import { foldLines } from "../views/engine/lexer.ts";

export interface FormatOptions {
	tabWidth?: number;
	useTabs?: boolean;
	printWidth?: number;
}
export type FormatLanguage = "spug" | "stpug" | "stug" | "stcss";

/** Shared by the CLI and Prettier plugin, with no subprocesses or write side effects. */
export async function formatSource(
	source: string,
	language: FormatLanguage,
	options: FormatOptions = {},
): Promise<string> {
	const prettier = await import("prettier");
	const scripts: string[] = [];
	let protectedSource = source.replace(
		/(^[\t ]*)(javascript!|typescript!|---)\s*\n([\s\S]*?)^\s*(end|---)\s*$/gm,
		(
			_match,
			indentation: string,
			directive: string,
			code: string,
			ending: string,
		) => {
			const index = scripts.length;
			scripts.push(JSON.stringify({ directive, code, ending }));
			return language === "stcss"
				? `/* MUDDLE_SCRIPT_${index} */`
				: `${indentation}MUDDLE_SCRIPT_${index}`;
		},
	);
	const rawBlocks: { marker: string; body: string[]; prefix: string }[] = [];
	if (language !== "stcss") {
		const sourceLines = protectedSource.split("\n");
		const output: string[] = [];
		for (let index = 0; index < sourceLines.length; index++) {
			const line = sourceLines[index]!;
			const match = /^(\s*)(?:[\w.#-]+(?:\([^]*\))?\.|\/\/-?|\$\$\$)\s*$/.exec(
				line,
			);
			if (!match) {
				output.push(line);
				continue;
			}
			const prefix = match[1]!;
			const body: string[] = [line.slice(prefix.length)];
			while (index + 1 < sourceLines.length) {
				const next = sourceLines[index + 1]!;
				if (
					next.trim() &&
					(next.match(/^\s*/)?.[0].length ?? 0) <= prefix.length
				)
					break;
				body.push(next.startsWith(prefix) ? next.slice(prefix.length) : next);
				index++;
			}
			const marker = `MUDDLE_RAW_${rawBlocks.length}`;
			rawBlocks.push({ marker, body, prefix });
			output.push(prefix + marker);
		}
		protectedSource = output.join("\n");
	}
	const unit = options.useTabs ? "\t" : " ".repeat(options.tabWidth ?? 2);
	let formatted: string;
	if (language === "stcss") {
		formatted = await prettier.format(protectedSource, {
			parser: "scss",
			plugins: [],
			tabWidth: options.tabWidth ?? 2,
			useTabs: options.useTabs ?? false,
			printWidth: options.printWidth ?? 80,
		});
	} else {
		const stack = [0];
		const lines: string[] = [];
		for (const line of foldLines(protectedSource)) {
			while (stack.length > 1 && line.indent < stack[stack.length - 1]!)
				stack.pop();
			if (line.indent > stack[stack.length - 1]!) stack.push(line.indent);
			const indent = unit.repeat(stack.length - 1);
			lines.push(`${indent}${line.text.trimEnd()}`);
		}
		formatted = `${lines.join("\n")}\n`;
	}
	for (let index = 0; index < scripts.length; index++) {
		const script = JSON.parse(scripts[index]!) as {
			directive: string;
			code: string;
			ending: string;
		};
		const code = await prettier.format(script.code, {
			parser: "typescript",
			plugins: [],
			tabWidth: options.tabWidth ?? 2,
			useTabs: options.useTabs ?? false,
		});
		const marker =
			language === "stcss"
				? new RegExp(`^[\\t ]*/\\* MUDDLE_SCRIPT_${index} \\*/`, "m")
				: new RegExp(`^([\\t ]*)MUDDLE_SCRIPT_${index}`, "m");
		formatted = formatted.replace(marker, (match) => {
			const indentation = match.match(/^[\t ]*/)?.[0] ?? "";
			return `${indentation}${script.directive}\n${code
				.trimEnd()
				.split("\n")
				.map((line) => `${indentation}${line}`)
				.join("\n")}\n${indentation}${script.ending}`;
		});
	}
	for (const block of rawBlocks)
		formatted = formatted.replace(
			new RegExp(`^([\\t ]*)${block.marker}$`, "m"),
			(_match, prefix: string) =>
				block.body.map((line) => prefix + line).join("\n"),
		);
	return formatted;
}