import json
import logging
import asyncio
import time
import uuid
from copy import deepcopy
from typing import Any, List, Optional

from fastapi import APIRouter, Body, Depends, HTTPException, Path
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select, delete as sa_delete
from sqlalchemy.exc import OperationalError
from pydantic import BaseModel, Field

from app.database import get_db
from app.auth import get_current_user
from app.models.user import User
from app.models.chat import ChatMessage
from app.models.evaluation import EvaluationResult
from app.models.evaluation_report import EvaluationReport, EvaluationReportSummary
from app.models.rag_config import RAGConfig
from app.services.chunking.base import Chunk
from app.services.evaluation.answer_relevancy import AnswerRelevancyEvaluator
from app.services.evaluation.context_quality import ContextQualityEvaluator
from app.services.evaluation.faithfulness import FaithfulnessEvaluator
from app.services.evaluation.retrieval_metrics import build_retrieval_metrics_report, unified_deep_evaluation
from app.services.pipeline_factory import PipelineFactory
from app.services.query_classifier import classify_query


router = APIRouter(prefix="/api/evaluation", tags=["evaluation"])
logger = logging.getLogger(__name__)


class EvaluationError(Exception):
    """Base exception for evaluation failures."""
    def __init__(self, message: str, status_code: int = 500):
        super().__init__(message)
        self.status_code = status_code


class EvaluationNotFoundError(EvaluationError):
    def __init__(self, message: str):
        super().__init__(message, status_code=404)


class EvaluationBadRequestError(EvaluationError):
    def __init__(self, message: str):
        super().__init__(message, status_code=400)


class EvaluationServiceUnavailableError(EvaluationError):
    def __init__(self, message: str):
        super().__init__(message, status_code=503)


def _is_missing_evaluation_table(exc: Exception) -> bool:
    message = str(exc).lower()
    return "no such table: evaluation_results" in message


class EvaluationReportRequest(BaseModel):
    message_id: Optional[uuid.UUID] = None
    query: Optional[str] = None
    answer: Optional[str] = None
    chunks: list[dict[str, Any] | str] = Field(default_factory=list)
    retrieval_config: Optional[dict[str, Any]] = None
    deep: bool = False


def _chunks_from_payload(raw_chunks):
    chunks = []
    for idx, item in enumerate(raw_chunks or []):
        if isinstance(item, Chunk):
            chunks.append(item)
            continue

        if isinstance(item, dict):
            if "text" not in item:
                raise EvaluationBadRequestError(f"Malformed chunk payload: missing 'text' key in element {idx}")
            metadata = dict(item.get("metadata", {}) or {})
            if "score" in item:
                metadata.setdefault("score", item.get("score"))
            chunks.append(
                Chunk(
                    text=str(item.get("text", "")),
                    metadata=metadata,
                )
            )
            continue

        chunks.append(Chunk(text=str(item), metadata={"position": idx}))
    return chunks


def score_message(
    db: AsyncSession,
    assistant_msg: ChatMessage,
    query_text: str,
    llm_client,
    chunks: list[Chunk] | None = None,
) -> EvaluationResult:
    if llm_client is None or getattr(llm_client, "llm", None) is None:
        raise EvaluationServiceUnavailableError("LLM client is unavailable for evaluation")

    parsed_chunks = chunks if chunks is not None else _chunks_from_payload(assistant_msg.retrieved_chunks or [])

    try:
        faithfulness = FaithfulnessEvaluator().evaluate(
            query=query_text,
            answer=assistant_msg.content,
            chunks=parsed_chunks,
            llm_client=llm_client,
        )
    except Exception:
        logger.warning("Faithfulness evaluation failed for message_id=%s", assistant_msg.id, exc_info=True)
        faithfulness = None

    try:
        answer_relevancy = AnswerRelevancyEvaluator().evaluate(
            query=query_text,
            answer=assistant_msg.content,
            llm_client=llm_client,
        )
    except Exception:
        logger.warning("Answer relevancy evaluation failed for message_id=%s", assistant_msg.id, exc_info=True)
        answer_relevancy = None

    try:
        context_quality = ContextQualityEvaluator().evaluate(
            query=query_text,
            answer=assistant_msg.content,
            chunks=parsed_chunks,
            llm_client=llm_client,
        )
    except Exception:
        logger.warning("Context quality evaluation failed for message_id=%s", assistant_msg.id, exc_info=True)
        context_quality = {}

    result = EvaluationResult(
        message_id=assistant_msg.id,
        faithfulness=faithfulness,
        answer_relevancy=answer_relevancy,
        context_precision=context_quality.get("context_precision"),
        context_recall=context_quality.get("context_recall"),
    )
    db.add(result)
    return result


def compute_answer_metrics(
    query_text: str,
    answer_text: str,
    llm_client,
    chunks: list[Chunk] | None = None,
) -> dict[str, Optional[float]]:
    if llm_client is None or getattr(llm_client, "llm", None) is None:
        return {
            "faithfulness": None,
            "answer_relevancy": None,
            "context_precision": None,
            "context_recall": None,
        }

    parsed_chunks = chunks or []

    try:
        faithfulness = FaithfulnessEvaluator().evaluate(
            query=query_text,
            answer=answer_text,
            chunks=parsed_chunks,
            llm_client=llm_client,
        )
    except Exception:
        faithfulness = None

    try:
        answer_relevancy = AnswerRelevancyEvaluator().evaluate(
            query=query_text,
            answer=answer_text,
            llm_client=llm_client,
        )
    except Exception:
        answer_relevancy = None

    try:
        context_quality = ContextQualityEvaluator().evaluate(
            query=query_text,
            answer=answer_text,
            chunks=parsed_chunks,
            llm_client=llm_client,
        )
    except Exception:
        context_quality = {}

    return {
        "faithfulness": faithfulness,
        "answer_relevancy": answer_relevancy,
        "context_precision": context_quality.get("context_precision"),
        "context_recall": context_quality.get("context_recall"),
    }


async def build_message_evaluation_report(
    db: AsyncSession,
    message_id: uuid.UUID,
    user_id: uuid.UUID,
    candidate_pool_size: int = 20,
    deep: bool = False,
) -> dict[str, Any]:
    started_at = time.perf_counter()
    msg_stmt = select(ChatMessage).where(ChatMessage.id == message_id, ChatMessage.user_id == user_id)
    msg = (await db.execute(msg_stmt)).scalars().first()
    if not msg:
        raise EvaluationNotFoundError("Message not found")
    if msg.role != "assistant":
        raise EvaluationBadRequestError("Evaluation is only available for assistant messages")

    query_stmt = (
        select(ChatMessage)
        .where(
            ChatMessage.document_id == msg.document_id,
            ChatMessage.config_id == msg.config_id,
            ChatMessage.user_id == user_id,
            ChatMessage.role == "user",
            ChatMessage.timestamp <= msg.timestamp,
        )
        .order_by(ChatMessage.timestamp.desc())
    )
    user_msg = (await db.execute(query_stmt)).scalars().first()
    if not user_msg:
        raise EvaluationNotFoundError("Associated user query was not found")

    config = await db.get(RAGConfig, msg.config_id)
    if not config:
        raise EvaluationNotFoundError("RAG config not found")

    pipeline_config = deepcopy(config.config_json or {})
    retrieval_config = deepcopy(pipeline_config.get("retriever", {}))
    query_mode = classify_query(user_msg.content)
    retrieved_chunks = _chunks_from_payload(msg.retrieved_chunks or [])
    eval_record = None
    try:
        eval_stmt = (
            select(EvaluationResult)
            .where(EvaluationResult.message_id == msg.id)
            .order_by(EvaluationResult.created_at.desc())
        )
        eval_record = (await db.execute(eval_stmt)).scalars().first()
    except OperationalError as exc:
        if not _is_missing_evaluation_table(exc):
            raise

    llm_client = None
    embedder = None
    candidate_chunks = retrieved_chunks

    if deep:
        vectorstore_cfg = deepcopy(pipeline_config.get("vectorstore", {}))
        if vectorstore_cfg.get("type") == "chroma":
            vectorstore_cfg["collection_name"] = f"user_{user_id}_rag_cfg_{config.id}"
            pipeline_config["vectorstore"] = vectorstore_cfg

        pipeline = PipelineFactory.create_pipeline(pipeline_config)
        llm_client = getattr(pipeline, "llm_client", None)
        embedder = getattr(pipeline, "embedder", None)
        top_k = int(retrieval_config.get("top_k", 5))
        pool_k = max(candidate_pool_size, top_k)
        candidate_results = await pipeline.aretrieve(user_msg.content, top_k=pool_k)
        candidate_chunks = [item[0] if isinstance(item, tuple) else item for item in candidate_results] or retrieved_chunks

    unified_result = None
    if deep and llm_client is not None:
        try:
            unified_result = unified_deep_evaluation(
                query=user_msg.content,
                answer=msg.content,
                retrieved_chunks=retrieved_chunks,
                candidate_chunks=candidate_chunks,
                llm_client=llm_client,
            )
        except Exception as e:
            err_msg = str(e)
            if "429" in err_msg or "RESOURCE_EXHAUSTED" in err_msg or "quota" in err_msg.lower():
                raise EvaluationServiceUnavailableError(
                    "Gemini API quota limit exceeded or rate limit hit. Please check your Google AI Studio quota limits or retry in a few seconds."
                )
            logger.error("Failed to run unified deep evaluation: %s", e, exc_info=True)

    if unified_result is not None:
        report = build_retrieval_metrics_report(
            query=user_msg.content,
            answer=msg.content,
            retrieved_chunks=retrieved_chunks,
            candidate_chunks=candidate_chunks,
            llm_client=llm_client,
            embedder=embedder,
            retrieval_config=retrieval_config,
            query_mode=query_mode,
            precomputed_retrieved_flags=unified_result["retrieved_flags"],
            precomputed_candidate_flags=unified_result["candidate_flags"],
        )
    else:
        report = build_retrieval_metrics_report(
            query=user_msg.content,
            answer=msg.content,
            retrieved_chunks=retrieved_chunks,
            candidate_chunks=candidate_chunks,
            llm_client=llm_client,
            embedder=embedder,
            retrieval_config=retrieval_config,
            query_mode=query_mode,
        )

    report["message_id"] = str(msg.id)
    report["mode"] = "message-deep" if deep else "message-fast"
    answer_metrics = report.get("answer_metrics", {})
    if deep:
        if unified_result is not None:
            for key in ("faithfulness", "answer_relevancy", "context_recall"):
                val = unified_result.get(key)
                if val is not None:
                    answer_metrics[key] = val
        else:
            computed_answer_metrics = compute_answer_metrics(
                query_text=user_msg.content,
                answer_text=msg.content,
                llm_client=llm_client,
                chunks=retrieved_chunks,
            )
            for key, value in computed_answer_metrics.items():
                if value is not None:
                    answer_metrics[key] = value

    if eval_record is not None:
        answer_metrics.update(
            {
                key: value
                for key, value in {
                    "faithfulness": eval_record.faithfulness,
                    "answer_relevancy": eval_record.answer_relevancy,
                    "context_precision": eval_record.context_precision,
                    "context_recall": eval_record.context_recall,
                }.items()
                if value is not None and (not deep or answer_metrics.get(key) is None)
            }
        )
    report["answer_metrics"] = answer_metrics
    report["timing_ms"] = round((time.perf_counter() - started_at) * 1000, 2)
    return report


def build_ad_hoc_evaluation_report(
    query: str,
    answer: str,
    chunks: list[dict[str, Any] | str],
    retrieval_config: Optional[dict[str, Any]] = None,
) -> dict[str, Any]:
    parsed_chunks = _chunks_from_payload(chunks or [])
    report = build_retrieval_metrics_report(
        query=query,
        answer=answer,
        retrieved_chunks=parsed_chunks,
        candidate_chunks=parsed_chunks,
        llm_client=None,
        embedder=None,
        retrieval_config=retrieval_config or {},
    )
    report["mode"] = "ad_hoc"
    return report


async def score_message_by_id(db: AsyncSession, message_id: uuid.UUID, user_id: uuid.UUID) -> EvaluationResult:
    msg_stmt = select(ChatMessage).where(ChatMessage.id == message_id, ChatMessage.user_id == user_id)
    msg = (await db.execute(msg_stmt)).scalars().first()
    if not msg:
        raise EvaluationNotFoundError("Message not found")
    if msg.role != "assistant":
        raise EvaluationBadRequestError("Scoring is only available for assistant messages")

    query_stmt = (
        select(ChatMessage)
        .where(
            ChatMessage.document_id == msg.document_id,
            ChatMessage.config_id == msg.config_id,
            ChatMessage.user_id == user_id,
            ChatMessage.role == "user",
            ChatMessage.timestamp <= msg.timestamp,
        )
        .order_by(ChatMessage.timestamp.desc())
    )
    user_msg = (await db.execute(query_stmt)).scalars().first()
    if not user_msg:
        raise EvaluationNotFoundError("Associated user query was not found")

    config = await db.get(RAGConfig, msg.config_id)
    if not config:
        raise EvaluationNotFoundError("RAG config not found")

    pipeline_config = deepcopy(config.config_json or {})
    vectorstore_cfg = deepcopy(pipeline_config.get("vectorstore", {}))
    if vectorstore_cfg.get("type") == "chroma":
        vectorstore_cfg["collection_name"] = f"user_{user_id}_rag_cfg_{config.id}"
        pipeline_config["vectorstore"] = vectorstore_cfg

    pipeline = PipelineFactory.create_pipeline(pipeline_config)
    llm_client = getattr(pipeline, "llm_client", None)
    chunks = _chunks_from_payload(msg.retrieved_chunks or [])
    result = score_message(
        db=db,
        assistant_msg=msg,
        query_text=user_msg.content,
        llm_client=llm_client,
        chunks=chunks,
    )
    return result


@router.post("/score")
async def evaluate_score(
    message_id: uuid.UUID = Body(..., embed=True),
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    try:
        result = await score_message_by_id(db=db, message_id=message_id, user_id=current_user.id)
    except EvaluationError as exc:
        raise HTTPException(status_code=exc.status_code, detail=str(exc))
    except Exception as exc:
        logger.exception("Unexpected error during evaluation")
        raise HTTPException(status_code=500, detail="Internal server error during evaluation")

    await db.commit()
    await db.refresh(result)

    return {
        "message_id": str(result.message_id),
        "faithfulness": result.faithfulness,
        "answer_relevancy": result.answer_relevancy,
        "context_precision": result.context_precision,
        "context_recall": result.context_recall,
        "created_at": result.created_at,
    }


@router.post("/faithfulness")
async def evaluate_faithfulness_alias(
    message_id: uuid.UUID = Body(..., embed=True),
    db: AsyncSession = Depends(get_db),
):
    return await evaluate_score(message_id=message_id, db=db)


@router.post("/report")
async def evaluate_report(
    payload: EvaluationReportRequest,
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    try:
        if payload.message_id:
            if payload.deep:
                timeout_seconds = float(
                    __import__("os").getenv("DEEP_EVALUATION_TIMEOUT_SECONDS", "120")
                )
                try:
                    report = await asyncio.wait_for(
                        build_message_evaluation_report(
                            db=db,
                            message_id=payload.message_id,
                            user_id=current_user.id,
                            deep=True,
                        ),
                        timeout=timeout_seconds,
                    )
                except asyncio.TimeoutError:
                    raise EvaluationServiceUnavailableError(
                        f"Deep evaluation timed out after {int(timeout_seconds)} seconds"
                    )
            else:
                report = await build_message_evaluation_report(
                    db=db,
                    message_id=payload.message_id,
                    user_id=current_user.id,
                    deep=False,
                )

            # Auto-save report to DB
            try:
                await _save_report(
                    db=db,
                    user_id=current_user.id,
                    message_id=payload.message_id,
                    report=report,
                )
                await db.commit()
            except Exception:
                logger.warning("Failed to auto-save evaluation report", exc_info=True)

            return report

        if not payload.query:
            raise EvaluationBadRequestError("Either message_id or query must be provided")

        return build_ad_hoc_evaluation_report(
            query=payload.query,
            answer=payload.answer or "",
            chunks=payload.chunks or [],
            retrieval_config=payload.retrieval_config or {},
        )
    except EvaluationError as exc:
        raise HTTPException(status_code=exc.status_code, detail=str(exc))
    except Exception:
        logger.exception("Unexpected error during evaluation report generation")
        raise HTTPException(status_code=500, detail="Internal server error during evaluation report generation")


async def _save_report(
    db: AsyncSession,
    user_id: uuid.UUID,
    report: dict,
    message_id: Optional[uuid.UUID] = None,
) -> EvaluationReport:
    """Persist a full evaluation report JSON to the evaluation_reports table."""
    record = EvaluationReport(
        user_id=user_id,
        message_id=message_id,
        mode=report.get("mode"),
        report_json=json.dumps(report),
    )
    db.add(record)
    return record


@router.get("/reports", response_model=List[EvaluationReportSummary])
async def list_evaluation_reports(
    limit: int = 50,
    offset: int = 0,
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """List saved evaluation reports for the current user, newest first."""
    try:
        stmt = (
            select(EvaluationReport)
            .where(EvaluationReport.user_id == current_user.id)
            .order_by(EvaluationReport.created_at.desc())
            .limit(limit)
            .offset(offset)
        )
        records = (await db.execute(stmt)).scalars().all()
    except OperationalError as exc:
        if "no such table" in str(exc).lower():
            return []
        raise HTTPException(status_code=500, detail="Database error listing reports")

    summaries = []
    for rec in records:
        try:
            data = json.loads(rec.report_json or "{}")
        except Exception:
            data = {}
        answer_metrics = data.get("answer_metrics", {})
        retrieval_metrics = data.get("retrieval_metrics", {})
        summaries.append(
            EvaluationReportSummary(
                id=rec.id,
                message_id=rec.message_id,
                mode=rec.mode,
                created_at=rec.created_at,
                query=data.get("query"),
                faithfulness=answer_metrics.get("faithfulness"),
                answer_relevancy=answer_metrics.get("answer_relevancy"),
                context_precision=answer_metrics.get("context_precision"),
                context_recall=answer_metrics.get("context_recall"),
                precision_at_k=retrieval_metrics.get("precision_at_k"),
                recall_at_k=retrieval_metrics.get("recall_at_k"),
            )
        )
    return summaries


@router.get("/reports/{report_id}")
async def get_evaluation_report(
    report_id: uuid.UUID = Path(...),
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Retrieve a single saved evaluation report (full JSON)."""
    stmt = select(EvaluationReport).where(
        EvaluationReport.id == report_id,
        EvaluationReport.user_id == current_user.id,
    )
    record = (await db.execute(stmt)).scalars().first()
    if not record:
        raise HTTPException(status_code=404, detail="Report not found")
    try:
        return json.loads(record.report_json)
    except Exception:
        raise HTTPException(status_code=500, detail="Failed to parse saved report")


@router.delete("/reports/{report_id}", status_code=204)
async def delete_evaluation_report(
    report_id: uuid.UUID = Path(...),
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Delete a saved evaluation report."""
    stmt = select(EvaluationReport).where(
        EvaluationReport.id == report_id,
        EvaluationReport.user_id == current_user.id,
    )
    record = (await db.execute(stmt)).scalars().first()
    if not record:
        raise HTTPException(status_code=404, detail="Report not found")
    await db.delete(record)
    await db.commit()