import { LoadInput } from "../common.ts";

/**
 * Calculate the sum of all calibration values in a document
 *
 * @param {string[]} document All lines of a document containing calibration values
 * @returns {number} The sum of all calibration values found in a document
 */
function CalculateCalibrationSum(document: string[]): number {
	return document.reduce((register, currVal) => register + extractCalibrationValue(currVal), 0);
}

/**
 * Extract a calibration value from a line of text
 *
 * Extracts the first and last digit from a string of text,
 * concatenates the two, and returns this as the calibration value.
 *
 * If only one digit is present, the one digit is concatenated to
 * itself.
 * 
 * Uses a lookahead regex group to handle nested words
 * @see https://mtsknn.fi/blog/how-to-do-overlapping-matches-with-regular-expressions/#capturing-groups-inside-lookahead-lookbehind-assertions
 *
 * @param {string} line The line of text to extract the calibration value out of
 * @returns {number} The two-digit calibration value hidden in that string 
 */
function extractCalibrationValue(line: string): number {
	const extracter = new RegExp("(?=(one|t(?:wo|hree)|f(?:our|ive)|s(?:ix|even)|eight|nine|[0-9]))", "g");
	const digitsInString = Array.from(line.matchAll(extracter), (match) => match[1]) || [];

	if (digitsInString.length == 0) {
		console.error("No digits found on line!");
		console.error(line);
	}

	const firstDigit = parseNumberWordToDigit(digitsInString[0]);
	const secondDigit = parseNumberWordToDigit(digitsInString[digitsInString.length - 1]);

	return Number(firstDigit + secondDigit);
}

/**
 * Turn the word representation of a digit into that digit
 *
 * @param {string|undefined} numberString A string containing either the word of a number, or the digit
 * @returns {string} A string of the digit that the input represents
 */
function parseNumberWordToDigit(numberString: string|undefined): string {
	switch (numberString) {
		case "0":
		case "1":
		case "2":
		case "3":
		case "4":
		case "5":
		case "6":
		case "7":
		case "8":
		case "9":
			return numberString;
		case "one":
			return "1";
		case "two":
			return "2";
		case "three":
			return "3";
		case "four":
			return "4";
		case "five":
			return "5";
		case "six":
			return "6";
		case "seven":
			return "7";
		case "eight":
			return "8";
		case "nine":
			return "9";
		default:
			return "0";
	}
}

const tests: string[] = [
	"two1nine",
	"eightwothree",
	"abcone2threexyz",
	"xtwone3four",
	"4nineeightseven2",
	"zoneight234",
	"7pqrstsixteen",
	"3pqrstsevenine",
];

const input = await LoadInput(1);

console.log("Test Cases");
console.log("Expected: 320")
console.log(`Actual: ${CalculateCalibrationSum(tests)}\n`);

console.log("Input");
console.log(`Your *true* calibration sum: ${CalculateCalibrationSum(input)}`);