"use client";

import { useState, useMemo, useRef, useEffect } from "react";
import { Shield, LayoutGrid, Sparkles, ChevronRight, TriangleAlert } from "lucide-react";
import { Sparkline } from "@/components/Sparkline";
import { ScrollFade } from "@/components/ScrollFade";
import { MONTH_NAMES } from "@/lib/data";
import type { InsuranceRow } from "@/lib/rows";
import type { RatePeriod } from "@/lib/insurance";
import { ZAR, ZAR2 } from "@/lib/utils";
import { VAT_NOTE } from "@/lib/insurance-rate-policy";

// Accent stays in the Running Costs family (#EDAE49) on purpose — Insurance is a
// sub-page of /running, not a sibling of it.
const ACCENT = "#EDAE49";

/** "Apr 2026 – current" for an open period, "Jan 2026 – Mar 2026" for a closed one. */
function periodLabel(p: RatePeriod): string {
  const from = `${MONTH_NAMES[p.from - 1]} 2026`;
  return p.to === 0 ? `${from} → current` : `${from} → ${MONTH_NAMES[p.to - 1]} 2026`;
}

/**
 * Sibling of `RunningView`: same toolbar, same card shape, same Cards/Grid pair, so
 * the two pages under Running Costs feel like one family.
 *
 * It is a client component for the view/sort/expand state only — every figure is
 * resolved on the server from the rate periods. Mobile checklist (AGENTS.md) is why
 * nothing drops below `text-[12px]` or `min-h-[44px]`, and why the wide grid table
 * scrolls inside its own container.
 */
export function InsuranceView({
  rows,
  totalMachines,
}: {
  rows: InsuranceRow[];
  totalMachines: number;
}) {
  // GRID opens first (client request, 2026-10-09). With Current / Previous / Year
  // total in five columns, the table reads as a register at a glance — where the card
  // list buried exactly those three figures behind a click, and a card per vehicle
  // only earns its keep when the month-by-month strip is what you came for.
  // Cards stay one tap away for anyone who wants the sparkline.
  const [view, setView] = useState<"cards" | "grid">("grid");
  const [sort, setSort] = useState<"ytd" | "code">("ytd");
  const [expanded, setExpanded] = useState<string | null>(null);

  const sorted = useMemo(
    () => [...rows].sort((a, b) => (sort === "ytd" ? b.ytd - a.ytd : a.code.localeCompare(b.code))),
    [rows, sort],
  );

  const grandTotal = rows.reduce((s, r) => s + r.ytd, 0);

  return (
    <>
      <div className="flex flex-col sm:flex-row sm:flex-wrap sm:items-center sm:justify-between gap-3 mb-5">
        <div className="flex items-center gap-2 text-xs text-gray-500 dark:text-gray-400 flex-wrap">
          <span className="px-2.5 py-1 rounded-md bg-[#EDAE49]/10 text-[#EDAE49] font-medium">
            {rows.length} of {totalMachines} vehicles insured
          </span>
          <span className="hidden md:inline">· sorted by {sort === "ytd" ? "total spend" : "code"}</span>
        </div>
        <div className="flex items-center gap-2 flex-wrap">
          <div className="flex items-center gap-1 p-0.5 rounded-lg bg-white dark:bg-white/5 border border-gray-200 dark:border-border">
            <button
              onClick={() => setView("cards")}
              aria-label="Cards view"
              className={`min-h-[44px] px-3 text-xs font-medium rounded-md transition flex items-center gap-1.5 ${
                view === "cards"
                  ? "bg-[#003D5B] text-white dark:bg-[#00798C]"
                  : "text-gray-500 dark:text-gray-400 hover:text-gray-900 dark:hover:text-white"
              }`}
            >
              <Sparkles className="w-3.5 h-3.5" /> Cards
            </button>
            <button
              onClick={() => setView("grid")}
              aria-label="Grid view"
              className={`min-h-[44px] px-3 text-xs font-medium rounded-md transition flex items-center gap-1.5 ${
                view === "grid"
                  ? "bg-[#003D5B] text-white dark:bg-[#00798C]"
                  : "text-gray-500 dark:text-gray-400 hover:text-gray-900 dark:hover:text-white"
              }`}
            >
              <LayoutGrid className="w-3.5 h-3.5" /> Grid
            </button>
          </div>
          <div className="hidden sm:flex items-center gap-1">
            <span className="text-xs text-gray-400 dark:text-text-soft mr-1">Sort:</span>
            {[
              { id: "ytd", label: "Total" },
              { id: "code", label: "Code" },
            ].map((s) => (
              <button
                key={s.id}
                onClick={() => setSort(s.id as typeof sort)}
                className={`min-h-[44px] px-2 text-xs font-medium rounded transition ${
                  sort === s.id
                    ? "bg-[#EDAE49] text-white"
                    : "text-gray-500 dark:text-gray-400 hover:bg-gray-100 dark:hover:bg-white/5"
                }`}
              >
                {s.label}
              </button>
            ))}
          </div>
          <div className="sm:hidden">
            <label className="sr-only" htmlFor="insurance-sort">Sort by</label>
            <select
              id="insurance-sort"
              value={sort}
              onChange={(e) => setSort(e.target.value as typeof sort)}
              className="min-h-[44px] px-3 text-xs rounded-lg border border-gray-200 dark:border-white/10 bg-white dark:bg-white/5"
            >
              <option value="ytd">Sort by Total</option>
              <option value="code">Sort by Code</option>
            </select>
          </div>
        </div>
      </div>

      {view === "cards" ? (
        <CardsView rows={sorted} expanded={expanded} setExpanded={setExpanded} />
      ) : (
        <GridView rows={sorted} grandTotal={grandTotal} />
      )}
    </>
  );
}

function CardsView({
  rows, expanded, setExpanded,
}: {
  rows: InsuranceRow[];
  expanded: string | null;
  setExpanded: (id: string | null) => void;
}) {
  return (
    <div className="space-y-2">
      {rows.map((r) => {
        const isOpen = expanded === r.id;
        return (
          <div
            key={r.id}
            className="bg-white dark:bg-surface border border-gray-100 dark:border-border rounded-xl overflow-hidden shadow-sm hover:shadow-md transition"
          >
            <button
              onClick={() => setExpanded(isOpen ? null : r.id)}
              className="w-full flex items-center gap-3 sm:gap-4 p-4 text-left min-h-[44px]"
              aria-expanded={isOpen}
            >
              <span className="font-mono text-xs px-2 py-1 rounded-md bg-[#00798C]/10 text-[#00798C] font-semibold shrink-0">
                {r.code}
              </span>
              <div className="flex-1 min-w-0">
                <div className="flex items-center gap-2 text-sm font-medium text-[#003D5B] dark:text-white">
                  <Shield className="w-3.5 h-3.5 text-[#EDAE49] shrink-0" />
                  <span className="truncate">{r.name}</span>
                </div>
              </div>
              {r.problems.length > 0 && (
                <TriangleAlert
                  className="w-4 h-4 text-[#D1495B] dark:text-[#D94F60] shrink-0"
                  aria-label="Rate history problem"
                />
              )}
              <div className="hidden sm:block shrink-0">
                <Sparkline data={r.months.map((v) => v ?? 0)} color={ACCENT} />
              </div>
              <div className="text-right shrink-0 w-32 hidden md:block">
                <div className="text-[12px] text-gray-400 uppercase tracking-wider">YTD premium</div>
                <div className="text-sm font-semibold tabular-nums text-[#003D5B] dark:text-white">
                  {r.ytd > 0 ? ZAR2(r.ytd) : "—"}
                </div>
              </div>
              <div className="shrink-0 px-2.5 py-1.5 rounded-lg text-xs font-semibold bg-[#EDAE49]/10 text-[#EDAE49] dark:bg-[#EDAE49]/20 whitespace-nowrap">
                {r.currentRate !== null ? `${ZAR2(r.currentRate)}/mo` : "no rate"}
              </div>
              <ChevronRight
                className={`w-4 h-4 text-gray-400 shrink-0 transition-transform ${isOpen ? "rotate-90" : ""}`}
              />
            </button>

            {isOpen && (
              <div className="border-t border-gray-100 dark:border-border px-4 py-4 bg-gray-50/50 dark:bg-white/[0.04]">
                {/* Mobile: 3 cols (4 rows × 3 = 12 months). md+: 6. lg+: 12. */}
                <div className="grid grid-cols-3 md:grid-cols-6 lg:grid-cols-12 gap-2 text-xs mb-5">
                  {r.months.map((v, i) => (
                    <div key={i} className="text-center">
                      <div className="text-gray-400 dark:text-text-soft text-xs mb-1">{MONTH_NAMES[i]}</div>
                      {/* A null month is unknown, not free — hence the dashed box. */}
                      <div
                        className={`py-1.5 px-0.5 rounded tabular-nums ${
                          v === null
                            ? "border border-dashed border-gray-300 dark:border-white/15 text-gray-400 dark:text-text-soft"
                            : "bg-[#EDAE49]/5 text-[#EDAE49] dark:bg-[#EDAE49]/15"
                        }`}
                      >
                        {v === null ? "no rate" : ZAR2(v)}
                      </div>
                    </div>
                  ))}
                </div>

                <div className="text-xs uppercase tracking-wider text-gray-400 mb-2">
                  Rate history <span className="normal-case tracking-normal text-gray-400 dark:text-text-soft">· {VAT_NOTE}</span>
                </div>
                <ul className="space-y-1.5">
                  {r.periods.map((p, i) => (
                    <li key={i} className="flex flex-wrap items-baseline justify-between gap-x-3 gap-y-0.5">
                      <span className="text-gray-600 dark:text-gray-300">{periodLabel(p)}</span>
                      <span className="tabular-nums font-semibold text-[#EDAE49]">
                        {ZAR2(p.rate)}
                        <span className="font-normal text-gray-400 dark:text-text-soft"> / mo</span>
                      </span>
                    </li>
                  ))}
                </ul>

                <div className="mt-4 pt-3 border-t border-gray-100 dark:border-border text-xs flex flex-wrap items-baseline gap-x-3">
                  <span className="text-gray-400 uppercase tracking-wider">YTD total</span>
                  <span className="font-semibold tabular-nums text-[#EDAE49]">{ZAR(r.ytd)}</span>
                  <span className="text-gray-500 dark:text-gray-400">
                    across {r.coveredMonths} of 12 months
                  </span>
                </div>
              </div>
            )}
          </div>
        );
      })}
    </div>
  );
}

function GridView({
  rows, grandTotal,
}: {
  rows: InsuranceRow[];
  grandTotal: number;
}) {
  const scroller = useRef<HTMLDivElement>(null);
  const [overflows, setOverflows] = useState(false);

  // The scroll affordance is shown ONLY when the table actually overflows. Five
  // narrow columns fit a phone outright, and a permanent right-edge fade on a table
  // that cannot scroll is a lie about the layout — it tells the reader to drag a
  // page that has nowhere to go.
  useEffect(() => {
    const el = scroller.current;
    if (!el) return;
    const check = () => setOverflows(el.scrollWidth > el.clientWidth + 1);
    check();
    const ro = new ResizeObserver(check);
    ro.observe(el);
    return () => ro.disconnect();
  }, [rows.length]);

  // A vehicle with no earlier period has NO previous rate — that is different from a
  // previous rate of R0, so the cell is a dash and says why on hover.
  const previousTotal = rows.reduce((s, r) => s + (r.periods[1]?.rate ?? 0), 0);
  const reRated = rows.filter((r) => r.periods.length > 1).length;

  return (
    <div className="bg-white dark:bg-surface rounded-2xl border border-gray-100 dark:border-border shadow-sm overflow-hidden">
      <div className="relative">
        <div ref={scroller} className="overflow-x-auto" style={{ WebkitOverflowScrolling: "touch" }}>
          <table className="w-full text-sm">
            <thead>
              <tr className="text-xs text-gray-500 dark:text-gray-400 uppercase tracking-wider border-y border-gray-100 dark:border-border bg-gray-50/50 dark:bg-white/[0.04]">
                <th className="text-left py-3 px-6 font-medium sticky left-0 z-10 bg-gray-50 dark:bg-surface-muted">Code</th>
                <th className="text-left py-3 px-3 font-medium">Vehicle</th>
                <th className="text-right py-3 px-3 font-medium whitespace-nowrap">
                  Current<span className="block normal-case tracking-normal text-[12px] text-gray-400 dark:text-text-soft">{VAT_NOTE}</span>
                </th>
                <th className="text-right py-3 px-3 font-medium whitespace-nowrap">
                  Previous
                </th>
                <th className="text-right py-3 px-6 font-medium whitespace-nowrap">
                  Year total<span className="block normal-case tracking-normal text-[12px] text-gray-400 dark:text-text-soft">{r_coveredLabel(rows)}</span>
                </th>
              </tr>
            </thead>
            <tbody>
              {rows.map((r) => {
                const prev = r.periods[1];
                return (
                  <tr key={r.id} className="border-b border-gray-50 dark:border-border hover:bg-gray-50/40 dark:hover:bg-white/[0.02]">
                    {/* OPAQUE: the row tint is translucent, so a transparent sticky
                        column would let the other columns bleed through it on scroll. */}
                    <td className="py-2.5 px-6 sticky left-0 z-10 bg-white dark:bg-surface">
                      <span className="font-mono text-xs px-2 py-1 rounded-md bg-[#00798C]/10 text-[#00798C] font-semibold">
                        {r.code}
                      </span>
                    </td>
                    <td className="py-2.5 px-3 font-medium text-[#003D5B] dark:text-white whitespace-nowrap">
                      <div className="flex items-center gap-2">
                        <Shield className="w-3 h-3 text-[#EDAE49] shrink-0" />
                        <span className="truncate">{r.name}</span>
                        {r.problems.length > 0 && (
                          <TriangleAlert className="w-3.5 h-3.5 text-[#D1495B] dark:text-[#D94F60] shrink-0" aria-label="Rate history problem" />
                        )}
                      </div>
                    </td>
                    <td
                      className="py-2.5 px-3 text-right tabular-nums font-semibold whitespace-nowrap text-[#EDAE49]"
                      title={r.periods[0] ? periodLabel(r.periods[0]) : undefined}
                    >
                      {r.currentRate !== null ? ZAR2(r.currentRate) : "—"}
                    </td>
                    <td
                      className="py-2.5 px-3 text-right tabular-nums whitespace-nowrap text-gray-500 dark:text-gray-400"
                      title={prev ? periodLabel(prev) : "No earlier rate period on record"}
                    >
                      {prev ? ZAR2(prev.rate) : <span className="text-gray-300 dark:text-text-soft">—</span>}
                    </td>
                    <td className="py-2.5 px-6 text-right tabular-nums font-semibold whitespace-nowrap text-[#003D5B] dark:text-white">
                      {ZAR(r.ytd)}
                      {r.coveredMonths < 12 && (
                        <span className="block text-[12px] font-normal text-gray-400 dark:text-text-soft">
                          {r.coveredMonths} of 12 mo
                        </span>
                      )}
                    </td>
                  </tr>
                );
              })}
              <tr className="bg-gray-50 dark:bg-surface-muted border-t-2 border-[#EDAE49]/40">
                <td className="py-3 px-6 sticky left-0 z-10 bg-gray-50 dark:bg-surface-muted" />
                <td className="py-3 pr-3 font-semibold text-right text-[#003D5B] dark:text-white">
                  Total · {rows.length} vehicles
                </td>
                <td className="py-3 px-3 text-right tabular-nums font-semibold whitespace-nowrap text-[#EDAE49]">
                  {ZAR(rows.reduce((s, r) => s + (r.currentRate ?? 0), 0))}
                </td>
                {/* Only the re-rated vehicles carry a previous rate, so this is a
                    partial figure — labelled as such rather than implying the fleet. */}
                <td className="py-3 px-3 text-right tabular-nums font-semibold whitespace-nowrap text-gray-500 dark:text-gray-400">
                  {reRated ? ZAR(previousTotal) : "—"}
                </td>
                <td className="py-3 px-6 text-right tabular-nums font-bold text-base text-[#EDAE49] whitespace-nowrap">
                  {ZAR(grandTotal)}
                </td>
              </tr>
            </tbody>
          </table>
        </div>
        {overflows && <ScrollFade />}
      </div>
    </div>
  );
}

/** "12 mo covered" / "1 gap" caption under the Year total header. */
function r_coveredLabel(rows: InsuranceRow[]): string {
  const gaps = rows.filter((r) => r.coveredMonths < 12).length;
  return gaps ? `${gaps} with a gap` : "12 mo covered";
}