import { URL } from 'url'
import HttpAgent from 'agentkeepalive'
import LRU from 'lru-cache'
import { getProxyAgent, ProxyAgentOptions } from '@pnpm/network.proxy-agent'
import { pickSettingByUrl  } from '@pnpm/network.config';

const HttpsAgent = HttpAgent.HttpsAgent

const DEFAULT_MAX_SOCKETS = 50

const AGENT_CACHE = new LRU({ max: 50 })

export type AgentOptions = ProxyAgentOptions & {
  noProxy?: boolean | string
}

export function getAgent (uri: string, opts: AgentOptions) {
  if ((opts.httpProxy || opts.httpsProxy) && !checkNoProxy(uri, opts)) {
    const proxyAgent = getProxyAgent(uri, opts)
    if (proxyAgent) return proxyAgent
  }
  return getNonProxyAgent(uri, opts)
}

function getNonProxyAgent (uri: string, opts: AgentOptions) {
  const parsedUri = new URL(uri)
  const isHttps = parsedUri.protocol === 'https:'

  const { ca, cert, key: certKey } = {
    ...opts,
    ...pickSettingByUrl(opts.clientCertificates, uri)
  }

  /* eslint-disable @typescript-eslint/prefer-nullish-coalescing */
  const key = [
    `https:${isHttps.toString()}`,
    `local-address:${opts.localAddress ?? '>no-local-address<'}`,
    `strict-ssl:${
      isHttps ? Boolean(opts.strictSsl).toString() : '>no-strict-ssl<'
    }`,
    `ca:${isHttps && (ca?.toString()) || '>no-ca<'}`,
    `cert:${isHttps && (cert?.toString()) || '>no-cert<'}`,
    `key:${isHttps && (certKey?.toString()) || '>no-key<'}`,
  ].join(':')
  /* eslint-enable @typescript-eslint/prefer-nullish-coalescing */

  if (AGENT_CACHE.peek(key)) {
    return AGENT_CACHE.get(key)
  }

  // If opts.timeout is zero, set the agentTimeout to zero as well. A timeout
  // of zero disables the timeout behavior (OS limits still apply). Else, if
  // opts.timeout is a non-zero value, set it to timeout + 1, to ensure that
  // the node-fetch-npm timeout will always fire first, giving us more
  // consistent errors.
  const agentTimeout =
    typeof opts.timeout !== 'number' || opts.timeout === 0
      ? 0
      : opts.timeout + 1

  // NOTE: localAddress is passed to the agent here even though it is an
  // undocumented option of the agent's constructor.
  //
  // This works because all options of the agent are merged with
  // all options of the request:
  // https://github.com/nodejs/node/blob/350a95b89faab526de852d417bbb8a3ac823c325/lib/_http_agent.js#L254
  const agent = isHttps
    ? new HttpsAgent({
        ca,
        cert,
        key: certKey,
        localAddress: opts.localAddress,
        maxSockets: opts.maxSockets ?? DEFAULT_MAX_SOCKETS,
        rejectUnauthorized: opts.strictSsl,
        timeout: agentTimeout,
      } as any) // eslint-disable-line @typescript-eslint/no-explicit-any
    : new HttpAgent({
        localAddress: opts.localAddress,
        maxSockets: opts.maxSockets ?? DEFAULT_MAX_SOCKETS,
        timeout: agentTimeout,
      } as any) // eslint-disable-line @typescript-eslint/no-explicit-any
  AGENT_CACHE.set(key, agent)
  return agent
}

function checkNoProxy (uri: string, opts: { noProxy?: boolean | string }) {
  const host = new URL(uri).hostname
    .split('.')
    .filter(x => x)
    .reverse()
  if (typeof opts.noProxy === 'string') {
    const noproxyArr = opts.noProxy.split(/\s*,\s*/g)
    return noproxyArr.some(no => {
      const noParts = no
        .split('.')
        .filter(x => x)
        .reverse()
      if (noParts.length === 0) {
        return false
      }
      for (let i = 0; i < noParts.length; i++) {
        if (host[i] !== noParts[i]) {
          return false
        }
      }
      return true
    })
  }
  return opts.noProxy
}