import React, { useEffect, useMemo, useState } from 'react';
import { Avatar, Button, Card, ErrorBox, Segmented, Spinner, inputClass } from '../ui/controls';
import { Icon } from '../ui/Icon';
import { Donut } from '../ui/charts';
import { EntryModal } from './EntryModal';
import { CopyDialog } from './CopyDialog';
import { ExportDialog } from './ExportDialog';
import { WeekView } from './WeekView';
import { MonthView } from './MonthView';
import { YearView } from './YearView';
import { EntryList } from './EntryList';
import { useAuth } from '../../lib/auth';
import { entriesApi, projectsApi, usersApi } from '../../lib/api';
import { useIsMobile, useLoader, usePersistentState, useCountUp } from '../../lib/hooks';
import {
  MONTHS,
  addDays,
  addMonths,
  formatDate,
  formatDuration,
  isoWeek,
  mondayOf,
  monthEnd,
  monthStart,
  todayIso,
  weekdayIndex,
} from '../../lib/format';
import { visibleTeam } from '../team/hierarchy';
import { atLeast, type DirectoryUser, type Project, type TimeEntry } from '../../types';

export type BookingMode = 'week' | 'month' | 'year';
/** Kalender = Wochen-/Monats-/Jahresraster, Liste = die einzelnen Buchungen als Tabelle. */
export type BookingLayout = 'calendar' | 'list';

function rangeFor(mode: BookingMode, anchor: string) {
  if (mode === 'week') {
    const from = mondayOf(anchor);
    return { from, to: addDays(from, 6) };
  }
  if (mode === 'month') return { from: monthStart(anchor), to: monthEnd(anchor) };
  return { from: `${anchor.slice(0, 4)}-01-01`, to: `${anchor.slice(0, 4)}-12-31` };
}

/** Arbeitstage Mo-Fr im Intervall, fuer das Soll. */
function workdays(from: string, to: string) {
  let count = 0;
  for (let d = from; d <= to; d = addDays(d, 1)) if (weekdayIndex(d) < 5) count++;
  return count;
}

export const Booking: React.FC = () => {
  const { user, settings } = useAuth();
  const isMobile = useIsMobile();
  const [mode, setMode] = usePersistentState<BookingMode>('pulse_booking_mode', 'week');
  const [layout, setLayout] = usePersistentState<BookingLayout>('pulse_booking_layout', 'calendar');
  const [anchor, setAnchor] = useState(todayIso());
  const [modal, setModal] = useState<{ date: string; entry?: TimeEntry | null } | null>(null);
  const [copyEntry, setCopyEntry] = useState<TimeEntry | null>(null);
  const [exportOpen, setExportOpen] = useState(false);
  const [viewUserId, setViewUserId] = useState<number>(user!.id);
  const isLead = atLeast(user, 'lead');
  const readOnly = viewUserId !== user!.id;

  const range = rangeFor(mode, anchor);
  const entries = useLoader(() => entriesApi.list(range.from, range.to, viewUserId), [range.from, range.to, viewUserId]);
  const projects = useLoader(() => projectsApi.list('mine'), []);
  const [team, setTeam] = useState<DirectoryUser[]>([]);

  useEffect(() => {
    if (!isLead) return;
    usersApi
      .directory()
      .then((list) => setTeam(visibleTeam(list, user!)))
      .catch(() => undefined);
  }, [isLead, user]);

  const list = entries.data ?? [];
  const total = list.reduce((s, e) => s + e.minutes, 0);
  const billable = list.filter((e) => e.billable).reduce((s, e) => s + e.minutes, 0);
  const viewedUser = team.find((t) => t.id === viewUserId);
  const weekly = (readOnly ? null : user!.weekly_hours) ?? settings.weekly_hours;
  const today = todayIso();
  // Soll bis heute (bzw. ganzer Zeitraum, wenn er vorbei ist).
  const targetTo = range.to < today ? range.to : today < range.from ? range.from : today;
  const target = today < range.from ? 0 : (weekly / 5) * workdays(range.from, targetTo) * 60;

  const shift = (step: number) => {
    if (mode === 'week') setAnchor(addDays(anchor, 7 * step));
    else if (mode === 'month') setAnchor(addMonths(anchor, step));
    else setAnchor(`${Number(anchor.slice(0, 4)) + step}-${anchor.slice(5)}`);
  };

  const label =
    mode === 'week'
      ? `KW ${isoWeek(range.from)} · ${formatDate(range.from).slice(0, 6)} – ${formatDate(range.to)}`
      : mode === 'month'
        ? `${MONTHS[Number(anchor.slice(5, 7)) - 1]} ${anchor.slice(0, 4)}`
        : anchor.slice(0, 4);

  const openNew = (date?: string) => {
    if (readOnly) return;
    setModal({ date: date ?? (today >= range.from && today <= range.to ? today : range.from) });
  };

  /** Kopieren: Tage im Monatskalender waehlen, auf die die Buchung kopiert wird. */
  const copy = (entry: TimeEntry) => {
    if (readOnly) return;
    setModal(null);
    setCopyEntry(entry);
  };

  /*
   * Im Export stehen nur die eigenen Projekte zur Wahl - auch fuer
   * Vorgesetzte. Wer einen Nachweis fuer einen Kunden erstellt, filtert nach
   * dem, was er selbst gebucht hat; eine Liste aller Projekte des Hauses war
   * dort nur Suchaufwand.
   */
  const openExport = () => setExportOpen(true);

  // Tastenkuerzel: N = neue Buchung, Pfeile = blaettern.
  useEffect(() => {
    const onKey = (e: KeyboardEvent) => {
      if (modal || exportOpen) return;
      const target = e.target as HTMLElement;
      if (['INPUT', 'TEXTAREA', 'SELECT'].includes(target.tagName)) return;
      if (e.key === 'n' || e.key === '+') {
        e.preventDefault();
        openNew();
      }
      if (e.key === 'ArrowLeft') shift(-1);
      if (e.key === 'ArrowRight') shift(1);
    };
    window.addEventListener('keydown', onKey);
    return () => window.removeEventListener('keydown', onKey);
  });

  const warnings = useMemo(
    () => (projects.data ?? []).flatMap((p) => p.pots.filter((pot) => pot.warning && pot.status !== 'expired' && pot.valid_to >= today).map((pot) => ({ project: p, pot }))),
    [projects.data, today]
  );

  return (
    <div className={`mx-auto max-w-[1500px] ${isMobile && !readOnly ? 'pb-16' : ''}`}>
      {/* Werkzeugleiste */}
      <div className="mb-4 flex flex-wrap items-center gap-2 sm:gap-3">
        <div className="flex items-center rounded-xl border border-ink-200 bg-surface shadow-card">
          <button onClick={() => shift(-1)} className="rounded-l-xl p-2.5 text-ink-500 hover:bg-ink-50 hover:text-ink-900" aria-label="Zurück">
            <Icon name="chevronLeft" className="h-4 w-4" strokeWidth={2.2} />
          </button>
          <button onClick={() => setAnchor(todayIso())} className="border-x border-ink-200 px-3 py-2 text-xs font-bold text-ink-600 hover:bg-ink-50">
            Heute
          </button>
          <button onClick={() => shift(1)} className="rounded-r-xl p-2.5 text-ink-500 hover:bg-ink-50 hover:text-ink-900" aria-label="Weiter">
            <Icon name="chevronRight" className="h-4 w-4" strokeWidth={2.2} />
          </button>
        </div>
        <h2 className="tabular min-w-0 flex-1 truncate text-base text-ink-900 sm:flex-none sm:text-lg">{label}</h2>

        <div className="order-last flex w-full flex-wrap items-center gap-2 sm:order-none sm:ml-auto sm:w-auto sm:flex-nowrap">
          <Segmented
            value={mode}
            onChange={setMode}
            className="flex-1 sm:flex-none"
            options={[
              { value: 'week', label: 'Woche' },
              { value: 'month', label: 'Monat' },
              { value: 'year', label: 'Jahr' },
            ]}
          />
          <Segmented
            value={layout}
            onChange={setLayout}
            className="flex-1 sm:flex-none"
            options={[
              { value: 'calendar', label: 'Kalender', icon: 'calendar', title: 'Kalenderansicht' },
              { value: 'list', label: 'Liste', icon: 'list', title: 'Alle Buchungen als Liste' },
            ]}
          />
          {isLead && team.length > 1 && (
            <select className={`${inputClass} w-auto max-w-[180px] py-2 text-xs font-bold`} value={viewUserId} onChange={(e) => setViewUserId(Number(e.target.value))} title="Zeiten ansehen von">
              {team.map((t) => (
                <option key={t.id} value={t.id}>
                  {t.id === user!.id ? 'Meine Zeiten' : t.name}
                </option>
              ))}
            </select>
          )}
          <Button variant="secondary" icon="download" onClick={openExport} className="py-2">
            <span className="hidden sm:inline">Export</span>
          </Button>
          {!isMobile && !readOnly && (
            <button
              onClick={() => openNew()}
              title="Zeit buchen (N)"
              aria-label="Zeit buchen"
              className="animate-glow flex h-11 w-11 items-center justify-center rounded-full bg-brand-500 text-white shadow-lift transition hover:scale-105 hover:bg-brand-600 active:scale-95"
            >
              <Icon name="plus" className="h-6 w-6" strokeWidth={2.6} />
            </button>
          )}
        </div>
      </div>

      {readOnly && viewedUser && (
        <div className="animate-fade mb-4 flex items-center gap-3 rounded-2xl border border-sky-200 bg-sky-50 px-4 py-3 text-sm font-semibold text-sky-700">
          <Avatar name={viewedUser.name} color={viewedUser.color} avatar={viewedUser.avatar} id={viewedUser.id} size={28} />
          Du siehst die Zeiten von {viewedUser.name} (nur lesen).
          <button className="ml-auto text-xs font-bold underline" onClick={() => setViewUserId(user!.id)}>
            Zurück zu meinen Zeiten
          </button>
        </div>
      )}

      {!readOnly && warnings.length > 0 && (
        <div className="animate-fade mb-4 space-y-2">
          {warnings.slice(0, 3).map(({ project, pot }) => (
            <div key={pot.id} className="flex items-start gap-3 rounded-2xl border border-amber-200 bg-amber-50 px-4 py-2.5 text-xs font-semibold text-amber-700">
              <Icon name="warning" className="mt-0.5 h-4 w-4 shrink-0" />
              <span>
                <b>{project.display_name}</b> – {pot.warning}
                {pot.remaining_hours != null && ` Noch ${pot.remaining_hours.toLocaleString('de-DE')} h frei.`}
              </span>
            </div>
          ))}
        </div>
      )}

      <SummaryStrip total={total} billable={billable} target={target} weekly={weekly} mode={mode} count={list.length} />

      {entries.error && <ErrorBox message={entries.error} onRetry={entries.reload} />}
      {entries.loading && !entries.data ? (
        <Spinner />
      ) : (
        <div key={`${layout}-${mode}-${range.from}`} className="animate-fade">
          {layout === 'list' && (
            <Card className="overflow-hidden">
              <EntryList
                entries={list}
                onEdit={readOnly ? undefined : (entry) => setModal({ date: entry.entry_date, entry })}
                onCopy={readOnly ? undefined : copy}
                emptyText={`Keine Buchungen ${mode === 'week' ? 'in dieser Woche' : mode === 'month' ? 'in diesem Monat' : 'in diesem Jahr'}.`}
              />
            </Card>
          )}
          {layout === 'calendar' && mode === 'week' && (
            <WeekView from={range.from} entries={list} readOnly={readOnly} dailyTarget={(weekly / 5) * 60} onAdd={openNew} onEdit={(entry) => !readOnly && setModal({ date: entry.entry_date, entry })} onCopy={copy} />
          )}
          {layout === 'calendar' && mode === 'month' && (
            <MonthView
              month={range.from}
              entries={list}
              dailyTarget={(weekly / 5) * 60}
              onOpenDay={(date) => {
                setAnchor(date);
                setMode('week');
              }}
              onAdd={openNew}
              readOnly={readOnly}
            />
          )}
          {layout === 'calendar' && mode === 'year' && (
            <YearView
              year={anchor.slice(0, 4)}
              entries={list}
              weeklyTarget={weekly}
              onOpenMonth={(month) => {
                setAnchor(`${month}-01`);
                setMode('month');
              }}
            />
          )}
        </div>
      )}

      {isMobile && !readOnly && (
        <button
          onClick={() => openNew()}
          aria-label="Zeit buchen"
          className="animate-glow fixed bottom-24 left-1/2 z-40 flex -translate-x-1/2 h-16 w-16 items-center justify-center rounded-full bg-brand-500 text-white shadow-lift transition active:scale-95"
        >
          <Icon name="plus" className="h-8 w-8" strokeWidth={2.6} />
        </button>
      )}

      {modal && projects.data && (
        <EntryModal
          projects={projects.data}
          date={modal.date}
          entry={modal.entry}
          onClose={() => setModal(null)}
          onSaved={() => { entries.reload(); projects.reload(); }}
          onDuplicate={copy}
        />
      )}
      {copyEntry && projects.data && (
        <CopyDialog
          entry={copyEntry}
          projects={projects.data}
          onClose={() => setCopyEntry(null)}
          onSaved={() => { entries.reload(); projects.reload(); }}
        />
      )}
      {exportOpen && (
        <ExportDialog
          month={anchor.slice(0, 7)}
          projects={projects.data ?? []}
          team={team}
          viewUserId={viewUserId}
          onClose={() => setExportOpen(false)}
        />
      )}
    </div>
  );
};

const SummaryStrip: React.FC<{ total: number; billable: number; target: number; weekly: number; mode: BookingMode; count: number }> = ({
  total,
  billable,
  target,
  weekly,
  mode,
  count,
}) => {
  const shown = useCountUp(total);
  const percent = target > 0 ? Math.round((total / target) * 100) : 0;
  const diff = total - target;
  return (
    <Card className="animate-rise mb-4 flex flex-wrap items-center gap-4 p-4 sm:gap-6 sm:p-5">
      <Donut percent={Math.min(100, percent)} size={isFinite(percent) ? 76 : 76} stroke={9} track="var(--color-ink-100)" label="Soll" />
      <div className="min-w-[120px]">
        <p className="text-[11px] font-extrabold uppercase tracking-[0.14em] text-ink-400">
          Gebucht {mode === 'week' ? 'diese Woche' : mode === 'month' ? 'im Monat' : 'im Jahr'}
        </p>
        <p className="tabular text-3xl font-extrabold text-ink-900">
          {formatDuration(shown)}
          <span className="ml-1 text-base text-ink-400">h</span>
        </p>
      </div>
      <div className="grid w-full grid-cols-3 gap-2 sm:w-auto sm:max-w-xl sm:flex-1 sm:gap-3">
        <Mini label="Soll bis heute" value={`${formatDuration(target)} h`} hint={`${weekly} h/Woche`} />
        <Mini label="Differenz" value={`${diff >= 0 ? '+' : '−'}${formatDuration(Math.abs(diff))} h`} tone={diff >= 0 ? 'good' : 'bad'} />
        <Mini label="Billable" value={total ? `${Math.round((billable / total) * 100)} %` : '–'} hint={`${count} Buchungen`} />
      </div>
    </Card>
  );
};

const Mini: React.FC<{ label: string; value: string; hint?: string; tone?: 'good' | 'bad' }> = ({ label, value, hint, tone }) => (
  <div className="min-w-0 rounded-xl bg-ink-50 px-3 py-2">
    <p className="truncate text-[10px] font-bold uppercase tracking-wider text-ink-400">{label}</p>
    <p className={`tabular truncate text-sm font-extrabold sm:text-base ${tone === 'good' ? 'text-brand-700' : tone === 'bad' ? 'text-red-600' : 'text-ink-900'}`}>{value}</p>
    {hint && <p className="truncate text-[10px] text-ink-400">{hint}</p>}
  </div>
);