const API_BASE_STORAGE_KEY = 'x-financial-api-base-url'

function normalizeApiBaseUrl(value) {
  return String(value || '/api/v1').replace(/\/$/, '')
}

function isLoopbackHost(hostname) {
  const normalized = String(hostname || '').trim().toLowerCase()
  return normalized === '127.0.0.1' || normalized === 'localhost' || normalized === '0.0.0.0' || normalized === '::1'
}

function resolveBrowserReachableApiBaseUrl(value) {
  const normalized = normalizeApiBaseUrl(value)

  if (typeof window === 'undefined') {
    return normalized
  }

  try {
    const apiUrl = new URL(normalized)
    const browserHost = window.location.hostname

    if (isLoopbackHost(apiUrl.hostname) && browserHost && !isLoopbackHost(browserHost)) {
      apiUrl.hostname = browserHost
      return normalizeApiBaseUrl(apiUrl.toString())
    }
  } catch {
    return normalized
  }

  return normalized
}

function readStoredApiBaseUrl() {
  if (typeof window === 'undefined') {
    return ''
  }

  return resolveBrowserReachableApiBaseUrl(window.localStorage.getItem(API_BASE_STORAGE_KEY) || '')
}

let runtimeApiBaseUrl = normalizeApiBaseUrl('/api/v1')

if (typeof window !== 'undefined') {
  window.localStorage.removeItem(API_BASE_STORAGE_KEY)
}

export function setRuntimeApiBaseUrl(value) {
  runtimeApiBaseUrl = resolveBrowserReachableApiBaseUrl(value)

  if (typeof window !== 'undefined') {
    window.localStorage.setItem(API_BASE_STORAGE_KEY, runtimeApiBaseUrl)
  }
}

export function getRuntimeApiBaseUrl() {
  return runtimeApiBaseUrl
}

function buildUrl(path) {
  if (!path.startsWith('/')) {
    return `${runtimeApiBaseUrl}/${path}`
  }

  return `${runtimeApiBaseUrl}${path}`
}

export async function apiRequest(path, options = {}) {
  let response

  try {
    response = await fetch(buildUrl(path), {
      headers: {
        'Content-Type': 'application/json',
        ...(options.headers || {})
      },
      ...options
    })
  } catch {
    throw new Error('无法连接 FastAPI 后端服务，请确认后端已启动且浏览器可访问后端端口。')
  }

  let payload = null

  try {
    payload = await response.json()
  } catch {
    payload = null
  }

  if (!response.ok) {
    throw new Error(payload?.detail || '接口请求失败，请稍后重试。')
  }

  return payload
}