import json
import secrets

from django.conf import settings
from django.db.models import Q
from django.http import JsonResponse
from django.views.decorators.csrf import csrf_exempt

from apps.tickets.models import Ticket, TicketStatus

TICKET_SEARCH_TOOL = {
    "name": "search_tickets",
    "title": "内部工单查询",
    "description": "按编号、标题或问题描述查询未归档工单，可选状态过滤。",
    "inputSchema": {
        "type": "object",
        "properties": {
            "query": {
                "type": "string",
                "description": "工单编号、标题或问题关键词",
            },
            "status": {
                "type": "string",
                "enum": [value for value, _label in TicketStatus.choices],
            },
            "limit": {
                "type": "integer",
                "minimum": 1,
                "maximum": 20,
            },
        },
    },
}


def _rpc_error(rpc_id, code: int, message: str, *, status: int = 200):
    return JsonResponse(
        {
            "jsonrpc": "2.0",
            "id": rpc_id,
            "error": {"code": code, "message": message},
        },
        status=status,
    )


def _authorized(request) -> bool:
    expected = settings.INTERNAL_MCP_TOKEN
    authorization = request.headers.get("Authorization", "")
    if not expected or not authorization.startswith("Bearer "):
        return False
    return secrets.compare_digest(authorization.removeprefix("Bearer "), expected)


def _search_tickets(arguments: dict) -> dict:
    query = str(arguments.get("query") or "").strip()
    status = str(arguments.get("status") or "").strip()
    try:
        limit = min(max(int(arguments.get("limit", 10)), 1), 20)
    except (TypeError, ValueError) as error:
        raise ValueError("limit 必须是 1 到 20 的整数") from error
    if status and status not in TicketStatus.values:
        raise ValueError("status 不是有效工单状态")
    queryset = Ticket.objects.select_related("category").filter(archived_at__isnull=True)
    if query:
        queryset = queryset.filter(
            Q(ticket_no__icontains=query)
            | Q(title__icontains=query)
            | Q(description__icontains=query)
        )
    if status:
        queryset = queryset.filter(status=status)
    tickets = [
        {
            "id": ticket.id,
            "ticket_no": ticket.ticket_no,
            "title": ticket.title,
            "description": ticket.description[:500],
            "status": ticket.status,
            "priority": ticket.priority,
            "category_code": ticket.category.code if ticket.category else None,
            "updated_at": ticket.updated_at.isoformat(),
        }
        for ticket in queryset[:limit]
    ]
    return {
        "query": query,
        "status": status or None,
        "count": len(tickets),
        "tickets": tickets,
    }


@csrf_exempt
def internal_mcp_view(request):
    if request.method != "POST":
        return _rpc_error(None, -32600, "仅支持 POST", status=405)
    if not settings.INTERNAL_MCP_TOKEN:
        return _rpc_error(None, -32001, "内部 MCP 尚未配置访问令牌", status=503)
    if not _authorized(request):
        return _rpc_error(None, -32000, "未授权的内部 MCP 请求", status=401)
    try:
        payload = json.loads(request.body)
    except (json.JSONDecodeError, UnicodeDecodeError):
        return _rpc_error(None, -32700, "JSON 解析失败", status=400)
    if not isinstance(payload, dict):
        return _rpc_error(None, -32600, "JSON-RPC 请求结构无效", status=400)
    rpc_id = payload.get("id")
    method = payload.get("method")
    params = payload.get("params")
    if not isinstance(params, dict):
        return _rpc_error(rpc_id, -32602, "params 必须是对象")
    if method == "tools/list":
        result = {"tools": [TICKET_SEARCH_TOOL]}
    elif method == "tools/call":
        if params.get("name") != TICKET_SEARCH_TOOL["name"]:
            return _rpc_error(rpc_id, -32601, "工具不存在")
        arguments = params.get("arguments", {})
        if not isinstance(arguments, dict):
            return _rpc_error(rpc_id, -32602, "arguments 必须是对象")
        try:
            structured = _search_tickets(arguments)
        except ValueError as error:
            return _rpc_error(rpc_id, -32602, str(error))
        result = {
            "content": [
                {
                    "type": "text",
                    "text": json.dumps(structured, ensure_ascii=False),
                }
            ],
            "structuredContent": structured,
            "isError": False,
        }
    else:
        return _rpc_error(rpc_id, -32601, "不支持的 MCP 方法")
    return JsonResponse({"jsonrpc": "2.0", "id": rpc_id, "result": result})