import { useCallback, useEffect, useState } from 'react';
import { Link, Navigate, useNavigate, useParams } from 'react-router-dom';
import { useAuth } from '@/hooks/useAuth';
import { AssignmentFormFields } from '@/components/assignments/AssignmentFormFields';
import {
  assignmentDayStatusLabel,
  assignmentStatusLabel,
  assignmentTypeLabel,
  createAssignmentEntry,
  fetchAssignment,
  isMultiDayAssignment,
  saveAssignmentDraft,
  startAssignment,
  submitAssignmentReport,
  updateAssignmentEntry,
  type AssignmentDayStatus,
  type AssignmentFormField,
  type AssignmentReportStatus,
  type UserAssignment,
} from '@/services/assignmentService';
import { useToast } from '@/components/ui/use-toast';
import { getFetchErrorMessage } from '@/lib/fetchError';
import { PageSkeleton } from '@/components/skeletons';
import { Button } from '@/components/ui/button';
import { cn } from '@/lib/utils';
import { ArrowRight, Check, Loader2 } from 'lucide-react';

function emptyDraftFromSchema(schema: AssignmentFormField[] | null): Record<string, unknown> {
  if (!schema) return { text: '' };
  const draft: Record<string, unknown> = {};
  for (const field of schema) {
    if (field.type === 'list') {
      draft[field.key] = [{}];
    } else if (field.type === 'checkbox') {
      draft[field.key] = false;
    } else {
      draft[field.key] = '';
    }
  }
  return draft;
}

function progressLabel(assignment: UserAssignment): string | null {
  const target = assignment.definition.expectedDurationDays;
  if (!target) return `${assignment.doneDayCount} روز انجام‌شده`;
  return `${assignment.doneDayCount} روز از ${target} روز هدف`;
}

/**
 * Assignment detail — one-time vs multi-day flows diverge deliberately.
 * Status is system-driven; experience notes are optional and soft.
 */
export default function AssignmentDetailPage() {
  const { id } = useParams<{ id: string }>();
  const { effectiveUserId, guestSessionHydrated, isGuest } = useAuth();
  const navigate = useNavigate();
  const { toast } = useToast();

  const [assignment, setAssignment] = useState<UserAssignment | null>(null);
  const [loading, setLoading] = useState(true);
  const [saving, setSaving] = useState(false);
  const [draft, setDraft] = useState<Record<string, unknown>>({});
  const [entryData, setEntryData] = useState<Record<string, unknown>>({});
  const [entryNote, setEntryNote] = useState('');
  const [dayStatus, setDayStatus] = useState<AssignmentDayStatus>('done');
  const [editingEntryId, setEditingEntryId] = useState<string | null>(null);
  const [experienceNote, setExperienceNote] = useState('');
  const [experienceStatus, setExperienceStatus] =
    useState<AssignmentReportStatus>('difficult');

  const load = useCallback(async () => {
    if (!id) return;
    setLoading(true);
    try {
      const row = await fetchAssignment(id);
      setAssignment(row);
      const schema = row.definition.formSchema;
      setDraft(
        (row.draftData as Record<string, unknown> | null) ?? emptyDraftFromSchema(schema),
      );
      const today = row.serverToday;
      const todayEntry = row.dailyEntries?.find((e) => e.entryDate === today);
      if (todayEntry) {
        setEditingEntryId(todayEntry.id);
        setEntryData(todayEntry.responseData);
        setEntryNote(todayEntry.note ?? '');
        setDayStatus(todayEntry.dayStatus);
      } else {
        setEditingEntryId(null);
        setEntryData(emptyDraftFromSchema(schema));
        setEntryNote('');
        setDayStatus('done');
      }
    } catch (err) {
      toast({
        title: 'خطا',
        description: getFetchErrorMessage(err, 'بارگذاری تکلیف ناموفق بود'),
        variant: 'destructive',
      });
      navigate('/assignments', { replace: true });
    } finally {
      setLoading(false);
    }
  }, [id, navigate, toast]);

  useEffect(() => {
    if (!effectiveUserId || isGuest) return;
    void load();
  }, [effectiveUserId, isGuest, load]);

  if (!guestSessionHydrated || loading) {
    return <PageSkeleton />;
  }

  if (!effectiveUserId) {
    return <Navigate to="/login" replace />;
  }

  if (isGuest || !assignment) {
    return <Navigate to="/assignments" replace />;
  }

  const isMultiDay = isMultiDayAssignment(assignment.definition.assignmentType);
  const isOneTime = assignment.definition.assignmentType === 'ONE_TIME';
  const schema = assignment.definition.formSchema;
  const completed = assignment.status === 'COMPLETED';
  const serverToday = assignment.serverToday;

  const updateDraftField = (key: string, value: unknown) => {
    setDraft((prev) => ({ ...prev, [key]: value }));
  };

  const updateEntryField = (key: string, value: unknown) => {
    setEntryData((prev) => ({ ...prev, [key]: value }));
  };

  const handleSaveDraft = async (completeIfValid: boolean) => {
    setSaving(true);
    try {
      await startAssignment(assignment.id);
      const updated = await saveAssignmentDraft(assignment.id, draft, { completeIfValid });
      setAssignment(updated);
      toast({
        title: updated.status === 'COMPLETED' ? 'پاسخ ثبت و تکلیف تکمیل شد' : 'پیش‌نویس ذخیره شد',
        description:
          updated.status === 'COMPLETED'
            ? undefined
            : completeIfValid
              ? undefined
              : 'برای تکمیل، فیلدهای الزامی را پر کن و «ثبت پاسخ» را بزن.',
      });
    } catch (err) {
      toast({
        title: 'خطا',
        description: getFetchErrorMessage(err, 'ذخیره پاسخ ناموفق بود'),
        variant: 'destructive',
      });
    } finally {
      setSaving(false);
    }
  };

  const handleSaveEntry = async () => {
    setSaving(true);
    try {
      await startAssignment(assignment.id);
      const payload = {
        dayStatus,
        responseData: dayStatus === 'done' ? entryData : {},
        note: entryNote || null,
      };
      if (editingEntryId) {
        await updateAssignmentEntry(assignment.id, editingEntryId, payload);
      } else {
        await createAssignmentEntry(assignment.id, {
          ...payload,
          entryDate: serverToday,
        });
      }
      await load();
      toast({ title: 'ثبت امروز ذخیره شد' });
    } catch (err) {
      toast({
        title: 'خطا',
        description: getFetchErrorMessage(err, 'ثبت روزانه ناموفق بود'),
        variant: 'destructive',
      });
    } finally {
      setSaving(false);
    }
  };

  const handleExperienceNote = async () => {
    const text = experienceNote.trim();
    if (text.length < 3) {
      toast({
        title: 'یادداشت کوتاه است',
        description: 'اگر می‌خواهی مانعی را ثبت کنی، چند کلمه بنویس.',
        variant: 'destructive',
      });
      return;
    }
    setSaving(true);
    try {
      const result = await submitAssignmentReport(assignment.id, text, experienceStatus);
      setAssignment(result.assignment);
      setExperienceNote('');
      toast({ title: 'یادداشت تجربه ثبت شد' });
    } catch (err) {
      toast({
        title: 'خطا',
        description: getFetchErrorMessage(err, 'ثبت یادداشت ناموفق بود'),
        variant: 'destructive',
      });
    } finally {
      setSaving(false);
    }
  };

  const dayOptions: Array<{ value: AssignmentDayStatus; label: string }> = [
    { value: 'done', label: 'بله، انجام دادم' },
    { value: 'skipped', label: 'امروز انجام ندادم' },
    { value: 'difficult', label: 'امروز برایم دشوار بود' },
  ];

  return (
    <div className="h-full min-h-0 flex-1 overflow-x-hidden overflow-y-auto bg-slate-50 px-4 py-6 dark:bg-slate-900">
      <div className="mx-auto w-full max-w-md space-y-5">
        <div>
          <Link
            to="/assignments"
            className="mb-3 inline-flex items-center gap-1 text-sm text-sky-700 dark:text-sky-300"
          >
            <ArrowRight className="h-4 w-4" />
            بازگشت به تکالیف
          </Link>
          <p className="text-[11px] font-medium text-sky-700 dark:text-sky-300">
            جلسه {assignment.definition.sessionOrder}
          </p>
          <h1 className="text-xl font-bold text-foreground">{assignment.definition.title}</h1>
          <div className="mt-3 flex flex-wrap gap-2 text-[11px] text-muted-foreground">
            <span className="rounded-md bg-slate-100 px-2 py-0.5 dark:bg-slate-700">
              {assignmentTypeLabel(assignment.definition.assignmentType)}
            </span>
            <span className="rounded-md bg-sky-50 px-2 py-0.5 text-sky-800 dark:bg-sky-950 dark:text-sky-200">
              {assignmentStatusLabel(assignment.status)}
            </span>
            {isMultiDay && <span>{progressLabel(assignment)}</span>}
          </div>
        </div>

        <section className="rounded-xl border border-sky-200/80 bg-sky-50/70 p-4 dark:border-sky-900 dark:bg-sky-950/40">
          <h2 className="mb-2 text-sm font-semibold text-foreground">راهنمای تمرین</h2>
          <p className="whitespace-pre-wrap text-sm leading-7 text-body">
            {assignment.definition.instructions}
          </p>
        </section>

        {completed && isOneTime && (
          <section className="space-y-3 rounded-xl border border-emerald-200 bg-emerald-50/60 p-4 dark:border-emerald-900 dark:bg-emerald-950/30">
            <h2 className="text-sm font-semibold text-foreground">پاسخ ثبت‌شده</h2>
            <AssignmentFormFields fields={schema} values={draft} onChange={() => {}} disabled />
          </section>
        )}

        {isOneTime && !completed && (
          <section className="space-y-3 rounded-xl border border-slate-200 bg-white p-4 dark:border-slate-700 dark:bg-slate-800">
            <h2 className="text-sm font-semibold text-foreground">پاسخ تمرین</h2>
            <p className="text-xs text-muted-foreground">
              فیلدهای ستاره‌دار لازم‌اند. می‌توانی پیش‌نویس ذخیره کنی و بعداً ادامه بدهی.
            </p>
            <AssignmentFormFields fields={schema} values={draft} onChange={updateDraftField} />
            <div className="grid grid-cols-1 gap-2 sm:grid-cols-2">
              <Button
                variant="outline"
                onClick={() => void handleSaveDraft(false)}
                disabled={saving}
                className="w-full"
              >
                {saving ? <Loader2 className="h-4 w-4 animate-spin" /> : 'ذخیره پیش‌نویس'}
              </Button>
              <Button onClick={() => void handleSaveDraft(true)} disabled={saving} className="w-full">
                {saving ? <Loader2 className="h-4 w-4 animate-spin" /> : 'ثبت پاسخ و تکمیل'}
              </Button>
            </div>
          </section>
        )}

        {isMultiDay && (
          <section className="space-y-3 rounded-xl border border-slate-200 bg-white p-4 dark:border-slate-700 dark:bg-slate-800">
            <div className="flex items-start justify-between gap-3">
              <div>
                <h2 className="text-sm font-semibold text-foreground">پیشرفت کلی</h2>
                <p className="mt-1 text-xs text-muted-foreground">{progressLabel(assignment)}</p>
              </div>
              {assignment.definition.minValidDays != null ? (
                <p className="text-[11px] text-muted-foreground">
                  تکمیل پس از {assignment.definition.minValidDays} روز انجام‌شده
                </p>
              ) : (
                <p className="max-w-[12rem] text-left text-[11px] leading-4 text-muted-foreground">
                  تکمیل خودکار فعلاً فعال نیست
                </p>
              )}
            </div>
            {assignment.completionBlockReason && !completed ? (
              <p className="text-xs text-amber-800 dark:text-amber-200">
                {assignment.completionBlockReason}
              </p>
            ) : null}
            {completed ? (
              <p className="text-sm text-emerald-700 dark:text-emerald-300">این تمرین تکمیل شده است.</p>
            ) : null}
          </section>
        )}

        {isMultiDay && !completed && (
          <section className="space-y-3 rounded-xl border border-slate-200 bg-white p-4 dark:border-slate-700 dark:bg-slate-800">
            <h2 className="text-sm font-semibold text-foreground">
              ثبت امروز ({serverToday})
              {editingEntryId ? ' — ویرایش' : ''}
            </h2>
            <p className="text-xs text-muted-foreground">آیا امروز این تمرین را انجام دادی؟</p>
            <div className="grid grid-cols-1 gap-2">
              {dayOptions.map((opt) => (
                <button
                  key={opt.value}
                  type="button"
                  onClick={() => setDayStatus(opt.value)}
                  className={cn(
                    'flex items-center gap-2 rounded-lg border px-3 py-2 text-right text-sm transition-colors',
                    dayStatus === opt.value
                      ? 'border-sky-500 bg-sky-50 dark:border-sky-400 dark:bg-sky-950'
                      : 'border-slate-200 dark:border-slate-600',
                  )}
                >
                  <span
                    className={cn(
                      'inline-flex h-4 w-4 items-center justify-center rounded border',
                      dayStatus === opt.value
                        ? 'border-sky-600 bg-sky-600 text-white'
                        : 'border-slate-300 dark:border-slate-500',
                    )}
                  >
                    {dayStatus === opt.value ? <Check className="h-2.5 w-2.5" /> : null}
                  </span>
                  {opt.label}
                </button>
              ))}
            </div>

            {dayStatus === 'done' ? (
              <>
                <AssignmentFormFields
                  fields={schema}
                  values={entryData}
                  onChange={updateEntryField}
                />
                <textarea
                  className="w-full rounded-xl border border-slate-200 bg-white px-3 py-2 text-sm dark:border-slate-600 dark:bg-slate-900"
                  rows={2}
                  dir="rtl"
                  placeholder="یادداشت روزانه (اختیاری)"
                  value={entryNote}
                  onChange={(e) => setEntryNote(e.target.value)}
                />
              </>
            ) : (
              <textarea
                className="w-full rounded-xl border border-slate-200 bg-white px-3 py-2 text-sm dark:border-slate-600 dark:bg-slate-900"
                rows={2}
                dir="rtl"
                placeholder="اگر مایلید، دلیل یا مانع را کوتاه بنویسید (اختیاری)"
                value={entryNote}
                onChange={(e) => setEntryNote(e.target.value)}
              />
            )}

            <Button onClick={() => void handleSaveEntry()} disabled={saving} className="w-full">
              {saving ? <Loader2 className="h-4 w-4 animate-spin" /> : 'ذخیره ثبت امروز'}
            </Button>

            {(assignment.dailyEntries?.length ?? 0) > 0 && (
              <div className="space-y-2 border-t border-slate-100 pt-3 dark:border-slate-700">
                <h3 className="text-xs font-medium text-muted-foreground">تاریخچه روزها</h3>
                {assignment.dailyEntries?.map((entry) => (
                  <button
                    key={entry.id}
                    type="button"
                    className="block w-full rounded-lg border border-slate-100 px-3 py-2 text-right text-xs hover:bg-slate-50 dark:border-slate-700 dark:hover:bg-slate-900"
                    onClick={() => {
                      setEditingEntryId(entry.id);
                      setEntryData(entry.responseData);
                      setEntryNote(entry.note ?? '');
                      setDayStatus(entry.dayStatus);
                    }}
                  >
                    <span className="font-medium text-foreground">{entry.entryDate}</span>
                    <span className="mt-0.5 block text-muted-foreground">
                      {assignmentDayStatusLabel(entry.dayStatus)}
                      {entry.note ? ` · ${entry.note}` : ''}
                    </span>
                  </button>
                ))}
              </div>
            )}
          </section>
        )}

        {!completed && (
          <section className="space-y-3 rounded-xl border border-dashed border-slate-200 bg-white/70 p-4 dark:border-slate-700 dark:bg-slate-800/60">
            <h2 className="text-sm font-semibold text-foreground">یادداشت تجربه (اختیاری)</h2>
            <p className="text-xs text-muted-foreground">
              اگر انجام تمرین برایت دشوار بود یا می‌خواهی مانعی را ثبت کنی — جدا از پاسخ اصلی تمرین.
            </p>
            <div className="grid grid-cols-1 gap-2">
              {(
                [
                  { value: 'difficult' as const, label: 'انجام آن برایم دشوار بود' },
                  { value: 'in_progress' as const, label: 'هنوز درگیر تمرین هستم' },
                  { value: 'not_started' as const, label: 'هنوز شروع نکرده‌ام' },
                ] as const
              ).map((opt) => (
                <button
                  key={opt.value}
                  type="button"
                  onClick={() => setExperienceStatus(opt.value)}
                  className={cn(
                    'rounded-lg border px-3 py-2 text-right text-sm',
                    experienceStatus === opt.value
                      ? 'border-slate-400 bg-slate-50 dark:border-slate-500 dark:bg-slate-900'
                      : 'border-slate-200 dark:border-slate-600',
                  )}
                >
                  {opt.label}
                </button>
              ))}
            </div>
            <textarea
              className="w-full rounded-xl border border-slate-200 bg-white px-3 py-2 text-sm dark:border-slate-600 dark:bg-slate-900"
              rows={2}
              dir="rtl"
              value={experienceNote}
              onChange={(e) => setExperienceNote(e.target.value)}
              placeholder="توضیح کوتاه (اختیاری اما توصیه‌شده)"
            />
            <Button
              variant="outline"
              onClick={() => void handleExperienceNote()}
              disabled={saving}
              className="w-full"
            >
              ثبت یادداشت تجربه
            </Button>
          </section>
        )}
      </div>
    </div>
  );
}