/**
 * Limits enforcement for workflow source and results.
 */

import { MAX_SOURCE_BYTES, MAX_RESULT_BYTES } from "./types.ts";

export interface LimitCheckResult {
  ok: boolean;
  reason?: string;
}

/**
 * Check that a workflow script does not exceed the source size limit.
 */
export function checkSourceLimit(source: string): LimitCheckResult {
  const bytes = Buffer.byteLength(source, "utf-8");
  if (bytes > MAX_SOURCE_BYTES) {
    return {
      ok: false,
      reason: `Workflow script is ${bytes} bytes; maximum is ${MAX_SOURCE_BYTES} bytes.`,
    };
  }
  return { ok: true };
}

/**
 * Truncate a step result to the max result bytes limit.
 * Returns the truncated string and whether truncation occurred.
 */
export function enforceResultLimit(
  output: string,
  maxBytes: number = MAX_RESULT_BYTES,
): { text: string; truncated: boolean } {
  const bytes = Buffer.byteLength(output, "utf-8");
  if (bytes <= maxBytes) return { text: output, truncated: false };

  // Truncate to byte limit, keeping valid UTF-8 at the boundary
  const buf = Buffer.from(output, "utf-8");
  let truncated = buf.subarray(0, maxBytes);
  // Walk back to last complete UTF-8 sequence
  while (truncated.length > 0) {
    try {
      const text = truncated.toString("utf-8");
      return {
        text: `${text}\n\n[Output truncated: ${bytes - Buffer.byteLength(text, "utf-8")} bytes omitted]`,
        truncated: true,
      };
    } catch {
      truncated = truncated.subarray(0, truncated.length - 1);
    }
  }
  return {
    text: "[Output truncated]",
    truncated: true,
  };
}

/**
 * Validate that all limits are satisfied for a workflow execution request.
 */
export function validateLimits(script: string): LimitCheckResult {
  const sourceCheck = checkSourceLimit(script);
  if (!sourceCheck.ok) return sourceCheck;
  return { ok: true };
}