src/ad_creative_env/renderer/backgrounds.py

"""Placeholder backgrounds for M1 (no image model). Deterministic solid colors.

Real generated backgrounds arrive in Plan 3 via the OpenRouter provider; this
module is the swappable stand-in behind the same 'label -> image' idea.
"""

from __future__ import annotations

import io
import logging

from PIL import Image

from ..config import (
    AD_SIZE,
    BACKGROUND_PROMPTS,
    GEN_PARAMS,
    OPENROUTER_IMAGE_URL,
    RENDERER_VERSION,
)
from .cache import CacheError, cache_key

logger = logging.getLogger(__name__)

# One distinct, deterministic color per known background label.
_LABEL_COLORS: dict[str, tuple[int, int, int]] = {
    "hotel_exterior": (38, 70, 83),
    "city_skyline": (42, 54, 110),
    "room_interior": (120, 66, 52),
    "generic": (90, 90, 90),
}
_FALLBACK_COLOR = (60, 60, 60)


def make_placeholder_background(label: str, size: tuple[int, int] = AD_SIZE) -> Image.Image:
    """Return a deterministic RGB placeholder background for ``label``."""
    color = _LABEL_COLORS.get(label, _FALLBACK_COLOR)
    return Image.new("RGB", size, color)


def background_cache_key(label: str, *, model: str) -> str:
    """The cache key for a generated background. Shared by generate + tooling."""
    return cache_key(
        {
            "provider": "openrouter",
            "model_slug": model,
            "endpoint": OPENROUTER_IMAGE_URL,
            "prompt": BACKGROUND_PROMPTS[label],
            "gen_params": GEN_PARAMS,
            "renderer_version": RENDERER_VERSION,
        }
    )


def generate_background(
    label: str,
    *,
    cache,
    provider,
    model: str,
    api_key: str | None = None,
    size: tuple[int, int] = AD_SIZE,
    replay: bool = False,
) -> Image.Image:
    """Provider-mode background: eval hit -> dev re-check -> provider fill.

    In replay/eval mode an eval miss is a hard fail (never touches the network).
    `provider(*, prompt, model, api_key, params, endpoint) -> (bytes, meta)`.
    """
    prompt = BACKGROUND_PROMPTS[label]
    key = background_cache_key(label, model=model)

    if cache.has(key, "eval"):
        logger.debug("bg eval hit", extra={"label": label, "model": model})
        return cache.get(key, "eval", expect_slug=model)[0]
    if replay:
        raise CacheError(
            f"replay/eval miss for background {label!r} (key {key[:12]}…) — "
            "no network in replay mode; promote a dev entry first"
        )

    with cache.lock(key):
        if cache.has(key, "dev"):  # re-check: a peer worker may have just filled it
            return cache.get(key, "dev")[0]
        image_bytes, meta = provider(
            prompt=prompt, model=model, api_key=api_key,
            params=GEN_PARAMS, endpoint=OPENROUTER_IMAGE_URL,
        )
        image = Image.open(io.BytesIO(image_bytes)).convert("RGB")
        if image.size != size:
            image = image.resize(size)  # safety net if the provider ignored size
        manifest = {
            "model_slug": model,
            "prompt": prompt,
            "gen_params": GEN_PARAMS,
            "endpoint": OPENROUTER_IMAGE_URL,
            "response_meta": meta,
        }
        cache.put(key, image, manifest)  # public put = DEV tier (held under lock above)
        logger.debug("bg dev fill", extra={"label": label, "model": model})
        return image