from __future__ import annotations

import asyncio
import hashlib
import hmac
import json
import os
import sys
from contextlib import asynccontextmanager
from pathlib import Path
from typing import Any

from fastapi import (
    Depends,
    FastAPI,
    Header,
    HTTPException,
    Request,
    Security,
    status,
)
from fastapi.responses import JSONResponse
from fastapi.security import APIKeyHeader
from pydantic import BaseModel, Field

PROJECT_ROOT = Path(__file__).resolve().parents[1]

if str(PROJECT_ROOT) not in sys.path:
    sys.path.insert(0, str(PROJECT_ROOT))

from scripts.common import DB_FILE, ZPWIKI_ROOT
from scripts.rebuild_index import (
    ReindexInProgressError,
    rebuild_index,
)
from scripts.search_utils import search_database


MIN_SECRET_LENGTH = 32

SEARCH_API_KEY_HEADER = "X-API-Key"
SYNC_API_KEY_HEADER = "X-API-Key"


search_api_key_scheme = APIKeyHeader(
    name=SEARCH_API_KEY_HEADER,
    auto_error=False,
    description="API kľúč pre vyhľadávanie v zpwiki.",
)

sync_api_key_scheme = APIKeyHeader(
    name=SYNC_API_KEY_HEADER,
    auto_error=False,
    description="API kľúč pre manuálne spustenie reindexovania.",
)


class SearchRequest(BaseModel):
    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=3,
        ge=0,
        le=10,
    )


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


def required_environment_value(name: str) -> str:
    value = os.getenv(name, "").strip()

    if not value:
        raise RuntimeError(
            f"Chýba povinná environment premenná {name}"
        )

    return value


def validate_secret(name: str) -> str:
    value = required_environment_value(name)

    if len(value) < MIN_SECRET_LENGTH:
        raise RuntimeError(
            f"{name} musí mať aspoň {MIN_SECRET_LENGTH} znakov"
        )

    return value


def expected_gitea_repository() -> str:
    value = required_environment_value(
        "EXPECTED_GITEA_REPOSITORY"
    )

    if "/" not in value:
        raise RuntimeError(
            "EXPECTED_GITEA_REPOSITORY musí mať tvar "
            "vlastník/repozitár"
        )

    return value


def webhook_should_pull_git() -> bool:
    value = os.getenv(
        "WEBHOOK_PULL_GIT",
        "false",
    ).strip().casefold()

    return value in {
        "1",
        "true",
        "yes",
        "on",
    }


def validate_security_configuration() -> None:
    validate_secret("WEBHOOK_SECRET")
    validate_secret("SYNC_API_KEY")
    validate_secret("SEARCH_API_KEY")
    expected_gitea_repository()


@asynccontextmanager
async def lifespan(_: FastAPI):
    validate_security_configuration()
    yield


app = FastAPI(
    title="ZP Agent API",
    description=(
        "API pre vyhľadávanie v repozitári "
        "záverečných prác zpwiki."
    ),
    version="0.6.0",
    lifespan=lifespan,
)


def require_search_api_key(
    api_key: str | None = Security(
        search_api_key_scheme
    ),
) -> None:
    expected = validate_secret(
        "SEARCH_API_KEY"
    )

    if (
        not api_key
        or not hmac.compare_digest(
            api_key,
            expected,
        )
    ):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Neplatný alebo chýbajúci API kľúč",
            headers={
                "WWW-Authenticate": "ApiKey",
            },
        )


def require_sync_api_key(
    api_key: str | None = Security(
        sync_api_key_scheme
    ),
) -> None:
    expected = validate_secret(
        "SYNC_API_KEY"
    )

    if (
        not api_key
        or not hmac.compare_digest(
            api_key,
            expected,
        )
    ):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Neplatný alebo chýbajúci API kľúč",
            headers={
                "WWW-Authenticate": "ApiKey",
            },
        )


def verify_gitea_signature(
    raw_body: bytes,
    signature: str | None,
    secret: str,
) -> bool:
    if not signature:
        return False

    supplied = signature.strip().casefold()

    # Kompatibilita podpisu.
    if supplied.startswith("sha256="):
        supplied = supplied.removeprefix(
            "sha256="
        )

    if len(supplied) != 64:
        return False

    try:
        int(supplied, 16)

    except ValueError:
        return False

    expected = hmac.new(
        secret.encode("utf-8"),
        raw_body,
        hashlib.sha256,
    ).hexdigest()

    return hmac.compare_digest(
        expected,
        supplied,
    )


def repository_name_from_payload(
    payload: dict[str, Any],
) -> str | None:
    repository = payload.get("repository")

    if not isinstance(repository, dict):
        return None

    value = (
        repository.get("full_name")
        or repository.get("name")
    )

    if not isinstance(value, str):
        return None

    value = value.strip()

    return value or None


def same_repository(
    actual: str,
    expected: str,
) -> bool:
    return hmac.compare_digest(
        actual.casefold(),
        expected.casefold(),
    )


@app.get("/health")
def health() -> dict[str, Any]:
    return {
        "status": "ok",
        "database_exists": DB_FILE.exists(),
        "database_path": str(DB_FILE),
        "search_engine": "sqlite_fts5",
        "zpwiki_root": str(ZPWIKI_ROOT),
        "zpwiki_exists": ZPWIKI_ROOT.exists(),
        "security_configured": all(
            bool(
                os.getenv(
                    name,
                    "",
                ).strip()
            )
            for name in (
                "WEBHOOK_SECRET",
                "SYNC_API_KEY",
                "SEARCH_API_KEY",
                "EXPECTED_GITEA_REPOSITORY",
            )
        ),
    }


@app.post(
    "/search",
    dependencies=[
        Depends(require_search_api_key)
    ],
)
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 FileNotFoundError as error:
        raise HTTPException(
            status_code=500,
            detail=str(error),
        ) from error

    except ValueError as error:
        raise HTTPException(
            status_code=400,
            detail=str(error),
        ) from error

    except RuntimeError as error:
        raise HTTPException(
            status_code=500,
            detail=str(error),
        ) from error

    results = response["results"]

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


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

    except ReindexInProgressError as error:
        raise HTTPException(
            status_code=409,
            detail=str(error),
        ) from error

    except RuntimeError as error:
        raise HTTPException(
            status_code=500,
            detail=str(error),
        ) from error

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


@app.post(
    "/webhook/gitea",
    response_model=None,
)
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 = validate_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=400,
            detail=(
                "Webhook payload nie je "
                "platný JSON"
            ),
        ) from error

    if not isinstance(payload, dict):
        raise HTTPException(
            status_code=400,
            detail=(
                "Webhook payload musí byť "
                "JSON objekt"
            ),
        )

    if not x_gitea_event:
        raise HTTPException(
            status_code=400,
            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=400,
            detail=(
                "Webhook payload neobsahuje "
                "repository.full_name"
            ),
        )

    expected_repository = (
        expected_gitea_repository()
    )

    if not same_repository(
        repository_name,
        expected_repository,
    ):
        raise HTTPException(
            status_code=403,
            detail=(
                "Webhook patrí neočakávanému "
                "repozitáru"
            ),
        )

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

    except ReindexInProgressError as error:
        raise HTTPException(
            status_code=409,
            detail=str(error),
        ) from error

    except RuntimeError as error:
        raise HTTPException(
            status_code=500,
            detail=str(error),
        ) from error

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