module.exports = {
  slug: "tip-and-split-bill",
  title: "Tip and split a bill",
  deck_category: "finance",
  description: "Computes the tip amount, the total bill, and each person's even share when a bill is split among a number of people.",
  inputs: [
    { name: "bill_amount", type: "number", unit: "currency units", required: true, description: "Pre-tip bill amount", min: 0 },
    { name: "tip_percent", type: "number", unit: "%", required: true, description: "Tip percentage", min: 0 },
    { name: "number_of_people", type: "integer", required: true, description: "Number of people splitting the bill evenly", min: 1 }
  ],
  outputs: [
    { name: "tip_amount", unit: "currency units", description: "Total tip amount" },
    { name: "total_amount", unit: "currency units", description: "Bill plus tip" },
    { name: "amount_per_person", unit: "currency units", description: "Even share of the total per person" }
  ],
  steps: [
    "Convert the tip percent to a decimal: t = tip_percent / 100.",
    "tip_amount = bill_amount * t.",
    "total_amount = bill_amount + tip_amount.",
    "amount_per_person = total_amount / number_of_people.",
    "Round tip_amount, total_amount, and amount_per_person 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 and tip calculation conventions", publisher: "Consumer Financial Protection Bureau", retrieved_utc: "2026-09-30T19:31:29Z", note: "Standard everyday-math tip and even-split convention: tip = bill*rate, per-person = (bill+tip)/people" }
  ],
  disclaimer: null,
  questionText(inputs) {
    return `A bill of $${inputs.bill_amount} gets a ${inputs.tip_percent}% tip and is split evenly among ${inputs.number_of_people} people. What is the tip, the total, and each person's share?`;
  },
  run(inputs) {
    const { bill_amount, tip_percent, number_of_people } = inputs;
    if (typeof bill_amount !== "number" || bill_amount < 0) throw new Error("bill_amount must be a non-negative number");
    if (typeof tip_percent !== "number" || tip_percent < 0) throw new Error("tip_percent must be a non-negative number");
    if (!Number.isInteger(number_of_people) || number_of_people <= 0) throw new Error("number_of_people must be a positive integer");
    const t = tip_percent / 100;
    const tip_amount = Math.round(bill_amount * t * 100) / 100;
    const total_amount = Math.round((bill_amount + tip_amount) * 100) / 100;
    const amount_per_person = Math.round((total_amount / number_of_people) * 100) / 100;
    return {
      answer: `Tip $${tip_amount.toFixed(2)}, total $${total_amount.toFixed(2)}, $${amount_per_person.toFixed(2)} per person`,
      values: { tip_amount, total_amount, amount_per_person }
    };
  },
  examples: [
    {
      name: "worked example",
      inputs: { bill_amount: 84.50, tip_percent: 18, number_of_people: 4 },
      expected: { answer: "Tip $15.21, total $99.71, $24.93 per person" },
      check: "hand computation: tip = 84.50*0.18 = 15.21; total = 84.50+15.21 = 99.71; per person = 99.71/4 = 24.9275, rounds to 24.93"
    },
    {
      name: "test vector: single diner, no tip",
      inputs: { bill_amount: 20, tip_percent: 0, number_of_people: 1 },
      expected: { answer: "Tip $0.00, total $20.00, $20.00 per person" },
      check: "hand computation: tip = 0.00; total = 20.00; per person = 20.00"
    }
  ]
};