import { useEffect, useState } from "react";
import { useTranslation } from "react-i18next";
import {
  ApiError,
  createSubscriptionPlan,
  deleteSubscriptionPlan,
  fetchSubscriptionPlans,
  fetchSubscriptions,
  reactivateSubscriptionPlan,
  retireSubscriptionPlan,
  type PlanTimeframes,
  type Subscription,
  type SubscriptionPeriod,
  type SubscriptionPlan,
} from "./api.js";
import { Modal } from "./ui/Modal.js";
import { formatDate } from "./lib/format.js";
import { currencyOptions } from "./lib/currencies.js";

// Admin-only subscription PLAN catalog. Plans are admin-composed, versioned config the
// operator sells from (so the operator never types a price). Editing a plan PUBLISHES A
// NEW VERSION (new effectiveFrom) — past sales keep their recorded version. Retire is
// soft (active=0). Mirrors the tariff composer. See wiki/entities/subscription.md.

const DEFAULT_CURRENCY = "ALL";
const PERIODS: SubscriptionPeriod[] = ["day", "week", "month"];
const PERIOD_KEY: Record<SubscriptionPeriod, string> = {
  day: "subs.perDay",
  week: "subs.perWeek",
  month: "subs.perMonth",
};

const STATUS_KEY: Record<Subscription["status"], string> = {
  active: "subs.statusActive",
  suspended: "subs.statusSuspended",
  revoked: "subs.statusRevoked",
};

/** minutes-of-day → "HH:MM" for the timeframes summary. */
function fmtMin(min: number): string {
  return `${String(Math.floor(min / 60)).padStart(2, "0")}:${String(min % 60).padStart(2, "0")}`;
}

/** A compact human summary of a plan's timeframes, e.g. "Mon–Fri 21:00–08:00" or "24/7".
 *  Uses the shared tariff.dow labels for day names. */
function timeframesSummary(tf: PlanTimeframes | null | undefined, t: (k: string) => string): string {
  if (!tf) return t("plans.allHours"); // 24/7
  const days = tf.days && tf.days.length > 0 ? tf.days : [0, 1, 2, 3, 4, 5, 6];
  // Render selected days Monday-first; collapse to a range label only when contiguous
  // Mon–Fri / Sat–Sun for the common cases, else list them.
  const set = new Set(days);
  const isWeekdays = [1, 2, 3, 4, 5].every((d) => set.has(d)) && ![0, 6].some((d) => set.has(d));
  const dayLabel = isWeekdays
    ? `${t("tariff.dow1")}–${t("tariff.dow5")}`
    : [1, 2, 3, 4, 5, 6, 0].filter((d) => set.has(d)).map((d) => t(`tariff.dow${d}`)).join(",");
  return `${dayLabel} ${fmtMin(tf.fromMin)}–${fmtMin(tf.toMin)}`;
}

// Day-of-week picker, Monday-first (mirrors the tariff composer). Labels come from the
// shared tariff.dow0..6 i18n keys (Hën..Die / Mon..Sun).
const DOW_ORDER = [1, 2, 3, 4, 5, 6, 0];

interface PlanForm {
  planId: string; // blank on a brand-new plan; set when publishing a new version
  name: string;
  period: SubscriptionPeriod;
  priceMajor: string;
  currency: string;
  // Timeframes (tariff bridge). Off → 24/7. On → an allowed window (enter-after /
  // exit-before as HH:MM) on the SELECTED days (0=Sun..6=Sat); on unselected days the
  // subscriber parks free. Plus grace minutes.
  restrictTimes: boolean;
  days: number[]; // days the window applies to; empty = every day
  winFrom: string; // window opens (HH:MM) — when the subscriber may enter
  winTo: string; // window closes (HH:MM) — by when they should exit
  graceMin: string;
}

function emptyForm(): PlanForm {
  return {
    planId: "",
    name: "",
    period: "month",
    priceMajor: "",
    currency: DEFAULT_CURRENCY,
    restrictTimes: false,
    days: [1, 2, 3, 4, 5], // default Mon–Fri (the common "night plan, free weekends")
    winFrom: "20:00",
    winTo: "08:00",
    graceMin: "0",
  };
}

/** "HH:MM" → minutes-of-day, or null if blank/invalid. */
function hhmmToMin(s: string): number | null {
  const m = /^(\d{1,2}):(\d{2})$/.exec(s.trim());
  if (!m) return null;
  const min = Number(m[1]) * 60 + Number(m[2]);
  return min >= 0 && min <= 1439 ? min : null;
}
/** minutes-of-day → "HH:MM". */
function minToHHMM(min: number): string {
  return `${String(Math.floor(min / 60)).padStart(2, "0")}:${String(min % 60).padStart(2, "0")}`;
}

export function SubscriptionPlansManager() {
  const { t } = useTranslation();
  const [plans, setPlans] = useState<SubscriptionPlan[] | null>(null);
  const [subs, setSubs] = useState<Subscription[]>([]);
  const [expanded, setExpanded] = useState<string | null>(null); // planId whose subscribers are shown
  const [form, setForm] = useState<PlanForm | null>(null);
  const [msg, setMsg] = useState<{ kind: "ok" | "err"; text: string } | null>(null);

  function reload() {
    // ?all=1 → every version (history), so the admin sees superseded prices too.
    fetchSubscriptionPlans(true)
      .then((r) => setPlans(r.plans))
      .catch((e) => setMsg({ kind: "err", text: (e as Error).message }));
    // Subscriptions carry planId — group them to show "who depends on this plan".
    fetchSubscriptions()
      .then((r) => setSubs(r.subscriptions))
      .catch(() => {
        /* non-fatal — counts just won't show */
      });
  }
  useEffect(reload, []);

  // Subscribers per planId (active first), for the count badge + expandable list.
  function subscribersOf(planId: string): Subscription[] {
    return subs.filter((s) => s.planId === planId);
  }

  async function save() {
    if (!form) return;
    setMsg(null);
    const major = Number(form.priceMajor);
    if (!form.name.trim()) return setMsg({ kind: "err", text: t("plans.needName") });
    if (!Number.isFinite(major) || major <= 0) return setMsg({ kind: "err", text: t("plans.needPrice") });
    // Build the timeframes blob from the form (null = 24/7). The window [winFrom, winTo)
    // (wraps midnight for a night plan) applies on the SELECTED days; unselected days are
    // unrestricted. Empty days = every day. The server stamps the site tz.
    let timeframes = null as Parameters<typeof createSubscriptionPlan>[0]["timeframes"];
    if (form.restrictTimes) {
      const from = hhmmToMin(form.winFrom);
      const to = hhmmToMin(form.winTo);
      if (from == null || to == null) return setMsg({ kind: "err", text: t("plans.needWindow") });
      if (form.days.length === 0) return setMsg({ kind: "err", text: t("plans.needDays") });
      timeframes = {
        days: [...form.days].sort((a, b) => a - b),
        fromMin: from,
        toMin: to,
        graceMin: Math.max(0, Math.round(Number(form.graceMin) || 0)),
      };
    }
    try {
      await createSubscriptionPlan({
        planId: form.planId.trim() || undefined,
        name: form.name.trim(),
        period: form.period,
        pricePerPeriodMinor: Math.round(major * 100),
        currency: form.currency.trim() || DEFAULT_CURRENCY,
        timeframes,
      });
      setForm(null);
      reload();
      setMsg({ kind: "ok", text: t("plans.saved") });
    } catch (e) {
      const problems = e instanceof ApiError ? (e as ApiError & { problems?: string[] }).problems : undefined;
      setMsg({ kind: "err", text: problems?.length ? `${(e as Error).message}: ${problems.join("; ")}` : (e as Error).message });
    }
  }

  async function retire(p: SubscriptionPlan) {
    if (!confirm(t("plans.confirmRetire", { name: p.name }))) return;
    await retireSubscriptionPlan(p.planId).catch((e) => setMsg({ kind: "err", text: (e as Error).message }));
    reload();
  }
  async function reactivate(p: SubscriptionPlan) {
    setMsg(null);
    try {
      await reactivateSubscriptionPlan(p.planId);
      setMsg({ kind: "ok", text: t("plans.reactivated", { name: p.name }) });
      reload();
    } catch (e) {
      setMsg({ kind: "err", text: (e as Error).message });
    }
  }
  async function del(p: SubscriptionPlan) {
    if (!confirm(t("plans.confirmDelete", { name: p.name }))) return;
    setMsg(null);
    try {
      await deleteSubscriptionPlan(p.planId);
      setMsg({ kind: "ok", text: t("plans.deleted", { name: p.name }) });
      reload();
    } catch (e) {
      // 409 → plan is in use; explain why it can't be deleted (retire instead).
      const inUse = e instanceof ApiError && e.status === 409;
      setMsg({ kind: "err", text: inUse ? t("plans.deleteInUse") : (e as Error).message });
    }
  }

  /** Publish a new version of an existing plan (pre-fills its identity + last values). */
  function newVersionOf(p: SubscriptionPlan) {
    const tf = p.timeframes ?? null;
    setForm({
      planId: p.planId,
      name: p.name,
      period: p.period,
      priceMajor: String(p.pricePerPeriodMinor / 100),
      currency: p.currency,
      restrictTimes: tf != null,
      days: tf?.days && tf.days.length > 0 ? [...tf.days] : [1, 2, 3, 4, 5],
      winFrom: tf?.fromMin != null ? minToHHMM(tf.fromMin) : "20:00",
      winTo: tf?.toMin != null ? minToHHMM(tf.toMin) : "08:00",
      graceMin: String(tf?.graceMin ?? 0),
    });
    setMsg(null);
  }

  if (!plans) return null;

  // GROUP versions by planId; the newest version (plans come newest-first) represents the
  // plan in the list. A planId is "in force" when its versions are active; "retired"
  // otherwise. One card per planId — avoids the cramped multi-version table.
  const now = new Date().toISOString();
  const groups: { planId: string; head: SubscriptionPlan; active: boolean; versions: number }[] = [];
  const seen = new Map<string, number>();
  for (const p of plans) {
    const idx = seen.get(p.planId);
    if (idx == null) {
      seen.set(p.planId, groups.length);
      groups.push({ planId: p.planId, head: p, active: p.active && p.effectiveFrom <= now, versions: 1 });
    } else {
      groups[idx]!.versions += 1;
      if (p.active && p.effectiveFrom <= now) groups[idx]!.active = true;
    }
  }

  return (
    <section className="px-4 py-6">
      <div className="mb-3 flex items-center justify-between">
        <h3 className="text-[0.8125rem] font-semibold uppercase tracking-wider text-term-muted">{t("plans.title")}</h3>
        <button type="button" className="btn btn-go btn-sm" onClick={() => setForm(emptyForm())}>
          {t("plans.add")}
        </button>
      </div>
      <p className="mb-3 text-[0.75rem] text-term-muted">{t("plans.intro")}</p>

      {msg && (
        <div className={`mb-3 text-[0.75rem] ${msg.kind === "ok" ? "text-term-green" : "text-term-red"}`}>{msg.text}</div>
      )}

      {groups.length === 0 ? (
        <p className="text-[0.8125rem] text-term-muted">{t("plans.noneYet")}</p>
      ) : (
        <div className="flex flex-col gap-2">
          {groups.map(({ planId, head: p, active, versions }) => {
            const users = subscribersOf(planId);
            const activeUsers = users.filter((s) => s.status === "active");
            const isOpen = expanded === planId;
            const canDelete = users.length === 0; // no sale references it → safe to delete
            return (
              <div key={planId} className={`card p-3 ${active ? "" : "opacity-70"}`}>
                {/* Header: name + status badge */}
                <div className="flex flex-wrap items-center gap-x-2 gap-y-1">
                  <span className="font-semibold text-term-text">{p.name}</span>
                  {active ? (
                    <span className="rounded border border-term-green px-1 text-[0.625rem] text-term-green">{t("plans.inForce")}</span>
                  ) : (
                    <span className="rounded border border-term-border px-1 text-[0.625rem] text-term-muted">{t("plans.retired")}</span>
                  )}
                  {versions > 1 && <span className="text-[0.625rem] text-term-muted">{t("plans.versionCount", { count: versions })}</span>}
                </div>

                {/* Details: price · hours · effective */}
                <div className="mt-1 flex flex-wrap gap-x-4 gap-y-0.5 text-[0.75rem] text-term-muted">
                  <span className="tabular-nums text-term-text">
                    {(p.pricePerPeriodMinor / 100).toLocaleString()} {p.currency} / {t(PERIOD_KEY[p.period])}
                  </span>
                  <span>{timeframesSummary(p.timeframes, t)}</span>
                  <span>{t("plans.colEffective")}: {formatDate(p.effectiveFrom, t)}</span>
                </div>

                {/* Used by */}
                <div className="mt-1 text-[0.75rem]">
                  {users.length > 0 ? (
                    <button
                      type="button"
                      className="text-term-cyan hover:underline tabular-nums"
                      onClick={() => setExpanded(isOpen ? null : planId)}
                      title={t("plans.usedByTitle")}
                    >
                      {t("plans.colUsedBy")}: {t("plans.usedByCount", { active: activeUsers.length, total: users.length })} {isOpen ? "▾" : "▸"}
                    </button>
                  ) : (
                    <span className="text-term-muted">{t("plans.colUsedBy")}: {t("plans.usedByNone")}</span>
                  )}
                </div>
                {isOpen && users.length > 0 && (
                  <ul className="mt-1 flex flex-wrap gap-x-4 gap-y-1 rounded-term bg-term-bg px-3 py-2 text-[0.75rem]">
                    {users.map((s) => (
                      <li key={s.id} className={s.status === "active" ? "text-term-text" : "text-term-muted"}>
                        {s.holderName || t("subs.unnamed")}
                        {s.quantity > 1 && <span className="text-term-muted"> ×{s.quantity}</span>}
                        {s.status !== "active" && <span className="ml-1 text-[0.625rem]">({t(STATUS_KEY[s.status])})</span>}
                      </li>
                    ))}
                  </ul>
                )}

                {/* Actions — own row, never overlapping */}
                <div className="mt-2 flex flex-wrap gap-1.5 border-t border-term-border pt-2">
                  {active ? (
                    <>
                      <button type="button" className="btn btn-sm" onClick={() => newVersionOf(p)}>{t("plans.newVersion")}</button>
                      <button type="button" className="btn btn-sm btn-danger" onClick={() => retire(p)}>{t("plans.retire")}</button>
                    </>
                  ) : (
                    <button type="button" className="btn btn-go btn-sm" onClick={() => reactivate(p)}>{t("plans.reactivate")}</button>
                  )}
                  {canDelete && (
                    <button
                      type="button"
                      className="btn btn-sm btn-danger"
                      onClick={() => del(p)}
                      title={t("plans.deleteTitle")}
                    >
                      {t("plans.delete")}
                    </button>
                  )}
                </div>
              </div>
            );
          })}
        </div>
      )}

      <Modal open={form != null} onClose={() => setForm(null)} title={form?.planId ? t("plans.newVersionTitle") : t("plans.newTitle")} width="max-w-lg">
        {form && (
          <>
            <div className="grid grid-cols-[max-content_1fr] items-center gap-x-4 gap-y-2">
              <label className="label">{t("plans.colName")}</label>
              <input className="input" value={form.name} onChange={(e) => setForm((f) => f && { ...f, name: e.target.value })} placeholder={t("plans.namePlaceholder")} />
              <label className="label">{t("plans.period")}</label>
              <select className="select input w-auto" value={form.period} onChange={(e) => setForm((f) => f && { ...f, period: e.target.value as SubscriptionPeriod })}>
                {PERIODS.map((p) => (
                  <option key={p} value={p}>{t(PERIOD_KEY[p])}</option>
                ))}
              </select>
              <label className="label">{t("plans.pricePer")}</label>
              <span className="flex items-center gap-2">
                <input className="input w-28" value={form.priceMajor} inputMode="decimal" onChange={(e) => setForm((f) => f && { ...f, priceMajor: e.target.value })} placeholder="e.g. 800" />
                <select className="input w-auto" value={form.currency} onChange={(e) => setForm((f) => f && { ...f, currency: e.target.value })}>
                  {currencyOptions(form.currency).map((c) => (
                    <option key={c} value={c}>{c}</option>
                  ))}
                </select>
                <span className="text-[0.75rem] text-term-muted">/ {t(PERIOD_KEY[form.period])}</span>
              </span>
            </div>

            {/* Timeframes (tariff bridge): restrict WHEN a subscriber may park. Outside the
                window they're charged the transient tariff for the gap. Off = 24/7. */}
            <div className="mt-3 border-t border-term-border pt-3">
              <label className="flex items-center gap-2 text-[0.75rem] text-term-text">
                <input
                  type="checkbox"
                  className="accent-term-amber"
                  checked={form.restrictTimes}
                  onChange={(e) => setForm((f) => f && { ...f, restrictTimes: e.target.checked })}
                />
                {t("plans.restrictTimes")}
              </label>
              {form.restrictTimes && (
                <div className="mt-2 grid grid-cols-[max-content_1fr] items-center gap-x-4 gap-y-2">
                  <label className="label">{t("plans.days")}</label>
                  <span className="flex flex-wrap gap-2">
                    {DOW_ORDER.map((d) => (
                      <label key={d} className="inline-flex items-center gap-1 text-[0.75rem] text-term-text">
                        <input
                          type="checkbox"
                          className="accent-term-amber"
                          checked={form.days.includes(d)}
                          onChange={() =>
                            setForm((f) =>
                              f && { ...f, days: f.days.includes(d) ? f.days.filter((x) => x !== d) : [...f.days, d] },
                            )
                          }
                        />
                        {t(`tariff.dow${d}`)}
                      </label>
                    ))}
                  </span>
                  <label className="label">{t("plans.window")}</label>
                  <span className="flex flex-wrap items-center gap-2 text-[0.75rem] text-term-muted">
                    {t("plans.enterAfter")}
                    <input type="time" className="input w-28" value={form.winFrom} onChange={(e) => setForm((f) => f && { ...f, winFrom: e.target.value })} />
                    {t("plans.exitBefore")}
                    <input type="time" className="input w-28" value={form.winTo} onChange={(e) => setForm((f) => f && { ...f, winTo: e.target.value })} />
                  </span>
                  <label className="label">{t("plans.grace")}</label>
                  <span className="flex items-center gap-2">
                    <input className="input w-16" value={form.graceMin} inputMode="numeric" onChange={(e) => setForm((f) => f && { ...f, graceMin: e.target.value })} />
                    <span className="text-[0.75rem] text-term-muted">{t("plans.graceHint")}</span>
                  </span>
                </div>
              )}
              <p className="mt-1.5 text-[0.6875rem] text-term-muted">{t("plans.timeframesHint")}</p>
            </div>

            {form.planId && <p className="mt-2 text-[0.6875rem] text-term-amber">{t("plans.newVersionHint")}</p>}
            <div className="mt-4 flex justify-end gap-2">
              <button type="button" className="btn btn-sm" onClick={() => setForm(null)}>{t("subs.cancel")}</button>
              <button type="button" className="btn btn-go btn-sm" onClick={save}>{t("subs.save")}</button>
            </div>
          </>
        )}
      </Modal>
    </section>
  );
}