"use client";

import { useState, useTransition, useRef } from "react";
import { Upload, FileText, CheckCircle, AlertCircle, Loader } from "lucide-react";
import {
  parseCSV,
  applyImport,
  type PreviewResult,
  type ImportOptions,
  type ApplyResult,
} from "@/app/admin/import-export/import-actions";

type Course = { id: string; title: string };

const inputStyle: React.CSSProperties = {
  border: "2px solid var(--border)",
  background: "var(--background)",
  outline: "none",
  width: "100%",
  padding: "0.5rem 0.75rem",
  fontSize: "16px",
  fontFamily: "inherit",
};
const focusHandlers = {
  onFocus: (e: React.FocusEvent<HTMLInputElement | HTMLSelectElement>) =>
    (e.currentTarget.style.borderColor = "var(--foreground)"),
  onBlur: (e: React.FocusEvent<HTMLInputElement | HTMLSelectElement>) =>
    (e.currentTarget.style.borderColor = "var(--border)"),
};

function Toggle({ label, hint, checked, onChange }: { label: string; hint?: string; checked: boolean; onChange: (v: boolean) => void }) {
  return (
    <div className="flex items-start gap-3">
      <button type="button" onClick={() => onChange(!checked)} className="mt-0.5 shrink-0">
        <span className="relative inline-block w-10 h-6" style={{ background: checked ? "var(--accent)" : "var(--border)", border: "2px solid var(--foreground)" }}>
          <span className="absolute top-0.5 w-4 h-4 transition-transform" style={{ background: "var(--foreground)", left: "2px", transform: checked ? "translateX(16px)" : "translateX(0)" }} />
        </span>
      </button>
      <div>
        <p className="text-sm font-medium">{label}</p>
        {hint && <p className="text-xs mt-0.5" style={{ color: "var(--muted-foreground)" }}>{hint}</p>}
      </div>
    </div>
  );
}

function StepIndicator({ step }: { step: number }) {
  const steps = ["Загрузка", "Предпросмотр", "Опции", "Готово"];
  return (
    <div className="flex items-center gap-0 mb-6">
      {steps.map((label, i) => {
        const num = i + 1;
        const active = num === step;
        const done = num < step;
        return (
          <div key={num} className="flex items-center">
            <div className="flex flex-col items-center gap-1">
              <div
                className="w-7 h-7 flex items-center justify-center text-xs font-bold"
                style={{
                  border: "2px solid var(--foreground)",
                  background: done || active ? "var(--foreground)" : "transparent",
                  color: done || active ? "var(--background)" : "var(--foreground)",
                }}
              >
                {done ? "✓" : num}
              </div>
              <span className="text-xs" style={{ color: active ? "var(--foreground)" : "var(--muted-foreground)", fontWeight: active ? 700 : 400 }}>
                {label}
              </span>
            </div>
            {i < steps.length - 1 && (
              <div className="w-12 h-0.5 mx-1 mb-5" style={{ background: done ? "var(--foreground)" : "var(--border)" }} />
            )}
          </div>
        );
      })}
    </div>
  );
}

// ── Main component ────────────────────────────────────────────────────────────

export function CsvImporter({ courses }: { courses: Course[] }) {
  const [step, setStep] = useState(1);
  const [pending, startTransition] = useTransition();
  const [error, setError] = useState<string | null>(null);
  const fileRef = useRef<HTMLInputElement>(null);

  // Step 1 state
  const [encoding, setEncoding] = useState<"utf8" | "win1251">("utf8");
  const [updateExisting, setUpdateExisting] = useState(false);
  const [fileBase64, setFileBase64] = useState<string | null>(null);
  const [fileName, setFileName] = useState<string | null>(null);

  // Step 2 state
  const [preview, setPreview] = useState<PreviewResult | null>(null);

  // Step 3 state
  const [autoVerifyEmail, setAutoVerifyEmail] = useState(true);
  const [courseId, setCourseId] = useState("");
  const [accessDays, setAccessDays] = useState("0");
  const [sendWelcome, setSendWelcome] = useState(false);

  // Step 4 state
  const [result, setResult] = useState<ApplyResult | null>(null);

  function handleFileChange(e: React.ChangeEvent<HTMLInputElement>) {
    const file = e.target.files?.[0];
    if (!file) return;
    setFileName(file.name);
    const reader = new FileReader();
    reader.onload = () => {
      const ab = reader.result as ArrayBuffer;
      const bytes = new Uint8Array(ab);
      let binary = "";
      bytes.forEach((b) => (binary += String.fromCharCode(b)));
      setFileBase64(btoa(binary));
    };
    reader.readAsArrayBuffer(file);
  }

  function handleParse() {
    if (!fileBase64) return;
    setError(null);
    startTransition(async () => {
      try {
        const result = await parseCSV(fileBase64, encoding, updateExisting);
        setPreview(result);
        setStep(2);
      } catch (e) {
        setError(e instanceof Error ? e.message : "Ошибка разбора файла");
      }
    });
  }

  function handleApply() {
    if (!preview) return;
    setError(null);
    const options: ImportOptions = {
      updateExisting,
      autoVerifyEmail,
      courseId: courseId || undefined,
      accessDays: parseInt(accessDays) || 0,
      sendWelcome,
      encoding,
    };
    startTransition(async () => {
      try {
        const r = await applyImport(preview.rows, options);
        setResult(r);
        setStep(4);
      } catch (e) {
        setError(e instanceof Error ? e.message : "Ошибка импорта");
      }
    });
  }

  function handleReset() {
    setStep(1);
    setFileBase64(null);
    setFileName(null);
    setPreview(null);
    setResult(null);
    setError(null);
    if (fileRef.current) fileRef.current.value = "";
  }

  return (
    <div>
      <StepIndicator step={step} />

      {/* ── Step 1: Upload ── */}
      {step === 1 && (
        <div className="space-y-5">
          {/* File picker */}
          <div
            className="flex flex-col items-center justify-center gap-3 p-8 cursor-pointer"
            style={{ border: "2px dashed var(--border)" }}
            onClick={() => fileRef.current?.click()}
          >
            <Upload size={28} style={{ color: "var(--muted-foreground)" }} />
            {fileName ? (
              <div className="text-center">
                <p className="font-medium flex items-center gap-1.5">
                  <FileText size={15} /> {fileName}
                </p>
                <p className="text-xs mt-0.5" style={{ color: "var(--muted-foreground)" }}>Нажмите чтобы выбрать другой файл</p>
              </div>
            ) : (
              <div className="text-center">
                <p className="font-medium">Выберите CSV-файл</p>
                <p className="text-xs mt-0.5" style={{ color: "var(--muted-foreground)" }}>Поддерживаются файлы из emdesell, Excel и любого табличного редактора</p>
              </div>
            )}
            <input ref={fileRef} type="file" accept=".csv,text/csv" className="hidden" onChange={handleFileChange} />
          </div>

          {/* Options */}
          <div className="grid grid-cols-2 gap-4">
            <div className="space-y-1.5">
              <label className="text-xs font-bold uppercase tracking-widest" style={{ color: "var(--muted-foreground)" }}>Кодировка</label>
              <select value={encoding} onChange={(e) => setEncoding(e.target.value as "utf8" | "win1251")} style={{ ...inputStyle, appearance: "none" }} {...focusHandlers}>
                <option value="utf8">UTF-8 (стандарт)</option>
                <option value="win1251">Windows-1251 (Excel)</option>
              </select>
            </div>
            <div className="flex items-end pb-0.5">
              <Toggle
                label="Обновлять существующих"
                hint="Если пользователь уже есть — обновить данные"
                checked={updateExisting}
                onChange={setUpdateExisting}
              />
            </div>
          </div>

          {/* Template download hint */}
          <p className="text-xs" style={{ color: "var(--muted-foreground)" }}>
            Ожидаемые колонки: <span className="font-mono">Email</span>, <span className="font-mono">Имя</span>, <span className="font-mono">Фамилия</span>, <span className="font-mono">Телефон</span> (порядок не важен, первая строка — заголовки).
          </p>

          {error && <p className="text-sm p-3" style={{ border: "2px solid oklch(0.577 0.245 27.325)", color: "oklch(0.577 0.245 27.325)" }}>{error}</p>}

          <button
            type="button"
            disabled={!fileBase64 || pending}
            onClick={handleParse}
            className="btn-aubade btn-aubade-accent px-5 py-2 text-sm flex items-center gap-2"
            style={{ opacity: !fileBase64 || pending ? 0.5 : 1 }}
          >
            {pending ? <><Loader size={14} className="animate-spin" /> Разбираю...</> : "Далее →"}
          </button>
        </div>
      )}

      {/* ── Step 2: Preview ── */}
      {step === 2 && preview && (
        <div className="space-y-4">
          {/* Stats */}
          <div className="grid grid-cols-3 gap-3">
            {[
              { label: "Будет создано", count: preview.countNew, color: "#3A6A3A" },
              { label: "Будет обновлено", count: preview.countUpdate, color: "var(--foreground)" },
              { label: "Ошибок", count: preview.countError, color: "oklch(0.577 0.245 27.325)" },
            ].map(({ label, count, color }) => (
              <div key={label} className="card-aubade p-4 text-center">
                <p className="text-2xl font-bold" style={{ color }}>{count}</p>
                <p className="text-xs mt-0.5" style={{ color: "var(--muted-foreground)" }}>{label}</p>
              </div>
            ))}
          </div>

          {/* Table */}
          <div className="overflow-auto max-h-72" style={{ border: "2px solid var(--border)" }}>
            <table className="w-full text-sm">
              <thead>
                <tr style={{ borderBottom: "2px solid var(--border)", background: "var(--background)" }}>
                  {["#", "Email", "Имя", "Телефон", "Статус"].map((h) => (
                    <th key={h} className="text-left px-3 py-2 text-xs font-bold uppercase tracking-widest" style={{ color: "var(--muted-foreground)" }}>{h}</th>
                  ))}
                </tr>
              </thead>
              <tbody>
                {preview.rows.map((row) => (
                  <tr key={row.index} style={{ borderBottom: "1px solid var(--border)" }}>
                    <td className="px-3 py-1.5 text-xs" style={{ color: "var(--muted-foreground)" }}>{row.index}</td>
                    <td className="px-3 py-1.5 font-mono text-xs">{row.email}</td>
                    <td className="px-3 py-1.5 text-xs">{row.name}</td>
                    <td className="px-3 py-1.5 text-xs">{row.phone || "—"}</td>
                    <td className="px-3 py-1.5">
                      {row.status === "new" && <span className="text-xs font-bold" style={{ color: "#3A6A3A" }}>✦ Новый</span>}
                      {row.status === "update" && <span className="text-xs font-bold">↻ Обновить</span>}
                      {row.status === "error" && (
                        <span className="text-xs font-bold flex items-center gap-1" style={{ color: "oklch(0.577 0.245 27.325)" }}>
                          <AlertCircle size={12} /> {row.errorMsg}
                        </span>
                      )}
                    </td>
                  </tr>
                ))}
              </tbody>
            </table>
          </div>

          <div className="flex gap-3">
            <button type="button" onClick={() => setStep(3)} disabled={preview.countNew + preview.countUpdate === 0}
              className="btn-aubade btn-aubade-accent px-5 py-2 text-sm"
              style={{ opacity: preview.countNew + preview.countUpdate === 0 ? 0.4 : 1 }}>
              Далее →
            </button>
            <button type="button" onClick={handleReset} className="btn-aubade px-4 py-2 text-sm">← Назад</button>
          </div>
        </div>
      )}

      {/* ── Step 3: Options ── */}
      {step === 3 && (
        <div className="space-y-5 max-w-md">
          <Toggle
            label="Подтвердить email автоматически"
            hint="Пользователи смогут войти сразу, без подтверждения почты."
            checked={autoVerifyEmail}
            onChange={setAutoVerifyEmail}
          />

          <div className="space-y-1.5">
            <label className="text-xs font-bold uppercase tracking-widest" style={{ color: "var(--muted-foreground)" }}>Курс для доступа</label>
            <select value={courseId} onChange={(e) => setCourseId(e.target.value)} style={{ ...inputStyle, appearance: "none" }} {...focusHandlers}>
              <option value="">— Не присваивать —</option>
              {courses.map((c) => <option key={c.id} value={c.id}>{c.title}</option>)}
            </select>
          </div>

          {courseId && (
            <div className="space-y-1.5">
              <label className="text-xs font-bold uppercase tracking-widest" style={{ color: "var(--muted-foreground)" }}>Срок доступа (дней)</label>
              <input
                type="number"
                min="0"
                value={accessDays}
                onChange={(e) => setAccessDays(e.target.value)}
                placeholder="0 — бессрочно"
                style={inputStyle}
                {...focusHandlers}
              />
              <p className="text-xs" style={{ color: "var(--muted-foreground)" }}>0 = бессрочный доступ</p>
            </div>
          )}

          <Toggle
            label="Отправить приветственное письмо"
            hint="Письмо будет отправлено каждому новому пользователю."
            checked={sendWelcome}
            onChange={setSendWelcome}
          />

          {error && <p className="text-sm p-3" style={{ border: "2px solid oklch(0.577 0.245 27.325)", color: "oklch(0.577 0.245 27.325)" }}>{error}</p>}

          <div className="flex gap-3 pt-2">
            <button type="button" onClick={handleApply} disabled={pending}
              className="btn-aubade btn-aubade-accent px-5 py-2 text-sm flex items-center gap-2"
              style={{ opacity: pending ? 0.5 : 1 }}>
              {pending ? <><Loader size={14} className="animate-spin" /> Импортирую...</> : "Применить импорт"}
            </button>
            <button type="button" onClick={() => setStep(2)} className="btn-aubade px-4 py-2 text-sm">← Назад</button>
          </div>
        </div>
      )}

      {/* ── Step 4: Result ── */}
      {step === 4 && result && (
        <div className="space-y-5">
          <div className="flex items-center gap-3 p-5" style={{ border: "2px solid #3A6A3A" }}>
            <CheckCircle size={24} style={{ color: "#3A6A3A", flexShrink: 0 }} />
            <div>
              <p className="font-bold">Импорт завершён</p>
              <p className="text-sm mt-0.5" style={{ color: "var(--muted-foreground)" }}>
                Создано: <strong>{result.created}</strong> · Обновлено: <strong>{result.updated}</strong>
              </p>
            </div>
          </div>

          {result.errors.length > 0 && (
            <div className="space-y-1">
              <p className="text-xs font-bold uppercase tracking-widest" style={{ color: "oklch(0.577 0.245 27.325)" }}>
                Ошибки ({result.errors.length})
              </p>
              <div className="max-h-40 overflow-y-auto space-y-1">
                {result.errors.map((e, i) => (
                  <p key={i} className="text-xs font-mono p-2" style={{ border: "1px solid oklch(0.577 0.245 27.325)", color: "oklch(0.577 0.245 27.325)" }}>{e}</p>
                ))}
              </div>
            </div>
          )}

          <button type="button" onClick={handleReset} className="btn-aubade px-4 py-2 text-sm">
            Импортировать ещё
          </button>
        </div>
      )}
    </div>
  );
}