.png"
    instance.image.save(filename, ContentFile(png_bytes), save=False)
    User.objects.filter(pk=instance.pk).update(
        image=instance.image.name,
    )