package api

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"strings"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/sandrodach/mindsift/internal/auth"
	"github.com/sandrodach/mindsift/internal/domain"
	"github.com/sandrodach/mindsift/internal/storage"
)

// --- HANDLERS ---

func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	writeJSON(w, http.StatusOK, map[string]interface{}{
		"status":  "ok",
		"service": "mindsift",
		"time":    domain.NowISO(),
	})
}

func (s *Server) handleAuthStatus(w http.ResponseWriter, r *http.Request) {
	count, _ := s.store.CountUsers()
	sys, _ := s.store.GetSystemSettings()
	allowReg := false
	instanceName := "MindSift"
	if sys != nil {
		allowReg = sys.AllowRegistration
		if sys.InstanceName != "" {
			instanceName = sys.InstanceName
		}
	}
	status := map[string]interface{}{
		"needsSetup":        count == 0,
		"allowRegistration": allowReg,
		"instanceName":      instanceName,
		"demoMode":          s.cfg.DemoMode,
		"sharingMode":       s.store.SharingMode(),
		"passwordReset":     s.passwordResetAvailable(),
		// Public so the login screen can link Impressum and Datenschutz
		"legal": map[string]interface{}{
			"imprintUrl":        s.cfg.Legal.ImprintURL,
			"hasImprintContent": s.cfg.Legal.ImprintContent != "",
			"privacyUrl":        s.cfg.Legal.PrivacyURL,
			"hasPrivacyContent": s.cfg.Legal.PrivacyContent != "",
		},
	}
	// Countdown to the next demo reset; seconds as well, so client clocks do not matter
	if next := s.demoNextReset(); !next.IsZero() {
		status["demoNextReset"] = next.UTC().Format(time.RFC3339)
		status["demoResetInSeconds"] = int(time.Until(next).Seconds())
		status["demoResetMinutes"] = s.cfg.DemoResetMinutes
	}
	writeJSON(w, http.StatusOK, status)
}

// handleLegalText serves the configured Markdown of the imprint or privacy notice (public, no login).
func (s *Server) handleLegalText(w http.ResponseWriter, r *http.Request) {
	content := ""
	switch chi.URLParam(r, "type") {
	case "imprint":
		content = s.cfg.Legal.ImprintContent
	case "privacy":
		content = s.cfg.Legal.PrivacyContent
	}
	if content == "" {
		writeError(w, http.StatusNotFound, "Kein Text hinterlegt")
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"content": content})
}

func (s *Server) handleFirstBootSetup(w http.ResponseWriter, r *http.Request) {
	count, err := s.store.CountUsers()
	if err != nil || count > 0 {
		writeError(w, http.StatusForbidden, "Ersteinrichtung wurde bereits abgeschlossen")
		return
	}

	var req struct {
		Email             string `json:"email"`
		Password          string `json:"password"`
		DisplayName       string `json:"displayName"`
		InstanceName      string `json:"instanceName"`
		AllowRegistration bool   `json:"allowRegistration"`
		SharingMode       string `json:"sharingMode"`
		CreateSampleData  bool   `json:"createSampleData"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "Ungültige Anfrage")
		return
	}
	if strings.TrimSpace(req.Email) == "" {
		writeError(w, http.StatusBadRequest, "E-Mail-Adresse erforderlich")
		return
	}
	if err := auth.ValidatePassword(req.Password); err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	if strings.TrimSpace(req.DisplayName) == "" {
		req.DisplayName = "Administrator"
	}

	hash, err := auth.HashPassword(req.Password)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Fehler beim Passwort-Hashing")
		return
	}

	user, err := s.store.CreateUser(req.Email, hash, req.DisplayName, "admin")
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}

	sys, _ := s.store.GetSystemSettings()
	if sys != nil {
		if strings.TrimSpace(req.InstanceName) != "" {
			sys.InstanceName = strings.TrimSpace(req.InstanceName)
		}
		sys.AllowRegistration = req.AllowRegistration
		sys.SharingMode = storage.NormalizeSharingMode(req.SharingMode)
		_ = s.store.UpdateSystemSettings(sys)
		// In organization mode the first admin starts in an organization named after the instance
		if sys.SharingMode == storage.SharingOrganizations {
			if org, err := s.store.CreateOrganization(sys.InstanceName); err == nil {
				_ = s.store.SetUserOrganization(user.ID, org.ID)
				user.OrganizationID = org.ID
			}
		}
	}

	if req.CreateSampleData {
		_ = s.store.SeedStarterContent(user)
	}

	token, err := auth.GenerateToken(s.cfg.JWTSecret, user.ID, user.Email, user.DisplayName, user.TokenVersion)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Token konnte nicht erstellt werden")
		return
	}

	writeJSON(w, http.StatusCreated, map[string]interface{}{
		"token": token,
		"user":  user,
	})
}

func (s *Server) handleRegister(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Email       string `json:"email"`
		Password    string `json:"password"`
		DisplayName string `json:"displayName"`
		InviteCode  string `json:"inviteCode"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "Ungültige Anfrage")
		return
	}
	if strings.TrimSpace(req.Email) == "" {
		writeError(w, http.StatusBadRequest, "E-Mail-Adresse erforderlich")
		return
	}
	if err := auth.ValidatePassword(req.Password); err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	if strings.TrimSpace(req.DisplayName) == "" {
		req.DisplayName = strings.Split(req.Email, "@")[0]
	}

	count, _ := s.store.CountUsers()
	role := "member"
	var validInvite *domain.UserInvite

	if strings.TrimSpace(req.InviteCode) != "" {
		inv, err := s.store.GetUserInviteByCode(req.InviteCode)
		if err != nil {
			writeError(w, http.StatusForbidden, err.Error())
			return
		}
		if inv.Email != "" && !strings.EqualFold(inv.Email, strings.TrimSpace(req.Email)) {
			writeError(w, http.StatusForbidden, "Dieser Einladungscode ist an eine andere E-Mail-Adresse gebunden")
			return
		}
		validInvite = inv
		role = inv.Role
	} else if count == 0 {
		role = "admin"
	} else {
		sysSettings, _ := s.store.GetSystemSettings()
		if sysSettings == nil || !sysSettings.AllowRegistration {
			writeError(w, http.StatusForbidden, "Öffentliche Registrierung ist deaktiviert – bitte nutze einen Einladungscode vom Administrator")
			return
		}
	}

	hash, err := auth.HashPassword(req.Password)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Fehler beim Passwort-Hashing")
		return
	}

	user, err := s.store.CreateUser(req.Email, hash, req.DisplayName, role)
	if err != nil {
		writeError(w, http.StatusConflict, "E-Mail-Adresse existiert bereits")
		return
	}

	if validInvite != nil {
		_ = s.store.MarkUserInviteUsed(validInvite.ID, user.ID)
		if validInvite.OrganizationID != "" {
			_ = s.store.SetUserOrganization(user.ID, validInvite.OrganizationID)
			user.OrganizationID = validInvite.OrganizationID
		}
	}

	token, err := auth.GenerateToken(s.cfg.JWTSecret, user.ID, user.Email, user.DisplayName, user.TokenVersion)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Token konnte nicht erstellt werden")
		return
	}

	writeJSON(w, http.StatusCreated, map[string]interface{}{
		"token": token,
		"user":  user,
	})
}

func (s *Server) handleLogin(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Email    string `json:"email"`
		Username string `json:"username"`
		Login    string `json:"login"`
		Password string `json:"password"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "Ungültige Anfrage")
		return
	}

	identifier := strings.TrimSpace(req.Login)
	if identifier == "" {
		identifier = strings.TrimSpace(req.Username)
	}
	if identifier == "" {
		identifier = strings.TrimSpace(req.Email)
	}

	if identifier == "" || req.Password == "" {
		writeError(w, http.StatusBadRequest, "Benutzername/E-Mail und Passwort erforderlich")
		return
	}

	user, err := s.store.GetUserByLogin(identifier)
	if err != nil {
		slog.Warn("Login fehlgeschlagen: Benutzer existiert nicht", "login", identifier, "remote_addr", r.RemoteAddr)
		writeError(w, http.StatusUnauthorized, "Benutzername/E-Mail oder Passwort ungültig")
		return
	}
	if !auth.CheckPassword(req.Password, user.PasswordHash) {
		slog.Warn("Login fehlgeschlagen: Falsches Passwort", "login", identifier, "user_id", user.ID, "display_name", user.DisplayName, "remote_addr", r.RemoteAddr)
		writeError(w, http.StatusUnauthorized, "Benutzername/E-Mail oder Passwort ungültig")
		return
	}
	if !user.IsActive {
		slog.Warn("Login verweigert: Benutzerkonto ist deaktiviert", "login", identifier, "user_id", user.ID, "display_name", user.DisplayName, "remote_addr", r.RemoteAddr)
		writeError(w, http.StatusForbidden, "Dieses Benutzerkonto ist deaktiviert")
		return
	}

	token, err := auth.GenerateToken(s.cfg.JWTSecret, user.ID, user.Email, user.DisplayName, user.TokenVersion)
	if err != nil {
		slog.Error("Login-Token konnte nicht erstellt werden", "login", identifier, "user_id", user.ID, "error", err)
		writeError(w, http.StatusInternalServerError, "Token konnte nicht erstellt werden")
		return
	}

	slog.Info("Login erfolgreich", "login", identifier, "user_id", user.ID, "display_name", user.DisplayName, "role", user.Role, "remote_addr", r.RemoteAddr)

	writeJSON(w, http.StatusOK, map[string]interface{}{
		"token": token,
		"user":  user,
	})
}

func (s *Server) handleQuickStart(w http.ResponseWriter, r *http.Request) {
	writeError(w, http.StatusForbidden, "Automatischer Gast-Login ist deaktiviert – bitte anmelden")
}

func (s *Server) handleMe(w http.ResponseWriter, r *http.Request) {
	userID := auth.GetUserID(r.Context())
	user, err := s.store.GetUserByID(userID)
	if err != nil {
		writeError(w, http.StatusNotFound, "Benutzer nicht gefunden")
		return
	}
	stats, _ := s.store.GetDashboardStats(userID)
	writeJSON(w, http.StatusOK, map[string]interface{}{
		"user":  user,
		"stats": stats,
		// The settings disable "Konto löschen" for the last administrator
		"isLastAdmin": s.store.IsLastAdmin(userID),
	})
}

func (s *Server) handleStats(w http.ResponseWriter, r *http.Request) {
	userID := auth.GetUserID(r.Context())
	stats, err := s.store.GetDashboardStats(userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, stats)
}

// handlePurgeOwnData deletes all notes, tasks, thoughts and lists of the caller; the account stays.
func (s *Server) handlePurgeOwnData(w http.ResponseWriter, r *http.Request) {
	user, ok := s.confirmPassword(w, r)
	if !ok {
		return
	}
	if err := s.store.PurgeUserData(user.ID); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	slog.Info("Benutzer hat alle eigenen Daten gelöscht", "user_id", user.ID)
	writeJSON(w, http.StatusOK, map[string]bool{"deleted": true})
}

// handleDeleteOwnAccount deletes the caller's account with all data; never the last administrator.
func (s *Server) handleDeleteOwnAccount(w http.ResponseWriter, r *http.Request) {
	user, ok := s.confirmPassword(w, r)
	if !ok {
		return
	}
	if err := s.store.DeleteOwnAccount(user.ID); err != nil {
		status := http.StatusInternalServerError
		if errors.Is(err, storage.ErrLastAdmin) {
			status = http.StatusForbidden
		}
		writeError(w, status, err.Error())
		return
	}
	slog.Info("Benutzer hat sein Konto gelöscht", "user_id", user.ID)
	writeJSON(w, http.StatusOK, map[string]bool{"deleted": true})
}

// importUpload reads the multipart field "file" (max. storage.MaxImportUploadBytes).
func importUpload(w http.ResponseWriter, r *http.Request) ([]byte, string, error) {
	r.Body = http.MaxBytesReader(w, r.Body, storage.MaxImportUploadBytes+1<<20)
	file, header, err := r.FormFile("file")
	if err != nil {
		return nil, "", fmt.Errorf("Keine Datei erhalten oder Datei zu groß (max. 100 MB)")
	}
	defer file.Close()
	data, err := io.ReadAll(io.LimitReader(file, storage.MaxImportUploadBytes+1))
	if err != nil || len(data) > storage.MaxImportUploadBytes {
		return nil, "", fmt.Errorf("Datei zu groß (max. 100 MB)")
	}
	return data, header.Filename, nil
}

// --- USER SETTINGS & ALARMS ---

func (s *Server) handleLogout(w http.ResponseWriter, r *http.Request) {
	userID := auth.GetUserID(r.Context())
	authHeader := r.Header.Get("Authorization")
	if strings.HasPrefix(authHeader, "Bearer ") {
		tokenStr := strings.TrimPrefix(authHeader, "Bearer ")
		if claims, err := auth.ValidateToken(s.cfg.JWTSecret, tokenStr); err == nil && claims != nil {
			var exp time.Time
			if claims.ExpiresAt != nil {
				exp = claims.ExpiresAt.Time
			} else {
				exp = time.Now().Add(30 * 24 * time.Hour)
			}
			_ = s.store.RevokeToken(tokenStr, userID, exp)
		}
	}
	writeJSON(w, http.StatusOK, map[string]bool{"success": true})
}

func (s *Server) handleRevokeAllSessions(w http.ResponseWriter, r *http.Request) {
	userID := auth.GetUserID(r.Context())
	if err := s.store.RevokeAllUserTokens(userID); err != nil {
		writeError(w, http.StatusInternalServerError, "Sitzungen konnten nicht beendet werden")
		return
	}
	writeJSON(w, http.StatusOK, map[string]bool{"success": true})
}

func (s *Server) handleUpdateUserSettings(w http.ResponseWriter, r *http.Request) {
	userID := auth.GetUserID(r.Context())
	var req struct {
		DisplayName         *string   `json:"displayName"`
		Email               *string   `json:"email"`
		Password            *string   `json:"password"`
		AvatarURL           *string   `json:"avatarUrl"`
		AlarmChannels       *[]string `json:"alarmChannels"`
		AlarmEmail          *string   `json:"alarmEmail"`
		DiscordWebhookURL   *string   `json:"discordWebhookUrl"`
		CustomWebhookURL    *string   `json:"customWebhookUrl"`
		NotifyBeforeMinutes *int      `json:"notifyBeforeMinutes"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "Ungültiges JSON")
		return
	}
	// Alarm URLs are checked before they are stored (SSRF protection, see netguard.go)
	allowPrivate := s.allowPrivateWebhooks()
	if req.DiscordWebhookURL != nil {
		if err := validateWebhookURL(*req.DiscordWebhookURL, true, allowPrivate); err != nil {
			writeError(w, http.StatusBadRequest, "Discord-Webhook: "+err.Error())
			return
		}
	}
	if req.CustomWebhookURL != nil {
		if err := validateWebhookURL(*req.CustomWebhookURL, false, allowPrivate); err != nil {
			writeError(w, http.StatusBadRequest, "Webhook-URL: "+err.Error())
			return
		}
	}
	if req.Password != nil && strings.TrimSpace(*req.Password) != "" {
		if err := auth.ValidatePassword(*req.Password); err != nil {
			writeError(w, http.StatusBadRequest, err.Error())
			return
		}
		hash, err := auth.HashPassword(*req.Password)
		if err != nil {
			writeError(w, http.StatusInternalServerError, "Fehler beim Hashen des Passworts")
			return
		}
		_ = s.store.UpdateUserPassword(userID, hash)
	}
	u, err := s.store.UpdateUserFull(
		userID,
		req.DisplayName,
		req.Email,
		nil,
		nil,
		req.AlarmChannels,
		req.AlarmEmail,
		req.DiscordWebhookURL,
		req.CustomWebhookURL,
		req.NotifyBeforeMinutes,
		req.AvatarURL,
	)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, u)
}

func (s *Server) handleTestUserAlarm(w http.ResponseWriter, r *http.Request) {
	userID := auth.GetUserID(r.Context())
	user, err := s.store.GetUserByID(userID)
	if err != nil || user == nil {
		writeError(w, http.StatusNotFound, "Benutzer nicht gefunden")
		return
	}

	var req struct {
		Channel string `json:"channel"` // email | discord | webhook
		Target  string `json:"target"`  // optional override URL or email
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "Ungültiges JSON")
		return
	}

	channel := strings.ToLower(strings.TrimSpace(req.Channel))
	target := strings.TrimSpace(req.Target)

	switch channel {
	case "discord":
		url := target
		if url == "" {
			url = user.DiscordWebhookURL
		}
		if url == "" {
			writeError(w, http.StatusBadRequest, "Bitte eine Discord Webhook URL angeben")
			return
		}
		if err := s.sendDiscordNotification(url, "Test-Alarm von MindSift", "Dein Discord-Alarmkanal funktioniert einwandfrei!", domain.NowISO()[:10], "normal"); err != nil {
			writeError(w, http.StatusBadGateway, "Discord-Fehler: "+err.Error())
			return
		}
	case "webhook":
		url := target
		if url == "" {
			url = user.CustomWebhookURL
		}
		if url == "" {
			writeError(w, http.StatusBadRequest, "Bitte eine Webhook-URL angeben")
			return
		}
		if err := s.sendCustomWebhookNotification(url, "test_alarm", "Test-Alarm von MindSift", "Dein eigener Webhook empfängt MindSift-Alarme!", domain.NowISO()[:10], "normal"); err != nil {
			writeError(w, http.StatusBadGateway, "Webhook-Fehler: "+err.Error())
			return
		}
	case "email":
		toEmail := target
		if toEmail == "" {
			toEmail = user.AlarmEmail
		}
		if toEmail == "" {
			toEmail = user.Email
		}
		if err := s.sendEmailNotification(toEmail, "⏰ MindSift Test-Alarm", "Hallo "+user.DisplayName+",\n\ndein E-Mail-Alarmkanal in MindSift ist erfolgreich eingerichtet und einsatzbereit.\n\nViele Grüße\nDeine MindSift Instanz"); err != nil {
			writeError(w, http.StatusBadGateway, "E-Mail-Versand fehlgeschlagen: "+err.Error())
			return
		}
	default:
		writeError(w, http.StatusBadRequest, "Unbekannter Alarm-Kanal (erlaubt: email, discord, webhook)")
		return
	}

	writeJSON(w, http.StatusOK, map[string]interface{}{
		"sent":    true,
		"channel": channel,
	})
}

func (s *Server) handleGetUsersDirectory(w http.ResponseWriter, r *http.Request) {
	userID := auth.GetUserID(r.Context())
	users, err := s.store.GetDiscoverableUsers(userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, users)
}