// Truncation logic derived from opencode (MIT) — https://github.com/sst/opencode

const MAX_LINES = 2000;
const MAX_BYTES = 50 * 1024; // 50 KB

export interface ITruncateResult {
  content: string;
  truncated: boolean;
  /** Set when truncated: describes what was dropped */
  notice?: string;
}

export function truncateOutput(
  text: string,
  options?: { maxLines?: number; maxBytes?: number },
): ITruncateResult {
  const maxLines = options?.maxLines ?? MAX_LINES;
  const maxBytes = options?.maxBytes ?? MAX_BYTES;
  const lines = text.split('\n');
  const totalBytes = Buffer.byteLength(text, 'utf-8');

  if (lines.length <= maxLines && totalBytes <= maxBytes) {
    return { content: text, truncated: false };
  }

  const out: string[] = [];
  let bytes = 0;
  for (let i = 0; i < lines.length && i < maxLines; i++) {
    const size = Buffer.byteLength(lines[i], 'utf-8') + (i > 0 ? 1 : 0);
    if (bytes + size > maxBytes) break;
    out.push(lines[i]);
    bytes += size;
  }

  const kept = out.length;
  const dropped = lines.length - kept;
  const notice = `\n[Output truncated: showing ${kept}/${lines.length} lines. ${dropped} lines omitted.]`;
  return { content: out.join('\n') + notice, truncated: true, notice };
}