"use strict";

function assertPositiveInt(name, value) {
  if (!Number.isInteger(value) || value <= 0) {
    throw new Error(`${name} must be a positive integer`);
  }
}

function validateCreditConfig(config) {
  assertPositiveInt("baseCredits", config.baseCredits);
  assertPositiveInt("includedChars", config.includedChars);
  assertPositiveInt("stepChars", config.stepChars);
  assertPositiveInt("stepCredits", config.stepCredits);
  assertPositiveInt("maxCharsPerArticle", config.maxCharsPerArticle);
}

function calculateCredits(charCount, config) {
  validateCreditConfig(config);

  if (!Number.isInteger(charCount) || charCount <= 0) {
    throw new Error("charCount must be a positive integer");
  }

  if (charCount > config.maxCharsPerArticle) {
    throw new Error("article_too_long");
  }

  const overage = Math.max(0, charCount - config.includedChars);
  const extraSteps = overage === 0 ? 0 : Math.ceil(overage / config.stepChars);
  return config.baseCredits + (extraSteps * config.stepCredits);
}

module.exports = {
  calculateCredits,
  validateCreditConfig,
};