// Package web 提供 HTTP 路由、会话、模板渲染与页面处理器。
package web

import (
	"bytes"
	"context"
	"crypto/rand"
	"crypto/sha256"
	"embed"
	"encoding/hex"
	"fmt"
	"html/template"
	"io/fs"
	"log"
	"net"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"daili/internal/domain"
	"daili/internal/store"
)

//go:embed templates/_layout.html templates/_screen_layout.html templates/_partials.html templates/pages/*.html
var templateFS embed.FS

//go:embed static
var staticFS embed.FS

const (
	cookieSession = "daili_sid"
	cookieFlash   = "daili_flash"
	cookieTheme   = "daili_theme"
	sessionTTL    = 7 * 24 * time.Hour
	pageSize      = 20
)

// Config 是服务配置。
type Config struct {
	Addr          string
	DBPath        string
	BackupKeep    int
	BackupDir     string
	BackupEnabled bool
	ScreenPublic  bool
	PortalPublic  bool
	ConfigPath    string
	Version       string
}

// Server 是应用服务。
type Server struct {
	db           *store.DB
	cfg          Config
	tpl          *renderer
	handler      http.Handler
	started      time.Time
	assetVersion string
}

type ctxKey int

const userCtxKey ctxKey = 1

// New 构造服务。
func New(db *store.DB, cfg Config) (*Server, error) {
	r, err := newRenderer()
	if err != nil {
		return nil, err
	}
	s := &Server{db: db, cfg: cfg, tpl: r, started: time.Now(), assetVersion: staticAssetVersion()}
	s.handler = s.routes()
	return s, nil
}

// staticAssetVersion 计算内嵌静态资源的内容指纹。
// 资源 URL 带上它之后可以放心长缓存；改了 CSS/JS 重新编译就会自动换 URL。
func staticAssetVersion() string {
	h := sha256.New()
	if err := fs.WalkDir(staticFS, "static", func(path string, d fs.DirEntry, err error) error {
		if err != nil || d.IsDir() {
			return nil
		}
		data, rerr := fs.ReadFile(staticFS, path)
		if rerr != nil {
			return nil
		}
		h.Write([]byte(path))
		h.Write([]byte{0})
		h.Write(data)
		return nil
	}); err != nil {
		return "dev"
	}
	return hex.EncodeToString(h.Sum(nil))[:12]
}

// Handler 返回 HTTP 处理器。
func (s *Server) Handler() http.Handler { return s.handler }

func (s *Server) routes() http.Handler {
	mux := http.NewServeMux()

	sub, err := fs.Sub(staticFS, "static")
	if err != nil {
		panic(err)
	}
	mux.Handle("GET /static/", s.staticFiles(http.StripPrefix("/static/", http.FileServerFS(sub))))
	mux.HandleFunc("GET /healthz", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		_, _ = w.Write([]byte("ok"))
	})

	mux.HandleFunc("GET /login", s.handleLoginPage)
	mux.HandleFunc("POST /login", s.handleLoginPost)
	mux.HandleFunc("GET /setup", s.handleSetupPage)
	mux.HandleFunc("POST /setup", s.handleSetupPost)
	mux.HandleFunc("POST /logout", s.handleLogout)

	mux.HandleFunc("GET /{$}", func(w http.ResponseWriter, r *http.Request) {
		http.Redirect(w, r, "/calendar", http.StatusFound)
	})
	mux.HandleFunc("GET /calendar", s.auth(s.handleCalendar))
	mux.HandleFunc("GET /customers", s.auth(s.handleCustomers))
	mux.HandleFunc("GET /customers/new", s.auth(s.handleCustomerNewPage))
	mux.HandleFunc("POST /customers", s.auth(s.handleCustomerCreate))
	mux.HandleFunc("GET /customers/{id}", s.auth(s.handleCustomerDetail))
	mux.HandleFunc("GET /customers/{id}/edit", s.auth(s.handleCustomerEditPage))
	mux.HandleFunc("POST /customers/{id}/edit", s.auth(s.handleCustomerUpdate))
	mux.HandleFunc("POST /customers/{id}/assignee", s.auth(s.handleCustomerAssignee))
	mux.HandleFunc("POST /customers/{id}/archive", s.auth(s.handleCustomerArchive))
	mux.HandleFunc("POST /customers/{id}/restore", s.auth(s.handleCustomerRestore))
	mux.HandleFunc("POST /customers/{id}/delete", s.auth(s.handleCustomerDelete))
	mux.HandleFunc("POST /customers/{id}/subscriptions", s.auth(s.handleSubCreate))
	mux.HandleFunc("GET /subscriptions", s.auth(s.handleSubscriptions))
	mux.HandleFunc("POST /subscriptions/{id}/extend", s.auth(s.handleSubExtend))
	mux.HandleFunc("POST /subscriptions/{id}/pause", s.auth(s.handleSubAction("pause")))
	mux.HandleFunc("POST /subscriptions/{id}/resume", s.auth(s.handleSubAction("resume")))
	mux.HandleFunc("POST /subscriptions/{id}/close", s.auth(s.handleSubAction("close")))
	mux.HandleFunc("POST /subscriptions/{id}/reopen", s.auth(s.handleSubAction("reopen")))
	mux.HandleFunc("POST /subscriptions/{id}/delete", s.auth(s.handleSubDelete))
	mux.HandleFunc("POST /subscriptions/{id}/season-done", s.auth(s.handleSeasonDone))
	mux.HandleFunc("POST /subscriptions/{id}/checkin", s.auth(s.handleCheckinSave))
	mux.HandleFunc("POST /checkins/{id}/delete", s.auth(s.handleCheckinDelete))
	mux.HandleFunc("POST /checkins/batch", s.auth(s.handleCheckinBatch))
	mux.HandleFunc("POST /checkins/quick", s.auth(s.handleQuickCheckin))
	mux.HandleFunc("POST /tasks/urgent", s.auth(s.handleUrgentToggle))
	mux.HandleFunc("GET /packages", s.auth(s.handlePackages))
	mux.HandleFunc("GET /packages/new", s.auth(s.handlePackageNewPage))
	mux.HandleFunc("POST /packages", s.auth(s.handlePackageCreate))
	mux.HandleFunc("GET /packages/{id}/edit", s.auth(s.handlePackageEditPage))
	mux.HandleFunc("POST /packages/{id}/edit", s.auth(s.handlePackageUpdate))
	mux.HandleFunc("POST /packages/{id}/archive", s.auth(s.handlePackageArchive))
	mux.HandleFunc("GET /packages/{id}", s.auth(s.handlePackageDetail))
	mux.HandleFunc("POST /packages/{id}/subscribe", s.auth(s.handlePackageBatchSubscribe))
	if s.cfg.PortalPublic {
		// 客户自助查询：独立开关，不受大屏 screen_public 影响
		mux.HandleFunc("GET /customer", s.handleCustomerPortal)
	}
	if s.cfg.ScreenPublic {
		// 大屏免登录：仅局域网部署时使用，内容为只读看板
		mux.HandleFunc("GET /screen", s.handleScreen)
		mux.HandleFunc("GET /api/screen/day", s.handleScreenDay)
	} else {
		mux.HandleFunc("GET /screen", s.auth(s.handleScreen))
		mux.HandleFunc("GET /api/screen/day", s.auth(s.handleScreenDay))
	}
	mux.HandleFunc("GET /logs", s.auth(s.handleLogs))
	mux.HandleFunc("GET /settings", s.auth(s.handleSettings))
	mux.HandleFunc("POST /settings", s.auth(s.handleSettingsSave))
	mux.HandleFunc("POST /settings/password", s.auth(s.handlePasswordChange))
	mux.HandleFunc("POST /settings/users", s.auth(s.handleUserCreate))
	mux.HandleFunc("POST /settings/users/{id}/toggle", s.auth(s.handleUserToggle))
	mux.HandleFunc("POST /settings/users/{id}/color", s.auth(s.handleUserColor))
	mux.HandleFunc("GET /settings/users/{id}/edit", s.auth(s.handleUserEditPage))
	mux.HandleFunc("POST /settings/users/{id}/edit", s.auth(s.handleUserEditSave))
	mux.HandleFunc("POST /settings/backup", s.auth(s.handleBackupNow))
	mux.HandleFunc("GET /export/{kind}", s.auth(s.handleExport))

	return s.noCacheHTML(mux)
}

// staticFiles 给内嵌静态资源加缓存策略：
// 只有带当前内容指纹（?v=）的 URL 才允许一年不可变缓存，其它一律回源。
func (s *Server) staticFiles(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Content-Type-Options", "nosniff")
		if r.URL.Query().Get("v") == s.assetVersion {
			w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
		} else {
			w.Header().Set("Cache-Control", "no-cache")
		}
		h.ServeHTTP(w, r)
	})
}

func (s *Server) noCacheHTML(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if !strings.HasPrefix(r.URL.Path, "/static/") {
			w.Header().Set("X-Content-Type-Options", "nosniff")
			w.Header().Set("Referrer-Policy", "same-origin")
		}
		h.ServeHTTP(w, r)
	})
}

// ---------- 会话与鉴权 ----------

func randomToken() string {
	b := make([]byte, 24)
	if _, err := rand.Read(b); err != nil {
		return strconv.FormatInt(time.Now().UnixNano(), 36)
	}
	return hex.EncodeToString(b)
}

func clientIP(r *http.Request) string {
	host, _, err := net.SplitHostPort(r.RemoteAddr)
	if err != nil {
		return r.RemoteAddr
	}
	return host
}

func (s *Server) startSession(w http.ResponseWriter, r *http.Request, u *store.User) {
	token := randomToken()
	if err := s.db.CreateSession(token, u.ID, sessionTTL, clientIP(r)); err != nil {
		log.Printf("创建会话失败: %v", err)
	}
	http.SetCookie(w, &http.Cookie{
		Name: cookieSession, Value: token, Path: "/", HttpOnly: true,
		SameSite: http.SameSiteLaxMode, MaxAge: int(sessionTTL.Seconds()),
	})
}

func (s *Server) userFromRequest(r *http.Request) *store.User {
	c, err := r.Cookie(cookieSession)
	if err != nil || c.Value == "" {
		return nil
	}
	u, err := s.db.SessionUser(c.Value)
	if err != nil {
		return nil
	}
	return u
}

func (s *Server) currentUser(r *http.Request) *store.User {
	if u, ok := r.Context().Value(userCtxKey).(*store.User); ok {
		return u
	}
	return nil
}

func sameOrigin(r *http.Request) bool {
	origin := r.Header.Get("Origin")
	if origin == "" {
		return true
	}
	u, err := url.Parse(origin)
	if err != nil {
		return false
	}
	return strings.EqualFold(u.Host, r.Host)
}

func (s *Server) auth(h http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method == http.MethodPost && !sameOrigin(r) {
			http.Error(w, "跨站请求被拒绝", http.StatusForbidden)
			return
		}
		u := s.userFromRequest(r)
		if u == nil {
			if r.Method == http.MethodGet {
				next := url.QueryEscape(r.URL.RequestURI())
				http.Redirect(w, r, "/login?next="+next, http.StatusFound)
				return
			}
			http.Redirect(w, r, "/login", http.StatusFound)
			return
		}
		ctx := context.WithValue(r.Context(), userCtxKey, u)
		h(w, r.WithContext(ctx))
	}
}

// ---------- 渲染 ----------

type renderer struct {
	pages map[string]*template.Template
}

func newRenderer() (*renderer, error) {
	funcs := template.FuncMap{
		"seq": func(n int) []int {
			out := make([]int, 0, n)
			for i := 0; i < n; i++ {
				out = append(out, i)
			}
			return out
		},
		"add": func(a, b int) int { return a + b },
		"sub": func(a, b int) int { return a - b },
		"money": func(cents int) string {
			return fmt.Sprintf("%.0f", float64(cents)/100)
		},
		"pct": func(f float64) string { return fmt.Sprintf("%.2f", f) },
		"md":  func(s string) string { return mdOf(s) },
		"dow": dowCN,
	}
	base, err := template.New("base").Funcs(funcs).ParseFS(templateFS,
		"templates/_layout.html", "templates/_partials.html")
	if err != nil {
		return nil, err
	}
	screenBase, err := template.New("screen").Funcs(funcs).ParseFS(templateFS,
		"templates/_screen_layout.html", "templates/_partials.html")
	if err != nil {
		return nil, err
	}

	pages := map[string]*template.Template{}
	entries, err := fs.Glob(templateFS, "templates/pages/*.html")
	if err != nil {
		return nil, err
	}
	for _, p := range entries {
		name := strings.TrimSuffix(strings.TrimPrefix(p, "templates/pages/"), ".html")
		var baseSet *template.Template
		if name == "screen" {
			baseSet = screenBase
		} else {
			baseSet = base
		}
		clone, err := baseSet.Clone()
		if err != nil {
			return nil, err
		}
		if _, err := clone.ParseFS(templateFS, p); err != nil {
			return nil, fmt.Errorf("解析模板 %s 失败: %w", p, err)
		}
		pages[name] = clone
	}
	return &renderer{pages: pages}, nil
}

func mdOf(s string) string {
	if len(s) >= 10 {
		return s[5:10]
	}
	return s
}

func dowCN(s string) string {
	t, err := domain.ParseDate(s)
	if err != nil {
		return ""
	}
	return [...]string{"一", "二", "三", "四", "五", "六", "日"}[domain.WeekdayIndex(t)]
}

// page 是所有页面模板的根数据。
type page struct {
	User     *store.User
	Title    string
	Nav      string
	Flash    string
	Error    string
	Today    time.Time
	TodayStr string
	WarnDays int
	Version  string
	// AssetVersion 是内嵌静态资源的内容指纹，用于 /static/*.css?v=... 的长缓存
	AssetVersion string
	Query        string
	Name         string
	InlineError  string
	InvalidField string
	Next         string
	DueToday     int
	Due3         int
	Due7         int
	Addr         string
	Theme        string // "" = 跟随系统；light / dark
	D            any
}

func (s *Server) warnDays() int {
	v, err := strconv.Atoi(s.db.Setting("warn_days", "3"))
	if err != nil || v <= 0 {
		return 3
	}
	return v
}

func (s *Server) screenRefresh() int {
	v, err := strconv.Atoi(s.db.Setting("screen_refresh", "30"))
	if err != nil || v < 5 {
		return 30
	}
	return v
}

func (s *Server) newPage(r *http.Request, title, nav string) *page {
	u := s.currentUser(r)
	today := domain.Today()
	p := &page{
		User:     u,
		Title:    title,
		Nav:      nav,
		Today:    today,
		TodayStr: domain.Date(today),
		WarnDays: s.warnDays(),
		Version:  s.cfg.Version,

		AssetVersion: s.assetVersion,
		Query:        r.URL.Query().Get("q"),
		Next:         r.URL.Query().Get("next"),
		Theme:        themeFromRequest(r),
	}
	if u != nil {
		if due, due3, due7, err := s.db.Badges(today); err == nil {
			p.DueToday, p.Due3, p.Due7 = due, due3, due7
		}
	}
	return p
}

// themeFromRequest 读取主题偏好："" = 跟随系统，light / dark = 手动指定。
func themeFromRequest(r *http.Request) string {
	c, err := r.Cookie(cookieTheme)
	if err != nil {
		return ""
	}
	switch c.Value {
	case "light", "dark":
		return c.Value
	}
	return ""
}

func (s *Server) popFlash(w http.ResponseWriter, r *http.Request) string {
	c, err := r.Cookie(cookieFlash)
	if err != nil || c.Value == "" {
		return ""
	}
	msg, _ := url.QueryUnescape(c.Value)
	http.SetCookie(w, &http.Cookie{Name: cookieFlash, Value: "", Path: "/", MaxAge: -1, HttpOnly: true})
	return msg
}

func setFlash(w http.ResponseWriter, msg string) {
	http.SetCookie(w, &http.Cookie{
		Name: cookieFlash, Value: url.QueryEscape(msg), Path: "/",
		MaxAge: 30, HttpOnly: true, SameSite: http.SameSiteLaxMode,
	})
}

func (s *Server) redirect(w http.ResponseWriter, r *http.Request, to, flash string) {
	if flash != "" {
		setFlash(w, flash)
	}
	http.Redirect(w, r, to, http.StatusSeeOther)
}

func (s *Server) render(w http.ResponseWriter, r *http.Request, name string, d *page) {
	if d.User == nil {
		d.User = s.currentUser(r)
	}
	if d.Flash == "" {
		d.Flash = s.popFlash(w, r)
	}
	if d.Today.IsZero() {
		d.Today = domain.Today()
		d.TodayStr = domain.Date(d.Today)
	}
	if d.WarnDays == 0 {
		d.WarnDays = s.warnDays()
	}
	tpl, ok := s.tpl.pages[name]
	if !ok {
		log.Printf("模板不存在: %s", name)
		http.Error(w, "页面不存在", http.StatusInternalServerError)
		return
	}
	layout := "layout"
	if name == "screen" {
		layout = "screenlayout"
	}
	var buf bytes.Buffer
	if err := tpl.ExecuteTemplate(&buf, layout, d); err != nil {
		log.Printf("渲染 %s 失败: %v", name, err)
		http.Error(w, "页面渲染失败: "+err.Error(), http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	_, _ = buf.WriteTo(w)
}

func (s *Server) fail(w http.ResponseWriter, r *http.Request, name string, msg string, d *page) {
	if d == nil {
		d = s.newPage(r, "出错了", "")
	}
	d.Error = msg
	w.WriteHeader(http.StatusBadRequest)
	s.render(w, r, name, d)
}

// ---------- 参数 ----------

func (s *Server) queryInt(r *http.Request, key string, def int) int {
	v, err := strconv.Atoi(r.URL.Query().Get(key))
	if err != nil {
		return def
	}
	return v
}

func (s *Server) formInt(r *http.Request, key string, def int) int {
	v, err := strconv.Atoi(strings.TrimSpace(r.PostFormValue(key)))
	if err != nil {
		return def
	}
	return v
}

func pathID(r *http.Request) int64 {
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		return 0
	}
	return id
}

// backURL 取安全的返回地址。
func backURL(r *http.Request, def string) string {
	if b := strings.TrimSpace(r.PostFormValue("back")); strings.HasPrefix(b, "/") && !strings.HasPrefix(b, "//") {
		return b
	}
	if ref := r.Referer(); ref != "" {
		if u, err := url.Parse(ref); err == nil && strings.EqualFold(u.Host, r.Host) {
			p := u.RequestURI()
			if strings.HasPrefix(p, "/") {
				return p
			}
		}
	}
	return def
}