from __future__ import annotations

import asyncio
import json
import logging
import sqlite3
from typing import (
    Any,
    Literal,
    NoReturn,
)

from fastapi import (
    APIRouter,
    Depends,
    Header,
    HTTPException,
    Request,
    status,
)
from fastapi.responses import JSONResponse
from pydantic import (
    BaseModel,
    ConfigDict,
    Field,
)

from app.security import (
    expected_gitea_repository,
    repository_name_from_payload,
    require_search_api_key,
    require_sync_api_key,
    same_repository,
    validate_secret,
    validate_security_configuration,
    verify_gitea_signature,
    webhook_should_pull_git,
)
from scripts.common import (
    DB_FILE,
    ZPWIKI_ROOT,
)
from scripts.rag_utils import build_rag_context
from scripts.rebuild_index import (
    ReindexInProgressError,
    rebuild_index,
)
from scripts.search_utils import search_database


logger = logging.getLogger(__name__)


router = APIRouter()


RETRIEVAL_UNAVAILABLE_DETAIL = (
    "Vyhľadávací index alebo embeddingový "
    "model momentálne nie je dostupný."
)

INTERNAL_ERROR_DETAIL = (
    "Nastala interná chyba servera."
)

REINDEX_FAILED_DETAIL = (
    "Reindexovanie zlyhalo."
)

WEBHOOK_CONFIGURATION_DETAIL = (
    "Webhook nie je správne nakonfigurovaný."
)


class StrictRequestModel(BaseModel):
    model_config = ConfigDict(
        extra="forbid",
        str_strip_whitespace=True,
    )


class SearchRequest(
    StrictRequestModel
):
    query: str = Field(
        ...,
        min_length=1,
        max_length=500,
    )

    limit: int = Field(
        default=10,
        ge=1,
        le=50,
    )

    published_only: bool = False

    max_per_document: int = Field(
        default=1,
        ge=0,
        le=10,
    )


class RagRequest(
    StrictRequestModel
):
    query: str = Field(
        ...,
        min_length=1,
        max_length=500,
        description=(
            "Otázka alebo vyhľadávací dotaz "
            "používateľa nad ZP Wiki."
        ),
    )

    limit: int = Field(
        default=5,
        ge=1,
        le=20,
        description=(
            "Maximálny počet relevantných "
            "zdrojov pre RAG kontext."
        ),
    )

    published_only: bool = Field(
        default=False,
        description=(
            "Ak je true, použijú sa iba "
            "publikované dokumenty."
        ),
    )

    max_per_document: int = Field(
        default=1,
        ge=0,
        le=10,
        description=(
            "Maximálny počet chunkov z jedného "
            "dokumentu. Hodnota 1 preferuje "
            "rôzne dokumenty."
        ),
    )


class SyncRequest(
    StrictRequestModel
):
    pull_git: bool = Field(
        default=False,
        description=(
            "Pred reindexovaním vykoná "
            "git pull --ff-only."
        ),
    )


class HealthResponse(BaseModel):
    status: Literal[
        "ok"
    ]

    ready: bool

    database_exists: bool
    database_path: str

    search_engine: str
    rag_enabled: bool

    zpwiki_root: str
    zpwiki_exists: bool

    security_configured: bool


class RagSource(BaseModel):
    # RAG source sa môže v budúcnosti
    # rozšíriť o ďalšie retrieval metadata
    # bez rozbitia response modelu.
    model_config = ConfigDict(
        extra="allow",
    )

    source_id: str
    title: str
    source_url: str

    author: str | None = None
    published: bool | None = None

    heading_paths: list[Any] | None = None
    text: str | None = None

    retrieval: dict[
        str,
        Any,
    ] | None = None


class RagResponse(BaseModel):
    model_config = ConfigDict(
        extra="forbid",
    )

    query: str
    engine: str

    strategies: list[str]

    source_count: int = Field(
        ge=0,
    )

    instructions: list[str]

    answer_format: dict[
        str,
        Any,
    ]

    context: str

    sources: list[
        RagSource
    ]


class SearchResponse(BaseModel):
    query: str
    engine: str

    strategies: list[str]

    count: int = Field(
        ge=0,
    )

    results: list[
        dict[str, Any]
    ]


class SyncResponse(BaseModel):
    status: Literal[
        "ok"
    ]

    pull_git: bool

    duration_seconds: float

    counts: dict[
        str,
        int,
    ]


class WebhookSuccessResponse(
    BaseModel
):
    status: Literal[
        "ok"
    ]

    event: str
    repository: str

    verified_by: Literal[
        "hmac_sha256"
    ]

    duration_seconds: float

    counts: dict[
        str,
        int,
    ]


class WebhookIgnoredResponse(
    BaseModel
):
    status: Literal[
        "ignored"
    ]

    reason: Literal[
        "unsupported_event"
    ]

    event: str


def raise_retrieval_error(
    error: Exception,
) -> NoReturn:
    if isinstance(
        error,
        ValueError,
    ):
        raise HTTPException(
            status_code=(
                status.HTTP_400_BAD_REQUEST
            ),
            detail=str(
                error
            ),
        ) from error

    if isinstance(
        error,
        (
            FileNotFoundError,
            sqlite3.Error,
            RuntimeError,
        ),
    ):
        logger.exception(
            "Retrieval nie je dostupný."
        )

        raise HTTPException(
            status_code=(
                status.HTTP_503_SERVICE_UNAVAILABLE
            ),
            detail=(
                RETRIEVAL_UNAVAILABLE_DETAIL
            ),
        ) from error

    logger.exception(
        "Neočakávaná chyba retrieval API."
    )

    raise HTTPException(
        status_code=(
            status.HTTP_500_INTERNAL_SERVER_ERROR
        ),
        detail=(
            INTERNAL_ERROR_DETAIL
        ),
    ) from error


def raise_reindex_error(
    error: Exception,
) -> NoReturn:
    if isinstance(
        error,
        ReindexInProgressError,
    ):
        raise HTTPException(
            status_code=(
                status.HTTP_409_CONFLICT
            ),
            detail=str(
                error
            ),
        ) from error

    logger.exception(
        "Reindexovanie zlyhalo."
    )

    raise HTTPException(
        status_code=(
            status.HTTP_500_INTERNAL_SERVER_ERROR
        ),
        detail=(
            REINDEX_FAILED_DETAIL
        ),
    ) from error


def webhook_secret() -> str:
    try:
        return validate_secret(
            "WEBHOOK_SECRET"
        )

    except RuntimeError as error:
        logger.exception(
            "WEBHOOK_SECRET nie je "
            "správne nakonfigurovaný."
        )

        raise HTTPException(
            status_code=(
                status.HTTP_503_SERVICE_UNAVAILABLE
            ),
            detail=(
                WEBHOOK_CONFIGURATION_DETAIL
            ),
        ) from error


def configured_repository() -> str:
    try:
        return (
            expected_gitea_repository()
        )

    except RuntimeError as error:
        logger.exception(
            "EXPECTED_GITEA_REPOSITORY "
            "nie je správne nakonfigurovaný."
        )

        raise HTTPException(
            status_code=(
                status.HTTP_503_SERVICE_UNAVAILABLE
            ),
            detail=(
                WEBHOOK_CONFIGURATION_DETAIL
            ),
        ) from error


@router.get(
    "/health",
    include_in_schema=False,
    response_model=HealthResponse,
)
def health() -> dict[str, Any]:
    database_exists = (
        DB_FILE.exists()
    )

    zpwiki_exists = (
        ZPWIKI_ROOT.exists()
    )

    try:
        validate_security_configuration()
        security_configured = True

    except RuntimeError:
        security_configured = False

    ready = (
        database_exists
        and zpwiki_exists
        and security_configured
    )

    return {
        "status": "ok",
        "ready": ready,
        "database_exists": (
            database_exists
        ),
        "database_path": str(
            DB_FILE
        ),
        "search_engine": (
            "hybrid_fts5_embeddings"
        ),
        "rag_enabled": True,
        "zpwiki_root": str(
            ZPWIKI_ROOT
        ),
        "zpwiki_exists": (
            zpwiki_exists
        ),
        "security_configured": (
            security_configured
        ),
    }


@router.post(
    "/rag",
    operation_id=(
        "retrieve_zpwiki_context"
    ),
    summary=(
        "Vyhľadaj informácie v ZP Wiki"
    ),
    description=(
        "Použi tento nástroj pri otázkach "
        "o ZP Wiki, študentoch, autoroch, "
        "záverečných prácach, témach, rokoch, "
        "projektoch alebo dokumentoch. "
        "Nástroj vykoná hybridné FTS5 a "
        "embeddingové vyhľadávanie a pripraví "
        "zdrojovo podložený RAG kontext."
    ),
    response_model=RagResponse,
    response_model_exclude_unset=True,
    status_code=(
        status.HTTP_200_OK
    ),
    responses={
        400: {
            "description": (
                "Neplatný dotaz."
            ),
        },
        401: {
            "description": (
                "Chýbajúci alebo neplatný "
                "API kľúč."
            ),
        },
        422: {
            "description": (
                "Neplatná štruktúra requestu."
            ),
        },
        500: {
            "description": (
                "Interná chyba servera."
            ),
        },
        503: {
            "description": (
                "Retrieval nie je momentálne "
                "dostupný."
            ),
        },
    },
    dependencies=[
        Depends(
            require_search_api_key
        )
    ],
)
def rag(
    request: RagRequest,
) -> dict[str, Any]:
    try:
        return build_rag_context(
            DB_FILE,
            request.query,
            limit=request.limit,
            published_only=(
                request.published_only
            ),
            max_per_document=(
                request.max_per_document
            ),
        )

    except Exception as error:
        raise_retrieval_error(
            error
        )


@router.post(
    "/search",
    dependencies=[
        Depends(
            require_search_api_key
        )
    ],
    include_in_schema=False,
    response_model=SearchResponse,
)
def search(
    request: SearchRequest,
) -> dict[str, Any]:
    try:
        response = search_database(
            DB_FILE,
            request.query,
            request.limit,
            published_only=(
                request.published_only
            ),
            max_per_document=(
                request.max_per_document
            ),
        )

    except Exception as error:
        raise_retrieval_error(
            error
        )

    results = response[
        "results"
    ]

    return {
        "query": request.query,
        "engine": response[
            "engine"
        ],
        "strategies": response[
            "strategies"
        ],
        "count": len(
            results
        ),
        "results": results,
    }


@router.post(
    "/sync",
    dependencies=[
        Depends(
            require_sync_api_key
        )
    ],
    include_in_schema=False,
    response_model=SyncResponse,
)
def sync(
    request: SyncRequest,
) -> dict[str, Any]:
    try:
        result = rebuild_index(
            pull_git=(
                request.pull_git
            )
        )

    except Exception as error:
        raise_reindex_error(
            error
        )

    return {
        "status": "ok",
        "pull_git": (
            request.pull_git
        ),
        "duration_seconds": (
            result[
                "duration_seconds"
            ]
        ),
        "counts": result[
            "counts"
        ],
    }


@router.post(
    "/webhook/gitea",
    response_model=(
        WebhookSuccessResponse
        | WebhookIgnoredResponse
    ),
    response_model_exclude_unset=True,
    include_in_schema=False,
)
async def gitea_webhook(
    request: Request,
    x_gitea_event: str | None = Header(
        default=None,
        alias="X-Gitea-Event",
    ),
    x_gitea_signature: str | None = Header(
        default=None,
        alias="X-Gitea-Signature",
    ),
) -> (
    dict[str, Any]
    | JSONResponse
):
    raw_body = await request.body()

    secret = webhook_secret()

    if not verify_gitea_signature(
        raw_body,
        x_gitea_signature,
        secret,
    ):
        raise HTTPException(
            status_code=(
                status.HTTP_401_UNAUTHORIZED
            ),
            detail=(
                "Neplatný webhook podpis"
            ),
        )

    try:
        payload = json.loads(
            raw_body.decode(
                "utf-8"
            )
        )

    except (
        UnicodeDecodeError,
        json.JSONDecodeError,
    ) as error:
        raise HTTPException(
            status_code=(
                status.HTTP_400_BAD_REQUEST
            ),
            detail=(
                "Webhook payload nie je "
                "platný JSON"
            ),
        ) from error

    if not isinstance(
        payload,
        dict,
    ):
        raise HTTPException(
            status_code=(
                status.HTTP_400_BAD_REQUEST
            ),
            detail=(
                "Webhook payload musí byť "
                "JSON objekt"
            ),
        )

    if not x_gitea_event:
        raise HTTPException(
            status_code=(
                status.HTTP_400_BAD_REQUEST
            ),
            detail=(
                "Chýba hlavička "
                "X-Gitea-Event"
            ),
        )

    if (
        x_gitea_event.casefold()
        != "push"
    ):
        return JSONResponse(
            status_code=(
                status.HTTP_202_ACCEPTED
            ),
            content={
                "status": (
                    "ignored"
                ),
                "reason": (
                    "unsupported_event"
                ),
                "event": (
                    x_gitea_event
                ),
            },
        )

    repository_name = (
        repository_name_from_payload(
            payload
        )
    )

    if repository_name is None:
        raise HTTPException(
            status_code=(
                status.HTTP_400_BAD_REQUEST
            ),
            detail=(
                "Webhook payload neobsahuje "
                "repository.full_name"
            ),
        )

    expected_repository = (
        configured_repository()
    )

    if not same_repository(
        repository_name,
        expected_repository,
    ):
        raise HTTPException(
            status_code=(
                status.HTTP_403_FORBIDDEN
            ),
            detail=(
                "Webhook patrí neočakávanému "
                "repozitáru"
            ),
        )

    try:
        result = await asyncio.to_thread(
            rebuild_index,
            pull_git=(
                webhook_should_pull_git()
            ),
        )

    except Exception as error:
        raise_reindex_error(
            error
        )

    return {
        "status": "ok",
        "event": (
            x_gitea_event
        ),
        "repository": (
            repository_name
        ),
        "verified_by": (
            "hmac_sha256"
        ),
        "duration_seconds": (
            result[
                "duration_seconds"
            ]
        ),
        "counts": result[
            "counts"
        ],
    }