"""
Backend-integrated MCP Streamable HTTP server.
"""
from __future__ import annotations

from datetime import datetime
import hmac
from pathlib import Path
from typing import Any, Dict, List

from fastapi import HTTPException, Response
from sqlalchemy import select

try:
    from mcp.server.fastmcp import FastMCP
except ImportError:  # pragma: no cover - runtime dependency
    FastMCP = None

from app.core.database import AsyncSessionLocal
from app.models.mcp_bot import MCPBot
from app.models.project import Project, ProjectMember
from app.models.user import User
from app.schemas.project import ProjectResponse
from app.services.notification_service import notification_service
from app.services.search_service import search_service
from app.services.storage import storage_service
from app.services.log_service import log_service
from app.api.v1.projects import get_document_count
from app.api.v1.files import check_project_access
from app.core.config import settings
from app.core.enums import OperationType
from app.mcp.context import MCPRequestContext, current_mcp_request


mcp = (
    FastMCP(
        "NexDocs MCP",
        host=settings.HOST,
        port=settings.PORT,
        stateless_http=True,
        json_response=True,
        streamable_http_path="/",
    )
    if FastMCP
    else None
)


async def _get_current_user(db) -> User:
    ctx = current_mcp_request.get()
    if ctx is None:
        raise RuntimeError("MCP request context is missing.")

    result = await db.execute(select(User).where(User.id == ctx.user_id, User.status == 1))
    user = result.scalar_one_or_none()
    if not user:
        raise RuntimeError("Authenticated MCP user does not exist or is disabled.")
    return user


async def _get_project_with_write_access(project_id: int, current_user: User, db):
    return await check_project_access(project_id, current_user, db, require_write=True)


def _ensure_file_exists(file_path: Path, path: str) -> None:
    if not file_path.exists():
        raise HTTPException(status_code=404, detail=f"文件不存在: {path}")
    if not file_path.is_file():
        raise HTTPException(status_code=400, detail=f"目标不是文件: {path}")


def _ensure_file_not_exists(file_path: Path, path: str) -> None:
    if file_path.exists():
        raise HTTPException(status_code=400, detail=f"文件已存在: {path}")


async def _update_markdown_index(project_id: int, path: str, content: str) -> None:
    if path.endswith(".md"):
        await search_service.update_doc(project_id, path, Path(path).stem, content)


async def _remove_markdown_index(project_id: int, path: str) -> None:
    if path.endswith(".md"):
        await search_service.remove_doc(project_id, path)


if mcp is not None:
    @mcp.tool(name="list_created_projects", description="Get projects created by the authenticated user.")
    async def list_created_projects(keyword: str = "", limit: int = 100) -> List[Dict[str, Any]]:
        async with AsyncSessionLocal() as db:
            current_user = await _get_current_user(db)
            result = await db.execute(
                select(Project).where(Project.owner_id == current_user.id, Project.status == 1)
            )
            projects = result.scalars().all()

            items = []
            keyword_lower = keyword.strip().lower()
            for project in projects:
                project_dict = ProjectResponse.from_orm(project).dict()
                project_dict["doc_count"] = get_document_count(project.storage_key)
                if keyword_lower:
                    haystack = f"{project.name} {project.description or ''}".lower()
                    if keyword_lower not in haystack:
                        continue
                items.append(project_dict)

            return items[: max(limit, 0)]


    @mcp.tool(name="get_project_tree", description="Get the directory tree of a specific project.")
    async def get_project_tree(project_id: int) -> Dict[str, Any]:
        async with AsyncSessionLocal() as db:
            current_user = await _get_current_user(db)
            project = await check_project_access(project_id, current_user, db)
            project_root = storage_service.get_secure_path(project.storage_key)
            tree = storage_service.generate_tree(project_root)

            user_role = "owner"
            if project.owner_id != current_user.id:
                member_result = await db.execute(
                    select(ProjectMember).where(
                        ProjectMember.project_id == project_id,
                        ProjectMember.user_id == current_user.id,
                    )
                )
                member = member_result.scalar_one_or_none()
                if member:
                    user_role = member.role

            return {
                "tree": [item.model_dump() for item in tree],
                "user_role": user_role,
                "project_name": project.name,
                "project_description": project.description,
            }


    @mcp.tool(name="get_file", description="Read a file from a specific project.")
    async def get_file(project_id: int, path: str) -> Dict[str, Any]:
        async with AsyncSessionLocal() as db:
            current_user = await _get_current_user(db)
            project = await check_project_access(project_id, current_user, db)
            file_path = storage_service.get_secure_path(project.storage_key, path)
            _ensure_file_exists(file_path, path)
            content = await storage_service.read_file(file_path)
            return {"path": path, "content": content}


    @mcp.tool(name="create_file", description="Create a new file in a specific project path.")
    async def create_file(project_id: int, path: str, content: str = "") -> Dict[str, Any]:
        async with AsyncSessionLocal() as db:
            current_user = await _get_current_user(db)
            project = await _get_project_with_write_access(project_id, current_user, db)
            file_path = storage_service.get_secure_path(project.storage_key, path)
            _ensure_file_not_exists(file_path, path)
            await storage_service.write_file(file_path, content)
            await _update_markdown_index(project_id, path, content)

            await log_service.log_file_operation(
                db=db,
                operation_type=OperationType.CREATE_FILE,
                project_id=project_id,
                file_path=path,
                user=current_user,
                detail={"content_length": len(content), "source": "mcp"},
                request=None,
            )

            await notification_service.notify_project_members(
                db=db,
                project_id=project_id,
                exclude_user_id=current_user.id,
                title="项目文档创建",
                content=(
                    f"项目 [{project.name}] 中的文档 [{path}] "
                    f"已被 {current_user.nickname or current_user.username} 通过 MCP 创建。"
                ),
                link=f"/projects/{project_id}/docs?file={path}",
                category="project",
            )

            return {
                "message": "文件创建成功",
                "project_id": project_id,
                "path": path,
            }


    @mcp.tool(name="update_file", description="Update an existing file in a specific project path.")
    async def update_file(project_id: int, path: str, content: str) -> Dict[str, Any]:
        async with AsyncSessionLocal() as db:
            current_user = await _get_current_user(db)
            project = await _get_project_with_write_access(project_id, current_user, db)
            file_path = storage_service.get_secure_path(project.storage_key, path)
            _ensure_file_exists(file_path, path)
            await storage_service.write_file(file_path, content)
            await _update_markdown_index(project_id, path, content)

            await log_service.log_file_operation(
                db=db,
                operation_type=OperationType.SAVE_FILE,
                project_id=project_id,
                file_path=path,
                user=current_user,
                detail={"content_length": len(content), "source": "mcp"},
                request=None,
            )

            await notification_service.notify_project_members(
                db=db,
                project_id=project_id,
                exclude_user_id=current_user.id,
                title="项目文档更新",
                content=(
                    f"项目 [{project.name}] 中的文档 [{path}] "
                    f"已被 {current_user.nickname or current_user.username} 通过 MCP 更新。"
                ),
                link=f"/projects/{project_id}/docs?file={path}",
                category="project",
            )

            return {
                "message": "文件更新成功",
                "project_id": project_id,
                "path": path,
            }


    @mcp.tool(name="delete_file", description="Delete an existing file in a specific project path.")
    async def delete_file(project_id: int, path: str) -> Dict[str, Any]:
        async with AsyncSessionLocal() as db:
            current_user = await _get_current_user(db)
            project = await _get_project_with_write_access(project_id, current_user, db)
            file_path = storage_service.get_secure_path(project.storage_key, path)
            _ensure_file_exists(file_path, path)
            await storage_service.delete_file(file_path)
            await _remove_markdown_index(project_id, path)

            await log_service.log_file_operation(
                db=db,
                operation_type=OperationType.DELETE_FILE,
                project_id=project_id,
                file_path=path,
                user=current_user,
                detail={"source": "mcp"},
                request=None,
            )

            await notification_service.notify_project_members(
                db=db,
                project_id=project_id,
                exclude_user_id=current_user.id,
                title="项目文档删除",
                content=(
                    f"项目 [{project.name}] 中的文档 [{path}] "
                    f"已被 {current_user.nickname or current_user.username} 通过 MCP 删除。"
                ),
                category="project",
            )

            return {
                "message": "文件删除成功",
                "project_id": project_id,
                "path": path,
            }


def create_mcp_http_app():
    """Return the MCP streamable HTTP ASGI app."""
    if mcp is None:
        raise RuntimeError("Package 'mcp' is required to run the MCP endpoint.")
    return mcp.streamable_http_app()


def get_mcp_session_manager():
    """Return the MCP streamable HTTP session manager."""
    if mcp is None:
        raise RuntimeError("Package 'mcp' is required to run the MCP endpoint.")
    return mcp.session_manager


class MCPHeaderAuthApp:
    """ASGI wrapper that authenticates incoming MCP requests via bot headers."""

    def __init__(self, app):
        self.app = app

    async def __call__(self, scope, receive, send):
        if scope["type"] != "http":
            await self.app(scope, receive, send)
            return

        headers = {
            key.decode("latin-1").lower(): value.decode("latin-1")
            for key, value in scope.get("headers", [])
        }
        bot_id = headers.get("x-bot-id", "").strip()
        bot_secret = headers.get("x-bot-secret", "").strip()

        if not bot_id or not bot_secret:
            response = Response(
                content='{"error":"Missing X-Bot-Id or X-Bot-Secret"}',
                status_code=401,
                media_type="application/json",
            )
            await response(scope, receive, send)
            return

        async with AsyncSessionLocal() as db:
            result = await db.execute(
                select(MCPBot, User)
                .join(User, User.id == MCPBot.user_id)
                .where(MCPBot.bot_id == bot_id, MCPBot.status == 1, User.status == 1)
            )
            row = result.first()

            if not row:
                response = Response(
                    content='{"error":"Invalid MCP bot"}',
                    status_code=403,
                    media_type="application/json",
                )
                await response(scope, receive, send)
                return

            mcp_bot, user = row
            if not hmac.compare_digest(mcp_bot.bot_secret, bot_secret):
                response = Response(
                    content='{"error":"Invalid MCP secret"}',
                    status_code=403,
                    media_type="application/json",
                )
                await response(scope, receive, send)
                return

            mcp_bot.last_used_at = datetime.utcnow()
            await db.commit()

            token = current_mcp_request.set(MCPRequestContext(bot_id=bot_id, user_id=user.id))
            try:
                await self.app(scope, receive, send)
            finally:
                current_mcp_request.reset(token)