"""
Query endpoint for RAG pipeline interactions.
"""

import json
import logging
import time
import uuid
from collections.abc import AsyncGenerator
from typing import TYPE_CHECKING, Any

from fastapi import APIRouter, HTTPException, Request
from fastapi.responses import StreamingResponse

from src.api.guardrails.pii_mask import PIIMask
from src.api.guardrails.semantic_cache import SemanticCache
from src.api.limiter import limiter
from src.api.middleware.metrics import update_ragas_metrics
from src.api.models import QueryRequest, QueryResponse
from src.api.query_tracker import query_tracker
from src.evaluation.ragas_evaluator import evaluate as evaluate_ragas
from src.reasoning.state import RAGState

if TYPE_CHECKING:
    from src.reasoning.pipeline import ReasoningPipeline
    from src.retrieval.hybrid_search import HybridRetriever

logger = logging.getLogger(__name__)

router = APIRouter()

# Lazy-loaded module instances
_reasoning_pipeline = None
_pii_mask = None
_semantic_cache = None


def get_pii_mask() -> PIIMask:
    """Lazy-load the PII mask."""
    global _pii_mask
    if _pii_mask is None:
        _pii_mask = PIIMask()
    return _pii_mask


def get_semantic_cache() -> SemanticCache:
    """Lazy-load the semantic cache."""
    global _semantic_cache
    if _semantic_cache is None:
        _semantic_cache = SemanticCache()
        logger.info("SemanticCache initialized for API")
    return _semantic_cache


def get_hybrid_retriever() -> "HybridRetriever":
    """Lazy-load the hybrid retriever (delegates to module singleton)."""
    from src.retrieval.hybrid_search import get_retriever

    return get_retriever()


def get_reasoning_pipeline() -> "ReasoningPipeline":
    """Lazy-load the reasoning pipeline."""
    global _reasoning_pipeline
    if _reasoning_pipeline is None:
        from src.reasoning.pipeline import ReasoningPipeline

        _reasoning_pipeline = ReasoningPipeline()
        logger.info("ReasoningPipeline initialized for API")
    return _reasoning_pipeline


def _build_pipeline_response(result: RAGState, start_time: float, include_sources: bool) -> dict:
    """Build structured response from raw pipeline result.

    Shared by /query and /query/stream endpoints so both return
    identical sources, node_evaluations, and metadata.
    """
    latency_ms = (time.time() - start_time) * 1000

    # Compute RAGAS metrics from pipeline output
    ragas_scores = evaluate_ragas(dict(result))
    if ragas_scores:
        update_ragas_metrics(ragas_scores)

    sources: list[dict[str, Any]] | None = None
    if include_sources and result.get("retrieved_context"):
        sources = [
            {
                "text": ctx.get("text", "")[:500],
                "score": round(ctx.get("rrf_score", 0), 4),
                "source": ctx.get("source", "unknown"),
                "source_file": ctx.get("metadata", {}).get("source_file", "unknown"),
                "chunk_index": ctx.get("metadata", {}).get("chunk_index", None),
            }
            for ctx in result.get("retrieved_context", [])[:5]
        ]

    # Unique source filenames cited in the answer
    source_files = result.get("source_files", [])

    node_evaluations: list[dict] = []
    node_latencies = result.get("node_latency_ms", {})
    node_order = [
        "planner",
        "router",
        "retrieval_agent",
        "calculation_agent",
        "summarization_agent",
        "gatekeeper",
        "auditor",
        "strategist",
    ]

    for node_name in node_order:
        latency = node_latencies.get(node_name, 0)
        entry: dict = {"node": node_name, "latency_ms": latency}
        if node_name in ("gatekeeper", "auditor", "strategist"):
            validation_passed = result.get("validation_passed", True)
            error_msg = (result.get("error_message") or "").lower()
            entry["evaluation"] = "passed" if validation_passed or node_name not in error_msg else "failed"
        else:
            entry["evaluation"] = "completed"
        node_evaluations.append(entry)

    return {
        "answer": result.get("generated_answer", ""),
        "sources": sources,
        "source_files": source_files,
        "latency_ms": latency_ms,
        "validation_passed": result.get("validation_passed", True),
        "error_message": result.get("error_message"),
        "node_evaluations": (node_evaluations if any(ne["latency_ms"] > 0 for ne in node_evaluations) else None),
        "ragas_scores": ragas_scores,
        "total_tokens_used": result.get("total_tokens_used", 0),
    }


@router.post("/query", response_model=QueryResponse)
@limiter.exempt
async def query(query_req: QueryRequest, request: Request) -> QueryResponse:
    """Submit a query to the RAG pipeline.

    Processes the query through the LangGraph reasoning engine
    and returns the generated answer with sources.

    Guardrails applied:
    - Semantic cache (return cached answer for similar queries)
    - PII redaction (redact PII from output answer)
    - Token budget (reject overly long queries)
    - Prompt injection hardening (in system prompts)
    """
    # Concurrent query gate — strict limit for system key, safety cap for user key
    active = query_tracker.active_count()
    if query_req.llm_api_key:
        if active >= 10:
            raise HTTPException(
                status_code=429,
                detail={
                    "error": "server_overloaded",
                    "message": "Server overloaded (10 concurrent queries max). Try again shortly.",
                    "solution": "Wait a moment and retry your query.",
                },
            )
    elif active >= 3:
        raise HTTPException(
            status_code=429,
            detail={
                "error": "too_many_concurrent",
                "message": "System at capacity (3 concurrent queries max). "
                "Provide your own OpenRouter API key in Settings to bypass.",
                "solution": "Add your OpenRouter key in Settings, or wait for an in-progress query to finish.",
            },
        )

    request_id = str(uuid.uuid4())
    start_time = time.time()
    tenant_id = getattr(request.state, "tenant_id", "")

    try:
        # Semantic cache check
        cache = get_semantic_cache()
        cached = cache.get(query_req.query)
        if cached is not None:
            logger.info("Returning cached response for query: %s...", query_req.query[:60])
            pii_mask = get_pii_mask()
            clean_answer = pii_mask.redact(cached) if pii_mask.contains_pii(cached) else cached
            return QueryResponse(
                answer=clean_answer,
                sources=None,
                latency_ms=(time.time() - start_time) * 1000,
                validation_passed=True,
                error_message=None,
                node_evaluations=None,
                ragas_scores=None,
                total_tokens_used=0,
            )

        pipeline = get_reasoning_pipeline()
        logger.info("Processing query (req=%s): %s...", request_id, query_req.query[:100])

        query_tracker.start(request_id, query_req.query, tenant_id)
        try:
            result = pipeline.run(
                query_req.query,
                llm_api_key=query_req.llm_api_key,
                request_id=request_id,
                tenant_id=tenant_id,
            )
        finally:
            query_tracker.finish(request_id)

        built = _build_pipeline_response(result, start_time, query_req.include_sources)

        # Cache the generated answer (skip timeout error answers)
        answer = built.get("answer", "")
        if answer and "Error" not in answer and "rejected" not in answer and "timed out" not in answer:
            cache.set(query_req.query, answer)

        # Output PII redaction on the answer
        pii_mask = get_pii_mask()
        if pii_mask.contains_pii(answer):
            built["answer"] = pii_mask.redact(answer)
            logger.info("PII redacted from output answer")

        return QueryResponse(
            answer=built["answer"],
            sources=built["sources"],
            source_files=built.get("source_files", []),
            latency_ms=built["latency_ms"],
            validation_passed=built["validation_passed"],
            error_message=built["error_message"],
            node_evaluations=built["node_evaluations"],
            ragas_scores=built["ragas_scores"],
            total_tokens_used=built.get("total_tokens_used", 0),
        )

    except Exception as e:
        logger.error("Query processing failed (req=%s): %s", request_id, str(e))
        error_str = str(e).lower()
        if "invalid_api_key" in error_str:
            raise HTTPException(
                status_code=401,
                detail={
                    "error": "invalid_api_key",
                    "message": "The OpenRouter API key you provided is invalid or expired. "
                    "Please check your key in Settings and try again.",
                    "solution": "Update your OpenRouter API key in Settings.",
                },
            ) from e
        if "all providers failed" in error_str or "no llm" in error_str:
            raise HTTPException(
                status_code=503,
                detail={
                    "error": "no_llm_available",
                    "message": "No LLM available. Provide your OpenRouter API key in settings, or run Ollama locally.",
                    "solution": "Add your OpenRouter key in Settings, or start Ollama with: ollama serve",
                },
            ) from e
        raise HTTPException(status_code=500, detail="Query processing failed") from e


@router.post("/query/retrieve")
async def retrieve_only(query_req: QueryRequest, request: Request) -> dict[str, Any]:
    """Retrieve documents without generating an answer.

    Useful for debugging retrieval quality or custom workflows.
    Returns only matched sources with no LLM call.
    """
    try:
        retriever = get_hybrid_retriever()
        logger.info(
            "Retrieving documents for: %s... (source_files=%s)",
            query_req.query[:100],
            query_req.source_files or "all",
        )

        source_filter = query_req.source_files if query_req.source_files else None
        tenant_id = getattr(request.state, "tenant_id", "")
        results = retriever.search(query_req.query, source_files=source_filter, tenant_id=tenant_id)

        sources = [
            {
                "text": r.get("text", "")[:500],
                "score": round(r.get("rrf_score", 0), 4),
                "source": r.get("source", "unknown"),
                "metadata": r.get("metadata", {}),
            }
            for r in results
        ]

        return {
            "query": query_req.query,
            "results": sources,
            "count": len(sources),
        }

    except Exception as e:
        logger.error("Retrieval failed: %s", str(e))
        raise HTTPException(status_code=500, detail="Retrieval failed") from e


@router.post("/query/stream")
@limiter.exempt
async def query_stream(query_req: QueryRequest, request: Request) -> StreamingResponse:
    """Submit a query with streaming response.

    Uses Server-Sent Events (SSE) to stream the answer text in
    50-char chunks as it's generated. After the answer, sends a
    JSON metadata event containing sources, node evaluations,
    and validation results.

    Event sequence:
      data: <text_chunk>  (repeated)
      data: <JSON metadata with sources, evaluations, etc.>
      data: [DONE]
    """
    # Concurrent query gate — strict limit for system key, safety cap for user key
    active = query_tracker.active_count()
    if query_req.llm_api_key:
        if active >= 10:
            raise HTTPException(
                status_code=429,
                detail={
                    "error": "server_overloaded",
                    "message": "Server overloaded (10 concurrent queries max). Try again shortly.",
                    "solution": "Wait a moment and retry your query.",
                },
            )
    elif active >= 3:
        raise HTTPException(
            status_code=429,
            detail={
                "error": "too_many_concurrent",
                "message": "System at capacity (3 concurrent queries max). "
                "Provide your own OpenRouter API key in Settings to bypass.",
                "solution": "Add your OpenRouter key in Settings, or wait for an in-progress query to finish.",
            },
        )

    if not query_req.stream:
        result = await query(query_req, request)

        async def convert_to_stream() -> AsyncGenerator[str, None]:
            _nl = "\n"
            for line in result.answer.split("\n"):
                if not line:
                    yield f"data: {json.dumps({'t': _nl})}\n\n"
                else:
                    yield f"data: {json.dumps({'t': line})}\n\n"
            yield "data: [DONE]\n\n"

        return StreamingResponse(convert_to_stream(), media_type="text/event-stream")

    async def generate_stream() -> AsyncGenerator[str, None]:
        request_id = str(uuid.uuid4())
        try:
            start_time = time.time()

            # Semantic cache check
            cache = get_semantic_cache()
            cached = cache.get(query_req.query)
            if cached is not None:
                logger.info(
                    "Returning cached response for stream query (req=%s): %s...",
                    request_id,
                    query_req.query[:60],
                )
                pii_mask = get_pii_mask()
                clean_answer = pii_mask.redact(cached) if pii_mask.contains_pii(cached) else cached
                chunk_size = 50
                _nl = "\n"
                for line in clean_answer.split("\n"):
                    if not line:
                        yield f"data: {json.dumps({'t': _nl})}\n\n"
                        continue
                    start = 0
                    while start < len(line):
                        if start + chunk_size >= len(line):
                            yield f"data: {json.dumps({'t': line[start:]})}\n\n"
                            break
                        end = start + chunk_size
                        if end < len(line) and not line[end].isspace() and end > start:
                            last_space = line.rfind(" ", start, end)
                            if last_space > start:
                                end = last_space + 1
                        yield f"data: {json.dumps({'t': line[start:end]})}\n\n"
                        start = end
                metadata: dict[str, object] = {
                    "answer": clean_answer,
                    "sources": None,
                    "source_files": [],
                    "latency_ms": int((time.time() - start_time) * 1000),
                    "validation_passed": True,
                    "error_message": None,
                    "node_evaluations": None,
                    "ragas_scores": None,
                    "total_tokens_used": 0,
                    "cached": True,
                }
                yield f"data: {json.dumps(metadata)}\n\n"
                yield "data: [DONE]\n\n"
                return

            pipeline = get_reasoning_pipeline()
            logger.info("Processing streaming query (req=%s): %s...", request_id, query_req.query[:100])
            tenant_id = getattr(request.state, "tenant_id", "")

            query_tracker.start(request_id, query_req.query, tenant_id)
            try:
                result = pipeline.run(
                    query_req.query,
                    llm_api_key=query_req.llm_api_key,
                    request_id=request_id,
                    tenant_id=tenant_id,
                )
            finally:
                query_tracker.finish(request_id)

            built = _build_pipeline_response(result, start_time, True)
            answer = built.pop("answer", "")

            # Cache the generated answer (skip timeout error answers)
            if answer and "Error" not in answer and "rejected" not in answer and "timed out" not in answer:
                cache.set(query_req.query, answer)

            # Stream answer text as SSE events, one per line.
            # Split on \n first so no data: line ever contains a newline —
            # otherwise the frontend's \n-based SSE parser drops text.
            # Stream as JSON-wrapped chunks: {"t":"text"}
            # JSON-escapes \n as \\n so no data: line ever contains a raw
            # newline — the frontend's \n-based SSE parser stays intact.
            chunk_size = 50
            _nl = "\n"
            for line in answer.split("\n"):
                if not line:
                    yield f"data: {json.dumps({'t': _nl})}\n\n"
                    continue
                start = 0
                while start < len(line):
                    if start + chunk_size >= len(line):
                        yield f"data: {json.dumps({'t': line[start:]})}\n\n"
                        break
                    end = start + chunk_size
                    if end < len(line) and not line[end].isspace() and end > start:
                        last_space = line.rfind(" ", start, end)
                        if last_space > start:
                            end = last_space + 1
                    yield f"data: {json.dumps({'t': line[start:end]})}\n\n"
                    start = end

            # Send metadata as a single JSON event
            yield f"data: {json.dumps(built)}\n\n"
            yield "data: [DONE]\n\n"

        except Exception as e:
            logger.error("Streaming query failed: %s", str(e))
            error_str = str(e).lower()
            if "invalid_api_key" in error_str:
                error_detail = {
                    "error": "invalid_api_key",
                    "message": "The OpenRouter API key you provided is invalid or expired. "
                    "Please check your key in Settings and try again.",
                }
                yield f"data: {json.dumps(error_detail)}\n\n"
            elif "all providers failed" in error_str or "no llm" in error_str:
                no_llm_msg = "No LLM available. Add your OpenRouter key in Settings, or run Ollama locally."
                yield f'data: {{"error":"no_llm_available","message":"{no_llm_msg}"}}\n\n'
            else:
                yield f"data: Error: {str(e)}\n\n"

    return StreamingResponse(
        generate_stream(),
        media_type="text/event-stream",
        headers={"X-Accel-Buffering": "no"},
    )


@router.post("/debug/active_queries")
async def debug_active_queries(request: Request) -> dict[str, Any]:
    """Return in-flight queries scoped to the caller's tenant.

    Useful for diagnosing stuck queries without restarting the server.
    """
    tenant_id = getattr(request.state, "tenant_id", "")
    active = query_tracker.get_active(tenant_id)
    stale_ids = query_tracker.get_stale()
    return {
        "active_count": len(active),
        "active_queries": active,
        "stale_ids": stale_ids,
        "hint": "If queries appear stuck, call /debug/clear_query with the request_id",
    }


@router.post("/debug/clear_query")
async def debug_clear_query(request: Request, request_id: str) -> dict[str, Any]:
    """Forcefully remove a query from the in-flight tracker (tenant-scoped).

    Does NOT stop the underlying pipeline execution — it only removes
    the tracker entry so a new query can proceed.
    """
    tenant_id = getattr(request.state, "tenant_id", "")
    existed = query_tracker.force_clear(request_id, tenant_id)
    if existed:
        logger.warning("Force-cleared tracker entry for request %s (tenant=%s)", request_id, tenant_id)
    return {
        "cleared": existed,
        "request_id": request_id,
        "message": "Tracker entry removed (pipeline thread may still be running)",
    }