import type { MarkdownIt, StateBlock, StateInline } from "markdown-it";

function commentInline(state: StateInline, silent: boolean): boolean {
	const src = state.src;
	const pos = state.pos;

	if (src.charCodeAt(pos) !== 0x25 || src.charCodeAt(pos + 1) !== 0x25)
		return false;

	const end = src.indexOf("%%", pos + 2);
	if (end === -1) return false;

	if (!silent) {
		state.pos = end + 2;
	}
	return true;
}

function commentBlock(
	state: StateBlock,
	startLine: number,
	endLine: number,
	silent: boolean,
): boolean {
	const startPos =
		(state.bMarks[startLine] ?? 0) + (state.tShift[startLine] ?? 0);
	const startMax = state.eMarks[startLine] ?? 0;

	if (startPos + 2 > startMax) return false;
	if (
		state.src.charCodeAt(startPos) !== 0x25 ||
		state.src.charCodeAt(startPos + 1) !== 0x25
	)
		return false;

	const restOfLine = state.src.slice(startPos + 2, startMax);
	const closeOnSameLine = restOfLine.indexOf("%%");
	if (closeOnSameLine !== -1) {
		// Whole-line comment only; if text follows the close, let the inline rule strip just the span.
		if (restOfLine.slice(closeOnSameLine + 2).trim() !== "") return false;
		if (silent) return true;
		state.line = startLine + 1;
		return true;
	}

	let nextLine = startLine;
	while (nextLine < endLine) {
		nextLine++;
		const lineStart =
			(state.bMarks[nextLine] ?? 0) + (state.tShift[nextLine] ?? 0);
		const lineEnd = state.eMarks[nextLine] ?? 0;
		const line = state.src.slice(lineStart, lineEnd);
		if (line.includes("%%")) {
			if (silent) return true;
			state.line = nextLine + 1;
			return true;
		}
	}

	return false;
}

export function commentPlugin(mdi: MarkdownIt): void {
	mdi.inline.ruler.before("escape", "obsidian_comment_inline", commentInline);
	mdi.block.ruler.before("paragraph", "obsidian_comment_block", commentBlock, {
		alt: ["paragraph", "reference", "blockquote"],
	});
}