// Admin 用户管理业务：列表、新增采购员、启停和重置密码。
package service

import (
	"database/sql"
	"errors"
	"strings"
	"time"

	"cmautobuy/admin/model"
	"cmautobuy/admin/repository"
)

var ErrAdminRequired = errors.New("只有管理员可以执行此管理操作")

// UserListResult 是用户管理页的分页结果。
type UserListResult struct {
	Rows       []model.User
	Keyword    string
	Status     model.UserStatus
	Page       int
	Total      int
	TotalPages int
}

// ListUsers 搜索并分页。用户页沿用全站统一的每页 20 条规则。
func ListUsers(db *sql.DB, actor *model.User, keyword string, status model.UserStatus, requestedPage int) (*UserListResult, error) {
	if actor == nil || !actor.IsAdmin() {
		return nil, ErrAdminRequired
	}
	keyword = strings.TrimSpace(keyword)
	if status != model.UserActive && status != model.UserDisabled {
		status = ""
	}
	page := requestedPage
	if page < 1 {
		page = 1
	}
	rows, total, err := repository.ListUsers(db, keyword, status, PageSize, (page-1)*PageSize)
	if err != nil {
		return nil, err
	}
	totalPages := TotalPages(total)
	clampedPage := ClampPage(page, totalPages)
	if clampedPage != page {
		page = clampedPage
		rows, _, err = repository.ListUsers(db, keyword, status, PageSize, (page-1)*PageSize)
		if err != nil {
			return nil, err
		}
	}
	return &UserListResult{
		Rows: rows, Keyword: keyword, Status: status,
		Page: page, Total: total, TotalPages: totalPages,
	}, nil
}

// CreatePurchaser 创建固定 purchaser 角色的账号，不提供第二管理员入口。
func CreatePurchaser(db *sql.DB, actor *model.User, username, password, confirmation string, now time.Time) error {
	if actor == nil || !actor.IsAdmin() {
		return ErrAdminRequired
	}
	username = strings.TrimSpace(username)
	if err := validateUsername(username); err != nil {
		return err
	}
	hash, err := hashConfirmedPassword(password, confirmation)
	if err != nil {
		return err
	}
	userID, err := randomID("USR-", 16)
	if err != nil {
		return err
	}
	at := now.UTC().Format(model.TimeLayout)
	return repository.CreateUser(db, model.User{
		UserID: userID, Username: username, PasswordHash: string(hash),
		Role: model.RolePurchaser, Status: model.UserActive,
		PasswordChangedAt: at, CreatedAt: at, UpdatedAt: at,
	})
}

// ChangeUserStatus 启用或禁用账号。数据库事务负责最后管理员保护和 Session 撤销。
func ChangeUserStatus(db *sql.DB, actor *model.User, userID string, status model.UserStatus, now time.Time) error {
	if actor == nil || !actor.IsAdmin() {
		return ErrAdminRequired
	}
	if status != model.UserActive && status != model.UserDisabled {
		return invalidInput("账号状态无效")
	}
	if strings.TrimSpace(userID) == "" {
		return invalidInput("用户编号不能为空")
	}
	return repository.SetUserStatusAndRevokeSessions(
		db, userID, status, now.UTC().Format(model.TimeLayout))
}

// ResetUserPassword 更新密码哈希，并在同一事务中撤销目标用户全部 Session。
func ResetUserPassword(db *sql.DB, actor *model.User, userID, password, confirmation string, now time.Time) error {
	if actor == nil || !actor.IsAdmin() {
		return ErrAdminRequired
	}
	if strings.TrimSpace(userID) == "" {
		return invalidInput("用户编号不能为空")
	}
	hash, err := hashConfirmedPassword(password, confirmation)
	if err != nil {
		return err
	}
	return repository.ResetUserPasswordAndRevokeSessions(
		db, userID, string(hash), now.UTC().Format(model.TimeLayout))
}