'use strict';

const blurFunctionArguments = require('../../utils/blurFunctionArguments');
const report = require('../../utils/report');
const ruleMessages = require('../../utils/ruleMessages');
const styleSearch = require('style-search');
const validateOptions = require('../../utils/validateOptions');

const ruleName = 'color-hex-length';

const messages = ruleMessages(ruleName, {
	expected: (actual, expected) => `Expected "${actual}" to be "${expected}"`,
});

function rule(expectation, _, context) {
	return (root, result) => {
		const validOptions = validateOptions(result, ruleName, {
			actual: expectation,
			possible: ['short', 'long'],
		});

		if (!validOptions) {
			return;
		}

		root.walkDecls((decl) => {
			const declString = blurFunctionArguments(decl.toString(), 'url');
			const fixPositions = [];

			styleSearch({ source: declString, target: '#' }, (match) => {
				const hexMatch = /^#[0-9A-Za-z]+/.exec(declString.substr(match.startIndex));

				if (!hexMatch) {
					return;
				}

				const hexValue = hexMatch[0];

				if (expectation === 'long' && hexValue.length !== 4 && hexValue.length !== 5) {
					return;
				}

				if (expectation === 'short' && (hexValue.length < 6 || !canShrink(hexValue))) {
					return;
				}

				const variant = expectation === 'long' ? longer : shorter;
				const expectedHex = variant(hexValue);

				if (context.fix) {
					fixPositions.unshift({
						expectedHex,
						currentHex: hexValue,
						startIndex: match.startIndex,
					});

					return;
				}

				report({
					message: messages.expected(hexValue, expectedHex),
					node: decl,
					index: match.startIndex,
					result,
					ruleName,
				});
			});

			if (fixPositions.length) {
				const declProp = decl.prop;
				const declBetween = decl.raws.between;

				fixPositions.forEach((fixPosition) => {
					// 1 — it's a # length
					decl.value = replaceHex(
						decl.value,
						fixPosition.currentHex,
						fixPosition.expectedHex,
						fixPosition.startIndex - declProp.length - declBetween.length - 1,
					);
				});
			}
		});
	};
}

function canShrink(hex) {
	hex = hex.toLowerCase();

	return (
		hex[1] === hex[2] &&
		hex[3] === hex[4] &&
		hex[5] === hex[6] &&
		(hex.length === 7 || (hex.length === 9 && hex[7] === hex[8]))
	);
}

function shorter(hex) {
	let hexVariant = '#';

	for (let i = 1; i < hex.length; i += 2) {
		hexVariant += hex[i];
	}

	return hexVariant;
}

function longer(hex) {
	let hexVariant = '#';

	for (let i = 1; i < hex.length; i++) {
		hexVariant += hex[i] + hex[i];
	}

	return hexVariant;
}

function replaceHex(input, searchString, replaceString, startIndex) {
	const offset = startIndex + 1;
	const stringStart = input.slice(0, offset);
	const stringEnd = input.slice(offset + searchString.length);

	return stringStart + replaceString + stringEnd;
}

rule.ruleName = ruleName;
rule.messages = messages;
module.exports = rule;