import type {
  SgsMapSDKConstructor
} from '@/types/sgs-map-sdk'

let loadingScriptUrl = ''
let loadRequest: Promise<SgsMapSDKConstructor> | null = null

const findExistingScript = (scriptUrl: string) => (
  Array.from(document.scripts).find((script) => script.src.endsWith(scriptUrl) || script.getAttribute('src') === scriptUrl)
)

export const loadSgsMapScript = (scriptUrl: string): Promise<SgsMapSDKConstructor> => {
  if (typeof window === 'undefined' || typeof document === 'undefined') {
    return Promise.reject(new Error('SGS Map SDK 只能在 H5 浏览器环境中加载'))
  }

  if (window.SGSMapSDK) {
    return Promise.resolve(window.SGSMapSDK)
  }

  if (loadRequest && loadingScriptUrl === scriptUrl) {
    return loadRequest
  }

  loadingScriptUrl = scriptUrl
  const request = new Promise<SgsMapSDKConstructor>((resolve, reject) => {
    const existingScript = findExistingScript(scriptUrl)
    const script = existingScript || document.createElement('script')

    const resolveLoadedSdk = () => {
      if (!window.SGSMapSDK) {
        reject(new Error('SGS Map SDK 脚本已加载，但未发现 window.SGSMapSDK'))
        return
      }

      resolve(window.SGSMapSDK)
    }

    script.addEventListener('load', resolveLoadedSdk, { once: true })
    script.addEventListener('error', () => {
      reject(new Error(`SGS Map SDK 脚本加载失败: ${scriptUrl}`))
    }, { once: true })

    if (!existingScript) {
      script.src = scriptUrl
      script.async = true
      document.head.appendChild(script)
      return
    }

    if (window.SGSMapSDK) {
      resolveLoadedSdk()
    }
  }).finally(() => {
    loadRequest = null
  })

  loadRequest = request
  return request
}