"use client";

import { useState, useRef, useEffect } from 'react';
import { useTranslations } from 'next-intl';
import { useEmailStore } from '@/stores/email-store';
import { useAuthStore } from '@/stores/auth-store';
import { useSettingsStore } from '@/stores/settings-store';
import { usePolicyStore } from '@/stores/policy-store';
import { toast } from '@/stores/toast-store';
import { SettingsSection, SettingItem, Select } from './settings-section';
import {
  Plus, Pencil, Trash2, Check, X, FolderPlus, Folder,
  Inbox, Send, FileText, Trash, ShieldAlert, Archive,
  Star, Heart, Bookmark, Tag, Flag, Briefcase, Users,
  Bell, Zap, Globe, Lock, Eye, MessageSquare, Mail,
  AlertTriangle, NotebookPen, CalendarClock, BellOff,
  type LucideIcon,
} from 'lucide-react';
import { cn, buildMailboxTree, type MailboxNode } from '@/lib/utils';
import { ChevronRight, ChevronDown, GripVertical } from 'lucide-react';
import {
  DndContext, closestCenter, PointerSensor, KeyboardSensor,
  useSensor, useSensors, type DragEndEvent,
} from '@dnd-kit/core';
import {
  SortableContext, verticalListSortingStrategy, useSortable,
  arrayMove, sortableKeyboardCoordinates,
} from '@dnd-kit/sortable';
import { CSS } from '@dnd-kit/utilities';

const STANDARD_ROLES = ['inbox', 'drafts', 'sent', 'trash', 'junk', 'archive'] as const;

const ROLE_ICONS: Record<string, LucideIcon> = {
  inbox: Inbox,
  drafts: FileText,
  sent: Send,
  trash: Trash,
  junk: ShieldAlert,
  archive: Archive,
  shared: Users,
  important: AlertTriangle,
  memos: NotebookPen,
  scheduled: CalendarClock,
  snoozed: BellOff,
};

const ICON_CHOICES: { name: string; icon: LucideIcon }[] = [
  { name: 'Folder', icon: Folder },
  { name: 'Star', icon: Star },
  { name: 'Heart', icon: Heart },
  { name: 'Bookmark', icon: Bookmark },
  { name: 'Tag', icon: Tag },
  { name: 'Flag', icon: Flag },
  { name: 'Briefcase', icon: Briefcase },
  { name: 'Users', icon: Users },
  { name: 'Bell', icon: Bell },
  { name: 'Zap', icon: Zap },
  { name: 'Globe', icon: Globe },
  { name: 'Lock', icon: Lock },
  { name: 'Eye', icon: Eye },
  { name: 'MessageSquare', icon: MessageSquare },
  { name: 'Mail', icon: Mail },
  { name: 'Inbox', icon: Inbox },
  { name: 'Archive', icon: Archive },
  { name: 'FileText', icon: FileText },
];

function IconPicker({ currentIcon, onSelect, onClose }: {
  currentIcon: string;
  onSelect: (iconName: string) => void;
  onClose: () => void;
}) {
  const ref = useRef<HTMLDivElement>(null);

  useEffect(() => {
    const handleClick = (e: MouseEvent) => {
      if (ref.current && !ref.current.contains(e.target as Node)) onClose();
    };
    const handleKey = (e: KeyboardEvent) => {
      if (e.key === 'Escape') onClose();
    };
    document.addEventListener('mousedown', handleClick);
    document.addEventListener('keydown', handleKey);
    return () => {
      document.removeEventListener('mousedown', handleClick);
      document.removeEventListener('keydown', handleKey);
    };
  }, [onClose]);

  return (
    <div
      ref={ref}
      className="absolute start-0 top-full mt-1 z-50 bg-background border border-border rounded-lg shadow-lg p-2 grid grid-cols-6 gap-1 w-52"
    >
      {ICON_CHOICES.map(({ name, icon: Icon }) => (
        <button
          key={name}
          onClick={() => onSelect(name)}
          className={cn(
            "p-1.5 rounded-md transition-colors flex items-center justify-center",
            currentIcon === name
              ? "bg-primary text-primary-foreground"
              : "hover:bg-accent text-muted-foreground hover:text-foreground"
          )}
          title={name}
        >
          <Icon className="w-4 h-4" />
        </button>
      ))}
    </div>
  );
}

/**
 * Wraps a folder row with a drag handle so it can be reordered within its
 * sibling group. The handle carries the dnd-kit listeners; the rest of the row
 * (buttons, inline editors) stays fully interactive.
 */
function SortableFolderRow({ id, title, children }: { id: string; title: string; children: React.ReactNode }) {
  const { attributes, listeners, setNodeRef, transform, transition, isDragging } = useSortable({ id });
  const style: React.CSSProperties = {
    transform: CSS.Transform.toString(transform),
    transition,
    opacity: isDragging ? 0.5 : 1,
    zIndex: isDragging ? 10 : undefined,
    position: isDragging ? 'relative' : undefined,
  };
  return (
    <div ref={setNodeRef} style={style} className="flex items-stretch">
      <button
        type="button"
        {...attributes}
        {...listeners}
        className="flex items-center px-1 text-muted-foreground/40 hover:text-foreground cursor-grab active:cursor-grabbing touch-none rounded-md focus:outline-none focus:ring-2 focus:ring-ring flex-shrink-0"
        title={title}
        aria-label={title}
      >
        <GripVertical className="w-3.5 h-3.5" />
      </button>
      <div className="flex-1 min-w-0">{children}</div>
    </div>
  );
}

export function FolderSettings() {
  const t = useTranslations('settings.folders');
  const { client } = useAuthStore();
  const { mailboxes, fetchMailboxes, createMailbox, renameMailbox, deleteMailbox, setMailboxRole, reorderMailboxes } = useEmailStore();

  const sensors = useSensors(
    // Small activation distance so clicking the row's buttons still works.
    useSensor(PointerSensor, { activationConstraint: { distance: 5 } }),
    useSensor(KeyboardSensor, { coordinateGetter: sortableKeyboardCoordinates }),
  );
  const { folderIcons, setFolderIcon } = useSettingsStore();
  const { isFeatureEnabled } = usePolicyStore();
  const folderIconsAllowed = isFeatureEnabled('folderIconsEnabled');

  useEffect(() => {
    if (client && mailboxes.length === 0) {
      fetchMailboxes(client);
    }
  }, [client, mailboxes.length, fetchMailboxes]);

  const [isCreating, setIsCreating] = useState(false);
  const [creatingParentId, setCreatingParentId] = useState<string | null>(null);
  const [newFolderName, setNewFolderName] = useState('');
  const [editingId, setEditingId] = useState<string | null>(null);
  const [editingName, setEditingName] = useState('');
  const [deletingId, setDeletingId] = useState<string | null>(null);
  const [iconPickerId, setIconPickerId] = useState<string | null>(null);
  const [isLoading, setIsLoading] = useState(false);
  const [expandedFolders, setExpandedFolders] = useState<Set<string>>(new Set());

  const ownMailboxes = mailboxes.filter(mb => !mb.isShared);
  const folderTree = buildMailboxTree(ownMailboxes);

  // Reorder folders within a sibling group (same parent). Drops onto a folder
  // in a different group are ignored — this reorders, it doesn't reparent.
  const handleFolderDragEnd = (event: DragEndEvent) => {
    const { active, over } = event;
    if (!over || active.id === over.id || !client) return;

    const groups: MailboxNode[][] = [];
    const collectGroups = (nodes: MailboxNode[]) => {
      groups.push(nodes);
      nodes.forEach(n => { if (n.children.length > 0) collectGroups(n.children); });
    };
    collectGroups(folderTree);

    const group = groups.find(g => g.some(n => n.id === active.id));
    if (!group) return;
    const oldIndex = group.findIndex(n => n.id === active.id);
    const newIndex = group.findIndex(n => n.id === over.id);
    if (newIndex < 0) return; // dropped outside the active folder's sibling group

    const orderedIds = arrayMove(group, oldIndex, newIndex).map(n => n.id);
    reorderMailboxes(client, orderedIds).catch(() => {
      toast.error(t('reorder_error'));
    });
  };

  const getRoleMailboxId = (role: string): string => {
    const mb = ownMailboxes.find(m => m.role === role);
    return mb?.id ?? '';
  };

  const getIconForMailbox = (mb: { id: string; role?: string }): LucideIcon => {
    // Custom icon takes priority for non-role folders
    const customIconName = folderIcons[mb.id];
    if (customIconName) {
      const found = ICON_CHOICES.find(c => c.name === customIconName);
      if (found) return found.icon;
    }
    // Role folders get their role icon
    if (mb.role && ROLE_ICONS[mb.role]) return ROLE_ICONS[mb.role];
    return Folder;
  };

  const getIconName = (mb: { id: string; role?: string }): string => {
    if (folderIcons[mb.id]) return folderIcons[mb.id];
    if (mb.role && ROLE_ICONS[mb.role]) {
      const entry = Object.entries(ROLE_ICONS).find(([r]) => r === mb.role);
      if (entry) {
        const found = ICON_CHOICES.find(c => c.icon === entry[1]);
        if (found) return found.name;
      }
    }
    return 'Folder';
  };

  const toggleExpanded = (id: string) => {
    setExpandedFolders(prev => {
      const next = new Set(prev);
      if (next.has(id)) next.delete(id);
      else next.add(id);
      return next;
    });
  };

  const startCreateSubfolder = (parentId: string) => {
    setCreatingParentId(parentId);
    setIsCreating(true);
    setNewFolderName('');
    setExpandedFolders(prev => new Set(prev).add(parentId));
  };

  const handleCreate = async () => {
    if (!client || !newFolderName.trim()) return;
    setIsLoading(true);
    try {
      await createMailbox(client, newFolderName.trim(), creatingParentId ?? undefined);
      setNewFolderName('');
      setIsCreating(false);
      setCreatingParentId(null);
      toast.success(t('folder_created'));
    } catch {
      toast.error(t('error_create'));
    } finally {
      setIsLoading(false);
    }
  };

  const handleRename = async (mailboxId: string) => {
    if (!client || !editingName.trim()) return;
    setIsLoading(true);
    try {
      await renameMailbox(client, mailboxId, editingName.trim());
      setEditingId(null);
      setEditingName('');
      toast.success(t('folder_renamed'));
    } catch {
      toast.error(t('error_rename'));
    } finally {
      setIsLoading(false);
    }
  };

  const handleDelete = async (mailboxId: string) => {
    if (!client) return;
    setIsLoading(true);
    try {
      await deleteMailbox(client, mailboxId);
      setDeletingId(null);
      toast.success(t('folder_deleted'));
    } catch (err: unknown) {
      const jmapType = (err as Error & { jmapType?: string })?.jmapType;
      switch (jmapType) {
        case 'mailboxHasChild':
          toast.error(t('error_delete_has_children'));
          break;
        case 'mailboxHasEmail':
          toast.error(t('error_delete_has_email'));
          break;
        default:
          toast.error(t('error_delete'));
      }
    } finally {
      setIsLoading(false);
    }
  };

  const handleRoleChange = async (role: string, mailboxId: string) => {
    if (!client) return;
    setIsLoading(true);
    try {
      if (mailboxId === '') {
        const current = ownMailboxes.find(m => m.role === role);
        if (current) {
          await setMailboxRole(client, current.id, null);
        }
      } else {
        await setMailboxRole(client, mailboxId, role);
      }
      toast.success(t('role_updated'));
    } catch {
      toast.error(t('error_role'));
    } finally {
      setIsLoading(false);
    }
  };

  const startEdit = (mb: { id: string; name: string }) => {
    setEditingId(mb.id);
    setEditingName(mb.name);
  };

  const cancelEdit = () => {
    setEditingId(null);
    setEditingName('');
  };

  const renderCreateInline = (parentId: string | null, depth: number) => {
    if (!isCreating || creatingParentId !== parentId) return null;
    const parentName = parentId ? ownMailboxes.find(m => m.id === parentId)?.name : null;
    return (
      <div
        className="flex items-center gap-2 mt-1 p-2.5 bg-muted/30 rounded-md border border-border"
        style={{ marginLeft: depth * 16 }}
      >
        <FolderPlus className="w-4 h-4 text-primary flex-shrink-0" />
        <div className="flex-1 flex flex-col gap-1">
          {parentName && (
            <span className="text-xs text-muted-foreground">
              {t('subfolder_of', { name: parentName })}
            </span>
          )}
          <input
            type="text"
            value={newFolderName}
            onChange={(e) => setNewFolderName(e.target.value)}
            onKeyDown={(e) => {
              if (e.key === 'Enter') handleCreate();
              if (e.key === 'Escape') {
                setIsCreating(false);
                setNewFolderName('');
                setCreatingParentId(null);
              }
            }}
            placeholder={parentId ? t('subfolder_name') : t('new_folder_name')}
            className="flex-1 px-2 py-1 text-sm rounded border border-border bg-background text-foreground placeholder:text-muted-foreground focus:outline-none focus:ring-2 focus:ring-ring"
            autoFocus
            disabled={isLoading}
          />
        </div>
        <button
          onClick={handleCreate}
          disabled={isLoading || !newFolderName.trim()}
          className="px-3 py-1 text-xs font-medium bg-primary text-primary-foreground rounded-md hover:bg-primary/90 disabled:opacity-50"
        >
          {t('create')}
        </button>
        <button
          onClick={() => {
            setIsCreating(false);
            setNewFolderName('');
            setCreatingParentId(null);
          }}
          className="px-3 py-1 text-xs bg-muted text-foreground rounded-md hover:bg-accent"
        >
          {t('cancel')}
        </button>
      </div>
    );
  };

  const renderFolderNode = (node: MailboxNode): React.ReactNode => {
    const mb = node;
    const hasChildren = node.children.length > 0;
    const isExpanded = expandedFolders.has(node.id);
    const depth = node.depth;
    const Icon = getIconForMailbox(mb);

    if (editingId === mb.id) {
      return (
        <div key={mb.id}>
        <div className="flex items-center gap-2 py-2 px-3" style={{ paddingLeft: 12 + depth * 16 }}>
          <Icon className="w-4 h-4 text-muted-foreground flex-shrink-0" />
          <input
            type="text"
            value={editingName}
            onChange={(e) => setEditingName(e.target.value)}
            onKeyDown={(e) => {
              if (e.key === 'Enter') handleRename(mb.id);
              if (e.key === 'Escape') cancelEdit();
            }}
            className="flex-1 px-2 py-1 text-sm rounded border border-border bg-background text-foreground focus:outline-none focus:ring-2 focus:ring-ring"
            autoFocus
            disabled={isLoading}
          />
          <button
            onClick={() => handleRename(mb.id)}
            disabled={isLoading || !editingName.trim()}
            className="p-1.5 text-primary hover:bg-accent rounded-md disabled:opacity-50"
            title={t('rename')}
          >
            <Check className="w-4 h-4" />
          </button>
          <button
            onClick={cancelEdit}
            className="p-1.5 text-muted-foreground hover:bg-accent rounded-md"
            title={t('cancel')}
          >
            <X className="w-4 h-4" />
          </button>
        </div>
        </div>
      );
    }

    if (deletingId === mb.id) {
      return (
        <div key={mb.id}>
        <div className="flex items-center gap-3 py-2.5 px-3 bg-destructive/5 rounded-md border border-destructive/20" style={{ marginLeft: depth * 16 }}>
          <Trash2 className="w-4 h-4 text-destructive flex-shrink-0" />
          <p className="text-sm text-foreground flex-1">
            {t('confirm_delete', { name: mb.name })}
          </p>
          <button
            onClick={() => handleDelete(mb.id)}
            disabled={isLoading}
            className="px-3 py-1 text-xs font-medium bg-destructive text-destructive-foreground rounded-md hover:bg-destructive/90 disabled:opacity-50"
          >
            {t('delete')}
          </button>
          <button
            onClick={() => setDeletingId(null)}
            className="px-3 py-1 text-xs bg-muted text-foreground rounded-md hover:bg-accent"
          >
            {t('cancel')}
          </button>
        </div>
        </div>
      );
    }

    return (
      <div key={mb.id}>
        <SortableFolderRow id={mb.id} title={t('reorder')}>
        <div
          className="flex items-center justify-between py-2 px-3 rounded-md hover:bg-muted/50"
          style={{ paddingLeft: 12 + depth * 16 }}
        >
          <div className="flex items-center gap-2.5 min-w-0">
            {/* Expand/collapse toggle for folders with children */}
            {hasChildren ? (
              <button
                onClick={() => toggleExpanded(mb.id)}
                className="p-0.5 text-muted-foreground hover:text-foreground rounded transition-colors flex-shrink-0"
              >
                {isExpanded
                  ? <ChevronDown className="w-3.5 h-3.5" />
                  : <ChevronRight className="w-3.5 h-3.5" />
                }
              </button>
            ) : (
              <span className="w-4.5 flex-shrink-0" />
            )}
            <div className="relative flex-shrink-0">
              {folderIconsAllowed ? (
                <button
                  onClick={() => setIconPickerId(iconPickerId === mb.id ? null : mb.id)}
                  className={cn(
                    "p-1 rounded-md transition-colors",
                    iconPickerId === mb.id
                      ? "bg-accent"
                      : "hover:bg-accent"
                  )}
                  title={t('change_icon')}
                >
                  <Icon className={cn(
                    "w-4 h-4",
                    mb.role ? "text-primary" : "text-muted-foreground"
                  )} />
                </button>
              ) : (
                <span className="p-1">
                  <Icon className={cn(
                    "w-4 h-4",
                    mb.role ? "text-primary" : "text-muted-foreground"
                  )} />
                </span>
              )}
              {folderIconsAllowed && iconPickerId === mb.id && (
                <IconPicker
                  currentIcon={getIconName(mb)}
                  onSelect={(iconName) => {
                    setFolderIcon(mb.id, iconName);
                    setIconPickerId(null);
                  }}
                  onClose={() => setIconPickerId(null)}
                />
              )}
            </div>
            <span className="text-sm text-foreground truncate">{mb.name}</span>
            {mb.role && (
              <span className="text-xs px-1.5 py-0.5 rounded-full bg-primary/10 text-primary font-medium flex-shrink-0">
                {t(`role_${mb.role}`)}
              </span>
            )}
            {mb.unreadEmails > 0 && (
              <span className="text-xs tabular-nums px-1.5 py-0.5 rounded-full bg-primary text-primary-foreground font-medium flex-shrink-0">
                {mb.unreadEmails}
              </span>
            )}
          </div>
          <div className="flex items-center gap-0.5">
            {mb.myRights?.mayCreateChild && (
              <button
                onClick={() => startCreateSubfolder(mb.id)}
                className="p-1.5 text-muted-foreground hover:text-foreground hover:bg-accent rounded-md transition-colors"
                title={t('create_subfolder')}
              >
                <FolderPlus className="w-3.5 h-3.5" />
              </button>
            )}
            {mb.myRights?.mayRename && (
              <button
                onClick={() => startEdit(mb)}
                className="p-1.5 text-muted-foreground hover:text-foreground hover:bg-accent rounded-md transition-colors"
                title={t('rename')}
              >
                <Pencil className="w-3.5 h-3.5" />
              </button>
            )}
            {mb.myRights?.mayDelete && !mb.role && (
              <button
                onClick={() => setDeletingId(mb.id)}
                className="p-1.5 text-muted-foreground hover:text-destructive hover:bg-destructive/10 rounded-md transition-colors"
                title={t('delete')}
              >
                <Trash2 className="w-3.5 h-3.5" />
              </button>
            )}
          </div>
        </div>
        </SortableFolderRow>
        {/* Inline subfolder creation */}
        {renderCreateInline(mb.id, depth + 1)}
        {/* Render children if expanded */}
        {hasChildren && isExpanded && (
          <div>
            <SortableContext items={node.children.map(c => c.id)} strategy={verticalListSortingStrategy}>
              {node.children.map(child => renderFolderNode(child))}
            </SortableContext>
          </div>
        )}
      </div>
    );
  };

  return (
    <div className="space-y-8">
      {/* Folder List - primary section */}
      <SettingsSection title={t('folder_list')} description={t('folder_list_description')}>
        <div className="space-y-0.5">
          {folderTree.length === 0 ? (
            <div className="flex flex-col items-center justify-center py-8 text-center">
              <Folder className="w-10 h-10 text-muted-foreground/40 mb-3" />
              <p className="text-sm text-muted-foreground">{t('no_folders')}</p>
            </div>
          ) : (
            <DndContext sensors={sensors} collisionDetection={closestCenter} onDragEnd={handleFolderDragEnd}>
              <SortableContext items={folderTree.map(n => n.id)} strategy={verticalListSortingStrategy}>
                {folderTree.map(node => renderFolderNode(node))}
              </SortableContext>
            </DndContext>
          )}
        </div>

        {/* Create top-level folder */}
        {renderCreateInline(null, 0)}
        {!isCreating && (
          <button
            onClick={() => { setIsCreating(true); setCreatingParentId(null); setNewFolderName(''); }}
            className="flex items-center gap-2 mt-3 px-3 py-2 text-sm text-primary hover:bg-primary/5 rounded-md transition-colors w-full border border-dashed border-primary/30 hover:border-primary/50"
          >
            <Plus className="w-4 h-4" />
            {t('create_folder')}
          </button>
        )}
      </SettingsSection>

      {/* Standard Folder Roles - advanced section */}
      <SettingsSection title={t('standard_roles')} description={t('standard_roles_description')}>
        {STANDARD_ROLES.map((role) => {
          // Disambiguate duplicate folder names by appending parent path
          const nameCounts = new Map<string, number>();
          ownMailboxes.forEach(mb => nameCounts.set(mb.name, (nameCounts.get(mb.name) || 0) + 1));
          const getParentPath = (mb: { parentId?: string; name: string }) => {
            if (!mb.parentId) return '';
            const parent = ownMailboxes.find(p => p.id === mb.parentId);
            return parent ? `${parent.name}/` : '';
          };

          return (
            <SettingItem key={role} label={t(`role_${role}`)}>
              <Select
                value={getRoleMailboxId(role)}
                onChange={(value) => handleRoleChange(role, value)}
                options={[
                  { value: '', label: t('role_none') },
                  ...ownMailboxes.map(mb => ({
                    value: mb.id,
                    label: (nameCounts.get(mb.name) || 0) > 1
                      ? `${getParentPath(mb)}${mb.name} (${mb.id.slice(-6)})`
                      : mb.name,
                  })),
                ]}
              />
            </SettingItem>
          );
        })}
      </SettingsSection>
    </div>
  );
}