package handler

import (
	"bytes"
	"fmt"
	"html/template"
	"log/slog"
	"net/http"
	"net/url"
	"path/filepath"
	"strings"
	"sync"

	"github.com/gabriel-vasile/mimetype"

	"vidarchive"
	"vidarchive/internal/config"
	"vidarchive/internal/models"
	"vidarchive/internal/service"
	"vidarchive/internal/util"
	"vidarchive/internal/worker"
)

type Handler struct {
	cfg             *config.Config
	templates       *template.Template
	presetSvc       *service.PresetService
	downloadSvc     *service.DownloadService
	librarySvc      *service.LibraryService
	settingsSvc     *service.SettingsService
	subscriptionSvc *service.SubscriptionService
	workerPool      *worker.Pool

	loginSem chan struct{}
	// sessionSecret is cached here because every guarded request reads it; Logout
	// rotates it.
	sessionMu     sync.RWMutex
	sessionSecret string
	tools         toolCache
}

func New(cfg *config.Config, presetSvc *service.PresetService, downloadSvc *service.DownloadService, librarySvc *service.LibraryService, settingsSvc *service.SettingsService, subscriptionSvc *service.SubscriptionService, workerPool *worker.Pool) (*Handler, error) {
	tmpl, err := loadTemplates(presetSvc)
	if err != nil {
		return nil, fmt.Errorf("load templates: %w", err)
	}

	sessionSecret, err := loadSessionSecret(settingsSvc)
	if err != nil {
		return nil, fmt.Errorf("load session secret: %w", err)
	}

	return &Handler{
		cfg:             cfg,
		templates:       tmpl,
		presetSvc:       presetSvc,
		downloadSvc:     downloadSvc,
		librarySvc:      librarySvc,
		settingsSvc:     settingsSvc,
		subscriptionSvc: subscriptionSvc,
		workerPool:      workerPool,
		loginSem:        make(chan struct{}, maxConcurrentLogins),
		sessionSecret:   sessionSecret,
	}, nil
}

func loadTemplates(presetSvc *service.PresetService) (*template.Template, error) {
	tmpl := template.New("").Funcs(template.FuncMap{
		"formatDuration": formatDuration,
		"formatFileSize": util.FormatBytes,
		"heatmapRange": func(hm models.HeatmapSegment) string {
			return fmt.Sprintf("%s to %s, activity %.2f", util.FormatClock(int(hm.StartTime+0.5)), util.FormatClock(int(hm.EndTime+0.5)), hm.Value)
		},
		"splitPath":     func(p string) []string { return strings.Split(strings.Trim(p, "/"), "/") },
		"baseName":      filepath.Base,
		"mimeType":      mimeTypeFromFile,
		"presetFlags":   func(p *models.Preset) string { return presetSvc.EffectiveFlags(p, "", "") },
		"urlEncodePath": util.URLEncodePath,
		"sub":           func(a, b int) int { return a - b },
		// A zero value lets the create page render the form partials it shares with
		// the edit page.
		"emptyPreset": func() *models.Preset { return nil },
		"newSubscription": func() *models.Subscription {
			return &models.Subscription{RefreshMode: "overwrite", ScheduleKind: "daily"}
		},
		// dict takes alternating key/value args, so a template can pass more than
		// one value into a sub-template.
		"dict": func(values ...interface{}) (map[string]interface{}, error) {
			if len(values)%2 != 0 {
				return nil, fmt.Errorf("dict expects an even number of arguments")
			}
			m := make(map[string]interface{}, len(values)/2)
			for i := 0; i < len(values); i += 2 {
				key, ok := values[i].(string)
				if !ok {
					return nil, fmt.Errorf("dict keys must be strings")
				}
				m[key] = values[i+1]
			}
			return m, nil
		},
		// isLongText drives the collapsible description. Rune count, not bytes, so
		// CJK text is not flagged early.
		"isLongText": func(s string) bool {
			return strings.Count(s, "\n") >= 2 || len([]rune(s)) > 180
		},
	})

	return tmpl.ParseFS(vidarchive.TemplatesFS, "web/templates/*.html")
}

func formatDuration(seconds int) string {
	if seconds <= 0 {
		return "--:--"
	}
	return util.FormatClock(seconds)
}

func mimeTypeFromFile(path string) string {
	mtype, err := mimetype.DetectFile(path)
	if err != nil || mtype == nil {
		return "application/octet-stream"
	}
	return mtype.String()
}

type PageData struct {
	Title       string
	ActiveTab   string
	Data        interface{}
	BaseURL     string
	AutoRefresh bool
	RefreshSec  int
	Theme       string
	Flash       *Flash
}

// Flash is a one-shot message shown after a redirect. Kind is "success" or
// "error".
type Flash struct {
	Kind    string
	Message string
}

const cookieMaxAge = 365 * 24 * 60 * 60

const flashCookie = "flash"

// setFlash stashes the message in a short-lived cookie; consumeFlash clears it.
func setFlash(w http.ResponseWriter, kind, message string) {
	http.SetCookie(w, &http.Cookie{
		Name:     flashCookie,
		Value:    url.QueryEscape(kind + "|" + message),
		Path:     "/",
		MaxAge:   30,
		HttpOnly: true,
		SameSite: http.SameSiteLaxMode,
	})
}

func flashSuccess(w http.ResponseWriter, message string) { setFlash(w, "success", message) }
func flashError(w http.ResponseWriter, message string)   { setFlash(w, "error", message) }

func consumeFlash(w http.ResponseWriter, r *http.Request) *Flash {
	c, err := r.Cookie(flashCookie)
	if err != nil || c.Value == "" {
		return nil
	}
	http.SetCookie(w, &http.Cookie{
		Name:     flashCookie,
		Value:    "",
		Path:     "/",
		MaxAge:   -1,
		HttpOnly: true,
		SameSite: http.SameSiteLaxMode,
	})
	decoded, err := url.QueryUnescape(c.Value)
	if err != nil {
		return nil
	}
	kind, message, ok := strings.Cut(decoded, "|")
	if !ok {
		return nil
	}
	// The cookie is client-editable, and kind becomes the banner's class name.
	if kind != "success" {
		kind = "error"
	}
	return &Flash{Kind: kind, Message: message}
}

func getCookie(r *http.Request, name, defaultVal string) string {
	cookie, err := r.Cookie(name)
	if err != nil {
		return defaultVal
	}
	return cookie.Value
}

func setCookie(w http.ResponseWriter, name, value string) {
	http.SetCookie(w, &http.Cookie{
		Name:     name,
		Value:    value,
		Path:     "/",
		MaxAge:   cookieMaxAge,
		HttpOnly: true,
		SameSite: http.SameSiteLaxMode,
	})
}

func (h *Handler) renderWithRequest(w http.ResponseWriter, r *http.Request, contentTmpl string, data PageData) {
	data.BaseURL = h.cfg.BaseURL
	if data.Theme == "" {
		data.Theme = getCookie(r, "theme", "auto")
	}
	if data.Flash == nil {
		data.Flash = consumeFlash(w, r)
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")

	var contentBuf bytes.Buffer
	if err := h.templates.ExecuteTemplate(&contentBuf, contentTmpl, data); err != nil {
		http.Error(w, fmt.Sprintf("render content: %v", err), http.StatusInternalServerError)
		return
	}

	layoutData := struct {
		PageData
		Content template.HTML
	}{
		PageData: data,
		Content:  template.HTML(contentBuf.String()),
	}

	if err := h.templates.ExecuteTemplate(w, "layout", layoutData); err != nil {
		http.Error(w, fmt.Sprintf("render layout: %v", err), http.StatusInternalServerError)
	}
}

// settingsOrDefault falls back to defaults rather than a nil deref when the
// store can't be read.
func (h *Handler) settingsOrDefault() *models.Settings {
	settings, err := h.settingsSvc.GetAll()
	if err != nil {
		slog.Error("settings load failed, using defaults", "err", err)
		return &models.Settings{RefreshInterval: 5, AutoRefreshDownloads: true}
	}
	return settings
}