'use strict';

const defaultValue = require("default-value");

const findEdge = require("./find-edge");
const drawCharacter = require("./draw-character");
const resetCanvas = require("./reset-canvas");
const createCanvas = require("./create-canvas");

module.exports = function measureFont(fontFamily, options = {}) {
	let fontSize = defaultValue(options.fontSize, 20);
	let canvasSize = defaultValue(options.tolerance, 6) * fontSize;

	let descenderCharacters = ["g", "j", "p", "q", "y"];
	let ascenderCharacters = ["h", "d", "t", "l"];
	let capHeightCharacters = ["H", "I", "T"];
	let medianCharacters = ["x", "v", "w", "z"];
	let topBoundingCharacters = ["O", "A", "8", "#", "%", "^", "!", "/", "|", "]"];

	let testingCanvas = createCanvas(canvasSize);

	function getLowest(characters) {
		resetCanvas(testingCanvas);

		characters.forEach((character) => {
			drawCharacter(testingCanvas, character, fontFamily, fontSize);
		});

		return findEdge.lowest(testingCanvas);
	}

	function getHighest(characters) {
		resetCanvas(testingCanvas);

		characters.forEach((character) => {
			drawCharacter(testingCanvas, character, fontFamily, fontSize);
		});

		return findEdge.highest(testingCanvas);
	}

	let lowestDescenderPoint = getLowest(descenderCharacters) - (testingCanvas.height / 2);
	let highestAscenderPoint = (testingCanvas.height / 2) - getHighest(ascenderCharacters);
	let highestCapHeightPoint = (testingCanvas.height / 2) - getHighest(capHeightCharacters);
	let highestMedianPoint = (testingCanvas.height / 2) - getHighest(medianCharacters);
	let highestTopBoundingPoint = (testingCanvas.height / 2) - getHighest(topBoundingCharacters);

	return {
		descender: lowestDescenderPoint / fontSize,
		ascender: -highestAscenderPoint / fontSize,
		capHeight: -highestCapHeightPoint / fontSize,
		median: -highestMedianPoint / fontSize,
		topBounding: -highestTopBoundingPoint / fontSize
	}
}