import type { LiteLLMModel, LiteLLMModelsResponse } from '../types'

export const DEFAULT_LITELLM_URL = 'http://localhost:4000'
const MODELS_ENDPOINT = '/v1/models'
const REQUEST_TIMEOUT_MS = 3000

/**
 * Normalise a base URL so the rest of the plugin can rely on a
 * predictable shape (no trailing slash, no `/v1` suffix).
 */
export function normalizeBaseURL(baseURL: string = DEFAULT_LITELLM_URL): string {
  let normalized = baseURL.replace(/\/+$/, '')
  if (normalized.endsWith('/v1')) {
    normalized = normalized.slice(0, -3)
  }
  return normalized
}

/** Build a full URL for a given API endpoint. */
export function buildAPIURL(baseURL: string, endpoint: string = MODELS_ENDPOINT): string {
  return `${normalizeBaseURL(baseURL)}${endpoint}`
}

function buildHeaders(apiKey?: string, customHeaders?: Record<string, string>): Record<string, string> {
  const headers: Record<string, string> = {
    'Content-Type': 'application/json',
  }
  const key = apiKey ?? process.env.LITELLM_API_KEY ?? process.env.LITELLM_MASTER_KEY
  if (key) {
    headers['Authorization'] = `Bearer ${key}`
  }
  if (customHeaders) {
    Object.assign(headers, customHeaders)
  }
  return headers
}

/** Lightweight ping to see whether a LiteLLM server is reachable. */
export async function checkLiteLLMHealth(
  baseURL: string = DEFAULT_LITELLM_URL,
  apiKey?: string,
  customHeaders?: Record<string, string>,
): Promise<boolean> {
  try {
    const response = await fetch(buildAPIURL(baseURL), {
      method: 'GET',
      headers: buildHeaders(apiKey, customHeaders),
      signal: AbortSignal.timeout(REQUEST_TIMEOUT_MS),
    })
    // 401 still means a server is alive — we just don't have the right
    // credentials. Surface that as "unhealthy" so the user is prompted
    // to set LITELLM_API_KEY.
    return response.ok
  } catch {
    return false
  }
}

/** Discover all models exposed by a LiteLLM proxy. */
export async function discoverLiteLLMModels(
  baseURL: string = DEFAULT_LITELLM_URL,
  apiKey?: string,
  customHeaders?: Record<string, string>,
): Promise<LiteLLMModel[]> {
  const url = buildAPIURL(baseURL)
  const response = await fetch(url, {
    method: 'GET',
    headers: buildHeaders(apiKey, customHeaders),
    signal: AbortSignal.timeout(REQUEST_TIMEOUT_MS),
  })

  if (!response.ok) {
    throw new Error(`LiteLLM responded with HTTP ${response.status} ${response.statusText}`)
  }

  const data = (await response.json()) as LiteLLMModelsResponse
  return data.data ?? []
}

/**
 * Try the most common ports a LiteLLM proxy is started on.
 * The default `litellm --port` is 4000, but 8000 is also widely used
 * and 8080 is a common reverse-proxy default.
 */
export async function autoDetectLiteLLM(apiKey?: string, customHeaders?: Record<string, string>): Promise<string | null> {
  const commonPorts = [4000, 8000, 8080]
  for (const port of commonPorts) {
    const baseURL = `http://localhost:${port}`
    if (await checkLiteLLMHealth(baseURL, apiKey, customHeaders)) {
      return baseURL
    }
  }
  return null
}