import { useEffect, useMemo, useState } from "react";
import { useTranslation } from "react-i18next";
import {
  fetchUsers,
  saveValidationProgram,
  type ManagedUser,
  type ValidationMode,
  type ValidationProgramView,
} from "./api.js";

// The /setup/site RIGHT panel: per-station merchant-validation config (Bar / Lavazh).
// The checkboxes on the left card toggle a station's `active`; this panel edits the
// enabled stations' programs — one panel, tabs when both are on. Storage is generic
// (validation_programs rows keyed "bar"/"lavazh"); the UI is deliberately these two
// fixed stations. Amounts are entered in MAJOR units and stored in integer minor
// units (the tariff-composer convention). See wiki/concepts/validation-discounts.md.

/** The two well-known stations the checkboxes toggle. */
export const STATIONS = ["bar", "lavazh"] as const;
export type StationId = (typeof STATIONS)[number];

/** A blank program draft for a station enabled for the first time. */
export function defaultProgram(id: StationId, label: string): Omit<ValidationProgramView, "id"> {
  return {
    name: label,
    mode: "comp",
    minutes: null,
    percent: null,
    maxAmountMinor: null,
    maxPerDay: null,
    active: true,
    userIds: [],
  };
}

const toMinor = (s: string): number | null => {
  const v = s.trim();
  if (v === "") return null;
  const n = Number(v);
  return Number.isFinite(n) && n > 0 ? Math.round(n * 100) : null;
};
const fromMinor = (m: number | null): string => (m == null ? "" : String(m / 100));
const toInt = (s: string): number | null => {
  const v = s.trim();
  if (v === "") return null;
  const n = Number(v);
  return Number.isInteger(n) && n > 0 ? n : null;
};

function StationForm({
  program,
  onSaved,
}: {
  program: ValidationProgramView;
  onSaved: (p: ValidationProgramView) => void;
}) {
  const { t } = useTranslation();
  const [name, setName] = useState(program.name);
  const [mode, setMode] = useState<ValidationMode>(program.mode);
  const [minutes, setMinutes] = useState(program.minutes == null ? "" : String(program.minutes));
  const [percent, setPercent] = useState(program.percent == null ? "" : String(program.percent));
  const [maxAmount, setMaxAmount] = useState(fromMinor(program.maxAmountMinor));
  const [maxPerDay, setMaxPerDay] = useState(program.maxPerDay == null ? "" : String(program.maxPerDay));
  const [userIds, setUserIds] = useState<Set<string>>(new Set(program.userIds));
  const [users, setUsers] = useState<ManagedUser[] | null>(null);
  const [msg, setMsg] = useState<string | null>(null);

  // Reset the form when the tab switches to another station.
  useEffect(() => {
    setName(program.name);
    setMode(program.mode);
    setMinutes(program.minutes == null ? "" : String(program.minutes));
    setPercent(program.percent == null ? "" : String(program.percent));
    setMaxAmount(fromMinor(program.maxAmountMinor));
    setMaxPerDay(program.maxPerDay == null ? "" : String(program.maxPerDay));
    setUserIds(new Set(program.userIds));
    setMsg(null);
  }, [program.id]); // eslint-disable-line react-hooks/exhaustive-deps

  useEffect(() => {
    fetchUsers()
      .then((r) => setUsers(r.users))
      .catch(() => setUsers([]));
  }, []);

  const valid = useMemo(() => {
    if (!name.trim()) return false;
    if (mode === "timeCredit") return toInt(minutes) != null;
    if (mode === "percent") {
      const p = toInt(percent);
      return p != null && p <= 100;
    }
    if (mode === "fixed") return toMinor(maxAmount) != null;
    return true;
  }, [name, mode, minutes, percent, maxAmount]);

  async function save() {
    setMsg(null);
    try {
      const saved = await saveValidationProgram(program.id, {
        name: name.trim(),
        mode,
        minutes: mode === "timeCredit" ? toInt(minutes) : null,
        percent: mode === "percent" ? toInt(percent) : null,
        maxAmountMinor: mode === "fixed" ? toMinor(maxAmount) : null,
        maxPerDay: toInt(maxPerDay),
        active: program.active,
        userIds: [...userIds],
      });
      onSaved(saved);
      setMsg(t("val.saved"));
    } catch (e) {
      setMsg((e as Error).message);
    }
  }

  const toggleUser = (id: string) =>
    setUserIds((prev) => {
      const next = new Set(prev);
      next.has(id) ? next.delete(id) : next.add(id);
      return next;
    });

  return (
    <div className="mt-3 grid gap-3">
      <div className="field">
        <span className="label">{t("val.labelName")}</span>
        <input className="input" value={name} onChange={(e) => setName(e.target.value)} placeholder={t("val.labelNamePh")} />
      </div>
      <div className="field">
        <span className="label">{t("val.mode")}</span>
        <select className="input w-fit" value={mode} onChange={(e) => setMode(e.target.value as ValidationMode)}>
          <option value="comp">{t("val.modeComp")}</option>
          <option value="timeCredit">{t("val.modeTimeCredit")}</option>
          <option value="fixed">{t("val.modeFixed")}</option>
          <option value="percent">{t("val.modePercent")}</option>
        </select>
      </div>
      {mode === "timeCredit" && (
        <div className="field">
          <span className="label">{t("val.minutes")}</span>
          <input className="input w-32" value={minutes} onChange={(e) => setMinutes(e.target.value)} placeholder="60" />
        </div>
      )}
      {mode === "percent" && (
        <div className="field">
          <span className="label">{t("val.percent")}</span>
          <input className="input w-32" value={percent} onChange={(e) => setPercent(e.target.value)} placeholder="100" />
        </div>
      )}
      {mode === "fixed" && (
        <div className="field">
          <span className="label">{t("val.maxAmount")}</span>
          <input className="input w-32" value={maxAmount} onChange={(e) => setMaxAmount(e.target.value)} placeholder="1000" />
        </div>
      )}
      <div className="field">
        <span className="label">{t("val.maxPerDay")}</span>
        <input className="input w-32" value={maxPerDay} onChange={(e) => setMaxPerDay(e.target.value)} />
      </div>
      <div>
        <div className="label">{t("val.users")}</div>
        <span className="hint block">{t("val.usersHint")}</span>
        <div className="mt-1 grid gap-1">
          {users == null ? (
            <span className="text-term-muted">…</span>
          ) : users.length === 0 ? (
            <span className="text-[0.75rem] text-term-muted">{t("val.noUsers")}</span>
          ) : (
            users.map((u) => (
              <label key={u.id} className="flex items-center gap-2 text-[0.75rem] text-term-text">
                <input
                  type="checkbox"
                  className="accent-term-amber"
                  checked={userIds.has(u.id)}
                  onChange={() => toggleUser(u.id)}
                />
                {u.username}
                {u.fullName && <span className="text-term-muted">({u.fullName})</span>}
              </label>
            ))
          )}
        </div>
      </div>
      <div className="flex items-center gap-3">
        <button type="button" className="btn btn-primary btn-sm" disabled={!valid} onClick={save}>
          {t("site.save")}
        </button>
        {msg && <span className="text-[0.75rem] text-term-muted">{msg}</span>}
      </div>
    </div>
  );
}

/** The right-column panel: tabs across the ENABLED stations, one form each. */
export function ValidationStationsPanel({
  programs,
  onSaved,
}: {
  programs: ValidationProgramView[];
  onSaved: (p: ValidationProgramView) => void;
}) {
  const { t } = useTranslation();
  const enabled = STATIONS.map((id) => programs.find((p) => p.id === id)).filter(
    (p): p is ValidationProgramView => p != null && p.active,
  );
  const [tab, setTab] = useState<string | null>(null);
  const current = enabled.find((p) => p.id === tab) ?? enabled[0];
  if (!current) return null;

  return (
    <section className="card w-full max-w-md p-4">
      <div className="text-[0.6875rem] uppercase tracking-wider text-term-muted">{t("val.sectionTitle")}</div>
      {enabled.length > 1 && (
        <div className="mt-2 flex gap-1">
          {enabled.map((p) => (
            <button
              key={p.id}
              type="button"
              className={`btn btn-sm ${p.id === current.id ? "btn-primary" : "btn-ghost"}`}
              onClick={() => setTab(p.id)}
            >
              {t(p.id === "bar" ? "val.enableBar" : "val.enableLavazh")}
            </button>
          ))}
        </div>
      )}
      <StationForm program={current} onSaved={onSaved} />
    </section>
  );
}