import type {Gen} from '@fuzdev/gro';
import {readFileSync} from 'node:fs';

const theme_css_path = 'src/lib/theme_highlight.css';

/** @nodocs */
export const gen: Gen = {
	dependencies: {files: [theme_css_path]},
	generate: ({origin_path}) => {
		// Read the theme_highlight.css file
		let css_content = readFileSync(theme_css_path, 'utf-8');

		// Strip CSS comments to avoid false positives
		css_content = css_content.replace(/\/\*[\s\S]*?\*\//g, '');

		// Extract ::highlight() rules by CSS rule blocks
		const highlight_priorities: Record<string, number> = {};
		let priority = 1;

		// Split CSS into rule blocks (roughly by closing braces)
		const rule_blocks = css_content.split('}');

		for (const block of rule_blocks) {
			// Find all ::highlight(token_name) declarations in this block
			const highlight_regex = /::highlight\(([^)]+)\)/g;
			const tokens_in_block: Array<string> = [];
			let match;

			while ((match = highlight_regex.exec(block)) !== null) {
				const token_name = match[1]!;
				if (!tokens_in_block.includes(token_name)) {
					tokens_in_block.push(token_name);
				}
			}

			// Assign the same priority to all tokens in this block
			if (tokens_in_block.length > 0) {
				for (const token_name of tokens_in_block) {
					if (!Object.hasOwn(highlight_priorities, token_name)) {
						highlight_priorities[token_name] = priority;
					}
				}
				priority++;
			}
		}

		const banner = `// generated by ${origin_path} - DO NOT EDIT OR RISK LOST DATA`;

		// Generate priority entries
		const priority_entries = Object.entries(highlight_priorities)
			.map(([token, priority]) => `\t${token}: ${priority}`)
			.join(',\n');

		// Generate the type
		const token_names = Object.keys(highlight_priorities)
			.map((name) => `'${name}'`)
			.join(' | ');

		return `
			${banner}

			export type HighlightTokenName = ${token_names};

			export const highlight_priorities: Record<HighlightTokenName, number | undefined> = {
			${priority_entries},
			} as const;

			${banner}
		`;
	},
};