import {
  type CreateUserInput,
  type DisableUserInput,
  ErrorCode,
  type ListResponse,
  Permission,
  SUPER_ADMIN_SOFT_LIMIT,
  ulid,
  type UpdateUserInput,
  type UserDetail,
  type UserListQuery,
  type UserSummary,
} from '@lingxi/shared';
import { Inject, Injectable, Logger } from '@nestjs/common';
import { Prisma } from '@prisma/client';

import { AppException } from '../../common/errors/app-exception';
import type { PrismaService } from '../../infra/prisma/prisma.service';
import { PRISMA } from '../../infra/tokens';
import { PasswordService } from './password.service';
import { toUserDetail, toUserSummary, type UserWithRelations } from './user.mapper';

const USER_INCLUDE = {
  department: { include: { parent: true } },
  roles: { include: { role: true } },
} satisfies Prisma.UserInclude;

function hasPermission(permissions: string[], code: string): boolean {
  return permissions.includes(code);
}

/** 用户管理：列表（游标 + 筛选 + 排序）、详情、新建、更新、停用 / 启用 */
@Injectable()
export class UsersService {
  private readonly logger = new Logger('UsersService');

  constructor(
    @Inject(PRISMA) private readonly prisma: PrismaService,
    @Inject(PasswordService) private readonly passwords: PasswordService,
  ) {}

  async list(query: UserListQuery): Promise<ListResponse<UserSummary>> {
    const where = this.buildWhere(query);
    const orderBy = this.buildOrderBy(query);
    const cursor = query.cursor;
    const rows = await this.prisma.user.findMany({
      where,
      orderBy,
      take: query.limit + 1,
      include: USER_INCLUDE,
      ...(cursor === undefined ? {} : { cursor: { id: cursor }, skip: 1 }),
    });
    const page = rows.slice(0, query.limit);
    const next = rows.length > query.limit ? (page[page.length - 1]?.id ?? null) : null;
    return { items: page.map((row) => toUserSummary(row)), next_cursor: next };
  }

  async detail(id: string, permissions: string[]): Promise<UserDetail> {
    const user = await this.findOrThrow(id);
    return toUserDetail(user, hasPermission(permissions, Permission.USER_MANAGE));
  }

  async create(
    input: CreateUserInput,
    actorId: string,
    permissions: string[],
  ): Promise<UserDetail> {
    await this.ensureDepartment(input.departmentId);
    await this.ensureRoles(input.roleIds);
    const account = input.account.trim().toLowerCase();
    const email = `${account}@lingxi.cn`;
    await this.ensureUnique({ account, phone: input.phone });
    const passwordHash = await this.passwords.hash(input.password);
    const id = ulid();
    try {
      await this.prisma.$transaction([
        this.prisma.user.create({
          data: {
            id,
            name: input.name,
            account,
            email,
            phone: input.phone,
            passwordHash,
            departmentId: input.departmentId,
            mustChangePassword: true,
            createdBy: actorId,
            ...(input.remark === undefined ? {} : { remark: input.remark }),
            roles: { create: input.roleIds.map((roleId) => ({ roleId })) },
          },
        }),
      ]);
    } catch (error) {
      throw this.mapUniqueError(error);
    }
    await this.warnIfSuperAdminExceeded(input.roleIds);
    return this.detail(id, permissions);
  }

  async update(id: string, input: UpdateUserInput, permissions: string[]): Promise<UserDetail> {
    const existing = await this.findOrThrow(id);
    if (input.departmentId !== undefined) {
      await this.ensureDepartment(input.departmentId);
    }
    if (input.roleIds !== undefined) {
      await this.ensureRoles(input.roleIds);
    }
    if (input.phone !== undefined && input.phone !== existing.phone) {
      await this.ensureUnique({ phone: input.phone });
    }
    const data: Prisma.UserUpdateInput = {
      ...(input.name === undefined ? {} : { name: input.name }),
      ...(input.phone === undefined ? {} : { phone: input.phone }),
      ...(input.departmentId === undefined
        ? {}
        : { department: { connect: { id: input.departmentId } } }),
      ...(input.remark === undefined ? {} : { remark: input.remark }),
    };
    try {
      await this.prisma.$transaction(async (tx) => {
        await tx.user.update({ where: { id }, data });
        if (input.roleIds !== undefined) {
          await tx.userRole.deleteMany({ where: { userId: id } });
          await tx.userRole.createMany({
            data: input.roleIds.map((roleId) => ({ userId: id, roleId })),
          });
        }
      });
    } catch (error) {
      throw this.mapUniqueError(error);
    }
    if (input.roleIds !== undefined) {
      await this.warnIfSuperAdminExceeded(input.roleIds);
    }
    return this.detail(id, permissions);
  }

  async disable(
    id: string,
    input: DisableUserInput,
    actorId: string,
    permissions: string[],
  ): Promise<UserDetail> {
    const existing = await this.findOrThrow(id);
    if (existing.status === 'DISABLED') {
      throw new AppException({ code: ErrorCode.STATE_NOT_ALLOWED, message: '账号已是停用状态' });
    }
    if (existing.id === actorId) {
      throw new AppException({
        code: ErrorCode.BUSINESS_RULE_VIOLATION,
        message: '不能停用当前登录账号',
      });
    }
    await this.prisma.$transaction([
      this.prisma.user.update({
        where: { id },
        data: {
          status: 'DISABLED',
          disabledAt: new Date(),
          ...(input.reason === undefined ? {} : { remark: input.reason }),
        },
      }),
      this.prisma.refreshToken.updateMany({
        where: { userId: id, revokedAt: null },
        data: { revokedAt: new Date() },
      }),
    ]);
    return this.detail(id, permissions);
  }

  async enable(id: string, permissions: string[]): Promise<UserDetail> {
    const existing = await this.findOrThrow(id);
    if (existing.status === 'ACTIVE') {
      throw new AppException({ code: ErrorCode.STATE_NOT_ALLOWED, message: '账号已是启用状态' });
    }
    await this.prisma.user.update({
      where: { id },
      data: { status: 'ACTIVE', disabledAt: null },
    });
    return this.detail(id, permissions);
  }

  /** 客户转交占位：A3 客户模块落地前按契约返回 42201（不自造 5xx 错误码） */
  transferCustomers(): never {
    throw new AppException({
      code: ErrorCode.BUSINESS_RULE_VIOLATION,
      message: '客户转交将在客户模块（A3）提供',
    });
  }

  /**
   * 超管人数软上限（PRD §5.4.1 建议 ≤ 2 人）：只记录告警，不阻断保存；
   * 前端「超管授予二次确认」是主要提示手段。A4 阈值迁 system_configs。
   */
  private async warnIfSuperAdminExceeded(roleIds: readonly string[]): Promise<void> {
    const superAdminRole = await this.prisma.role.findUnique({
      where: { code: 'super_admin' },
      select: { id: true },
    });
    if (superAdminRole === null || !roleIds.includes(superAdminRole.id)) {
      return;
    }
    const count = await this.prisma.user.count({
      where: { status: 'ACTIVE', roles: { some: { roleId: superAdminRole.id } } },
    });
    if (count > SUPER_ADMIN_SOFT_LIMIT) {
      this.logger.warn(
        `超级管理员 ${String(count)} 人已超过建议上限 ${String(SUPER_ADMIN_SOFT_LIMIT)} 人（仅提示，不阻断）`,
      );
    }
  }

  private async findOrThrow(id: string): Promise<UserWithRelations> {
    const user = await this.prisma.user.findUnique({ where: { id }, include: USER_INCLUDE });
    if (user === null) {
      throw new AppException({ code: ErrorCode.NOT_FOUND, message: '用户不存在' });
    }
    return user;
  }

  private async ensureDepartment(departmentId: string): Promise<void> {
    const department = await this.prisma.department.findUnique({
      where: { id: departmentId },
      select: { status: true },
    });
    if (department === null) {
      throw new AppException({ code: ErrorCode.PARAM_INVALID, message: '所属部门不存在' });
    }
    if (department.status !== 'ACTIVE') {
      throw new AppException({
        code: ErrorCode.BUSINESS_RULE_VIOLATION,
        message: '所属部门已停用，请选择启用中的部门',
      });
    }
  }

  private async ensureRoles(roleIds: string[]): Promise<void> {
    const count = await this.prisma.role.count({
      where: { id: { in: roleIds }, status: 'ACTIVE' },
    });
    if (count !== new Set(roleIds).size) {
      throw new AppException({ code: ErrorCode.PARAM_INVALID, message: '角色不存在或已停用' });
    }
  }

  private async ensureUnique(input: { account?: string; phone?: string }): Promise<void> {
    const existing = await this.prisma.user.findFirst({
      where: {
        OR: [
          ...(input.account === undefined ? [] : [{ account: input.account }]),
          ...(input.phone === undefined ? [] : [{ phone: input.phone }]),
        ],
      },
      select: { account: true, phone: true },
    });
    if (existing !== null) {
      throw new AppException({
        code: ErrorCode.STATE_NOT_ALLOWED,
        message: existing.account === input.account ? '登录账号已存在' : '手机号已存在',
      });
    }
  }

  private mapUniqueError(error: unknown): AppException {
    if (error instanceof Prisma.PrismaClientKnownRequestError && error.code === 'P2002') {
      return new AppException({ code: ErrorCode.STATE_NOT_ALLOWED, message: '账号或手机号已存在' });
    }
    return error instanceof AppException
      ? error
      : new AppException({ code: ErrorCode.INTERNAL_ERROR, message: '用户保存失败' });
  }

  private buildWhere(query: UserListQuery): Prisma.UserWhereInput {
    const where: Prisma.UserWhereInput = {};
    if (query.status !== 'all') {
      where.status = query.status === 'active' ? 'ACTIVE' : 'DISABLED';
    }
    if (query.keyword !== undefined && query.keyword.length > 0) {
      where.OR = [
        { name: { contains: query.keyword, mode: 'insensitive' } },
        { account: { contains: query.keyword, mode: 'insensitive' } },
        { phone: { contains: query.keyword } },
      ];
    }
    if (query.department_id !== undefined) {
      where.department = {
        OR: [{ id: query.department_id }, { parentId: query.department_id }],
      };
    }
    if (query.role_id !== undefined) {
      where.roles = { some: { roleId: query.role_id } };
    }
    return where;
  }

  private buildOrderBy(query: UserListQuery): Prisma.UserOrderByWithRelationInput[] {
    const direction: Prisma.SortOrder = query.order === 'asc' ? 'asc' : 'desc';
    if (query.sort === 'created_at') {
      return [{ createdAt: direction }, { id: 'asc' }];
    }
    return [{ lastLoginAt: { sort: direction, nulls: 'last' } }, { id: 'asc' }];
  }
}