import asyncio
import json
import logging
import time

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

from app.core.config import get_settings
from app.models.query import QueryRequest
from app.models.common import SourceMetadata
from app.services.history_service import HistoryService
from app.services.llm_client import LLMClient
from app.services.prompt_service import PromptService
from app.services.query_decomposer import QueryDecomposer
from app.services.relevance_filter import RelevanceFilter
from app.services.rag import RAGService

logger = logging.getLogger(__name__)
router = APIRouter(tags=["query"])

NO_RESULTS_ANSWER = "I could not find any relevant information to answer your question."


def _format_sse(data: dict) -> str:
    return f"data: {json.dumps(data)}\n\n"


def format_chunks_retrieved_xml(chunks: list) -> str:
    """Format retrieved chunks as XML-tagged string.
    chunks = [(text, metadata, distance), ...] from RAGService.retrieve()
    """
    parts = []
    for i, (text, meta, _dist) in enumerate(chunks, start=1):
        lines = [f"<chunk_{i}>"]
        lines.append(f"Filename: {meta.get('filename', 'unknown')}")
        page = meta.get("page_number")
        if page is not None:
            lines.append(f"Page: {page}")
        lines.append(f"Content: {text}")
        lines.append(f"</chunk_{i}>")
        parts.append("\n".join(lines))
    return "\n".join(parts)


def format_chunks_filtered_xml(filtered: list) -> str:
    """Format filtered chunks as XML-tagged string with relevance scores.
    filtered = [(text, meta), ...] — score embedded in meta["relevance_score"]
    """
    parts = []
    for i, (text, meta) in enumerate(filtered, start=1):
        lines = [f"<chunk_{i}>"]
        lines.append(f"Filename: {meta.get('filename', 'unknown')}")
        page = meta.get("page_number")
        if page is not None:
            lines.append(f"Page: {page}")
        score = meta.get("relevance_score")
        if score is not None:
            lines.append(f"Relevance: {score}")
        lines.append(f"Content: {text}")
        lines.append(f"</chunk_{i}>")
        parts.append("\n".join(lines))
    return "\n".join(parts)


async def _record_history(history_service, input_text, extracted_questions,
    decompose_prompt, decomposer_time_ms, retriever_time_ms,
    chunks_retrieved_count, chunks_retrieved, filter_prompt,
    filter_time_ms, chunks_filtered_count, chunks_filtered,
    generate_prompt, generator_time_ms, profile_used,
    final_answer, sources, total_time_ms):
    """Record a query to history. Runs as a fire-and-forget task."""
    try:
        history_service.record({
            "input_text": input_text,
            "extracted_questions": json.dumps(extracted_questions) if isinstance(extracted_questions, list) else extracted_questions,
            "decompose_prompt": decompose_prompt,
            "decomposer_time_ms": decomposer_time_ms,
            "retriever_time_ms": retriever_time_ms,
            "chunks_retrieved": chunks_retrieved,
            "chunks_retrieved_count": chunks_retrieved_count,
            "filter_prompt": filter_prompt,
            "filter_time_ms": filter_time_ms,
            "chunks_filtered": chunks_filtered,
            "chunks_filtered_count": chunks_filtered_count,
            "generate_prompt": generate_prompt,
            "generator_time_ms": generator_time_ms,
            "total_time_ms": total_time_ms,
            "final_answer": final_answer,
            "sources": sources,
            "profile_used": profile_used,
        })
    except Exception:
        logger.warning("History recording failed", exc_info=True)


def _schedule_history(history_service, request, extracted_questions,
    decompose_prompt, decomposer_time_ms, retriever_time_ms,
    chunks_retrieved_count, chunks_retrieved, filter_prompt,
    filter_time_ms, chunks_filtered_count, chunks_filtered,
    generate_prompt, generator_time_ms, active_profile,
    final_answer, sources_json, total_time_ms):
    """Fire-and-forget history recording. Never blocks the SSE stream."""
    try:
        asyncio.create_task(
            _record_history(
                history_service, request.question, extracted_questions,
                decompose_prompt, decomposer_time_ms, retriever_time_ms,
                chunks_retrieved_count, chunks_retrieved, filter_prompt,
                filter_time_ms, chunks_filtered_count, chunks_filtered,
                generate_prompt, generator_time_ms, active_profile,
                final_answer, sources_json, total_time_ms
            )
        )
    except Exception:
        logger.warning("Failed to schedule history recording", exc_info=True)


async def _query_stream(request: QueryRequest):
    settings = get_settings()
    prompt_service = PromptService(db_path=settings.prompts_db_path)
    overall_start = time.perf_counter()

    try:
        history_service = HistoryService(db_path=settings.history_db_path)

        llm_client = LLMClient(settings)
        rag = RAGService(llm_client=llm_client, settings=settings, prompt_service=prompt_service)
        active_profile = prompt_service.get_active_profile_name()

        logger.info("Query: %s. Active prompt profile: %s", request.question, active_profile)

        decomposer = QueryDecomposer(llm_client, prompt_service=prompt_service)

        # Stage 1: Decompose
        stage_start = time.perf_counter()
        decompose_result = await decomposer.decompose(request.question)
        if isinstance(decompose_result, tuple):
            extracted_questions, decompose_prompt = decompose_result
        else:
            extracted_questions, decompose_prompt = decompose_result, ""
        decomposer_time_ms = int((time.perf_counter() - stage_start) * 1000)
        logger.info("Extracted questions: %s", extracted_questions)

        yield _format_sse({
            "phase": "decomposed",
            "extracted_questions": extracted_questions,
        })

        # Stage 2: Retrieve
        stage_start = time.perf_counter()
        chunks = rag.retrieve(extracted_questions, n_results=settings.retrieval_n_results)
        retriever_time_ms = int((time.perf_counter() - stage_start) * 1000)
        chunks_retrieved_count = len(chunks)
        chunks_retrieved = format_chunks_retrieved_xml(chunks)

        yield _format_sse({"phase": "retrieving"})

        if not chunks:
            _schedule_history(history_service, request, extracted_questions,
                decompose_prompt, decomposer_time_ms, 0, 0, "", "",
                0, 0, "", "", 0, active_profile, NO_RESULTS_ANSWER,
                "[]", int((time.perf_counter() - overall_start) * 1000))
            yield _format_sse({
                "phase": "completed",
                "answer": NO_RESULTS_ANSWER,
                "sources": [],
            })
            return

        # Stage 3: Filter
        chunks_for_filter = [(text, meta) for text, meta, _dist in chunks]
        relevance_filter = RelevanceFilter(llm_client, prompt_service=prompt_service)

        yield _format_sse({"phase": "filtering"})

        filter_result = await relevance_filter.filter(
            request.question, chunks_for_filter, threshold=settings.relevance_threshold
        )
        if isinstance(filter_result, tuple):
            filtered, filter_prompt = filter_result
        else:
            filtered, filter_prompt = filter_result, ""

        filter_time_ms = int((time.perf_counter() - stage_start) * 1000)
        chunks_filtered_count = len(filtered)
        chunks_filtered = format_chunks_filtered_xml(filtered)

        if not filtered:
            _schedule_history(history_service, request, extracted_questions,
                decompose_prompt, decomposer_time_ms, retriever_time_ms,
                chunks_retrieved_count, chunks_retrieved, filter_prompt,
                filter_time_ms, 0, "", "", 0, active_profile,
                NO_RESULTS_ANSWER, "[]",
                int((time.perf_counter() - overall_start) * 1000))
            yield _format_sse({
                "phase": "completed",
                "answer": NO_RESULTS_ANSWER,
                "sources": [],
            })
            return

        # Stage 4: Generate
        stage_start = time.perf_counter()
        chunk_texts = [chunk for chunk, _meta in filtered]
        chunk_metadata = [meta for _chunk, meta in filtered]

        yield _format_sse({"phase": "generating"})

        gen_result = await rag.generate_response(request.question, chunk_texts, chunk_metadata)
        if isinstance(gen_result, tuple):
            answer, generate_prompt = gen_result
        else:
            answer, generate_prompt = gen_result, ""

        generator_time_ms = int((time.perf_counter() - stage_start) * 1000)
        logger.info("Answer generated: %d chars, %d sources", len(answer), len(filtered))

        total_time_ms = int((time.perf_counter() - overall_start) * 1000)

        sources = [
            SourceMetadata(
                filename=meta.get("filename", "unknown"),
                upload_date=meta.get("upload_date", ""),
                content_summary=meta.get("content_summary", ""),
                chunk_index=meta.get("chunk_index", 0),
                page_number=meta.get("page_number"),
                chunk_file_path=meta.get("chunk_file_path"),
            )
            for meta in chunk_metadata
        ]

        _schedule_history(history_service, request, extracted_questions,
            decompose_prompt, decomposer_time_ms, retriever_time_ms,
            chunks_retrieved_count, chunks_retrieved, filter_prompt,
            filter_time_ms, chunks_filtered_count, chunks_filtered,
            generate_prompt, generator_time_ms, active_profile,
            answer, json.dumps([s.model_dump() for s in sources]),
            total_time_ms)

        yield _format_sse({
            "phase": "completed",
            "answer": answer,
            "sources": [s.model_dump() for s in sources],
        })

    except HTTPException:
        raise
    except Exception as e:
        logger.error("Query stream failed: %s", str(e))
        yield _format_sse({
            "phase": "error",
            "message": f"Query failed: {str(e)}",
        })


@router.post("/query")
async def query(request: QueryRequest):
    if not request.question or not request.question.strip():
        raise HTTPException(status_code=400, detail="Question is required")

    return StreamingResponse(
        _query_stream(request),
        media_type="text/event-stream",
        headers={
            "Cache-Control": "no-cache",
            "X-Accel-Buffering": "no",
        },
    )