import {
  Injectable,
  CanActivate,
  ExecutionContext,
  ForbiddenException,
  BadRequestException,
  Logger,
} from "@nestjs/common";
import { PrismaService } from "../../prisma/prisma.service";
import type { AuthenticatedRequest } from "../types/user.types";

/**
 * WorkspaceGuard ensures that:
 * 1. A workspace is specified in the request (header, param, or body)
 * 2. The authenticated user is a member of that workspace
 *
 * This guard should be used in combination with AuthGuard:
 *
 * @example
 * ```typescript
 * @Controller('tasks')
 * @UseGuards(AuthGuard, WorkspaceGuard)
 * export class TasksController {
 *   @Get()
 *   async getTasks(@Workspace() workspaceId: string) {
 *     // workspaceId is verified and available
 *     // Service layer must use withUserContext() for RLS
 *   }
 * }
 * ```
 *
 * The workspace ID can be provided via:
 * - Header: `X-Workspace-Id`
 * - URL parameter: `:workspaceId`
 * - Request body: `workspaceId` field
 *
 * Priority: Header > Param > Body
 *
 * Note: RLS context must be set at the service layer using withUserContext()
 * or withUserTransaction() to ensure proper transaction scoping with connection pooling.
 */
@Injectable()
export class WorkspaceGuard implements CanActivate {
  private readonly logger = new Logger(WorkspaceGuard.name);

  constructor(private readonly prisma: PrismaService) {}

  async canActivate(context: ExecutionContext): Promise<boolean> {
    const request = context.switchToHttp().getRequest<AuthenticatedRequest>();
    const user = request.user;

    if (!user?.id) {
      throw new ForbiddenException("User not authenticated");
    }

    // Extract workspace ID from request
    const workspaceId = this.extractWorkspaceId(request);

    if (!workspaceId) {
      throw new BadRequestException(
        "Workspace ID is required (via header X-Workspace-Id, URL parameter, or request body)"
      );
    }

    // Verify user is a member of the workspace
    const isMember = await this.verifyWorkspaceMembership(user.id, workspaceId);

    if (!isMember) {
      this.logger.warn(
        `Access denied: User ${user.id} is not a member of workspace ${workspaceId}`
      );
      throw new ForbiddenException("You do not have access to this workspace");
    }

    // Attach workspace info to request for convenience
    request.workspace = {
      id: workspaceId,
    };

    // Also attach workspaceId to user object for backward compatibility
    if (request.user) {
      request.user.workspaceId = workspaceId;
    }

    this.logger.debug(`Workspace access granted: User ${user.id} → Workspace ${workspaceId}`);

    return true;
  }

  /**
   * Extracts workspace ID from request in order of priority:
   * 1. X-Workspace-Id header
   * 2. :workspaceId URL parameter
   * 3. workspaceId in request body
   */
  private extractWorkspaceId(request: AuthenticatedRequest): string | undefined {
    // 1. Check header
    const headerWorkspaceId = request.headers["x-workspace-id"];
    if (typeof headerWorkspaceId === "string") {
      return headerWorkspaceId;
    }

    // 2. Check URL params
    const paramWorkspaceId = request.params.workspaceId;
    if (paramWorkspaceId) {
      return paramWorkspaceId;
    }

    // 3. Check request body
    const bodyWorkspaceId = request.body.workspaceId;
    if (typeof bodyWorkspaceId === "string") {
      return bodyWorkspaceId;
    }

    return undefined;
  }

  /**
   * Verifies that a user is a member of the specified workspace
   */
  private async verifyWorkspaceMembership(userId: string, workspaceId: string): Promise<boolean> {
    try {
      const member = await this.prisma.workspaceMember.findUnique({
        where: {
          workspaceId_userId: {
            workspaceId,
            userId,
          },
        },
      });

      return member !== null;
    } catch (error) {
      this.logger.error(
        `Failed to verify workspace membership: ${error instanceof Error ? error.message : "Unknown error"}`,
        error instanceof Error ? error.stack : undefined
      );
      return false;
    }
  }
}