// SPDX-License-Identifier: AGPL-3.0-or-later

package handler

import (
	"crypto/rand"
	"encoding/hex"
	"errors"
	"log/slog"
	"net/http"
	"strconv"
	"strings"

	"kode.naiv.no/olemd/favoritter/internal/image"
	"kode.naiv.no/olemd/favoritter/internal/middleware"
	"kode.naiv.no/olemd/favoritter/internal/render"
	"kode.naiv.no/olemd/favoritter/internal/store"
)

// handleAdminDashboard shows admin overview stats.
func (h *Handler) handleAdminDashboard(w http.ResponseWriter, r *http.Request) {
	userCount, _ := h.deps.Users.Count()
	faveCount, _ := h.deps.Faves.Count()
	pendingCount, _ := h.deps.SignupRequests.PendingCount()
	settings, _ := h.deps.Settings.Get()

	h.deps.Renderer.Page(w, r, "admin_dashboard", render.PageData{
		Title: "Administrasjon",
		Data: map[string]any{
			"UserCount":    userCount,
			"FaveCount":    faveCount,
			"PendingCount": pendingCount,
			"Settings":     settings,
		},
	})
}

// handleAdminUsers lists all users.
func (h *Handler) handleAdminUsers(w http.ResponseWriter, r *http.Request) {
	users, err := h.deps.Users.ListAll()
	if err != nil {
		slog.Error("list users error", "error", err)
		http.Error(w, "Internal error", http.StatusInternalServerError)
		return
	}

	h.deps.Renderer.Page(w, r, "admin_users", render.PageData{
		Title: "Brukere",
		Data:  map[string]any{"Users": users},
	})
}

// handleAdminCreateUser creates a new user with a temporary password.
func (h *Handler) handleAdminCreateUser(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		http.Error(w, "Bad request", http.StatusBadRequest)
		return
	}

	username := strings.TrimSpace(r.FormValue("username"))
	role := r.FormValue("role")

	if !usernameRegexp.MatchString(username) {
		h.adminUsersFlash(w, r, "Ugyldig brukernavn.", "error")
		return
	}
	if role != "user" && role != "admin" {
		role = "user"
	}

	// Generate a temporary password the admin can share with the user.
	tempPassword := generateTempPassword()

	_, err := h.deps.Users.CreateWithReset(username, tempPassword, role)
	if err != nil {
		if errors.Is(err, store.ErrUserExists) {
			h.adminUsersFlash(w, r, "Brukernavnet er allerede i bruk.", "error")
			return
		}
		slog.Error("admin create user error", "error", err)
		h.adminUsersFlash(w, r, "Noe gikk galt.", "error")
		return
	}

	h.adminUsersFlash(w, r,
		"Bruker opprettet. Midlertidig passord: "+tempPassword+" — brukeren må endre det ved første innlogging.",
		"success")
}

// handleAdminResetPassword resets a user's password to a temporary one.
func (h *Handler) handleAdminResetPassword(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		http.NotFound(w, r)
		return
	}

	tempPassword := generateTempPassword()
	if err := h.deps.Users.UpdatePassword(id, tempPassword); err != nil {
		slog.Error("admin reset password error", "error", err)
		h.adminUsersFlash(w, r, "Noe gikk galt.", "error")
		return
	}

	if err := h.deps.Users.SetMustResetPassword(id, true); err != nil {
		slog.Error("set must-reset-password error", "error", err)
	}

	// Invalidate all sessions for this user.
	if delErr := h.deps.Sessions.DeleteAllForUser(id); delErr != nil {
		slog.Error("session cleanup error", "error", delErr)
	}

	h.adminUsersFlash(w, r,
		"Passord tilbakestilt. Midlertidig passord: "+tempPassword,
		"success")
}

// handleAdminToggleDisabled enables or disables a user.
func (h *Handler) handleAdminToggleDisabled(w http.ResponseWriter, r *http.Request) {
	admin := middleware.UserFromContext(r.Context())

	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		http.NotFound(w, r)
		return
	}

	// Don't allow disabling yourself.
	if id == admin.ID {
		h.adminUsersFlash(w, r, "Du kan ikke deaktivere din egen konto.", "error")
		return
	}

	user, err := h.deps.Users.GetByID(id)
	if err != nil {
		slog.Error("get user error", "error", err)
		h.adminUsersFlash(w, r, "Noe gikk galt.", "error")
		return
	}

	if err := h.deps.Users.SetDisabled(id, !user.Disabled); err != nil {
		slog.Error("toggle disabled error", "error", err)
		h.adminUsersFlash(w, r, "Noe gikk galt.", "error")
		return
	}

	if !user.Disabled {
		// Was enabled, now disabled — invalidate sessions.
		if delErr := h.deps.Sessions.DeleteAllForUser(id); delErr != nil {
			slog.Error("session cleanup error", "error", delErr)
		}
	}

	action := "aktivert"
	if !user.Disabled {
		action = "deaktivert"
	}
	h.adminUsersFlash(w, r, "Bruker "+user.Username+" er "+action+".", "success")
}

// handleAdminSetRole changes a user's role.
func (h *Handler) handleAdminSetRole(w http.ResponseWriter, r *http.Request) {
	admin := middleware.UserFromContext(r.Context())

	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		http.NotFound(w, r)
		return
	}

	if id == admin.ID {
		h.adminUsersFlash(w, r, "Du kan ikke endre din egen rolle.", "error")
		return
	}

	if err := r.ParseForm(); err != nil {
		http.Error(w, "Bad request", http.StatusBadRequest)
		return
	}

	role := r.FormValue("role")
	if role != "user" && role != "admin" {
		h.adminUsersFlash(w, r, "Ugyldig rolle.", "error")
		return
	}

	if err := h.deps.Users.SetRole(id, role); err != nil {
		slog.Error("set role error", "error", err)
		h.adminUsersFlash(w, r, "Noe gikk galt.", "error")
		return
	}

	user, _ := h.deps.Users.GetByID(id)
	h.adminUsersFlash(w, r, "Rollen til "+user.Username+" er endret til "+role+".", "success")
}

// handleAdminDeleteUser permanently deletes a user and all their data.
func (h *Handler) handleAdminDeleteUser(w http.ResponseWriter, r *http.Request) {
	admin := middleware.UserFromContext(r.Context())

	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		http.NotFound(w, r)
		return
	}

	if id == admin.ID {
		h.adminUsersFlash(w, r, "Du kan ikke slette din egen konto.", "error")
		return
	}

	user, err := h.deps.Users.GetByID(id)
	if err != nil {
		slog.Error("get user error", "error", err)
		h.adminUsersFlash(w, r, "Noe gikk galt.", "error")
		return
	}

	// Delete user's images from disk before database deletion.
	imagePaths, _ := h.deps.Faves.ImagePathsByUser(id)
	for _, p := range imagePaths {
		if delErr := image.Delete(h.deps.Config.UploadDir, p); delErr != nil {
			slog.Error("image delete error", "error", delErr)
		}
	}
	if user.AvatarPath != "" {
		if delErr := image.Delete(h.deps.Config.UploadDir, user.AvatarPath); delErr != nil {
			slog.Error("avatar delete error", "user_id", id, "error", delErr)
		}
	}

	if err := h.deps.Users.Delete(id); err != nil {
		slog.Error("delete user error", "error", err)
		h.adminUsersFlash(w, r, "Noe gikk galt.", "error")
		return
	}

	h.adminUsersFlash(w, r, "Bruker "+user.Username+" er permanent slettet.", "success")
}

// handleAdminTags lists all tags.
func (h *Handler) handleAdminTags(w http.ResponseWriter, r *http.Request) {
	tags, err := h.deps.Tags.ListAll()
	if err != nil {
		slog.Error("list tags error", "error", err)
		http.Error(w, "Internal error", http.StatusInternalServerError)
		return
	}

	h.deps.Renderer.Page(w, r, "admin_tags", render.PageData{
		Title: "Merkelapper",
		Data:  map[string]any{"Tags": tags},
	})
}

// handleAdminRenameTag renames a tag.
func (h *Handler) handleAdminRenameTag(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		http.Error(w, "Bad request", http.StatusBadRequest)
		return
	}

	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		http.NotFound(w, r)
		return
	}

	newName := strings.TrimSpace(r.FormValue("name"))
	if newName == "" {
		h.adminTagsFlash(w, r, "Navn kan ikke være tomt.", "error")
		return
	}

	if err := h.deps.Tags.Rename(id, newName); err != nil {
		slog.Error("rename tag error", "error", err)
		h.adminTagsFlash(w, r, "Noe gikk galt. Kanskje navnet allerede finnes?", "error")
		return
	}

	h.adminTagsFlash(w, r, "Merkelapp omdøpt.", "success")
}

// handleAdminDeleteTag deletes a tag.
func (h *Handler) handleAdminDeleteTag(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		http.NotFound(w, r)
		return
	}

	if err := h.deps.Tags.Delete(id); err != nil {
		slog.Error("delete tag error", "error", err)
		h.adminTagsFlash(w, r, "Noe gikk galt.", "error")
		return
	}

	h.adminTagsFlash(w, r, "Merkelapp slettet.", "success")
}

// handleAdminSignupRequests lists pending signup requests.
func (h *Handler) handleAdminSignupRequests(w http.ResponseWriter, r *http.Request) {
	requests, err := h.deps.SignupRequests.ListPending()
	if err != nil {
		slog.Error("list signup requests error", "error", err)
		http.Error(w, "Internal error", http.StatusInternalServerError)
		return
	}

	h.deps.Renderer.Page(w, r, "admin_requests", render.PageData{
		Title: "Registreringsforespørsler",
		Data:  map[string]any{"Requests": requests},
	})
}

// handleAdminSignupRequestAction approves or rejects a signup request.
func (h *Handler) handleAdminSignupRequestAction(w http.ResponseWriter, r *http.Request) {
	admin := middleware.UserFromContext(r.Context())

	if err := r.ParseForm(); err != nil {
		http.Error(w, "Bad request", http.StatusBadRequest)
		return
	}

	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		http.NotFound(w, r)
		return
	}

	action := r.FormValue("action")
	switch action {
	case "approve":
		if err := h.deps.SignupRequests.Approve(id, admin.ID); err != nil {
			slog.Error("approve signup request error", "error", err)
			h.adminRequestsFlash(w, r, "Noe gikk galt ved godkjenning.", "error")
			return
		}
		h.adminRequestsFlash(w, r, "Forespørsel godkjent. Brukeren må endre passord ved første innlogging.", "success")
	case "reject":
		if err := h.deps.SignupRequests.Reject(id, admin.ID); err != nil {
			slog.Error("reject signup request error", "error", err)
			h.adminRequestsFlash(w, r, "Noe gikk galt.", "error")
			return
		}
		h.adminRequestsFlash(w, r, "Forespørsel avvist.", "success")
	default:
		http.Error(w, "Bad request", http.StatusBadRequest)
	}
}

// handleAdminSettingsGet shows the site settings page.
func (h *Handler) handleAdminSettingsGet(w http.ResponseWriter, r *http.Request) {
	settings, err := h.deps.Settings.Get()
	if err != nil {
		slog.Error("get settings error", "error", err)
		http.Error(w, "Internal error", http.StatusInternalServerError)
		return
	}

	h.deps.Renderer.Page(w, r, "admin_settings", render.PageData{
		Title: "Nettstedsinnstillinger",
		Data:  map[string]any{"Settings": settings},
	})
}

// handleAdminSettingsPost updates site settings.
func (h *Handler) handleAdminSettingsPost(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		http.Error(w, "Bad request", http.StatusBadRequest)
		return
	}

	siteName := strings.TrimSpace(r.FormValue("site_name"))
	siteDescription := strings.TrimSpace(r.FormValue("site_description"))
	signupMode := r.FormValue("signup_mode")

	if siteName == "" {
		siteName = "Favoritter"
	}
	if signupMode != "open" && signupMode != "requests" && signupMode != "closed" {
		signupMode = "open"
	}

	if err := h.deps.Settings.Update(siteName, siteDescription, signupMode); err != nil {
		slog.Error("update settings error", "error", err)
		h.adminSettingsFlash(w, r, "Noe gikk galt.", "error")
		return
	}

	h.adminSettingsFlash(w, r, "Innstillingene er lagret.", "success")
}

// Flash helpers that redirect back to the relevant admin page.
func (h *Handler) adminUsersFlash(w http.ResponseWriter, r *http.Request, msg, flashType string) {
	// Re-fetch and re-render the users page with flash.
	users, _ := h.deps.Users.ListAll()
	h.deps.Renderer.Page(w, r, "admin_users", render.PageData{
		Title: "Brukere", Flash: msg, FlashType: flashType,
		Data: map[string]any{"Users": users},
	})
}

func (h *Handler) adminTagsFlash(w http.ResponseWriter, r *http.Request, msg, flashType string) {
	tags, _ := h.deps.Tags.ListAll()
	h.deps.Renderer.Page(w, r, "admin_tags", render.PageData{
		Title: "Merkelapper", Flash: msg, FlashType: flashType,
		Data: map[string]any{"Tags": tags},
	})
}

func (h *Handler) adminRequestsFlash(w http.ResponseWriter, r *http.Request, msg, flashType string) {
	requests, _ := h.deps.SignupRequests.ListPending()
	h.deps.Renderer.Page(w, r, "admin_requests", render.PageData{
		Title: "Registreringsforespørsler", Flash: msg, FlashType: flashType,
		Data: map[string]any{"Requests": requests},
	})
}

func (h *Handler) adminSettingsFlash(w http.ResponseWriter, r *http.Request, msg, flashType string) {
	settings, _ := h.deps.Settings.Get()
	h.deps.Renderer.Page(w, r, "admin_settings", render.PageData{
		Title: "Nettstedsinnstillinger", Flash: msg, FlashType: flashType,
		Data: map[string]any{"Settings": settings},
	})
}

func generateTempPassword() string {
	b := make([]byte, 12)
	rand.Read(b)
	return hex.EncodeToString(b)
}