'use strict';

var defaults = require('../core/core.defaults');
var helpers = require('./helpers.core');

var valueOrDefault = helpers.valueOrDefault;

/**
 * Converts the given font object into a CSS font string.
 * @param {object} font - A font object.
 * @return {string} The CSS font string. See https://developer.mozilla.org/en-US/docs/Web/CSS/font
 * @private
 */
function toFontString(font) {
	if (!font || helpers.isNullOrUndef(font.size) || helpers.isNullOrUndef(font.family)) {
		return null;
	}

	return (font.style ? font.style + ' ' : '')
		+ (font.weight ? font.weight + ' ' : '')
		+ font.size + 'px '
		+ font.family;
}

/**
 * @alias Chart.helpers.options
 * @namespace
 */
module.exports = {
	/**
	 * Converts the given line height `value` in pixels for a specific font `size`.
	 * @param {number|string} value - The lineHeight to parse (eg. 1.6, '14px', '75%', '1.6em').
	 * @param {number} size - The font size (in pixels) used to resolve relative `value`.
	 * @returns {number} The effective line height in pixels (size * 1.2 if value is invalid).
	 * @see https://developer.mozilla.org/en-US/docs/Web/CSS/line-height
	 * @since 2.7.0
	 */
	toLineHeight: function(value, size) {
		var matches = ('' + value).match(/^(normal|(\d+(?:\.\d+)?)(px|em|%)?)$/);
		if (!matches || matches[1] === 'normal') {
			return size * 1.2;
		}

		value = +matches[2];

		switch (matches[3]) {
		case 'px':
			return value;
		case '%':
			value /= 100;
			break;
		default:
			break;
		}

		return size * value;
	},

	/**
	 * Converts the given value into a padding object with pre-computed width/height.
	 * @param {number|object} value - If a number, set the value to all TRBL component,
	 *  else, if and object, use defined properties and sets undefined ones to 0.
	 * @returns {object} The padding values (top, right, bottom, left, width, height)
	 * @since 2.7.0
	 */
	toPadding: function(value) {
		var t, r, b, l;

		if (helpers.isObject(value)) {
			t = +value.top || 0;
			r = +value.right || 0;
			b = +value.bottom || 0;
			l = +value.left || 0;
		} else {
			t = r = b = l = +value || 0;
		}

		return {
			top: t,
			right: r,
			bottom: b,
			left: l,
			height: t + b,
			width: l + r
		};
	},

	/**
	 * Parses font options and returns the font object.
	 * @param {object} options - A object that contains font options to be parsed.
	 * @return {object} The font object.
	 * @todo Support font.* options and renamed to toFont().
	 * @private
	 */
	_parseFont: function(options) {
		var globalDefaults = defaults.global;
		var size = valueOrDefault(options.fontSize, globalDefaults.defaultFontSize);
		var font = {
			family: valueOrDefault(options.fontFamily, globalDefaults.defaultFontFamily),
			lineHeight: helpers.options.toLineHeight(valueOrDefault(options.lineHeight, globalDefaults.defaultLineHeight), size),
			size: size,
			style: valueOrDefault(options.fontStyle, globalDefaults.defaultFontStyle),
			weight: null,
			string: ''
		};

		font.string = toFontString(font);
		return font;
	},

	/**
	 * Evaluates the given `inputs` sequentially and returns the first defined value.
	 * @param {Array} inputs - An array of values, falling back to the last value.
	 * @param {object} [context] - If defined and the current value is a function, the value
	 * is called with `context` as first argument and the result becomes the new input.
	 * @param {number} [index] - If defined and the current value is an array, the value
	 * at `index` become the new input.
	 * @since 2.7.0
	 */
	resolve: function(inputs, context, index) {
		var i, ilen, value;

		for (i = 0, ilen = inputs.length; i < ilen; ++i) {
			value = inputs[i];
			if (value === undefined) {
				continue;
			}
			if (context !== undefined && typeof value === 'function') {
				value = value(context);
			}
			if (index !== undefined && helpers.isArray(value)) {
				value = value[index];
			}
			if (value !== undefined) {
				return value;
			}
		}
	}
};
