import type { CommitType } from "../../commit/types";

export interface TrivialChangeResult {
	isTrivial: true;
	type: CommitType;
	summary: string;
}

const WHITESPACE_ONLY_PATTERN = /^[-+][\t ]*$/;
const IMPORT_LINE_PATTERN = /^[-+]\s*(import\s|from\s|export\s.*from|require\(|module\.exports)/;
const EMPTY_LINE_PATTERN = /^[-+]\s*$/;

export function detectTrivialChange(diff: string): TrivialChangeResult | null {
	const lines = diff.split("\n");
	const changeLines = lines.filter(line => line.startsWith("+") || line.startsWith("-"));
	const contentLines = changeLines.filter(
		line => !line.startsWith("+++") && !line.startsWith("---") && !line.startsWith("@@"),
	);

	if (contentLines.length === 0) return null;

	if (isOnlyWhitespace(contentLines)) {
		return { isTrivial: true, type: "style", summary: "formatted code" };
	}

	if (isOnlyImports(contentLines)) {
		return { isTrivial: true, type: "style", summary: "reorganized imports" };
	}

	return null;
}

function isOnlyWhitespace(lines: string[]): boolean {
	for (const line of lines) {
		const content = line.slice(1);
		if (content.trim().length > 0 && !WHITESPACE_ONLY_PATTERN.test(line)) {
			return false;
		}
	}
	return true;
}

function isOnlyImports(lines: string[]): boolean {
	for (const line of lines) {
		if (EMPTY_LINE_PATTERN.test(line)) continue;
		if (!IMPORT_LINE_PATTERN.test(line)) {
			return false;
		}
	}
	return true;
}