// TODO: P2-F12 — Replace hardcoded GROUP_FIELDS with shared constant
/**
 * SmartSuite-style Group Panel for contacts.
 * Multi-field grouping with priority ordering.
 */

import React, { useState, useRef, useEffect, useMemo } from 'react';
import { Group as GroupIcon, Plus, X } from 'lucide-react';
import type { UnifiedContact } from '@/api/unifiedContacts';
import { useCustomFieldDefinitions } from '@/api/customFieldDefinitions';

// ─── Field definitions ────────────────────────────────────────────────────────

type FieldType = 'text' | 'number' | 'select' | 'date';

interface GroupFieldDef {
  key: string;
  label: string;
  type: FieldType;
  group?: 'general' | 'company' | 'person' | 'address' | 'notes' | 'meta' | 'custom';
}

let GROUP_FIELDS: GroupFieldDef[] = [
  // General
  { key: 'type', label: 'Typ', type: 'select', group: 'general' },
  { key: 'displayname', label: 'Anzeigename', type: 'text', group: 'general' },
  { key: 'email_1', label: 'E-Mail 1', type: 'text', group: 'general' },
  { key: 'phone_1', label: 'Telefon 1', type: 'text', group: 'general' },
  { key: 'website', label: 'Website', type: 'text', group: 'general' },
  { key: 'tags', label: 'Tags', type: 'text', group: 'general' },

  // Company
  { key: 'name', label: 'Firmenname', type: 'text', group: 'company' },
  { key: 'code', label: 'Kunden-Nr.', type: 'text', group: 'company' },
  { key: 'accounting_code', label: 'Buchhaltungs-Code', type: 'text', group: 'company' },
  { key: 'vat_code', label: 'USt-IdNr.', type: 'text', group: 'company' },
  { key: 'fiscal_code', label: 'Steuernummer', type: 'text', group: 'company' },
  { key: 'commerce_code', label: 'Handelsregister-Nr.', type: 'text', group: 'company' },
  { key: 'bic', label: 'BIC', type: 'text', group: 'company' },
  { key: 'bank_account', label: 'Bankkonto', type: 'text', group: 'company' },

  // Person
  { key: 'firstname', label: 'Vorname', type: 'text', group: 'person' },
  { key: 'surname', label: 'Nachname', type: 'text', group: 'person' },
  { key: 'suffix', label: 'Suffix', type: 'text', group: 'person' },
  { key: 'gender', label: 'Geschlecht', type: 'select', group: 'person' },
  { key: 'ext_name_line', label: 'Zusatzname', type: 'text', group: 'person' },

  // Address
  { key: 'mailing_street', label: 'Straße (Post)', type: 'text', group: 'address' },
  { key: 'mailing_postalcode', label: 'PLZ (Post)', type: 'text', group: 'address' },
  { key: 'mailing_city', label: 'Stadt (Post)', type: 'text', group: 'address' },
  { key: 'mailing_state', label: 'Bundesland (Post)', type: 'text', group: 'address' },
  { key: 'mailing_country', label: 'Land (Post)', type: 'text', group: 'address' },
  { key: 'visit_city', label: 'Stadt (Besuch)', type: 'text', group: 'address' },
  { key: 'visit_postalcode', label: 'PLZ (Besuch)', type: 'text', group: 'address' },
  { key: 'invoice_city', label: 'Stadt (Rechnung)', type: 'text', group: 'address' },
  { key: 'invoice_postalcode', label: 'PLZ (Rechnung)', type: 'text', group: 'address' },

  // Notes
  { key: 'projectnote', label: 'Projektnotiz', type: 'text', group: 'notes' },
  { key: 'projectnote_title', label: 'Notiztitel', type: 'text', group: 'notes' },
  { key: 'contact_warning', label: 'Warnung', type: 'text', group: 'notes' },

  // Meta
  { key: 'folder_id', label: 'Ordner-ID', type: 'text', group: 'meta' },
  { key: 'created_at', label: 'Erstellt am', type: 'date', group: 'meta' },
  { key: 'updated_at', label: 'Geändert am', type: 'date', group: 'meta' },
];

// ─── Types ────────────────────────────────────────────────────────────────────

export interface GroupCondition {
  id: string;
  field: string;
}

export interface GroupState {
  conditions: GroupCondition[];
}

export const emptyGroupState: GroupState = {
  conditions: [],
};

// ─── Group logic ──────────────────────────────────────────────────────────────

function getFieldValue(contact: UnifiedContact, field: string): any {
  if (field.startsWith('custom.')) {
    const customField = field.slice(7);
    return contact.custom?.[customField];
  }
  return (contact as any)[field];
}

export interface GroupedContacts {
  key: string;
  label: string;
  contacts: UnifiedContact[];
}

export function applyGrouping(contacts: UnifiedContact[], groupState: GroupState, allDefs?: GroupFieldDef[]): GroupedContacts[] {
  const defs = allDefs || GROUP_FIELDS;
  if (!groupState.conditions.length) {
    return [{ key: 'all', label: 'Alle', contacts }];
  }

  // Multi-level grouping
  let groups: GroupedContacts[] = [{ key: 'all', label: 'Alle', contacts: [...contacts] }];

  for (const cond of groupState.conditions) {
    const def = defs.find((f) => f.key === cond.field);
    if (!def) continue;

    const newGroups: GroupedContacts[] = [];
    for (const group of groups) {
      const subGroups = new Map<string, UnifiedContact[]>();
      for (const contact of group.contacts) {
        const val = getFieldValue(contact, cond.field);
        const groupKey = val == null || val === '' ? '(leer)' : String(val);
        if (!subGroups.has(groupKey)) {
          subGroups.set(groupKey, []);
        }
        subGroups.get(groupKey)!.push(contact);
      }
      // Sort group keys alphabetically
      const sortedKeys = Array.from(subGroups.keys()).sort((a, b) => {
        if (a === '(leer)') return 1;
        if (b === '(leer)') return -1;
        return a.localeCompare(b);
      });
      for (const key of sortedKeys) {
        const label = group.key === 'all'
          ? `${def.label}: ${key}`
          : `${group.label} > ${key}`;
        newGroups.push({ key: `${group.key}::${key}`, label, contacts: subGroups.get(key)! });
      }
    }
    groups = newGroups;
  }

  return groups;
}

// ─── Context-sensitive field ordering ──────────────────────────────────────────

function getOrderedFields(contactType?: 'company' | 'person' | undefined, allDefs?: GroupFieldDef[]): GroupFieldDef[] {
  const defs = allDefs || GROUP_FIELDS;
  if (contactType === 'company') {
    const order = ['general', 'company', 'address', 'notes', 'meta', 'custom', 'person'];
    return [...defs].sort((a, b) => order.indexOf(a.group || 'general') - order.indexOf(b.group || 'general'));
  }
  if (contactType === 'person') {
    const order = ['general', 'person', 'address', 'notes', 'meta', 'custom', 'company'];
    return [...defs].sort((a, b) => order.indexOf(a.group || 'general') - order.indexOf(b.group || 'general'));
  }
  const order = ['general', 'company', 'person', 'address', 'notes', 'meta', 'custom'];
  return [...defs].sort((a, b) => order.indexOf(a.group || 'general') - order.indexOf(b.group || 'general'));
}

// ─── Component ────────────────────────────────────────────────────────────────

interface GroupPanelProps {
  groupState: GroupState;
  onGroupChange: (groupState: GroupState) => void;
  contactType?: 'company' | 'person' | undefined;
}

let groupIdCounter = 0;
function newGroupId() {
  return `grp-${Date.now()}-${++groupIdCounter}`;
}

export function GroupPanel({ groupState, onGroupChange, contactType }: GroupPanelProps) {
  const [open, setOpen] = useState(false);
  const btnRef = useRef<HTMLDivElement>(null);
  const panelRef = useRef<HTMLDivElement>(null);
  const [panelPos, setPanelPos] = useState({ top: 0, left: 0 });

  // Fetch custom field definitions (Feature 4)
  const { data: customFieldDefs } = useCustomFieldDefinitions('contact');

  // Merge custom field definitions into GROUP_FIELDS
  const allGroupFields = useMemo(() => {
    const baseFields = GROUP_FIELDS.filter((f) => !f.key.startsWith('custom.'));
    if (!customFieldDefs || !customFieldDefs.items || customFieldDefs.items.length === 0) return baseFields;
    const customFields: GroupFieldDef[] = customFieldDefs.items
      .filter((def) => def.is_active)
      .map((def) => {
        const fieldType: FieldType =
          def.field_type === 'number' ? 'number' :
          def.field_type === 'date' ? 'date' :
          def.field_type === 'select' || def.field_type === 'multiselect' ? 'select' :
          'text';
        return {
          key: `custom.${def.name}`,
          label: def.label || def.name,
          type: fieldType,
          group: 'custom' as const,
        };
      });
    return [...baseFields, ...customFields];
  }, [customFieldDefs]);

  useEffect(() => {
    if (!open) return;
    const handler = (e: MouseEvent) => {
      const target = e.target as Node;
      if (btnRef.current?.contains(target) || panelRef.current?.contains(target)) return;
      setOpen(false);
    };
    document.addEventListener('mousedown', handler);
    return () => document.removeEventListener('mousedown', handler);
  }, [open]);

  const handleToggle = () => {
    if (!open && btnRef.current) {
      const rect = btnRef.current.getBoundingClientRect();
      const panelWidth = Math.min(420, window.innerWidth * 0.9);
      const left = Math.min(rect.left, window.innerWidth - panelWidth - 10);
      setPanelPos({ top: rect.bottom + 4, left: Math.max(10, left) });
    }
    setOpen(!open);
  };

  const orderedFields = useMemo(() => getOrderedFields(contactType, allGroupFields), [contactType, allGroupFields]);
  const activeCount = groupState.conditions.length;

  const addCondition = () => {
    onGroupChange({
      conditions: [...groupState.conditions, {
        id: newGroupId(),
        field: orderedFields[0]?.key || 'type',
      }],
    });
  };

  const removeCondition = (id: string) => {
    onGroupChange({
      conditions: groupState.conditions.filter((c) => c.id !== id),
    });
  };

  const updateCondition = (id: string, updates: Partial<GroupCondition>) => {
    onGroupChange({
      conditions: groupState.conditions.map((c) =>
        c.id === id ? { ...c, ...updates } : c
      ),
    });
  };

  const clearAll = () => {
    onGroupChange({ ...emptyGroupState });
  };

  const moveCondition = (id: string, direction: 'up' | 'down') => {
    const conds = [...groupState.conditions];
    const idx = conds.findIndex((c) => c.id === id);
    if (idx < 0) return;
    const newIdx = direction === 'up' ? idx - 1 : idx + 1;
    if (newIdx < 0 || newIdx >= conds.length) return;
    [conds[idx], conds[newIdx]] = [conds[newIdx], conds[idx]];
    onGroupChange({ conditions: conds });
  };

  // Group fields for dropdown
  const groupedFields = useMemo(() => {
    const groups: Record<string, GroupFieldDef[]> = {};
    for (const f of orderedFields) {
      const g = f.group || 'general';
      if (!groups[g]) groups[g] = [];
      groups[g].push(f);
    }
    return groups;
  }, [orderedFields]);

  const groupLabels: Record<string, string> = {
    general: 'Allgemein',
    company: 'Firma',
    person: 'Person',
    address: 'Adresse',
    notes: 'Notizen',
    meta: 'Metadaten',
    custom: 'Benutzerdefinierte Felder',
  };

  return (
    <>
      <div ref={btnRef} className="relative flex-shrink-0">
        <button
          onClick={handleToggle}
          title="Gruppierung"
          aria-label="Gruppierung"
          className={`
            inline-flex items-center gap-1.5 px-2 py-1 rounded text-xs font-medium
            transition-colors duration-100 cursor-pointer relative
            ${open || activeCount > 0 ? 'bg-primary-100 text-primary-700' : 'text-secondary-600 hover:bg-secondary-100 hover:text-secondary-900'}
          `}
        >
          <GroupIcon className="w-3.5 h-3.5" strokeWidth={2} />
          {activeCount > 0 && (
            <span className="inline-flex items-center justify-center min-w-[16px] h-4 px-1 text-[10px] font-bold rounded-full bg-primary-600 text-white">
              {activeCount}
            </span>
          )}
          <svg className={`w-3 h-3 transition-transform ${open ? 'rotate-180' : ''}`} fill="none" stroke="currentColor" strokeWidth={2} viewBox="0 0 24 24">
            <polyline points="6 9 12 15 18 9" />
          </svg>
        </button>
      </div>

      {open && (
        <div
          ref={panelRef}
          className="fixed bg-white border border-secondary-200 rounded-lg shadow-lg"
          style={{
            top: panelPos.top,
            left: panelPos.left,
            width: 'min(420px, 90vw)',
            maxHeight: '70vh',
            overflowY: 'auto',
            zIndex: 3000,
          }}
        >
          {/* Header */}
          <div className="flex items-center justify-between px-4 py-3 border-b border-secondary-100">
            <span className="text-sm font-semibold text-secondary-800">Gruppierung</span>
            <div className="flex items-center gap-2">
              {activeCount > 0 && (
                <button
                  onClick={clearAll}
                  className="text-xs text-secondary-500 hover:text-red-600 transition-colors"
                >
                  Alle löschen
                </button>
              )}
              <button
                onClick={() => setOpen(false)}
                className="p-1 rounded hover:bg-secondary-100 text-secondary-400 hover:text-secondary-600"
              >
                <X className="w-3.5 h-3.5" />
              </button>
            </div>
          </div>

          {/* Info text */}
          {activeCount === 0 && (
            <div className="px-4 py-3 border-b border-secondary-100">
              <div className="text-center py-4 text-xs text-secondary-400">
                Keine Gruppierung aktiv. Alle Datensätze werden in einer flachen Liste angezeigt.
              </div>
            </div>
          )}

          {/* Active group badges */}
          {activeCount > 0 && (
            <div className="flex flex-wrap gap-1.5 px-4 py-2 border-b border-secondary-100">
              {groupState.conditions.map((cond, idx) => {
                const def = allGroupFields.find((f) => f.key === cond.field);
                return (
                  <span
                    key={cond.id}
                    className="inline-flex items-center gap-1 px-2 py-0.5 text-[11px] rounded-full bg-primary-50 text-primary-700 border border-primary-200"
                  >
                    <span className="font-bold text-primary-500">{idx + 1}.</span>
                    {def?.label}
                    <button onClick={() => removeCondition(cond.id)} className="hover:text-red-600">
                      <X className="w-3 h-3" />
                    </button>
                  </span>
                );
              })}
            </div>
          )}

          {/* Group rows */}
          <div className="px-4 py-3 space-y-2">
            {groupState.conditions.map((cond, idx) => (
              <div key={cond.id} className="flex items-center gap-1.5">
                {/* Priority number + reorder */}
                <div className="flex flex-col items-center w-6 flex-shrink-0">
                  <span className="text-[10px] font-bold text-primary-600">{idx + 1}</span>
                  <div className="flex flex-col">
                    <button
                      onClick={() => moveCondition(cond.id, 'up')}
                      disabled={idx === 0}
                      className="text-secondary-300 hover:text-secondary-600 disabled:opacity-30 leading-none"
                    >
                      <svg className="w-3 h-3" fill="none" stroke="currentColor" strokeWidth={2.5} viewBox="0 0 24 24">
                        <polyline points="18 15 12 9 6 15" />
                      </svg>
                    </button>
                    <button
                      onClick={() => moveCondition(cond.id, 'down')}
                      disabled={idx === groupState.conditions.length - 1}
                      className="text-secondary-300 hover:text-secondary-600 disabled:opacity-30 leading-none"
                    >
                      <svg className="w-3 h-3" fill="none" stroke="currentColor" strokeWidth={2.5} viewBox="0 0 24 24">
                        <polyline points="6 9 12 15 18 9" />
                      </svg>
                    </button>
                  </div>
                </div>

                {/* Field dropdown */}
                <select
                  value={cond.field}
                  onChange={(e) => updateCondition(cond.id, { field: e.target.value })}
                  className="flex-1 min-w-0 px-2 py-1.5 text-xs border border-secondary-200 rounded bg-white cursor-pointer focus:outline-none focus:border-primary-400"
                >
                  {Object.entries(groupedFields).map(([group, fields]) => (
                    <optgroup key={group} label={groupLabels[group] || group}>
                      {fields.map((f) => (
                        <option key={f.key} value={f.key}>{f.label}</option>
                      ))}
                    </optgroup>
                  ))}
                </select>

                {/* Remove button */}
                <button
                  onClick={() => removeCondition(cond.id)}
                  className="p-1 rounded hover:bg-red-50 text-secondary-400 hover:text-red-600 transition-colors flex-shrink-0"
                >
                  <X className="w-3.5 h-3.5" />
                </button>
              </div>
            ))}
          </div>

          {/* Footer */}
          <div className="flex items-center justify-between px-4 py-3 border-t border-secondary-100">
            <button
              onClick={addCondition}
              className="inline-flex items-center gap-1 px-2 py-1 text-xs font-medium text-primary-600 hover:bg-primary-50 rounded transition-colors"
            >
              <Plus className="w-3.5 h-3.5" />
              Gruppierung hinzufügen
            </button>
            <button
              onClick={() => setOpen(false)}
              className="px-3 py-1 text-xs font-medium text-white bg-primary-600 hover:bg-primary-700 rounded transition-colors"
            >
              Fertig
            </button>
          </div>
        </div>
      )}
    </>
  );
}