package web

import (
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"strings"
	"time"

	"github.com/gin-gonic/gin"

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

// AdminRequired 叠加在已认证路由上。采购员能使用业务页，但不能执行管理操作。
func AdminRequired() gin.HandlerFunc {
	return func(c *gin.Context) {
		user := currentUser(c)
		if user != nil && user.IsAdmin() {
			c.Next()
			return
		}
		fail(c, http.StatusForbidden, "只有管理员可以执行此管理操作。当前账号仍可使用其他业务页面。")
		c.Abort()
	}
}

// UserList 显示用户搜索、分页和管理操作。
func (h *Handler) UserList(c *gin.Context) {
	h.renderUserList(c, http.StatusOK, c.Query("msg"), c.Query("error"), false, "")
}

func (h *Handler) renderUserList(c *gin.Context, httpStatus int, message, errorMessage string, needCreate bool, createUsername string) {
	keyword := strings.TrimSpace(userListValue(c, "q"))
	listStatus := userListValue(c, "status")
	pageSize := service.ParsePageSize(userListValue(c, "page_size"))
	if c.Request.Method == http.MethodPost {
		listStatus = c.PostForm("list_status")
	}
	result, err := service.ListUsersWithPageSize(h.db, currentUser(c), keyword,
		model.UserStatus(listStatus), service.ParsePage(userListValue(c, "page")), pageSize)
	if err != nil {
		fail(c, http.StatusInternalServerError, "读取用户列表失败，账号数据没有被改动。刷新后重试。")
		return
	}
	values := url.Values{}
	if keyword != "" {
		values.Set("q", keyword)
	}
	if result.Status != "" {
		values.Set("status", string(result.Status))
	}
	status := fmt.Sprintf("共 %d 个用户 · 第 %d/%d 页", result.Total, result.Page, result.TotalPages)
	c.HTML(httpStatus, "user/list", page(c, "users", "用户管理", gin.H{
		"Rows": result.Rows, "Keyword": result.Keyword, "Status": status,
		"Pagination":   service.NewPaginationView(result.Page, pageSize, result.TotalPages, values.Encode()),
		"StatusFilter": result.Status, "Message": message, "Error": errorMessage,
		"NeedCreate": needCreate, "CreateUsername": createUsername,
		"CurrentPage":     result.Page,
		"CurrentPageSize": pageSize,
	}))
}

func userListValue(c *gin.Context, key string) string {
	if c.Request.Method == http.MethodPost {
		return c.PostForm(key)
	}
	return c.Query(key)
}

// UserCreate 只创建固定 purchaser 角色，密码不写入 URL、不回显。
func (h *Handler) UserCreate(c *gin.Context) {
	err := service.CreatePurchaser(h.db, currentUser(c), c.PostForm("username"),
		c.PostForm("password"), c.PostForm("password_confirm"), time.Now())
	if err != nil {
		if isExpectedUserError(err) {
			h.renderUserList(c, http.StatusBadRequest, "", err.Error(), true,
				strings.TrimSpace(c.PostForm("username")))
			return
		}
		fail(c, http.StatusInternalServerError, "创建采购员失败，已有账号数据保持不变。刷新后重试。")
		return
	}
	redirectUsers(c, "采购员创建成功", "")
}

// UserSetStatus 启用或禁用账号，并由 Repository 在同一事务撤销全部 Session。
func (h *Handler) UserSetStatus(c *gin.Context) {
	status := model.UserStatus(c.PostForm("status"))
	err := service.ChangeUserStatus(h.db, currentUser(c), c.PostForm("user_id"), status, time.Now())
	if err != nil {
		h.userActionFailure(c, err, "修改账号状态失败")
		return
	}
	message := "账号已启用"
	if status == model.UserDisabled {
		message = "账号已禁用，原有登录已撤销"
	}
	redirectUsers(c, message, "")
}

// UserResetPassword 重置密码并撤销目标用户全部 Session。密码不会回显。
func (h *Handler) UserResetPassword(c *gin.Context) {
	err := service.ResetUserPassword(h.db, currentUser(c), c.PostForm("user_id"),
		c.PostForm("password"), c.PostForm("password_confirm"), time.Now())
	if err != nil {
		h.userActionFailure(c, err, "重置密码失败")
		return
	}
	redirectUsers(c, "密码已重置，原有登录已撤销", "")
}

func (h *Handler) userActionFailure(c *gin.Context, err error, fallback string) {
	if isExpectedUserError(err) {
		redirectUsers(c, "", err.Error())
		return
	}
	fail(c, http.StatusInternalServerError, fallback+"，已有账号数据保持不变。刷新后重试。")
}

func isExpectedUserError(err error) bool {
	return service.IsValidationError(err) || errors.Is(err, repository.ErrUsernameExists) ||
		errors.Is(err, repository.ErrUserNotFound) || errors.Is(err, repository.ErrLastActiveAdmin)
}

func redirectUsers(c *gin.Context, message, errorMessage string) {
	query := url.Values{}
	if keyword := c.PostForm("q"); keyword != "" {
		query.Set("q", keyword)
	}
	if status := c.PostForm("list_status"); status != "" {
		query.Set("status", status)
	}
	if page := c.PostForm("page"); page != "" {
		query.Set("page", page)
	}
	query.Set("page_size", fmt.Sprintf("%d", service.ParsePageSize(c.PostForm("page_size"))))
	if message != "" {
		query.Set("msg", message)
	}
	if errorMessage != "" {
		query.Set("error", errorMessage)
	}
	location := "/users"
	if encoded := query.Encode(); encoded != "" {
		location += "?" + encoded
	}
	c.Redirect(http.StatusSeeOther, location)
}