"use client";

import { Check, Plus, Repeat2 } from "lucide-react";
import { useState } from "react";

export interface OverlapDish {
  id: string;
  title: string;
  cuisine: string;
  standaloneCheckout: number;
}

export interface OverlapComboSnapshot {
  checkoutTotal: number;
  usedTotal: number;
  carryoverValue: number;
  sharedNames: string[];
  packageCount: number;
}

interface OverlapExplorerProps {
  dishes: OverlapDish[];
  /** Keyed by sorted comma-joined dish IDs; precomputed on the server so zero catalog data ships to the landing bundle. */
  combos: Record<string, OverlapComboSnapshot>;
}

const fmt = (n: number) => `$${n.toFixed(2)}`;

export function OverlapExplorer({ dishes, combos }: OverlapExplorerProps) {
  const [selected, setSelected] = useState<string[]>(() => dishes.slice(0, 2).map((d) => d.id));

  function toggleDish(id: string) {
    setSelected((prev) => {
      if (prev.includes(id)) {
        return prev.length > 1 ? prev.filter((x) => x !== id) : prev; // keep at least 1 selected
      }
      return [...prev, id];
    });
  }

  const comboKey = [...selected].sort().join(",");
  const current = combos[comboKey];
  const naiveSum = dishes.filter((d) => selected.includes(d.id)).reduce((acc, d) => acc + d.standaloneCheckout, 0);
  const saved = Math.max(0, naiveSum - (current?.checkoutTotal ?? 0));

  return (
    <div className="grid gap-6 rounded-xl border border-line-strong bg-surface p-5 sm:p-7 lg:grid-cols-[1.15fr_1fr]">
      <div>
        <p className="font-mono text-xs tracking-wider text-brand-300 uppercase">Interactive checkout math · 2 people</p>
        <h3 className="mt-1 font-serif text-2xl font-semibold tracking-tight text-balance">
          Toggle dishes to watch shared packages drop the bill
        </h3>
        <p className="mt-2 text-sm leading-relaxed text-ink-muted">
          Grocery stores sell whole bags of onions, rice, and spices—not single tablespoons. Selecting meals that reuse open
          packages slashes what each extra dinner adds at the register.
        </p>

        <ul className="mt-5 space-y-2" aria-label="Sample dishes">
          {dishes.map((dish) => {
            const active = selected.includes(dish.id);
            return (
              <li key={dish.id}>
                <button
                  type="button"
                  aria-pressed={active}
                  onClick={() => toggleDish(dish.id)}
                  className={`flex min-h-12 w-full items-center justify-between gap-3 rounded-lg border px-3.5 py-2.5 text-left transition-colors ${
                    active
                      ? "border-selected-line bg-selected text-ink"
                      : "border-line bg-canvas text-ink-muted hover:border-line-strong hover:text-ink"
                  }`}
                >
                  <span className="flex items-center gap-3 min-w-0">
                    <span
                      className={`grid size-5 shrink-0 place-items-center rounded border ${
                        active ? "border-brand-600 bg-brand-600 text-on-accent" : "border-line-strong bg-surface"
                      }`}
                    >
                      {active ? <Check className="size-3.5" strokeWidth={2.5} aria-hidden /> : <Plus className="size-3 text-ink-faint" aria-hidden />}
                    </span>
                    <span className="min-w-0">
                      <span className="block truncate text-sm font-semibold text-ink">{dish.title}</span>
                      <span className="block text-xs text-ink-faint">{dish.cuisine}</span>
                    </span>
                  </span>
                  <span className="shrink-0 font-mono text-xs text-ink-muted tabular-nums">
                    {fmt(dish.standaloneCheckout)} alone
                  </span>
                </button>
              </li>
            );
          })}
        </ul>
      </div>

      {/* Simulated paper receipt */}
      <div className="paper-grain flex flex-col justify-between rounded-lg border border-line bg-canvas p-5 font-mono text-sm">
        <div>
          <div className="flex items-center justify-between border-b border-line pb-3 text-xs text-ink-faint uppercase">
            <span>Checkout Receipt</span>
            <span>{selected.length} {selected.length === 1 ? "meal" : "meals"}</span>
          </div>

          <dl className="mt-4 space-y-2.5 text-xs sm:text-sm">
            <div className="flex justify-between text-ink-muted">
              <dt>Buying each meal separately</dt>
              <dd className="line-through tabular-nums">{fmt(naiveSum)}</dd>
            </div>
            {saved > 0.01 && (
              <div className="flex justify-between font-semibold text-status-ok">
                <dt>Shared-package savings</dt>
                <dd className="tabular-nums">−{fmt(saved)}</dd>
              </div>
            )}
            <div className="receipt-rule flex items-baseline justify-between pt-3 text-base font-bold text-ink">
              <dt className="font-sans text-sm font-semibold">Combined register total</dt>
              <dd className="text-lg tabular-nums">{fmt(current?.checkoutTotal ?? 0)}</dd>
            </div>
          </dl>

          <dl className="mt-4 grid grid-cols-2 gap-3 rounded-md border border-line bg-surface p-3 font-sans text-xs">
            <div>
              <dt className="text-ink-faint">Food eaten</dt>
              <dd className="mt-0.5 font-mono text-sm font-semibold text-ink tabular-nums">{fmt(current?.usedTotal ?? 0)}</dd>
            </div>
            <div>
              <dt className="text-ink-faint">Kept in pantry</dt>
              <dd className="mt-0.5 font-mono text-sm font-semibold text-ink tabular-nums">{fmt(current?.carryoverValue ?? 0)}</dd>
            </div>
          </dl>
        </div>

        <div className="mt-4 border-t border-line pt-3 font-sans text-xs text-ink-muted">
          {current && current.sharedNames.length > 0 ? (
            <p className="flex items-start gap-1.5">
              <Repeat2 className="mt-0.5 size-3.5 shrink-0 text-status-ok" strokeWidth={2} aria-hidden />
              <span>
                <strong className="font-semibold text-ink">Reused across meals:</strong> {current.sharedNames.slice(0, 5).join(", ")}
                {current.sharedNames.length > 5 ? ` +${current.sharedNames.length - 5} more` : ""}
              </span>
            </p>
          ) : (
            <p>Select a second dish to see which store packages overlap in your cart.</p>
          )}
        </div>
      </div>
    </div>
  );
}