/**
 * Sanitize a JSON Schema for OpenAI's structured-output API.
 *
 * OpenAI's `response_format` imposes constraints beyond standard JSON Schema:
 *
 * 1. Every object node **must** include `"type": "object"`.
 * 2. `additionalProperties` must be a boolean or a valid sub-schema with a
 *    `type` key — bare `{}` is rejected.
 * 3. `additionalProperties: true` is accepted but tells the model it can
 *    return extra keys — set to `false` if you want strict conformance.
 *
 * Zod v4's `toJSONSchema()` can violate (1) when `z.looseObject()` is used:
 * it emits `{ additionalProperties: true }` without `"type": "object"`.
 *
 * This module provides a single function to fix these issues so any agent
 * (Codex, future OpenAI-backed agents, etc.) can safely convert a Zod
 * schema to a JSON Schema for OpenAI.
 */

/**
 * Convert a Zod schema to an OpenAI-safe JSON Schema object.
 *
 * Usage:
 * ```ts
 * import { zodToOpenAISchema } from "./schema";
 * const jsonSchema = zodToOpenAISchema(myZodSchema);
 * ```
 */
export async function zodToOpenAISchema(zodSchema: unknown): Promise<Record<string, unknown>> {
  const { z } = await import("zod");
  const jsonSchema = z.toJSONSchema(zodSchema as any) as Record<string, unknown>;
  sanitizeForOpenAI(jsonSchema);
  return jsonSchema;
}

/**
 * In-place sanitize an existing JSON Schema object for OpenAI compatibility.
 * Useful when you already have a JSON Schema and just need to fix it up.
 */
export function sanitizeForOpenAI(node: unknown): void {
  if (node == null || typeof node !== "object") return;
  const obj = node as Record<string, unknown>;

  // Rule 1 & 2: If a node has `additionalProperties`, it must also
  // have `"type": "object"`.  Zod's toJSONSchema omits `type` on
  // passthrough objects, which OpenAI rejects.
  if ("additionalProperties" in obj && !("type" in obj)) {
    obj.type = "object";
  }

  // Rule 2b: If `additionalProperties` is an empty object `{}`,
  // OpenAI rejects it because it lacks a `type` key.  Coerce to `true`
  // which is semantically equivalent and accepted by OpenAI.
  if (
    typeof obj.additionalProperties === "object" &&
    obj.additionalProperties !== null &&
    !Array.isArray(obj.additionalProperties) &&
    Object.keys(obj.additionalProperties as object).length === 0
  ) {
    obj.additionalProperties = true;
  }

  // Recurse into all sub-schemas
  for (const value of Object.values(obj)) {
    if (Array.isArray(value)) {
      for (const item of value) sanitizeForOpenAI(item);
    } else if (typeof value === "object" && value !== null) {
      sanitizeForOpenAI(value);
    }
  }
}