Selector.ts

import MagicString from 'magic-string';
import Stylesheet from './Stylesheet';
import { gather_possible_values, UNKNOWN } from './gather_possible_values';
import { Node } from '../../interfaces';
import Component from '../Component';

export default class Selector {
	node: Node;
	stylesheet: Stylesheet;
	blocks: Block[];
	local_blocks: Block[];
	used: boolean;

	constructor(node: Node, stylesheet: Stylesheet) {
		this.node = node;
		this.stylesheet = stylesheet;

		this.blocks = group_selectors(node);

		// take trailing :global(...) selectors out of consideration
		let i = this.blocks.length;
		while (i > 0) {
			if (!this.blocks[i - 1].global) break;
			i -= 1;
		}

		this.local_blocks = this.blocks.slice(0, i);
		this.used = this.blocks[0].global;
	}

	apply(node: Node, stack: Node[]) {
		const to_encapsulate: Node[] = [];

		apply_selector(this.stylesheet, this.local_blocks.slice(), node, stack.slice(), to_encapsulate);

		if (to_encapsulate.length > 0) {
			to_encapsulate.filter((_, i) => i === 0 || i === to_encapsulate.length - 1).forEach(({ node, block }) => {
				this.stylesheet.nodes_with_css_class.add(node);
				block.should_encapsulate = true;
			});

			this.used = true;
		}
	}

	minify(code: MagicString) {
		let c: number = null;
		this.blocks.forEach((block, i) => {
			if (i > 0) {
				if (block.start - c > 1) {
					code.overwrite(c, block.start, block.combinator.name || ' ');
				}
			}

			c = block.end;
		});
	}

	transform(code: MagicString, attr: string) {
		function encapsulate_block(block: Block) {
			let i = block.selectors.length;
			while (i--) {
				const selector = block.selectors[i];
				if (selector.type === 'PseudoElementSelector' || selector.type === 'PseudoClassSelector') {
					if (selector.name !== 'root') {
						if (i === 0) code.prependRight(selector.start, attr);
					}
					continue;
				}

				if (selector.type === 'TypeSelector' && selector.name === '*') {
					code.overwrite(selector.start, selector.end, attr);
				} else {
					code.appendLeft(selector.end, attr);
				}

				break;
			}
		}

		this.blocks.forEach((block) => {
			if (block.global) {
				const selector = block.selectors[0];
				const first = selector.children[0];
				const last = selector.children[selector.children.length - 1];
				code.remove(selector.start, first.start).remove(last.end, selector.end);
			}

			if (block.should_encapsulate) encapsulate_block(block);
		});
	}

	validate(component: Component) {
		this.blocks.forEach((block) => {
			let i = block.selectors.length;
			while (i-- > 1) {
				const selector = block.selectors[i];
				if (selector.type === 'PseudoClassSelector' && selector.name === 'global') {
					component.error(selector, {
						code: `css-invalid-global`,
						message: `:global(...) must be the first element in a compound selector`
					});
				}
			}
		});

		let start = 0;
		let end = this.blocks.length;

		for (; start < end; start += 1) {
			if (!this.blocks[start].global) break;
		}

		for (; end > start; end -= 1) {
			if (!this.blocks[end - 1].global) break;
		}

		for (let i = start; i < end; i += 1) {
			if (this.blocks[i].global) {
				component.error(this.blocks[i].selectors[0], {
					code: `css-invalid-global`,
					message: `:global(...) can be at the start or end of a selector sequence, but not in the middle`
				});
			}
		}
	}
}

function apply_selector(stylesheet: Stylesheet, blocks: Block[], node: Node, stack: Node[], to_encapsulate: any[]): boolean {
	const block = blocks.pop();
	if (!block) return false;

	if (!node) {
		return blocks.every(block => block.global);
	}

	let i = block.selectors.length;

	while (i--) {
		const selector = block.selectors[i];
		const name = typeof selector.name === 'string' && selector.name.replace(/\\(.)/g, '$1');

		if (selector.type === 'PseudoClassSelector' && name === 'global') {
			// TODO shouldn't see this here... maybe we should enforce that :global(...)
			// cannot be sandwiched between non-global selectors?
			return false;
		}

		if (selector.type === 'PseudoClassSelector' || selector.type === 'PseudoElementSelector') {
			continue;
		}

		if (selector.type === 'ClassSelector') {
			if (!attribute_matches(node, 'class', name, '~=', false) && !node.classes.some(c => c.name === name)) return false;
		}

		else if (selector.type === 'IdSelector') {
			if (!attribute_matches(node, 'id', name, '=', false)) return false;
		}

		else if (selector.type === 'AttributeSelector') {
			if (!attribute_matches(node, selector.name.name, selector.value && unquote(selector.value), selector.matcher, selector.flags)) return false;
		}

		else if (selector.type === 'TypeSelector') {
			if (node.name.toLowerCase() !== name.toLowerCase() && name !== '*') return false;
		}

		else {
			// bail. TODO figure out what these could be
			to_encapsulate.push({ node, block });
			return true;
		}
	}

	if (block.combinator) {
		if (block.combinator.type === 'WhiteSpace') {
			while (stack.length) {
				if (apply_selector(stylesheet, blocks.slice(), stack.pop(), stack, to_encapsulate)) {
					to_encapsulate.push({ node, block });
					return true;
				}
			}

			if (blocks.every(block => block.global)) {
				to_encapsulate.push({ node, block });
				return true;
			}

			return false;
		} else if (block.combinator.name === '>') {
			if (apply_selector(stylesheet, blocks, stack.pop(), stack, to_encapsulate)) {
				to_encapsulate.push({ node, block });
				return true;
			}

			return false;
		}

		// TODO other combinators
		to_encapsulate.push({ node, block });
		return true;
	}

	to_encapsulate.push({ node, block });
	return true;
}

function test_attribute(operator, expected_value, case_insensitive, value) {
	if (case_insensitive) {
		expected_value = expected_value.toLowerCase();
		value = value.toLowerCase();
	}
	switch (operator) {
		case '=': return value === expected_value;
		case '~=': return ` ${value} `.includes(` ${expected_value} `);
		case '|=': return `${value}-`.startsWith(`${expected_value}-`);
		case '^=': return value.startsWith(expected_value);
		case '$=': return value.endsWith(expected_value);
		case '*=': return value.includes(expected_value);
		default: throw new Error(`this shouldn't happen`);
	}
}

function attribute_matches(node: Node, name: string, expected_value: string, operator: string, case_insensitive: boolean) {
	const spread = node.attributes.find(attr => attr.type === 'Spread');
	if (spread) return true;

	if (node.bindings.some((binding: Node) => binding.name === name)) return true;

	const attr = node.attributes.find((attr: Node) => attr.name === name);
	if (!attr) return false;
	if (attr.is_true) return operator === null;
	if (attr.chunks.length > 1) return true;
	if (!expected_value) return true;

	const value = attr.chunks[0];

	if (!value) return false;
	if (value.type === 'Text') return test_attribute(operator, expected_value, case_insensitive, value.data);

	const possible_values = new Set();
	gather_possible_values(value.node, possible_values);
	if (possible_values.has(UNKNOWN)) return true;

	for (const value of possible_values) {
		if (test_attribute(operator, expected_value, case_insensitive, value)) return true;
	}

	return false;
}

function unquote(value: Node) {
	if (value.type === 'Identifier') return value.name;
	const str = value.value;
	if (str[0] === str[str.length - 1] && str[0] === "'" || str[0] === '"') {
		return str.slice(1, str.length - 1);
	}
	return str;
}

class Block {
	global: boolean;
	combinator: Node;
	selectors: Node[]
	start: number;
	end: number;
	should_encapsulate: boolean;

	constructor(combinator: Node) {
		this.combinator = combinator;
		this.global = false;
		this.selectors = [];

		this.start = null;
		this.end = null;

		this.should_encapsulate = false;
	}

	add(selector: Node) {
		if (this.selectors.length === 0) {
			this.start = selector.start;
			this.global = selector.type === 'PseudoClassSelector' && selector.name === 'global';
		}

		this.selectors.push(selector);
		this.end = selector.end;
	}
}

function group_selectors(selector: Node) {
	let block: Block = new Block(null);

	const blocks = [block];

	selector.children.forEach((child: Node) => {
		if (child.type === 'WhiteSpace' || child.type === 'Combinator') {
			block = new Block(child);
			blocks.push(block);
		} else {
			block.add(child);
		}
	});

	return blocks;
}