from __future__ import annotations

import asyncio
import hashlib
import hmac
import time
import uuid
from datetime import datetime, timedelta, timezone
from pathlib import Path
from typing import Any, Literal

import httpx
from fastapi import status
from jose import JWTError, jwt

from app.core.config import settings
from app.core.exceptions import AppException
from app.schemas.onlyoffice import OnlyOfficePreviewConfigRead

OnlyOfficeDocumentType = Literal["word", "cell", "slide"]
OnlyOfficeResourceType = Literal["attachment", "version"]

WORD_FORMATS = frozenset({
    "doc", "docx", "docm", "dot", "dotx", "dotm", "odt", "ott", "rtf", "txt", "wps", "wpt",
})
CELL_FORMATS = frozenset({
    "xls", "xlsx", "xlsm", "xlsb", "xlt", "xltx", "xltm", "ods", "ots", "csv", "et", "ett",
})
SLIDE_FORMATS = frozenset({
    "ppt", "pptx", "pptm", "pps", "ppsx", "ppsm", "pot", "potx", "potm", "odp", "otp", "dps", "dpt",
})

_health_lock = asyncio.Lock()
_health_checked_at = 0.0
_health_available = False
_HEALTH_CACHE_SECONDS = 15.0


def onlyoffice_error(code: str, message: str, status_code: int) -> AppException:
    return AppException(code=code, message=message, status_code=status_code)


def office_format_for_filename(filename: str) -> tuple[str, OnlyOfficeDocumentType] | None:
    suffix = Path(filename).suffix.lower().lstrip(".")
    if suffix in WORD_FORMATS:
        return suffix, "word"
    if suffix in CELL_FORMATS:
        return suffix, "cell"
    if suffix in SLIDE_FORMATS:
        return suffix, "slide"
    return None


def onlyoffice_content_url(resource_type: OnlyOfficeResourceType, resource_id: uuid.UUID) -> str:
    plural = "attachments" if resource_type == "attachment" else "versions"
    return (
        f"{settings.ONLYOFFICE_STORAGE_BASE_URL.rstrip('/')}"
        f"/internal/onlyoffice/{plural}/{resource_id}/content"
    )


def onlyoffice_document_key(
    resource_type: OnlyOfficeResourceType,
    resource_id: uuid.UUID,
    *,
    file_hash: str | None = None,
) -> str:
    instance_id = (settings.ONLYOFFICE_INSTANCE_ID or "").strip()
    fingerprint = f"{instance_id}{resource_type}{resource_id}"
    if resource_type == "version":
        fingerprint = f"{fingerprint}{file_hash or ''}"
    return f"ctms-{hashlib.sha256(fingerprint.encode('utf-8')).hexdigest()}"


async def ensure_onlyoffice_available() -> None:
    global _health_available, _health_checked_at
    if not settings.ONLYOFFICE_ENABLED:
        raise onlyoffice_error(
            "ONLYOFFICE_DISABLED",
            "Office 预览服务尚未启用",
            status.HTTP_503_SERVICE_UNAVAILABLE,
        )

    now = time.monotonic()
    if now - _health_checked_at < _HEALTH_CACHE_SECONDS:
        if _health_available:
            return
        raise onlyoffice_error(
            "ONLYOFFICE_UNAVAILABLE",
            "Office 预览服务暂不可用，请稍后重试",
            status.HTTP_503_SERVICE_UNAVAILABLE,
        )

    async with _health_lock:
        now = time.monotonic()
        if now - _health_checked_at >= _HEALTH_CACHE_SECONDS:
            available = False
            try:
                async with httpx.AsyncClient(timeout=2.0, follow_redirects=False) as client:
                    response = await client.get(f"{settings.ONLYOFFICE_INTERNAL_URL.rstrip('/')}/healthcheck")
                available = response.status_code == status.HTTP_200_OK
            except httpx.HTTPError:
                available = False
            _health_available = available
            _health_checked_at = now

    if not _health_available:
        raise onlyoffice_error(
            "ONLYOFFICE_UNAVAILABLE",
            "Office 预览服务暂不可用，请稍后重试",
            status.HTTP_503_SERVICE_UNAVAILABLE,
        )


def build_preview_config(
    *,
    resource_type: OnlyOfficeResourceType,
    resource_id: uuid.UUID,
    file_name: str,
    user_id: uuid.UUID,
    user_name: str,
    file_hash: str | None = None,
) -> OnlyOfficePreviewConfigRead:
    format_info = office_format_for_filename(file_name)
    if not format_info:
        raise onlyoffice_error(
            "ONLYOFFICE_FORMAT_UNSUPPORTED",
            "该文件格式不支持 Office 在线预览",
            status.HTTP_415_UNSUPPORTED_MEDIA_TYPE,
        )
    file_type, document_type = format_info
    now = datetime.now(timezone.utc)
    expires_at = now + timedelta(seconds=settings.ONLYOFFICE_CONFIG_TTL_SECONDS)
    config: dict[str, Any] = {
        "type": "desktop",
        "documentType": document_type,
        "document": {
            "fileType": file_type,
            "key": onlyoffice_document_key(resource_type, resource_id, file_hash=file_hash),
            "title": file_name,
            "url": onlyoffice_content_url(resource_type, resource_id),
            "permissions": {
                "copy": False,
                "comment": False,
                "download": False,
                "edit": False,
                "fillForms": False,
                "modifyContentControl": False,
                "modifyFilter": False,
                "print": False,
                "review": False,
            },
        },
        "editorConfig": {
            "coEditing": {"mode": "strict", "change": False},
            "customization": {
                "chat": False,
                "comments": False,
                "forcesave": False,
            },
            "lang": "zh-CN",
            "mode": "view",
            "user": {"id": str(user_id), "name": user_name},
        },
    }
    token_payload = {
        **config,
        "iat": int(now.timestamp()),
        "exp": int(expires_at.timestamp()),
    }
    config["token"] = jwt.encode(
        token_payload,
        settings.ONLYOFFICE_JWT_SECRET or "",
        algorithm="HS256",
    )
    return OnlyOfficePreviewConfigRead(
        resource_type=resource_type,
        resource_id=resource_id,
        file_name=file_name,
        expires_at=expires_at,
        config=config,
    )


def validate_outbox_token(token: str | None, expected_url: str) -> dict[str, Any]:
    if not token:
        raise onlyoffice_error(
            "ONLYOFFICE_SOURCE_UNAUTHORIZED",
            "无法验证 Office 文件请求",
            status.HTTP_401_UNAUTHORIZED,
        )
    token = token.strip()
    if " " in token:
        scheme, credential = token.split(" ", 1)
        if scheme.lower() != "bearer" or not credential.strip():
            raise onlyoffice_error(
                "ONLYOFFICE_SOURCE_UNAUTHORIZED",
                "无法验证 Office 文件请求",
                status.HTTP_401_UNAUTHORIZED,
            )
        token = credential.strip()
    try:
        header = jwt.get_unverified_header(token)
        if header.get("alg") != "HS256":
            raise JWTError("unexpected algorithm")
        payload = jwt.decode(
            token,
            settings.ONLYOFFICE_JWT_SECRET or "",
            algorithms=["HS256"],
            options={"verify_aud": False},
        )
    except JWTError as exc:
        raise onlyoffice_error(
            "ONLYOFFICE_SOURCE_UNAUTHORIZED",
            "无法验证 Office 文件请求",
            status.HTTP_401_UNAUTHORIZED,
        ) from exc

    request_payload = payload.get("payload")
    token_url = request_payload.get("url") if isinstance(request_payload, dict) else None
    if not isinstance(token_url, str) or not hmac.compare_digest(token_url, expected_url):
        raise onlyoffice_error(
            "ONLYOFFICE_SOURCE_URL_MISMATCH",
            "Office 文件请求地址不匹配",
            status.HTTP_401_UNAUTHORIZED,
        )
    return payload