backend/src/main.py

"""FastAPI entrypoint exposing the DeepResearchAgent via HTTP."""

from __future__ import annotations

import json
import os
import sys
from pathlib import Path
from typing import Any, Dict, Iterator, Optional

from dotenv import load_dotenv

# Load .env file before importing config
load_dotenv()

from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import FileResponse, StreamingResponse
from fastapi.staticfiles import StaticFiles
from loguru import logger
from pydantic import BaseModel, Field

from config import Configuration, SearchAPI
from agent import DeepResearchAgent

# Static files directory (for production deployment)
STATIC_DIR = Path(__file__).parent.parent / "static"

# Add console log handler
logger.add(
    sys.stderr,
    level="INFO",
    format="<green>{time:YYYY-MM-DD HH:mm:ss}</green> | <level>{level: <4}</level> | <cyan>using_function:{function}</cyan> | <cyan>{file}:{line}</cyan> | <level>{message}</level>",
    colorize=True,
)


# Add error log handler
logger.add(
    sink=sys.stderr,
    level="ERROR",
    format="<green>{time:YYYY-MM-DD HH:mm:ss}</green> | <level>{level: <4}</level> | <cyan>using_function:{function}</cyan> | <cyan>{file}:{line}</cyan> | <level>{message}</level>",
    colorize=True,
)


class ResearchRequest(BaseModel):
    """Payload for triggering a research run."""

    topic: str = Field(..., description="Research topic supplied by the user")
    search_api: SearchAPI | None = Field(
        default=None,
        description="Override the default search backend configured via env",
    )


class ResearchResponse(BaseModel):
    """HTTP response containing the generated report and structured tasks."""

    report_markdown: str = Field(
        ..., description="Markdown-formatted research report including sections"
    )
    todo_items: list[dict[str, Any]] = Field(
        default_factory=list,
        description="Structured TODO items with summaries and sources",
    )


def _mask_secret(value: Optional[str], visible: int = 4) -> str:
    """Mask sensitive tokens while keeping leading and trailing characters."""
    if not value:
        return "unset"

    if len(value) <= visible * 2:
        return "*" * len(value)

    return f"{value[:visible]}...{value[-visible:]}"


def _build_config(payload: ResearchRequest) -> Configuration:
    overrides: Dict[str, Any] = {}

    if payload.search_api is not None:
        overrides["search_api"] = payload.search_api

    return Configuration.from_env(overrides=overrides)


def create_app() -> FastAPI:
    app = FastAPI(title="LangGraph Deep Researcher")

    app.add_middleware(
        CORSMiddleware,
        allow_origins=["*"],
        allow_credentials=True,
        allow_methods=["*"],
        allow_headers=["*"],
    )

    @app.on_event("startup")
    def log_startup_configuration() -> None:
        config = Configuration.from_env()

        if config.llm_provider == "ollama":
            base_url = config.sanitized_ollama_url()
        elif config.llm_provider == "lmstudio":
            base_url = config.lmstudio_base_url
        else:
            base_url = config.llm_base_url or "unset"

        logger.info(
            "DeepResearch configuration loaded: provider=%s model=%s base_url=%s search_api=%s "
            "max_loops=%s fetch_full_page=%s tool_calling=%s strip_thinking=%s api_key=%s",
            config.llm_provider,
            config.resolved_model() or "unset",
            base_url,
            (config.search_api.value if isinstance(config.search_api, SearchAPI) else config.search_api),
            config.max_web_research_loops,
            config.fetch_full_page,
            config.use_tool_calling,
            config.strip_thinking_tokens,
            _mask_secret(config.llm_api_key),
        )

    @app.get("/healthz")
    def health_check() -> Dict[str, str]:
        return {"status": "ok"}

    @app.post("/research", response_model=ResearchResponse)
    def run_research(payload: ResearchRequest) -> ResearchResponse:
        try:
            config = _build_config(payload)
            agent = DeepResearchAgent(config=config)
            result = agent.run(payload.topic)
        except ValueError as exc:  # Likely due to unsupported configuration
            raise HTTPException(status_code=400, detail=str(exc)) from exc
        except Exception as exc:  # pragma: no cover - defensive guardrail
            raise HTTPException(status_code=500, detail="Research failed") from exc

        todo_payload = [
            {
                "id": item.id,
                "title": item.title,
                "intent": item.intent,
                "query": item.query,
                "status": item.status,
                "summary": item.summary,
                "sources_summary": item.sources_summary,
                "note_id": item.note_id,
                "note_path": item.note_path,
            }
            for item in result.todo_items
        ]

        return ResearchResponse(
            report_markdown=(result.report_markdown or result.running_summary or ""),
            todo_items=todo_payload,
        )

    @app.post("/research/stream")
    def stream_research(payload: ResearchRequest) -> StreamingResponse:
        try:
            config = _build_config(payload)
            agent = DeepResearchAgent(config=config)
        except ValueError as exc:
            raise HTTPException(status_code=400, detail=str(exc)) from exc

        def event_iterator() -> Iterator[str]:
            try:
                for event in agent.run_stream(payload.topic):
                    yield f"data: {json.dumps(event, ensure_ascii=False)}\n\n"
            except Exception as exc:  # pragma: no cover - defensive guardrail
                logger.exception("Streaming research failed")
                error_payload = {"type": "error", "detail": str(exc)}
                yield f"data: {json.dumps(error_payload, ensure_ascii=False)}\n\n"

        return StreamingResponse(
            event_iterator(),
            media_type="text/event-stream",
            headers={
                "Cache-Control": "no-cache",
                "Connection": "keep-alive",
            },
        )

    # Serve static frontend files in production (when static directory exists)
    if STATIC_DIR.exists() and STATIC_DIR.is_dir():
        logger.info(f"Serving static files from {STATIC_DIR}")

        # Mount assets directory first (CSS, JS, images)
        assets_dir = STATIC_DIR / "assets"
        if assets_dir.exists():
            app.mount("/assets", StaticFiles(directory=assets_dir), name="assets")

        # Serve index.html for root path
        @app.get("/")
        async def serve_index() -> FileResponse:
            """Serve the main index.html."""
            return FileResponse(STATIC_DIR / "index.html")

        # Serve favicon and other root-level static files
        @app.get("/favicon.ico")
        async def serve_favicon() -> FileResponse:
            """Serve favicon."""
            favicon_path = STATIC_DIR / "favicon.ico"
            if favicon_path.exists():
                return FileResponse(favicon_path)
            raise HTTPException(status_code=404, detail="Favicon not found")

        # Catch-all for SPA routing (must be last)
        @app.get("/{full_path:path}")
        async def serve_spa(full_path: str) -> FileResponse:
            """Serve the SPA index.html for client-side routing."""
            # Check if requesting a static file that exists
            file_path = STATIC_DIR / full_path
            if file_path.exists() and file_path.is_file():
                return FileResponse(file_path)
            # Otherwise serve index.html for SPA routing
            return FileResponse(STATIC_DIR / "index.html")

    return app


app = create_app()


if __name__ == "__main__":
    import uvicorn

    uvicorn.run(
        "main:app",
        host="0.0.0.0",
        port=8000,
        reload=True,
        log_level="info"
    )