module.exports = {
  slug: "discount-and-markup",
  title: "Discount and markup",
  deck_category: "finance",
  description: "Applies a percentage discount or a percentage markup to a price and returns the new price and the dollar change.",
  inputs: [
    { name: "price", type: "number", unit: "currency units", required: true, description: "Original price", min: 0 },
    { name: "percent", type: "number", unit: "%", required: true, description: "Discount or markup percentage", min: 0 },
    { name: "mode", type: "string", required: true, description: "Whether to apply a discount or a markup", enum: ["discount", "markup"] }
  ],
  outputs: [
    { name: "new_price", unit: "currency units", description: "Price after the discount or markup" },
    { name: "amount_change", unit: "currency units", description: "Dollar amount of the discount or markup" }
  ],
  steps: [
    "Convert the percent to a decimal: p = percent / 100.",
    "amount_change = price * p.",
    "If mode is discount, new_price = price - amount_change; if mode is markup, new_price = price + amount_change.",
    "Round new_price and amount_change to 2 decimals (money to cents)."
  ],
  constants: [],
  sources: [
    { kind: "url", value: "https://www.consumerfinance.gov/consumer-tools/educator-tools/your-money-your-goals/toolkit/", title: "Your Money, Your Goals: percentage discount and markup conventions", publisher: "Consumer Financial Protection Bureau", retrieved_utc: "2026-09-30T19:31:29Z", note: "Standard retail-math discount/markup convention applied to the original price" }
  ],
  disclaimer: null,
  questionText(inputs) {
    const verb = inputs.mode === "discount" ? "discounted by" : "marked up by";
    return `A $${inputs.price} price is ${verb} ${inputs.percent}%. What is the new price?`;
  },
  run(inputs) {
    const { price, percent, mode } = inputs;
    if (typeof price !== "number" || price < 0) throw new Error("price must be a non-negative number");
    if (typeof percent !== "number" || percent < 0) throw new Error("percent must be a non-negative number");
    if (mode !== "discount" && mode !== "markup") throw new Error("mode must be 'discount' or 'markup'");
    const p = percent / 100;
    const amount_change = Math.round(price * p * 100) / 100;
    const new_price = Math.round((mode === "discount" ? price - amount_change : price + amount_change) * 100) / 100;
    const fmt = (n) => n.toFixed(2).replace(/\B(?=(\d{3})+(?!\d))/g, ",");
    return {
      answer: `$${fmt(new_price)}`,
      values: { new_price, amount_change }
    };
  },
  examples: [
    {
      name: "worked example",
      inputs: { price: 80, percent: 25, mode: "discount" },
      expected: { answer: "$60.00" },
      check: "hand computation: amount_change = 80*0.25 = 20.00; new_price = 80-20 = 60.00"
    },
    {
      name: "test vector: markup",
      inputs: { price: 150, percent: 40, mode: "markup" },
      expected: { answer: "$210.00" },
      check: "hand computation: amount_change = 150*0.40 = 60.00; new_price = 150+60 = 210.00"
    }
  ]
};