'use strict';
const eslintTemplateVisitor = require('eslint-template-visitor');
const {getParenthesizedText} = require('./utils/parentheses.js');

const MESSAGE_ID_SUBSTR = 'substr';
const MESSAGE_ID_SUBSTRING = 'substring';
const messages = {
	[MESSAGE_ID_SUBSTR]: 'Prefer `String#slice()` over `String#substr()`.',
	[MESSAGE_ID_SUBSTRING]: 'Prefer `String#slice()` over `String#substring()`.',
};

const templates = eslintTemplateVisitor();

const objectVariable = templates.variable();
const argumentsVariable = templates.spreadVariable();

const substrCallTemplate = templates.template`${objectVariable}.substr(${argumentsVariable})`;
const substringCallTemplate = templates.template`${objectVariable}.substring(${argumentsVariable})`;

const isLiteralNumber = node => node && node.type === 'Literal' && typeof node.value === 'number';

const getNumericValue = node => {
	if (isLiteralNumber(node)) {
		return node.value;
	}

	if (node.type === 'UnaryExpression' && node.operator === '-') {
		return -getNumericValue(node.argument);
	}
};

// This handles cases where the argument is very likely to be a number, such as `.substring('foo'.length)`.
const isLengthProperty = node => (
	node
	&& node.type === 'MemberExpression'
	&& node.computed === false
	&& node.property.type === 'Identifier'
	&& node.property.name === 'length'
);

const isLikelyNumeric = node => isLiteralNumber(node) || isLengthProperty(node);

/** @param {import('eslint').Rule.RuleContext} context */
const create = context => {
	const sourceCode = context.getSourceCode();

	return templates.visitor({
		[substrCallTemplate](node) {
			const objectNode = substrCallTemplate.context.getMatch(objectVariable);
			const argumentNodes = substrCallTemplate.context.getMatch(argumentsVariable);

			const problem = {
				node,
				messageId: MESSAGE_ID_SUBSTR,
			};

			const firstArgument = argumentNodes[0] ? sourceCode.getText(argumentNodes[0]) : undefined;
			const secondArgument = argumentNodes[1] ? sourceCode.getText(argumentNodes[1]) : undefined;

			let sliceArguments;

			switch (argumentNodes.length) {
				case 0: {
					sliceArguments = [];
					break;
				}

				case 1: {
					sliceArguments = [firstArgument];
					break;
				}

				case 2: {
					if (firstArgument === '0') {
						sliceArguments = [firstArgument];
						if (isLiteralNumber(secondArgument) || isLengthProperty(argumentNodes[1])) {
							sliceArguments.push(secondArgument);
						} else if (typeof getNumericValue(argumentNodes[1]) === 'number') {
							sliceArguments.push(Math.max(0, getNumericValue(argumentNodes[1])));
						} else {
							sliceArguments.push(`Math.max(0, ${secondArgument})`);
						}
					} else if (
						isLiteralNumber(argumentNodes[0])
						&& isLiteralNumber(argumentNodes[1])
					) {
						sliceArguments = [
							firstArgument,
							argumentNodes[0].value + argumentNodes[1].value,
						];
					} else if (
						isLikelyNumeric(argumentNodes[0])
						&& isLikelyNumeric(argumentNodes[1])
					) {
						sliceArguments = [firstArgument, firstArgument + ' + ' + secondArgument];
					}

					break;
				}
				// No default
			}

			if (sliceArguments) {
				const objectText = getParenthesizedText(objectNode, sourceCode);
				const optionalMemberSuffix = node.callee.optional ? '?' : '';
				const optionalCallSuffix = node.optional ? '?.' : '';

				problem.fix = fixer => fixer.replaceText(node, `${objectText}${optionalMemberSuffix}.slice${optionalCallSuffix}(${sliceArguments.join(', ')})`);
			}

			context.report(problem);
		},

		[substringCallTemplate](node) {
			const objectNode = substringCallTemplate.context.getMatch(objectVariable);
			const argumentNodes = substringCallTemplate.context.getMatch(argumentsVariable);

			const problem = {
				node,
				messageId: MESSAGE_ID_SUBSTRING,
			};

			const firstArgument = argumentNodes[0] ? sourceCode.getText(argumentNodes[0]) : undefined;
			const secondArgument = argumentNodes[1] ? sourceCode.getText(argumentNodes[1]) : undefined;

			const firstNumber = argumentNodes[0] ? getNumericValue(argumentNodes[0]) : undefined;

			let sliceArguments;

			switch (argumentNodes.length) {
				case 0: {
					sliceArguments = [];
					break;
				}

				case 1: {
					if (firstNumber !== undefined) {
						sliceArguments = [Math.max(0, firstNumber)];
					} else if (isLengthProperty(argumentNodes[0])) {
						sliceArguments = [firstArgument];
					} else {
						sliceArguments = [`Math.max(0, ${firstArgument})`];
					}

					break;
				}

				case 2: {
					const secondNumber = getNumericValue(argumentNodes[1]);

					if (firstNumber !== undefined && secondNumber !== undefined) {
						sliceArguments = firstNumber > secondNumber
							? [Math.max(0, secondNumber), Math.max(0, firstNumber)]
							: [Math.max(0, firstNumber), Math.max(0, secondNumber)];
					} else if (firstNumber === 0 || secondNumber === 0) {
						sliceArguments = [0, `Math.max(0, ${firstNumber === 0 ? secondArgument : firstArgument})`];
					} else {
					// As values aren't Literal, we can not know whether secondArgument will become smaller than the first or not, causing an issue:
					//   .substring(0, 2) and .substring(2, 0) returns the same result
					//   .slice(0, 2) and .slice(2, 0) doesn't return the same result
					// There's also an issue with us now knowing whether the value will be negative or not, due to:
					//   .substring() treats a negative number the same as it treats a zero.
					// The latter issue could be solved by wrapping all dynamic numbers in Math.max(0, <value>), but the resulting code would not be nice
					}

					break;
				}
				// No default
			}

			if (sliceArguments) {
				const objectText = getParenthesizedText(objectNode, sourceCode);
				const optionalMemberSuffix = node.callee.optional ? '?' : '';
				const optionalCallSuffix = node.optional ? '?.' : '';

				problem.fix = fixer => fixer.replaceText(node, `${objectText}${optionalMemberSuffix}.slice${optionalCallSuffix}(${sliceArguments.join(', ')})`);
			}

			context.report(problem);
		},
	});
};

/** @type {import('eslint').Rule.RuleModule} */
module.exports = {
	create,
	meta: {
		type: 'suggestion',
		docs: {
			description: 'Prefer `String#slice()` over `String#substr()` and `String#substring()`.',
		},
		fixable: 'code',
		messages,
	},
};