// File generated from our OpenAPI spec by Stainless. See CONTRIBUTING.md for details.

import fs from 'fs/promises';
import { getLogger } from './logger';
import { readEnv } from './util';

const INSTRUCTIONS_CACHE_TTL_MS = 15 * 60 * 1000; // 15 minutes

interface InstructionsCacheEntry {
  fetchedInstructions: string;
  fetchedAt: number;
}

const instructionsCache = new Map<string, InstructionsCacheEntry>();

export async function getInstructions({
  stainlessApiKey,
  customInstructionsPath,
}: {
  stainlessApiKey?: string | undefined;
  customInstructionsPath?: string | undefined;
}): Promise<string> {
  const now = Date.now();
  const cacheKey = customInstructionsPath ?? stainlessApiKey ?? '';
  const cached = instructionsCache.get(cacheKey);

  if (cached && now - cached.fetchedAt <= INSTRUCTIONS_CACHE_TTL_MS) {
    return cached.fetchedInstructions;
  }

  // Evict stale entries so the cache doesn't grow unboundedly.
  for (const [key, entry] of instructionsCache) {
    if (now - entry.fetchedAt > INSTRUCTIONS_CACHE_TTL_MS) {
      instructionsCache.delete(key);
    }
  }

  let fetchedInstructions: string;

  if (customInstructionsPath) {
    fetchedInstructions = await fetchLatestInstructionsFromFile(customInstructionsPath);
  } else {
    fetchedInstructions = await fetchLatestInstructionsFromApi(stainlessApiKey);
  }

  instructionsCache.set(cacheKey, { fetchedInstructions, fetchedAt: now });
  return fetchedInstructions;
}

async function fetchLatestInstructionsFromFile(path: string): Promise<string> {
  try {
    return await fs.readFile(path, 'utf-8');
  } catch (error) {
    getLogger().error({ error, path }, 'Error fetching instructions from file');
    throw error;
  }
}

async function fetchLatestInstructionsFromApi(stainlessApiKey: string | undefined): Promise<string> {
  // Setting the stainless API key is optional, but may be required
  // to authenticate requests to the Stainless API.
  const response = await fetch(
    readEnv('CODE_MODE_INSTRUCTIONS_URL') ?? 'https://api.stainless.com/api/ai/instructions/sgp-dev',
    {
      method: 'GET',
      headers: { ...(stainlessApiKey && { Authorization: stainlessApiKey }) },
    },
  );

  let instructions: string | undefined;
  if (!response.ok) {
    getLogger().warn(
      'Warning: failed to retrieve MCP server instructions. Proceeding with default instructions...',
    );

    instructions =
      '\n  This is the sgp-dev MCP server.\n\n  Available tools:\n  - search_docs: Search SDK documentation to find the right methods and parameters.\n  - execute: Run TypeScript code against a pre-authenticated SDK client. Define an async run(client) function.\n\n  Workflow:\n  - If unsure about the API, call search_docs first.\n  - Write complete solutions in a single execute call when possible. For large datasets, use API filters to narrow results or paginate within a single execute block.\n  - If execute returns an error, read the error and fix your code rather than retrying the same approach.\n  - Variables do not persist between execute calls. Return or log all data you need.\n  - Individual HTTP requests to the API have a 30-second timeout. If a request times out, try a smaller query or add filters.\n  - Code execution has a total timeout of approximately 5 minutes. If your code times out, simplify it or break it into smaller steps.\n  ';
  }

  instructions ??= ((await response.json()) as { instructions: string }).instructions;

  return instructions;
}