// TODO: P2-F16 — Replace hardcoded GROUP_FIELDS with shared constant
/**
 * SmartSuite-style Group Panel for Mail.
 * Multi-field grouping.
 * Based on contacts/GroupPanel.tsx
 */

import React, { useState, useRef, useEffect } from 'react';
import { Group as GroupIcon, Plus, X } from 'lucide-react';

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

interface GroupFieldDef {
  key: string;
  label: string;
  type: FieldType;
  group?: string;
}

const GROUP_FIELDS: GroupFieldDef[] = [
  { key: 'from', label: 'Absender', type: 'text', group: 'Allgemein' },
  { key: 'folder_name', label: 'Ordner', type: 'text', group: 'Allgemein' },
  { key: 'is_read', label: 'Gelesen', type: 'text', group: 'Allgemein' },
  { key: 'is_flagged', label: 'Markiert', type: 'text', group: 'Allgemein' },
  { key: 'has_attachments', label: 'Anhänge', type: 'text', group: 'Allgemein' },
  { key: 'date_day', label: 'Datum (Tag)', type: 'date', group: 'Datum' },
  { key: 'date_week', label: 'Kalenderwoche', type: 'date', group: 'Datum' },
  { key: 'date_month', label: 'Monat', type: 'date', group: 'Datum' },
  { key: 'date_year', label: 'Jahr', type: 'date', group: 'Datum' },
];

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

export interface GroupState {
  conditions: GroupCondition[];
}

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

function getFieldValue(mail: any, field: string): any {
  // Virtual date grouping fields
  if (field === 'date_day') {
    const d = new Date(mail.date);
    return d.toISOString().split('T')[0]; // YYYY-MM-DD
  }
  if (field === 'date_week') {
    const d = new Date(mail.date);
    const onejan = new Date(d.getFullYear(), 0, 1);
    const week = Math.ceil(((d.getTime() - onejan.getTime()) / 86400000 + onejan.getDay() + 1) / 7);
    return `KW ${week} ${d.getFullYear()}`;
  }
  if (field === 'date_month') {
    const d = new Date(mail.date);
    const months = ['Januar', 'Februar', 'März', 'April', 'Mai', 'Juni', 'Juli', 'August', 'September', 'Oktober', 'November', 'Dezember'];
    return `${months[d.getMonth()]} ${d.getFullYear()}`;
  }
  if (field === 'date_year') {
    const d = new Date(mail.date);
    return String(d.getFullYear());
  }
  return (mail as any)[field];
}

export interface GroupedMails {
  key: string;
  label: string;
  mails: any[];
  subGroups?: GroupedMails[];
}

export function applyGrouping(mails: any[], groupState: GroupState): GroupedMails[] {
  if (!(groupState.conditions?.length ?? 0)) return [{ key: 'all', label: 'Alle', mails }];
  const defs = GROUP_FIELDS;

  function groupRecursive(items: any[], conditions: GroupCondition[], depth: number): GroupedMails[] {
    if (depth >= conditions.length) return [{ key: 'all', label: 'Alle', mails: items }];
    const cond = conditions[depth];
    const def = defs.find((f) => f.key === cond.field);
    if (!def) return [{ key: 'all', label: 'Alle', mails: items }];
    const subGroups = new Map<string, any[]>();
    for (const mail of items) {
      const val = getFieldValue(mail, cond.field);
      const groupKey = val == null || val === '' ? '(leer)' : String(val);
      if (!subGroups.has(groupKey)) subGroups.set(groupKey, []);
      subGroups.get(groupKey)!.push(mail);
    }
    const sortedKeys = Array.from(subGroups.keys()).sort();
    return sortedKeys.map((key) => {
      const groupMails = subGroups.get(key)!;
      const childGroups = groupRecursive(groupMails, conditions, depth + 1);
      if (childGroups.length === 1 && childGroups[0].key === 'all') {
        return { key, label: key, mails: groupMails };
      }
      return { key, label: key, mails: [], subGroups: childGroups };
    });
  }

  return groupRecursive(mails, groupState.conditions, 0);
}

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

interface MailGroupPanelProps {
  groupState: GroupState;
  onGroupChange: (groupState: GroupState) => void;
}

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

  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(400, 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 activeCount = groupState.conditions?.length ?? 0;

  const addCondition = () => {
    onGroupChange({ conditions: [...groupState.conditions, { id: newGroupId(), field: 'from' }] });
  };

  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 groupedFields: Record<string, GroupFieldDef[]> = {};
  for (const f of GROUP_FIELDS) {
    const g = f.group || 'Allgemein';
    if (!groupedFields[g]) groupedFields[g] = [];
    groupedFields[g].push(f);
  }

  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(400px, 90vw)', maxHeight: '70vh', overflowY: 'auto', zIndex: 3000 }}>
          <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>
          <div className="px-4 py-3 space-y-2">
            {groupState.conditions.length === 0 && <div className="text-center py-6 text-xs text-secondary-400">Keine Gruppierung aktiv. Klicke unten um ein Feld hinzuzufügen.</div>}
            {groupState.conditions.map((cond, idx) => (
              <div key={cond.id} className="flex items-center gap-1.5">
                <span className="text-[10px] font-bold text-secondary-400 w-6 text-center">{idx + 1}.</span>
                <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={group}>{fields.map((f) => (<option key={f.key} value={f.key}>{f.label}</option>))}</optgroup>
                  ))}
                </select>
                <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>
          <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" />Feld 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>
      )}
    </>
  );
}