src/ad_creative_env/hm/composition.py

"""Fixed product-card compositor and renderer-integrity checks."""

from __future__ import annotations

import hashlib
import io
from dataclasses import dataclass
from pathlib import Path
from typing import Protocol

from PIL import Image, ImageDraw, ImageFont, ImageOps, UnidentifiedImageError

from ad_creative_env.config import FONT_PATH_BOLD

from .models import AdCopy, CheckResult, Product

CARD_SIZE = (1200, 628)
_REGULAR_FONT = str(Path(FONT_PATH_BOLD).with_name("DejaVuSans.ttf"))


class CompositionError(RuntimeError):
    def __init__(self, code: str, message: str) -> None:
        super().__init__(message)
        self.code = code


@dataclass(frozen=True, slots=True)
class CompositionResult:
    png_bytes: bytes
    source_image_sha256: str
    width: int
    height: int
    all_text_fit: bool


class CardCompositor(Protocol):
    def compose(self, image_path: Path, product: Product, action: AdCopy) -> CompositionResult: ...


def image_sha256(path: Path) -> str:
    try:
        return hashlib.sha256(Path(path).read_bytes()).hexdigest()
    except OSError as exc:
        raise CompositionError("image_missing", "supplied product image cannot be read") from exc


def _font(path: str, size: int) -> ImageFont.FreeTypeFont:
    try:
        return ImageFont.truetype(path, size)
    except OSError as exc:  # pragma: no cover - deployment image test exercises the installed font
        raise CompositionError("font_missing", "card font is unavailable") from exc


def _wrap(
    draw: ImageDraw.ImageDraw,
    text: str,
    font: ImageFont.FreeTypeFont,
    max_width: int,
    max_lines: int,
) -> tuple[str, ...] | None:
    words = text.split()
    lines: list[str] = []
    current = ""
    for word in words:
        if draw.textlength(word, font=font) > max_width:
            return None
        candidate = f"{current} {word}".strip()
        if draw.textlength(candidate, font=font) <= max_width:
            current = candidate
        else:
            lines.append(current)
            current = word
            if len(lines) >= max_lines:
                return None
    if current:
        lines.append(current)
    return tuple(lines) if len(lines) <= max_lines else None


class PillowCardCompositor:
    """Deterministic fallback while the referenced internal OpenCV module is unavailable."""

    def compose(self, image_path: Path, product: Product, action: AdCopy) -> CompositionResult:
        source_hash = image_sha256(image_path)
        try:
            with Image.open(image_path) as source:
                product_image = ImageOps.exif_transpose(source).convert("RGB")
        except (OSError, UnidentifiedImageError) as exc:
            raise CompositionError("image_invalid", "supplied product image is invalid") from exc

        canvas = Image.new("RGB", CARD_SIZE, "#f4f1eb")
        product_panel = Image.new("RGB", (620, CARD_SIZE[1]), "#ffffff")
        fitted = ImageOps.contain(product_image, (540, 548), method=Image.Resampling.LANCZOS)
        product_panel.paste(fitted, ((620 - fitted.width) // 2, (628 - fitted.height) // 2))
        canvas.paste(product_panel, (0, 0))
        draw = ImageDraw.Draw(canvas)
        draw.rectangle((620, 0, 1200, 628), fill="#161616")

        eyebrow_font = _font(FONT_PATH_BOLD, 18)
        headline_font = _font(FONT_PATH_BOLD, 40)
        body_font = _font(_REGULAR_FONT, 23)
        product_font = _font(FONT_PATH_BOLD, 20)
        cta_font = _font(FONT_PATH_BOLD, 19)
        max_width = 484
        headline_lines = _wrap(draw, action.headline, headline_font, max_width, 3)
        body_lines = _wrap(draw, action.body, body_font, max_width, 5)
        cta_lines = _wrap(draw, action.cta, cta_font, 210, 1) if action.cta else ()
        if headline_lines is None or body_lines is None or cta_lines is None:
            raise CompositionError("text_overflow", "supplied copy does not fit the fixed card")

        left = 674
        draw.text((left, 58), "PERSONALIZED STYLE", font=eyebrow_font, fill="#c8b99d")
        draw.text((left, 92), product.name.upper(), font=product_font, fill="#ffffff")
        y = 148
        for line in headline_lines:
            draw.text((left, y), line, font=headline_font, fill="#ffffff")
            y += 49
        y += 20
        for line in body_lines:
            draw.text((left, y), line, font=body_font, fill="#d8d8d8")
            y += 34
        if action.cta:
            cta_y = 526
            draw.rounded_rectangle((left, cta_y, left + 246, cta_y + 54), 7, fill="#f3e8d4")
            draw.text((left + 18, cta_y + 15), cta_lines[0], font=cta_font, fill="#161616")

        output = io.BytesIO()
        canvas.save(output, format="PNG", optimize=False, compress_level=9)
        return CompositionResult(output.getvalue(), source_hash, *CARD_SIZE, all_text_fit=True)


def run_renderer_checks(
    expected_image_path: Path, composition: CompositionResult
) -> tuple[CheckResult, ...]:
    expected_hash = image_sha256(expected_image_path)
    return (
        CheckResult(
            "renderer.image_identity",
            composition.source_image_sha256 == expected_hash,
            "The compositor used the supplied product image."
            if composition.source_image_sha256 == expected_hash
            else "The composed card does not match the supplied product image.",
        ),
        CheckResult(
            "renderer.text_fit",
            composition.all_text_fit,
            "All supplied copy fits the fixed card."
            if composition.all_text_fit
            else "Some supplied copy does not fit the fixed card.",
        ),
    )