strat-chatbot/adapters/inbound/api.py

"""FastAPI inbound adapter — thin HTTP layer over ChatService.

This module contains only routing / serialisation logic.  All business rules
live in domain.services.ChatService; all storage / LLM calls live in outbound
adapters.  The router reads ChatService and RuleRepository from app.state so
that the container (config/container.py) remains the single wiring point and
tests can substitute fakes without monkey-patching.
"""

import logging
from typing import Annotated, Optional

from fastapi import APIRouter, Depends, HTTPException, Request
from pydantic import BaseModel, Field

from domain.ports import RuleRepository
from domain.services import ChatService

logger = logging.getLogger(__name__)

router = APIRouter()


# ---------------------------------------------------------------------------
# Request / response Pydantic models
# ---------------------------------------------------------------------------


class ChatRequest(BaseModel):
    """Payload accepted by POST /chat."""

    message: str = Field(
        ...,
        min_length=1,
        max_length=4000,
        description="The user's question (1–4000 characters).",
    )
    user_id: str = Field(
        ...,
        min_length=1,
        max_length=64,
        description="Opaque caller identifier, e.g. Discord snowflake.",
    )
    channel_id: str = Field(
        ...,
        min_length=1,
        max_length=64,
        description="Opaque channel identifier, e.g. Discord channel snowflake.",
    )
    conversation_id: Optional[str] = Field(
        default=None,
        description="Continue an existing conversation; omit to start a new one.",
    )
    parent_message_id: Optional[str] = Field(
        default=None,
        description="Thread parent message ID for Discord thread replies.",
    )


class ChatResponse(BaseModel):
    """Payload returned by POST /chat."""

    response: str
    conversation_id: str
    message_id: str
    parent_message_id: Optional[str] = None
    cited_rules: list[str]
    confidence: float
    needs_human: bool


# ---------------------------------------------------------------------------
# Dependency helpers — read from app.state set by the container
# ---------------------------------------------------------------------------


def _get_chat_service(request: Request) -> ChatService:
    """Extract the ChatService wired by the container from app.state."""
    return request.app.state.chat_service


def _get_rule_repository(request: Request) -> RuleRepository:
    """Extract the RuleRepository wired by the container from app.state."""
    return request.app.state.rule_repository


# ---------------------------------------------------------------------------
# Endpoints
# ---------------------------------------------------------------------------


@router.post("/chat", response_model=ChatResponse)
async def chat(
    body: ChatRequest,
    service: Annotated[ChatService, Depends(_get_chat_service)],
    rules: Annotated[RuleRepository, Depends(_get_rule_repository)],
) -> ChatResponse:
    """Handle a rules Q&A request.

    Delegates entirely to ChatService.answer_question — no business logic here.
    Returns HTTP 503 when the LLM adapter cannot be constructed (missing API key)
    rather than producing a fake success response, so callers can distinguish
    genuine answers from configuration errors.
    """
    # The container raises at startup if the API key is required but absent;
    # however if the service was created without a real LLM (e.g. missing key
    # detected at request time), surface a clear service-unavailable rather than
    # leaking a misleading 200 OK.
    if not hasattr(service, "llm") or service.llm is None:
        raise HTTPException(
            status_code=503,
            detail="LLM service is not available — check OPENROUTER_API_KEY configuration.",
        )

    try:
        result = await service.answer_question(
            message=body.message,
            user_id=body.user_id,
            channel_id=body.channel_id,
            conversation_id=body.conversation_id,
            parent_message_id=body.parent_message_id,
        )
    except Exception as exc:
        logger.exception("Unhandled error in ChatService.answer_question")
        raise HTTPException(status_code=500, detail=str(exc)) from exc

    return ChatResponse(
        response=result.response,
        conversation_id=result.conversation_id,
        message_id=result.message_id,
        parent_message_id=result.parent_message_id,
        cited_rules=result.cited_rules,
        confidence=result.confidence,
        needs_human=result.needs_human,
    )


@router.get("/health")
async def health(
    rules: Annotated[RuleRepository, Depends(_get_rule_repository)],
) -> dict:
    """Return service health and a summary of the loaded knowledge base."""
    stats = rules.get_stats()
    return {
        "status": "healthy",
        "rules_count": stats.get("total_rules", 0),
        "sections": stats.get("sections", {}),
    }


@router.get("/stats")
async def stats(
    rules: Annotated[RuleRepository, Depends(_get_rule_repository)],
    request: Request,
) -> dict:
    """Return extended statistics about the knowledge base and configuration."""
    kb_stats = rules.get_stats()

    # Pull optional config snapshot from app.state (set by container).
    config_snapshot: dict = getattr(request.app.state, "config_snapshot", {})

    return {
        "knowledge_base": kb_stats,
        "config": config_snapshot,
    }