import { useEffect, useState } from "react";
import { useTranslation } from "react-i18next";
import { ApiError, fetchTariff, publishTariffVersion, type TariffState, type TariffVersion } from "./api.js";
import { TariffEditorForm, emptyForm, formFromActive, formFromVersion, toStructure, type FormState } from "./TariffEditorForm.js";

// Tariff composer — the admin edits + publishes the LIVE rate card. Publishing
// creates a new IMMUTABLE version (the active card); old versions are kept so past
// sessions reprice correctly. A right sidebar lists the published history (named
// since 2026-07-05); clicking a version loads it into the editor as the STARTING
// POINT — publishing always creates a new version effective now, it never edits the
// clicked one. The form machinery is shared with the Tariff Lab's draft modal — see
// TariffEditorForm.tsx. To experiment without publishing, use the lab. See
// wiki/concepts/tariff.md.

export function TariffComposer() {
  const { t } = useTranslation();
  const [state, setState] = useState<TariffState | null>(null);
  const [form, setForm] = useState<FormState>(emptyForm);
  // Which published version the editor was last loaded from (sidebar highlight).
  const [loadedId, setLoadedId] = useState<string | null>(null);
  // Optional label for the version about to be published. Deliberately NOT prefilled
  // from the active version — a tweaked card republished under last season's name
  // would mislabel the history.
  const [versionName, setVersionName] = useState("");
  const [saving, setSaving] = useState(false);
  const [msg, setMsg] = useState<{ kind: "ok" | "err"; text: string } | null>(null);

  useEffect(() => {
    fetchTariff()
      .then((s) => {
        setState(s);
        setForm(formFromActive(s));
        setLoadedId(s.active?.id ?? null);
      })
      .catch((e) => setMsg({ kind: "err", text: (e as Error).message }));
  }, []);

  function loadVersion(v: TariffVersion) {
    setForm(formFromVersion(v.currency, v.structure));
    setLoadedId(v.id);
    setMsg(null);
  }

  async function publish() {
    setSaving(true);
    setMsg(null);
    try {
      await publishTariffVersion({
        currency: form.currency.trim().toUpperCase(),
        structure: toStructure(form),
        ...(versionName.trim() ? { name: versionName.trim() } : {}),
      });
      const fresh = await fetchTariff();
      setState(fresh);
      setLoadedId(fresh.active?.id ?? null);
      setVersionName("");
      setMsg({ kind: "ok", text: t("tariff.publishedOk") });
    } catch (e) {
      const text =
        e instanceof ApiError && e.problems?.length
          ? `${e.message}: ${e.problems.join("; ")}`
          : (e as Error).message;
      setMsg({ kind: "err", text });
    } finally {
      setSaving(false);
    }
  }

  return (
    <section className="px-4 py-6">
      <h2 className="mb-1 text-h4 font-semibold text-term-text">{t("tariff.title")}</h2>
      {!state?.active ? (
        <p className="mb-4 rounded-term border border-term-amber/50 bg-term-amber/10 px-3 py-2 text-[0.75rem] text-term-amber">
          {t("tariff.noRateCard")}
        </p>
      ) : (
        <p className="mb-4 text-[0.75rem] text-term-muted">
          {state.active.name ? `${state.active.name} — ` : ""}
          {t("tariff.activeSince", {
            date: new Date(state.active.effectiveFrom).toLocaleString(),
            count: state.versions.length,
          })}
        </p>
      )}

      <div className="flex flex-col gap-4 lg:flex-row">
        <div className="min-w-0 flex-1">
          <TariffEditorForm form={form} onChange={setForm} />

          <div className="mt-6 flex flex-wrap items-center gap-3">
            <input
              className="input w-64"
              value={versionName}
              onChange={(e) => setVersionName(e.target.value)}
              placeholder={t("tariff.versionNamePh")}
            />
            <button type="button" className="btn btn-primary btn-lg" onClick={publish} disabled={saving}>
              {saving ? t("tariff.publishing") : t("tariff.publishNewVersion")}
            </button>
            {msg && (
              <span className={msg.kind === "ok" ? "text-[0.75rem] text-term-green" : "text-[0.75rem] text-term-red"}>{msg.text}</span>
            )}
          </div>
        </div>

        {/* Published history — click a version to load it into the editor. Same list
            the lab's sidebar shows; here it seeds the next publish. */}
        {state && state.versions.length > 0 && (
          <aside className="w-full shrink-0 lg:w-72">
            <h3 className="mb-1 text-h6 font-semibold uppercase tracking-wider text-term-text">
              {t("tariff.versionsTitle")}
            </h3>
            <p className="hint mb-2">{t("tariff.versionsHint")}</p>
            <ul className="flex flex-col gap-1">
              {state.versions.map((v) => {
                const isActive = v.id === state.active?.id;
                return (
                  <li key={v.id}>
                    <button
                      type="button"
                      onClick={() => loadVersion(v)}
                      className={`w-full rounded-term border px-3 py-2 text-left text-[0.8125rem] ${
                        loadedId === v.id
                          ? "border-term-amber bg-term-amber/10 text-term-text"
                          : "border-term-border text-term-muted hover:text-term-text"
                      }`}
                    >
                      <span className="flex items-center gap-2 font-semibold">
                        {v.name ?? new Date(v.effectiveFrom).toLocaleString()}
                        {isActive && (
                          <span className="rounded border border-term-green px-1 text-[0.625rem] uppercase text-term-green">
                            {t("tariff.activeBadge")}
                          </span>
                        )}
                      </span>
                      <span className="block text-[0.6875rem] text-term-muted">
                        {v.name ? `${new Date(v.effectiveFrom).toLocaleString()} · ` : ""}
                        {v.currency}
                      </span>
                    </button>
                  </li>
                );
              })}
            </ul>
          </aside>
        )}
      </div>
    </section>
  );
}