package web

import (
	"database/sql"
	"errors"
	"net/http"
	"net/url"
	"strings"
	"time"

	"github.com/gin-gonic/gin"

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

const (
	authCookieName = "cmautobuy_session"
	currentUserKey = "cmautobuy_current_user"
)

// SetupPage 只在数据库完全没有用户时显示首次管理员表单。
func (h *Handler) SetupPage(c *gin.Context) {
	hasUsers, err := service.HasUsers(h.db)
	if err != nil {
		fail(c, http.StatusInternalServerError, "检查管理员初始化状态失败，数据没有被改动。刷新后重试。")
		return
	}
	if hasUsers {
		c.Redirect(http.StatusSeeOther, "/login?msg="+url.QueryEscape("管理员已经初始化，请登录"))
		return
	}
	h.renderSetup(c, http.StatusOK, "", "admin")
}

// SetupSubmit 创建首位管理员。密码无论成功失败都不回显。
func (h *Handler) SetupSubmit(c *gin.Context) {
	username := strings.TrimSpace(c.PostForm("username"))
	err := service.SetupInitialAdmin(
		h.db, username, c.PostForm("password"), c.PostForm("password_confirm"), time.Now())
	if errors.Is(err, repository.ErrUsersAlreadyExist) {
		c.Redirect(http.StatusSeeOther, "/login?msg="+url.QueryEscape("管理员已经初始化，请登录"))
		return
	}
	if err != nil {
		h.renderSetup(c, http.StatusBadRequest, err.Error(), username)
		return
	}
	c.Redirect(http.StatusSeeOther, "/login?msg="+url.QueryEscape("管理员创建成功，请登录"))
}

func (h *Handler) renderSetup(c *gin.Context, status int, message, username string) {
	c.HTML(status, "auth/setup", gin.H{
		"Title": "初始化管理员", "CSRFToken": csrfToken(c),
		"Message": message, "Username": username,
	})
}

// LoginPage 显示登录页。没有用户时先去初始化；已有有效 Session 时直接返回目标页。
func (h *Handler) LoginPage(c *gin.Context) {
	hasUsers, err := service.HasUsers(h.db)
	if err != nil {
		fail(c, http.StatusInternalServerError, "检查登录状态失败。刷新后重试。")
		return
	}
	if !hasUsers {
		c.Redirect(http.StatusSeeOther, "/setup")
		return
	}
	next := safeNext(c.Query("next"))
	if token, err := c.Cookie(authCookieName); err == nil {
		if _, authErr := service.Authenticate(h.db, token, time.Now()); authErr == nil {
			c.Redirect(http.StatusSeeOther, next)
			return
		}
	}
	h.renderLogin(c, http.StatusOK, c.Query("msg"), "", next)
}

// LoginSubmit 校验凭据。用户名不存在、密码错误和账号禁用使用同一句提示。
func (h *Handler) LoginSubmit(c *gin.Context) {
	username := strings.TrimSpace(c.PostForm("username"))
	next := safeNext(c.PostForm("next"))
	token, _, expiresAt, err := service.Login(h.db, username, c.PostForm("password"), time.Now())
	if errors.Is(err, service.ErrInvalidCredentials) {
		h.renderLogin(c, http.StatusUnauthorized, service.ErrInvalidCredentials.Error(), username, next)
		return
	}
	if err != nil {
		fail(c, http.StatusInternalServerError, "登录失败，但账号数据没有被修改。请稍后重试。")
		return
	}
	setAuthCookie(c, token, expiresAt)
	c.Redirect(http.StatusSeeOther, next)
}

func (h *Handler) renderLogin(c *gin.Context, status int, message, username, next string) {
	c.HTML(status, "auth/login", gin.H{
		"Title": "登录 Admin", "CSRFToken": csrfToken(c),
		"Message": message, "Username": username, "Next": safeNext(next),
	})
}

// Logout 撤销服务端 Session 并清除浏览器 Cookie。退出必须走 POST + CSRF。
func (h *Handler) Logout(c *gin.Context) {
	token, _ := c.Cookie(authCookieName)
	if err := service.Logout(h.db, token); err != nil {
		fail(c, http.StatusInternalServerError, "退出登录失败，请刷新页面后重试。")
		return
	}
	clearAuthCookie(c)
	c.Redirect(http.StatusSeeOther, "/login?msg="+url.QueryEscape("已退出登录"))
}

// ChangePassword 修改当前管理员自己的密码；目标身份只取 Session，不读表单用户编号。
func (h *Handler) ChangePassword(c *gin.Context) {
	returnPath := passwordReturnPath(c.PostForm("next"))
	err := service.ChangeAdminPassword(h.db, currentUser(c), c.PostForm("current_password"),
		c.PostForm("new_password"), c.PostForm("password_confirm"), time.Now())
	if service.IsValidationError(err) {
		query := url.Values{
			"change_password": {"1"},
			"password_error":  {err.Error()},
		}
		if field := service.ValidationField(err); field != "" {
			query.Set("password_field", field)
		}
		separator := "?"
		if strings.Contains(returnPath, "?") {
			separator = "&"
		}
		c.Redirect(http.StatusSeeOther, returnPath+separator+query.Encode())
		return
	}
	if errors.Is(err, repository.ErrUserPasswordChanged) {
		clearAuthCookie(c)
		c.Redirect(http.StatusSeeOther, "/login?msg="+url.QueryEscape("密码已在其他操作中变更，请重新登录"))
		return
	}
	if err != nil {
		fail(c, http.StatusInternalServerError, "修改密码失败，原密码和现有登录保持不变。刷新后重试。")
		return
	}
	clearAuthCookie(c)
	c.Redirect(http.StatusSeeOther, "/login?msg="+url.QueryEscape("密码修改成功，请使用新密码重新登录"))
}

// AuthRequired 只挂在 Web 业务路由组。Client API 注册在另一个组，不能经过这里。
func AuthRequired(db *sql.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		token, _ := c.Cookie(authCookieName)
		user, err := service.Authenticate(db, token, time.Now())
		if err == nil {
			c.Set(currentUserKey, user)
			c.Next()
			return
		}
		if !errors.Is(err, service.ErrUnauthenticated) {
			fail(c, http.StatusInternalServerError, "检查登录状态失败。刷新页面后重试。")
			c.Abort()
			return
		}
		hasUsers, countErr := service.HasUsers(db)
		if countErr != nil {
			fail(c, http.StatusInternalServerError, "检查管理员初始化状态失败。刷新页面后重试。")
			c.Abort()
			return
		}
		if !hasUsers {
			c.Redirect(http.StatusSeeOther, "/setup")
		} else {
			next := safeNext(c.Request.URL.RequestURI())
			c.Redirect(http.StatusSeeOther, "/login?next="+url.QueryEscape(next))
		}
		c.Abort()
	}
}

func currentUser(c *gin.Context) *model.User {
	value, ok := c.Get(currentUserKey)
	if !ok {
		return nil
	}
	user, _ := value.(*model.User)
	return user
}

// safeNext 只接受本站绝对路径，阻止登录成功后跳转到外部网站。
func safeNext(raw string) string {
	raw = strings.TrimSpace(raw)
	if raw == "" || !strings.HasPrefix(raw, "/") || strings.HasPrefix(raw, "//") {
		return "/shopee"
	}
	parsed, err := url.Parse(raw)
	if err != nil || parsed.IsAbs() || parsed.Host != "" {
		return "/shopee"
	}
	return raw
}

func setAuthCookie(c *gin.Context, token string, expiresAt time.Time) {
	http.SetCookie(c.Writer, &http.Cookie{
		Name: authCookieName, Value: token, Path: "/", HttpOnly: true,
		Secure: c.Request.TLS != nil, SameSite: http.SameSiteLaxMode,
		Expires: expiresAt, MaxAge: int(service.WebSessionDuration.Seconds()),
	})
}

func clearAuthCookie(c *gin.Context) {
	http.SetCookie(c.Writer, &http.Cookie{
		Name: authCookieName, Value: "", Path: "/", HttpOnly: true,
		Secure: c.Request.TLS != nil, SameSite: http.SameSiteLaxMode,
		Expires: time.Unix(1, 0), MaxAge: -1,
	})
}