"use strict";

module.exports = {
  slug: "number-base-conversion",
  title: "Number base conversion",
  deck_category: "other",
  description: "Converts a number represented in one base (2 to 36) to its representation in another base.",
  inputs: [
    { name: "value", type: "string", required: true, description: "The number to convert, as digits/letters valid in from_base." },
    { name: "from_base", type: "integer", required: true, description: "Base of the input value.", min: 2, max: 36 },
    { name: "to_base", type: "integer", required: true, description: "Base to convert the value into.", min: 2, max: 36 }
  ],
  outputs: [
    { name: "result", description: "value represented in to_base, using digits 0-9 then letters A-Z for digits above 9." }
  ],
  steps: [
    "Positional notation: a number in base b is a sum of digit_i * b^i, where digits range from 0 to b-1 and digits above 9 are written as letters A (10) through Z (35).",
    "Parse value as an integer in from_base to get its numeric value.",
    "Re-express that numeric value in to_base, most significant digit first, using the same digit/letter convention.",
    "Digits/letters in the output are uppercase."
  ],
  constants: [],
  sources: [
    { kind: "edition_page", value: "Knuth, Donald E. The Art of Computer Programming, Volume 2: Seminumerical Algorithms, 3rd ed. Addison-Wesley, 1997, section 4.1 (Positional Number Systems).", title: "The Art of Computer Programming, Vol. 2 (positional number systems)", publisher: "Addison-Wesley", retrieved_utc: "2026-09-30T20:00:00Z", note: "Standard reference for positional notation and base conversion." }
  ],
  disclaimer: null,
  questionText(inputs) {
    return `What is ${inputs.value} (base ${inputs.from_base}) written in base ${inputs.to_base}?`;
  },
  run(inputs) {
    const { value, from_base, to_base } = inputs || {};
    if (typeof value !== "string" || value.length === 0) throw new Error("value must be a non-empty string");
    if (!Number.isInteger(from_base) || from_base < 2 || from_base > 36) throw new Error("from_base must be an integer between 2 and 36");
    if (!Number.isInteger(to_base) || to_base < 2 || to_base > 36) throw new Error("to_base must be an integer between 2 and 36");
    const n = parseInt(value, from_base);
    if (Number.isNaN(n)) throw new Error(`value ${value} is not valid in base ${from_base}`);
    const result = n.toString(to_base).toUpperCase();
    return { answer: result, values: { result } };
  },
  examples: [
    {
      name: "worked example",
      inputs: { value: "FF", from_base: 16, to_base: 10 },
      expected: { answer: "255" },
      check: "By hand: hex FF = 15*16 + 15 = 240 + 15 = 255, a well known hexadecimal fact."
    },
    {
      name: "test vector: decimal to binary",
      inputs: { value: "255", from_base: 10, to_base: 2 },
      expected: { answer: "11111111" },
      check: "255 = 2^8 - 1, the well known fact that eight binary 1s equal 255, i.e. 11111111 in binary."
    }
  ]
};