import { useEffect, useMemo, useRef, useState } from "react";
import { useTranslation } from "react-i18next";
import { api } from "../api";
import { useSettings } from "../settings";
import { useConfirm } from "../confirm";
import { useToast } from "../toast";
import Icon from "../components/Icon";
import { formatMoney } from "../format";

const DATE_FORMATS = [
  { v: "%d.%m.%Y", l: "TT.MM.JJJJ" },
  { v: "%Y-%m-%d", l: "JJJJ-MM-TT" },
  { v: "%d/%m/%Y", l: "TT/MM/JJJJ" },
  { v: "%m/%d/%Y", l: "MM/TT/JJJJ" },
  { v: "%d.%m.%y", l: "TT.MM.JJ" },
];

function defaultConfig() {
  return {
    delimiter: ";",
    decimal_sep: ",",
    date_format: "%d.%m.%Y",
    encoding: "utf-8",
    has_header: true,
    skip_rows: 0,
    amount_mode: "signed",
    column_map: {},
  };
}

export default function Import() {
  const { t } = useTranslation();
  const { formatDate } = useSettings();
  const confirm = useConfirm();
  const toast = useToast();
  const fileRef = useRef(null);

  const [accounts, setAccounts] = useState([]);
  const [groups, setGroups] = useState([]);
  const [templates, setTemplates] = useState([]);
  const [presets, setPresets] = useState([]);
  const [batches, setBatches] = useState([]);

  const [mode, setMode] = useState("csv"); // "csv" | "doc"
  const [accountId, setAccountId] = useState("");
  const [file, setFile] = useState(null);
  const [config, setConfig] = useState(defaultConfig());
  const [raw, setRaw] = useState(null);
  const [rows, setRows] = useState(null);
  const [docText, setDocText] = useState("");
  const [busy, setBusy] = useState(false);
  const [saveName, setSaveName] = useState("");

  const accountById = useMemo(() => Object.fromEntries(accounts.map((a) => [a.id, a])), [accounts]);

  async function loadStamm() {
    try {
      const [a, g, tp, pr, b] = await Promise.all([
        api.listAccounts(), api.listCategories(), api.importTemplates(), api.importPresets(), api.importBatches(),
      ]);
      setAccounts(a); setGroups(g); setTemplates(tp); setPresets(pr); setBatches(b);
      if (a[0] && !accountId) setAccountId(String(a[0].id));
    } catch (e) { toast(e.message, "error"); }
  }
  useEffect(() => { loadStamm(); }, []);

  function setCfg(patch) { setConfig((c) => ({ ...c, ...patch })); }
  function setCol(field, value) {
    setConfig((c) => ({ ...c, column_map: { ...c.column_map, [field]: value === "" ? null : Number(value) } }));
  }

  function applyConfig(src) {
    setConfig({
      delimiter: src.delimiter, decimal_sep: src.decimal_sep, date_format: src.date_format,
      encoding: src.encoding, has_header: src.has_header, skip_rows: src.skip_rows,
      amount_mode: src.amount_mode, column_map: src.column_map || {},
    });
  }
  function applyTemplate(id) {
    const tpl = templates.find((x) => String(x.id) === String(id));
    if (tpl) applyConfig(tpl);
  }
  function applyPreset(idx) {
    const p = presets[Number(idx)];
    if (p) applyConfig(p);
  }

  function baseForm() {
    const fd = new FormData();
    fd.append("file", file);
    fd.append("delimiter", config.delimiter);
    fd.append("encoding", config.encoding);
    fd.append("has_header", config.has_header ? "true" : "false");
    fd.append("skip_rows", String(config.skip_rows || 0));
    return fd;
  }

  async function loadRaw() {
    if (!file) { toast(t("import.needFile"), "error"); return; }
    setBusy(true);
    try {
      setRaw(await api.importRaw(baseForm()));
      setRows(null);
    } catch (e) { toast(e.message, "error"); } finally { setBusy(false); }
  }

  async function loadPreview() {
    if (!file || !accountId) { toast(t("import.needFileAccount"), "error"); return; }
    setBusy(true);
    try {
      const fd = baseForm();
      fd.append("account_id", accountId);
      fd.append("decimal_sep", config.decimal_sep);
      fd.append("date_format", config.date_format);
      fd.append("amount_mode", config.amount_mode);
      fd.append("column_map", JSON.stringify(config.column_map));
      const res = await api.importPreview(fd);
      setRows(res.rows.map((r) => ({ ...r })));
    } catch (e) { toast(e.message, "error"); } finally { setBusy(false); }
  }

  async function loadDoc() {
    if (!file || !accountId) { toast(t("import.needFileAccount"), "error"); return; }
    setBusy(true);
    try {
      const fd = new FormData();
      fd.append("file", file);
      fd.append("account_id", accountId);
      const res = await api.documentPreview(fd);
      setRows(res.rows.map((r) => ({ ...r })));
      setDocText(res.text || "");
    } catch (e) { toast(e.message, "error"); } finally { setBusy(false); }
  }

  async function commit() {
    setBusy(true);
    try {
      const batch = await api.importCommit({
        account_id: Number(accountId),
        template_id: null,
        filename: file?.name || "",
        rows,
      });
      toast(t("import.imported", { n: batch.imported_count }));
      setRows(null); setRaw(null); setFile(null);
      if (fileRef.current) fileRef.current.value = "";
      loadStamm();
    } catch (e) { toast(e.message, "error"); } finally { setBusy(false); }
  }

  async function saveTemplate() {
    if (!saveName.trim()) { toast(t("import.templateName"), "error"); return; }
    try {
      await api.createImportTemplate({ name: saveName.trim(), ...config });
      setSaveName("");
      setTemplates(await api.importTemplates());
      toast(t("settings.saved"));
    } catch (e) { toast(e.message, "error"); }
  }

  async function undo(b) {
    if (!(await confirm({ title: t("import.undo"), message: t("import.undoConfirm", { file: b.filename }), danger: true, confirmLabel: t("import.undo") }))) return;
    try { await api.undoImportBatch(b.id); loadStamm(); } catch (e) { toast(e.message, "error"); }
  }

  const colOptions = useMemo(() => {
    const n = raw ? Math.max(raw.header?.length || 0, ...(raw.rows || []).map((r) => r.length), 0) : 0;
    return Array.from({ length: n }, (_, i) => ({
      i, label: `${i}${raw?.header?.[i] ? ` · ${raw.header[i]}` : ""}`,
    }));
  }, [raw]);

  const expenseGroups = useMemo(() => groups.filter((g) => g.kind === "expense"), [groups]);
  const incomeGroups = useMemo(() => groups.filter((g) => g.kind === "income"), [groups]);

  const includeCount = rows ? rows.filter((r) => r.include).length : 0;

  function updateRow(idx, patch) {
    setRows((rs) => rs.map((r, i) => (i === idx ? { ...r, ...patch } : r)));
  }

  const acc = accountById[Number(accountId)];

  return (
    <div>
      <div className="page-head">
        <h1>{t("import.title")}</h1>
        <div className="seg" style={{ width: 240, marginBottom: 0 }}>
          <button type="button" className={`seg-btn${mode === "csv" ? " active" : ""}`}
                  onClick={() => { setMode("csv"); setRows(null); setRaw(null); setDocText(""); }}>{t("import.modeCsv")}</button>
          <button type="button" className={`seg-btn${mode === "doc" ? " active" : ""}`}
                  onClick={() => { setMode("doc"); setRows(null); setRaw(null); setDocText(""); }}>{t("import.modeDoc")}</button>
        </div>
      </div>

      {/* Schritt 1: Konto + Datei */}
      <div className="card">
        <h2>{t("import.step1")}</h2>
        <div className="row">
          <label className="grow">
            <span>{t("import.account")}</span>
            <select value={accountId} onChange={(e) => setAccountId(e.target.value)}>
              {accounts.map((a) => <option key={a.id} value={a.id}>{a.name} ({a.currency})</option>)}
            </select>
          </label>
          <label className="grow">
            <span>{t("import.file")}</span>
            <input ref={fileRef} type="file"
                   accept={mode === "doc" ? ".pdf,application/pdf,image/*" : ".csv,text/csv,text/plain"}
                   onChange={(e) => { setFile(e.target.files?.[0] || null); setRaw(null); setRows(null); setDocText(""); }} />
          </label>
        </div>
        {mode === "doc" && (
          <>
            <button className="btn primary" onClick={loadDoc} disabled={busy || !file}>
              <Icon name="search" size={15} /> {t("import.readDoc")}
            </button>
            <p className="muted small" style={{ marginTop: "var(--sp-2)" }}>{t("import.docHint")}</p>
          </>
        )}
        <div className="row" style={{ display: mode === "csv" ? undefined : "none" }}>
          {presets.length > 0 && (
            <label className="grow">
              <span>{t("import.preset")}</span>
              <select defaultValue="" onChange={(e) => applyPreset(e.target.value)}>
                <option value="">{t("import.templateManual")}</option>
                {presets.map((p, i) => <option key={i} value={i}>{p.name}</option>)}
              </select>
            </label>
          )}
          {templates.length > 0 && (
            <label className="grow">
              <span>{t("import.template")}</span>
              <select defaultValue="" onChange={(e) => applyTemplate(e.target.value)}>
                <option value="">{t("import.templateManual")}</option>
                {templates.map((tp) => <option key={tp.id} value={tp.id}>{tp.name}</option>)}
              </select>
            </label>
          )}
        </div>
      </div>

      {/* Schritt 2: Format (nur CSV) */}
      {mode === "csv" && (
      <div className="card">
        <h2>{t("import.step2")}</h2>
        <div className="row">
          <label>
            <span>{t("import.delimiter")}</span>
            <select value={config.delimiter} onChange={(e) => setCfg({ delimiter: e.target.value })}>
              <option value=";">Semikolon ;</option>
              <option value=",">Komma ,</option>
              <option value={"\t"}>Tab</option>
            </select>
          </label>
          <label>
            <span>{t("import.decimal")}</span>
            <select value={config.decimal_sep} onChange={(e) => setCfg({ decimal_sep: e.target.value })}>
              <option value=",">Komma (1.234,56)</option>
              <option value=".">Punkt (1,234.56)</option>
            </select>
          </label>
          <label>
            <span>{t("import.dateFormat")}</span>
            <select value={config.date_format} onChange={(e) => setCfg({ date_format: e.target.value })}>
              {DATE_FORMATS.map((f) => <option key={f.v} value={f.v}>{f.l}</option>)}
            </select>
          </label>
        </div>
        <div className="row">
          <label>
            <span>{t("import.encoding")}</span>
            <select value={config.encoding} onChange={(e) => setCfg({ encoding: e.target.value })}>
              <option value="utf-8">UTF-8</option>
              <option value="latin-1">ISO-8859-1 / Latin-1</option>
              <option value="cp1252">Windows-1252</option>
            </select>
          </label>
          <label>
            <span>{t("import.amountMode")}</span>
            <select value={config.amount_mode} onChange={(e) => setCfg({ amount_mode: e.target.value })}>
              <option value="signed">{t("import.modeSigned")}</option>
              <option value="debit_credit">{t("import.modeDebitCredit")}</option>
              <option value="abs_expense">{t("import.modeAbsExpense")}</option>
            </select>
          </label>
          <label style={{ maxWidth: 160 }}>
            <span>{t("import.skipRows")}</span>
            <input type="number" min="0" value={config.skip_rows}
                   onChange={(e) => setCfg({ skip_rows: Math.max(0, Number(e.target.value) || 0) })} />
          </label>
          <label className="checkline" style={{ alignSelf: "flex-end", marginBottom: 14 }}>
            <input type="checkbox" checked={config.has_header}
                   onChange={(e) => setCfg({ has_header: e.target.checked })} />
            <span>{t("import.hasHeader")}</span>
          </label>
        </div>
        <button className="btn" onClick={loadRaw} disabled={busy || !file}>
          <Icon name="search" size={15} /> {t("import.readFile")}
        </button>
      </div>
      )}

      {/* Extrahierter Text (PDF/Bild) */}
      {mode === "doc" && docText && (
        <div className="card">
          <details>
            <summary className="muted">{t("import.extractedText")}</summary>
            <pre className="doc-text">{docText}</pre>
          </details>
        </div>
      )}

      {/* Schritt 3: Spaltenzuordnung */}
      {raw && (
        <div className="card">
          <h2>{t("import.step3")}</h2>
          <div className="table-scroll">
            <table className="table raw-table">
              <thead>
                <tr>{colOptions.map((c) => <th key={c.i}>{c.label}</th>)}</tr>
              </thead>
              <tbody>
                {raw.rows.map((r, ri) => (
                  <tr key={ri}>{colOptions.map((c) => <td key={c.i}>{r[c.i] ?? ""}</td>)}</tr>
                ))}
              </tbody>
            </table>
          </div>

          <div className="map-grid">
            {[
              ["date", t("import.colDate"), true],
              ...(config.amount_mode === "debit_credit"
                ? [["debit", t("import.colDebit"), true], ["credit", t("import.colCredit"), true]]
                : [["amount", t("import.colAmount"), true]]),
              ["payee", t("import.colPayee"), false],
              ["purpose", t("import.colPurpose"), false],
              ["counterparty_iban", t("import.colIban"), false],
            ].map(([field, label]) => (
              <label key={field}>
                <span>{label}</span>
                <select value={config.column_map[field] ?? ""} onChange={(e) => setCol(field, e.target.value)}>
                  <option value="">—</option>
                  {colOptions.map((c) => <option key={c.i} value={c.i}>{c.label}</option>)}
                </select>
              </label>
            ))}
          </div>

          <div className="field-inline" style={{ marginTop: "var(--sp-3)" }}>
            <button className="btn primary" onClick={loadPreview} disabled={busy}>
              <Icon name="chevron-right" size={15} /> {t("import.makePreview")}
            </button>
            <div className="input-with-button" style={{ maxWidth: 320 }}>
              <input placeholder={t("import.templateName")} value={saveName} onChange={(e) => setSaveName(e.target.value)} />
              <button className="btn sm" onClick={saveTemplate}>{t("import.saveTemplate")}</button>
            </div>
          </div>
        </div>
      )}

      {/* Schritt 4: Prüfansicht */}
      {rows && (
        <div className="card">
          <div className="page-head">
            <h2 style={{ margin: 0 }}>{t("import.step4")}</h2>
            <button className="btn primary" onClick={commit} disabled={busy || includeCount === 0}>
              <Icon name="download" size={15} /> {t("import.commit", { n: includeCount })}
            </button>
          </div>
          <div className="table-scroll">
            <table className="table">
              <thead>
                <tr>
                  <th></th>
                  <th>{t("transactions.date")}</th>
                  <th>{t("transactions.amount")}</th>
                  <th>{t("import.typeCol")}</th>
                  <th>{t("import.payeeCol")}</th>
                  <th>{t("transactions.category")}</th>
                </tr>
              </thead>
              <tbody>
                {rows.map((r, idx) => (
                  <tr key={idx} className={!r.valid ? "row-invalid" : r.is_duplicate ? "row-dup" : ""}>
                    <td>
                      <input type="checkbox" checked={!!r.include} disabled={!r.valid}
                             onChange={(e) => updateRow(idx, { include: e.target.checked })} style={{ width: "auto" }} />
                    </td>
                    <td className="nowrap">{r.date ? formatDate(r.date) : <span className="amount neg">{t("import.badDate")}</span>}</td>
                    <td className="nowrap">
                      <span className={`amount ${(r.amount_cents || 0) < 0 ? "neg" : "pos"}`}>
                        {formatMoney(Math.abs(r.amount_cents || 0), acc?.currency || "EUR")}
                      </span>
                    </td>
                    <td>
                      <select value={r.type} onChange={(e) => updateRow(idx, { type: e.target.value })} style={{ minWidth: 110 }}>
                        <option value="expense">{t("transactions.expense")}</option>
                        <option value="income">{t("transactions.income")}</option>
                        <option value="transfer">{t("transactions.transfer")}</option>
                      </select>
                    </td>
                    <td className="ellipsis" style={{ maxWidth: 200 }}>
                      {r.payee || r.purpose || ""}
                      {r.is_duplicate && <span className="badge" style={{ marginLeft: 6 }}>{t("import.duplicate")}</span>}
                    </td>
                    <td>
                      {r.type === "transfer" ? (
                        <select value={r.to_account_id || ""} onChange={(e) => updateRow(idx, { to_account_id: e.target.value ? Number(e.target.value) : null })} style={{ minWidth: 150 }}>
                          <option value="">{t("import.chooseAccount")}</option>
                          {accounts.filter((a) => a.id !== Number(accountId)).map((a) => <option key={a.id} value={a.id}>{a.name}</option>)}
                        </select>
                      ) : (
                        <select value={r.category_id || ""} onChange={(e) => updateRow(idx, { category_id: e.target.value ? Number(e.target.value) : null })} style={{ minWidth: 150 }}>
                          <option value="">{t("transactions.uncategorized")}</option>
                          {(r.type === "income" ? incomeGroups : expenseGroups).map((g) => (
                            <optgroup key={g.id} label={g.name}>
                              {g.categories.map((c) => <option key={c.id} value={c.id}>{c.name}</option>)}
                            </optgroup>
                          ))}
                        </select>
                      )}
                    </td>
                  </tr>
                ))}
              </tbody>
            </table>
          </div>
        </div>
      )}

      {/* Verlauf */}
      {batches.length > 0 && (
        <div className="card">
          <h2>{t("import.history")}</h2>
          <table className="table">
            <tbody>
              {batches.map((b) => (
                <tr key={b.id} className={b.status === "undone" ? "row-dup" : ""}>
                  <td><strong>{b.filename || "—"}</strong> <span className="muted small">{accountById[b.account_id]?.name}</span></td>
                  <td className="nowrap">{formatDate(b.created_at)}</td>
                  <td className="nowrap">{t("import.importedCount", { n: b.imported_count })}</td>
                  <td style={{ textAlign: "right" }}>
                    {b.status === "committed" ? (
                      <button className="btn sm danger" onClick={() => undo(b)}>
                        <Icon name="refresh-ccw" size={14} /> {t("import.undo")}
                      </button>
                    ) : <span className="muted small">{t("import.undone")}</span>}
                  </td>
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      )}
    </div>
  );
}