feat: add resource library and real image workflow

app/application/services/image_generation_service.py

@@ -0,0 +1,163 @@
+"""Application-facing orchestration for image-generation providers."""
+
+from __future__ import annotations
+
+import base64
+
+import httpx
+from fastapi import HTTPException, status
+
+from app.config.settings import get_settings
+from app.infra.image_generation.base import GeneratedImageResult, SourceImage
+from app.infra.image_generation.gemini_provider import GeminiImageProvider
+
+TRYON_PROMPT = (
+    "Use the first image as the base person image and the second image as the garment reference. "
+    "Generate a realistic virtual try-on result where the person in the first image is wearing the garment from "
+    "the second image. Preserve the person's identity, body proportions, pose, camera angle, lighting direction, "
+    "and background composition from the first image. Preserve the garment's key silhouette, material feel, color, "
+    "and visible design details from the second image. Produce a clean e-commerce quality result without adding "
+    "extra accessories, text, watermarks, or duplicate limbs."
+)
+
+SCENE_PROMPT = (
+    "Use the first image as the finished subject image and the second image as the target scene reference. "
+    "Generate a realistic composite where the person, clothing, body proportions, facial identity, pose, and camera "
+    "framing from the first image are preserved, while the environment is adapted to match the second image. "
+    "Keep the garment details, colors, and texture from the first image intact. Blend the subject naturally into the "
+    "target scene with coherent perspective, lighting, shadows, and depth. Do not add extra people, accessories, "
+    "text, logos, watermarks, or duplicate body parts."
+)
+
+MOCK_PNG_BASE64 = (
+    "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mP8/x8AAwMCAO5Ww4QAAAAASUVORK5CYII="
+)
+
+
+class MockImageGenerationService:
+    """Deterministic fallback used in tests and when no real provider is configured."""
+
+    async def generate_tryon_image(self, *, person_image_url: str, garment_image_url: str) -> GeneratedImageResult:
+        return GeneratedImageResult(
+            image_bytes=base64.b64decode(MOCK_PNG_BASE64),
+            mime_type="image/png",
+            provider="mock",
+            model="mock-image-provider",
+            prompt=TRYON_PROMPT,
+        )
+
+    async def generate_scene_image(self, *, source_image_url: str, scene_image_url: str) -> GeneratedImageResult:
+        return GeneratedImageResult(
+            image_bytes=base64.b64decode(MOCK_PNG_BASE64),
+            mime_type="image/png",
+            provider="mock",
+            model="mock-image-provider",
+            prompt=SCENE_PROMPT,
+        )
+
+
+class ImageGenerationService:
+    """Download source assets and dispatch them to the configured provider."""
+
+    def __init__(
+        self,
+        *,
+        provider: GeminiImageProvider | None = None,
+        downloader: httpx.AsyncClient | None = None,
+    ) -> None:
+        self.settings = get_settings()
+        self.provider = provider or GeminiImageProvider(
+            api_key=self.settings.gemini_api_key,
+            base_url=self.settings.gemini_base_url,
+            model=self.settings.gemini_model,
+            timeout_seconds=self.settings.gemini_timeout_seconds,
+            max_attempts=self.settings.gemini_max_attempts,
+        )
+        self._downloader = downloader
+
+    async def generate_tryon_image(
+        self,
+        *,
+        person_image_url: str,
+        garment_image_url: str,
+    ) -> GeneratedImageResult:
+        """Generate a try-on image using the configured provider."""
+
+        if not self.settings.gemini_api_key:
+            raise HTTPException(
+                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+                detail="GEMINI_API_KEY is required when image_generation_provider=gemini",
+            )
+
+        person_image, garment_image = await self._download_inputs(
+            first_image_url=person_image_url,
+            second_image_url=garment_image_url,
+        )
+        return await self.provider.generate_tryon_image(
+            prompt=TRYON_PROMPT,
+            person_image=person_image,
+            garment_image=garment_image,
+        )
+
+    async def generate_scene_image(
+        self,
+        *,
+        source_image_url: str,
+        scene_image_url: str,
+    ) -> GeneratedImageResult:
+        """Generate a scene-composited image using the configured provider."""
+
+        if not self.settings.gemini_api_key:
+            raise HTTPException(
+                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+                detail="GEMINI_API_KEY is required when image_generation_provider=gemini",
+            )
+
+        source_image, scene_image = await self._download_inputs(
+            first_image_url=source_image_url,
+            second_image_url=scene_image_url,
+        )
+        return await self.provider.generate_scene_image(
+            prompt=SCENE_PROMPT,
+            source_image=source_image,
+            scene_image=scene_image,
+        )
+
+    async def _download_inputs(
+        self,
+        *,
+        first_image_url: str,
+        second_image_url: str,
+    ) -> tuple[SourceImage, SourceImage]:
+        owns_client = self._downloader is None
+        client = self._downloader or httpx.AsyncClient(timeout=self.settings.gemini_timeout_seconds)
+        try:
+            first_response = await client.get(first_image_url)
+            first_response.raise_for_status()
+            second_response = await client.get(second_image_url)
+            second_response.raise_for_status()
+        finally:
+            if owns_client:
+                await client.aclose()
+
+        first_mime = first_response.headers.get("content-type", "image/png").split(";")[0].strip()
+        second_mime = second_response.headers.get("content-type", "image/png").split(";")[0].strip()
+
+        return (
+            SourceImage(url=first_image_url, mime_type=first_mime or "image/png", data=first_response.content),
+            SourceImage(url=second_image_url, mime_type=second_mime or "image/png", data=second_response.content),
+        )
+
+
+def build_image_generation_service():
+    """Return the configured image-generation service."""
+
+    settings = get_settings()
+    if settings.image_generation_provider.lower() == "mock":
+        return MockImageGenerationService()
+    if settings.image_generation_provider.lower() == "gemini":
+        return ImageGenerationService()
+    raise HTTPException(
+        status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+        detail=f"Unsupported image_generation_provider: {settings.image_generation_provider}",
+    )