import { useCallback, useEffect, useState } from 'react';
import Notice from '../components/Notice';
import { ApiError, api, uploadFile } from '../lib/api';
import { PLAN_LABEL, formatDate } from '../lib/format';
import type { ImportPlan, ImportRecord } from '../lib/types';

interface UploadResult {
  importId: number;
  columns: string[];
  rowCount: number;
  sample: Record<string, string>[];
}

interface MappingForm {
  playerKey: string;
  playerName: string;
  product: string;
  orderId: string;
  purchasedAt: string;
  createMissingPlayers: boolean;
}

const EMPTY_MAPPING: MappingForm = {
  playerKey: '',
  playerName: '',
  product: '',
  orderId: '',
  purchasedAt: '',
  createMissingPlayers: false,
};

// Trifft die üblichen Spaltennamen, damit das Formular meist schon passt.
const GUESSES: Record<keyof Omit<MappingForm, 'createMissingPlayers'>, string[]> = {
  playerKey: ['steamid', 'steam_id', 'steam', 'identifier', 'user', 'kunde'],
  playerName: ['name', 'username', 'displayname', 'spieler'],
  product: ['product', 'produkt', 'item', 'artikel', 'package', 'paket'],
  orderId: ['order', 'bestell', 'transaction', 'id', 'purchase'],
  purchasedAt: ['date', 'datum', 'created', 'time', 'kauf'],
};

function guessMapping(columns: string[]): MappingForm {
  const result = { ...EMPTY_MAPPING };
  for (const [field, needles] of Object.entries(GUESSES) as [
    keyof typeof GUESSES,
    string[],
  ][]) {
    const hit = columns.find((column) =>
      needles.some((needle) => column.toLowerCase().includes(needle)),
    );
    if (hit) result[field] = hit;
  }
  return result;
}

export default function Import() {
  const [upload, setUpload] = useState<UploadResult | null>(null);
  const [mapping, setMapping] = useState<MappingForm>(EMPTY_MAPPING);
  const [preview, setPreview] = useState<{
    summary: Record<ImportPlan, number>;
    import: ImportRecord;
  } | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [flash, setFlash] = useState<string | null>(null);
  const [busy, setBusy] = useState(false);
  const [open, setOpen] = useState<ImportRecord[]>([]);

  const loadOpen = useCallback(async () => {
    try {
      const result = await api<{ items: ImportRecord[] }>('/api/imports');
      setOpen(result.items.filter((entry) => entry.status === 'PENDING'));
    } catch {
      // Die Liste ist Beiwerk; ein Fehler hier darf den Upload nicht blockieren.
    }
  }, []);

  useEffect(() => {
    void loadOpen();
  }, [loadOpen]);

  const reset = () => {
    setUpload(null);
    setPreview(null);
    setMapping(EMPTY_MAPPING);
    setError(null);
    void loadOpen();
  };

  /** Einen bereits angelegten Import (etwa aus dem GExtension-Abgleich) oeffnen. */
  const openExisting = async (record: ImportRecord) => {
    setBusy(true);
    setError(null);
    try {
      const full = await api<ImportRecord>(`/api/imports/${record.id}`);
      const rows = full.rows ?? [];
      const summary = {
        BOOK: 0,
        CREATE_PLAYER_AND_BOOK: 0,
        SKIP_DUPLICATE: 0,
        SKIP_IGNORED: 0,
        SKIP_UNMAPPED: 0,
        SKIP_NO_PLAYER: 0,
      } as Record<ImportPlan, number>;
      for (const row of rows) summary[row.plan] += 1;

      setUpload({ importId: full.id, columns: [], rowCount: full.rowCount, sample: [] });
      setPreview({ summary, import: full });
    } catch (err) {
      setError(err instanceof ApiError ? err.message : 'Import konnte nicht geoeffnet werden');
    } finally {
      setBusy(false);
    }
  };

  const handleUpload = async (file: File) => {
    setBusy(true);
    setError(null);
    setPreview(null);
    try {
      const result = await uploadFile<UploadResult>('/api/imports', file);
      setUpload(result);
      setMapping(guessMapping(result.columns));
    } catch (err) {
      setError(err instanceof ApiError ? err.message : 'Upload fehlgeschlagen');
    } finally {
      setBusy(false);
    }
  };

  const handlePreview = async (event: React.FormEvent) => {
    event.preventDefault();
    if (!upload) return;
    setBusy(true);
    setError(null);
    try {
      const body = {
        playerKey: mapping.playerKey,
        product: mapping.product,
        createMissingPlayers: mapping.createMissingPlayers,
        ...(mapping.playerName ? { playerName: mapping.playerName } : {}),
        ...(mapping.orderId ? { orderId: mapping.orderId } : {}),
        ...(mapping.purchasedAt ? { purchasedAt: mapping.purchasedAt } : {}),
      };
      const result = await api<{ summary: Record<ImportPlan, number>; import: ImportRecord }>(
        `/api/imports/${upload.importId}/mapping`,
        { method: 'POST', body },
      );
      setPreview(result);
    } catch (err) {
      setError(err instanceof ApiError ? err.message : 'Vorschau fehlgeschlagen');
    } finally {
      setBusy(false);
    }
  };

  const handleCommit = async () => {
    if (!upload) return;
    setBusy(true);
    setError(null);
    try {
      const result = await api<{ booked: number; skipped: number; createdPlayers: number }>(
        `/api/imports/${upload.importId}/commit`,
        { method: 'POST', body: {} },
      );
      const teile = [`${result.booked} Buchungen angelegt`];
      if (result.createdPlayers > 0) teile.push(`${result.createdPlayers} Spieler neu erfasst`);
      if (result.skipped > 0) teile.push(`${result.skipped} bereits gebucht, übersprungen`);
      setFlash(teile.join(', ') + '.');
      reset();
    } catch (err) {
      setError(err instanceof ApiError ? err.message : 'Buchen fehlgeschlagen');
    } finally {
      setBusy(false);
    }
  };

  const handleDiscard = async () => {
    if (!upload) return;
    try {
      await api(`/api/imports/${upload.importId}/discard`, { method: 'POST', body: {} });
    } finally {
      reset();
    }
  };

  const bookable = preview
    ? preview.summary.BOOK + preview.summary.CREATE_PLAYER_AND_BOOK
    : 0;

  return (
    <div className="page">
      <div className="page-head">
        <h1>Import</h1>
      </div>

      {error && <Notice kind="error" onDismiss={() => setError(null)}>{error}</Notice>}
      {flash && <Notice kind="success" onDismiss={() => setFlash(null)}>{flash}</Notice>}

      {!upload && open.length > 0 && (
        <section className="block block-flag">
          <h2>Wartet auf Bestätigung ({open.length})</h2>
          <Notice kind="warn">
            Diese Importe sind angelegt, aber noch nicht gebucht. Der GExtension-Abgleich landet
            ebenfalls hier — erst nach dem Bestätigen entstehen Guthaben.
          </Notice>

          <ul className="cc-list">
            {open.map((record) => (
              <li key={record.id} className="cc-item">
                <div>
                  <strong>{record.filename}</strong>
                  <p className="muted small">
                    {record.rowCount} {record.rowCount === 1 ? 'Zeile' : 'Zeilen'} · angelegt{' '}
                    {formatDate(record.createdAt)}
                    {record.importedBy && ` von ${record.importedBy.username}`}
                  </p>
                </div>
                <div className="cc-actions">
                  <button
                    type="button"
                    className="btn btn-small btn-primary"
                    disabled={busy}
                    onClick={() => void openExisting(record)}
                  >
                    Öffnen
                  </button>
                </div>
              </li>
            ))}
          </ul>
        </section>
      )}

      {!upload && (
        <section className="block">
          <Notice kind="info">
            CSV oder JSON hochladen. Danach werden die Spalten zugeordnet und eine Vorschau
            gezeigt — gebucht wird erst nach Bestätigung. Bereits importierte Bestell-IDs
            werden automatisch übersprungen.
          </Notice>

          <label className="file-drop">
            <input
              type="file"
              accept=".csv,.json,.tsv,.txt"
              onChange={(event) => {
                const file = event.target.files?.[0];
                if (file) void handleUpload(file);
              }}
              disabled={busy}
            />
            <span>{busy ? 'Lade hoch …' : 'Datei auswählen'}</span>
          </label>
        </section>
      )}

      {upload && !preview && (
        <section className="block">
          <h2>Spalten zuordnen</h2>
          <p className="muted">
            {upload.rowCount} Zeilen aus <strong>{upload.columns.length}</strong> Spalten gelesen.
          </p>

          <form onSubmit={handlePreview}>
            <div className="grid-2">
              <MappingSelect
                label="Spieler-Kennung (Pflicht)"
                value={mapping.playerKey}
                columns={upload.columns}
                required
                onChange={(value) => setMapping({ ...mapping, playerKey: value })}
              />
              <MappingSelect
                label="Produktname (Pflicht)"
                value={mapping.product}
                columns={upload.columns}
                required
                onChange={(value) => setMapping({ ...mapping, product: value })}
              />
              <MappingSelect
                label="Anzeigename"
                value={mapping.playerName}
                columns={upload.columns}
                onChange={(value) => setMapping({ ...mapping, playerName: value })}
              />
              <MappingSelect
                label="Bestell-ID (für Dedup)"
                value={mapping.orderId}
                columns={upload.columns}
                onChange={(value) => setMapping({ ...mapping, orderId: value })}
              />
              <MappingSelect
                label="Kaufdatum"
                value={mapping.purchasedAt}
                columns={upload.columns}
                onChange={(value) => setMapping({ ...mapping, purchasedAt: value })}
              />
            </div>

            <label className="checkbox">
              <input
                type="checkbox"
                checked={mapping.createMissingPlayers}
                onChange={(event) =>
                  setMapping({ ...mapping, createMissingPlayers: event.target.checked })
                }
              />
              <span>Unbekannte Spieler automatisch anlegen</span>
            </label>

            {!mapping.orderId && (
              <Notice kind="warn">
                Ohne Bestell-ID kann ein zweiter Import dieselben Käufe erneut buchen.
              </Notice>
            )}

            <div className="form-actions">
              <button type="button" className="btn btn-ghost" onClick={() => void handleDiscard()}>
                Abbrechen
              </button>
              <button type="submit" className="btn btn-primary" disabled={busy}>
                {busy ? 'Berechne …' : 'Vorschau erzeugen'}
              </button>
            </div>
          </form>

          <h3>Beispielzeilen</h3>
          <div className="table-wrap">
            <table className="table small">
              <thead>
                <tr>
                  {upload.columns.map((column) => (
                    <th key={column}>{column}</th>
                  ))}
                </tr>
              </thead>
              <tbody>
                {upload.sample.map((row, index) => (
                  <tr key={index}>
                    {upload.columns.map((column) => (
                      <td key={column} className="muted">
                        {row[column] ?? ''}
                      </td>
                    ))}
                  </tr>
                ))}
              </tbody>
            </table>
          </div>
        </section>
      )}

      {preview && (
        <section className="block">
          <h2>Vorschau</h2>

          <div className="summary-grid">
            {(Object.keys(PLAN_LABEL) as ImportPlan[]).map((plan) => (
              <div
                key={plan}
                className={`summary-card${
                  plan === 'BOOK' || plan === 'CREATE_PLAYER_AND_BOOK' ? ' is-active' : ''
                }`}
              >
                <span className="summary-value">{preview.summary[plan] ?? 0}</span>
                <span className="summary-label">{PLAN_LABEL[plan]}</span>
              </div>
            ))}
          </div>

          {bookable === 0 ? (
            <Notice kind="warn">
              Keine Zeile würde gebucht. Prüfe die Spaltenzuordnung oder die Produkt-Mappings
              in der Verwaltung.
            </Notice>
          ) : (
            <Notice kind="info">
              {bookable} Zeilen werden gebucht. Ein CC-Paket erzeugt dabei automatisch ein
              CC-Guthaben <em>und</em> ein bezahltes Redesign-Guthaben.
            </Notice>
          )}

          <div className="table-wrap scroll">
            <table className="table small">
              <thead>
                <tr>
                  <th>#</th>
                  <th>Spieler</th>
                  <th>Produkt</th>
                  <th>Bestell-ID</th>
                  <th>Datum</th>
                  <th>Ergebnis</th>
                </tr>
              </thead>
              <tbody>
                {(preview.import.rows ?? []).map((row) => (
                  <tr key={row.id} className={row.plan.startsWith('SKIP') ? 'is-skipped' : undefined}>
                    <td className="muted">{row.lineNo}</td>
                    <td>
                      {row.playerName || row.playerKey || '—'}
                      {row.resolvedPlayerId === null && row.plan === 'CREATE_PLAYER_AND_BOOK' && (
                        <span className="badge badge-new">neu</span>
                      )}
                    </td>
                    <td className="muted">{row.productName ?? '—'}</td>
                    <td className="mono muted">{row.externalId ?? '—'}</td>
                    <td className="muted">{formatDate(row.purchasedAt)}</td>
                    <td className={row.plan.startsWith('SKIP') ? 'muted' : 'pos'}>
                      {PLAN_LABEL[row.plan]}
                    </td>
                  </tr>
                ))}
              </tbody>
            </table>
          </div>

          <div className="form-actions">
            <button type="button" className="btn btn-ghost" onClick={() => void handleDiscard()}>
              Verwerfen
            </button>
            <button type="button" className="btn btn-ghost" onClick={() => setPreview(null)}>
              Zuordnung ändern
            </button>
            <button
              type="button"
              className="btn btn-primary"
              disabled={busy || bookable === 0}
              onClick={() => void handleCommit()}
            >
              {busy ? 'Buche …' : `${bookable} Zeilen buchen`}
            </button>
          </div>
        </section>
      )}
    </div>
  );
}

function MappingSelect({
  label,
  value,
  columns,
  required,
  onChange,
}: {
  label: string;
  value: string;
  columns: string[];
  required?: boolean;
  onChange: (value: string) => void;
}) {
  return (
    <div className="field">
      <label>{label}</label>
      <select value={value} onChange={(event) => onChange(event.target.value)} required={required}>
        <option value="">— nicht zuordnen —</option>
        {columns.map((column) => (
          <option key={column} value={column}>
            {column}
          </option>
        ))}
      </select>
    </div>
  );
}