import { truncateHead, type TruncationOptions, type TruncationResult } from "@mariozechner/pi-coding-agent";

function validateRange(start: number, end: number): void {
	if (!Number.isInteger(start) || start <= 0) {
		throw new Error(`Invalid start line "${start}". Line numbers must be positive integers.`);
	}
	if (!Number.isInteger(end) || end <= 0) {
		throw new Error(`Invalid end line "${end}". Line numbers must be positive integers.`);
	}
	if (end < start) {
		throw new Error(`Invalid range ${start}-${end}. End line must be greater than or equal to start line.`);
	}
}

export function splitLines(text: string): string[] {
	return text.split("\n");
}

export function sliceByLineRange(text: string, start: number, end: number): string {
	validateRange(start, end);
	const lines = splitLines(text);
	if (start > lines.length) {
		return "";
	}

	const clampedEnd = Math.min(end, lines.length);
	return lines.slice(start - 1, clampedEnd).join("\n");
}

export function compareSlices(oldText: string, newText: string, start: number, end: number): boolean {
	return sliceByLineRange(oldText, start, end) === sliceByLineRange(newText, start, end);
}

export function estimateTokens(text: string): number {
	if (text.length === 0) {
		return 0;
	}
	return Math.ceil(Buffer.byteLength(text, "utf-8") / 4);
}

export function truncateForReadcache(content: string, options?: TruncationOptions): TruncationResult {
	return truncateHead(content, options);
}