'use strict';

module.exports.create = function (deps, conf) {
  function dnsType(addr) {
    if (/^\d+\.\d+\.\d+\.\d+$/.test(addr)) {
      return 'A';
    }
    if (-1 !== addr.indexOf(':') && /^[a-f:\.\d]+$/i.test(addr)) {
      return 'AAAA';
    }
  }

  var tldCache = {};
  async function getTlds(provider) {
    async function updateCache() {
      var reqObj = {
        url: deps.OAUTH3.url.normalize(provider)+'/api/com.daplie.domains/prices'
      , method: 'GET'
      , json: true
      };

      var resp = await deps.OAUTH3.request(reqObj);
      var tldObj = {};
      resp.data.forEach(function (tldInfo) {
        if (tldInfo.enabled) {
          tldObj[tldInfo.tld] = true;
        }
      });

      tldCache[provider] = {
        time: Date.now()
      , tlds: tldObj
      };
      return tldObj;
    }

    // If we've never cached the results we need to return the promise that will fetch the recult,
    // otherwise we can return the cached value. If the cached value has "expired", we can still
    // return the cached value we just want to update the cache in parellel (making sure we only
    // update once).
    if (!tldCache[provider]) {
      return updateCache();
    }
    if (!tldCache[provider].updating && Date.now() - tldCache[provider].time > 24*60*60*1000) {
      tldCache[provider].updating = true;
      updateCache();
    }

    return tldCache[provider].tlds;
  }

  async function splitDomains(provider, domains) {
    var tlds = await getTlds(provider);
    return domains.map(function (domain) {
      var split = domain.split('.');
      var tldSegCnt = tlds[split.slice(-2).join('.')] ? 2 : 1;

      // Currently assuming that the sld can't contain dots, and that the tld can have at
      // most one dot. Not 100% sure this is a valid assumption, but exceptions should be
      // rare even if the assumption isn't valid.
      return {
        tld: split.slice(-tldSegCnt).join('.')
      , sld: split.slice(-tldSegCnt-1, -tldSegCnt).join('.')
      , sub: split.slice(0, -tldSegCnt-1).join('.')
      };
    });
  }

  async function setDeviceAddress(session, addr, domains) {
    var directives = await deps.OAUTH3.discover(session.token.aud);

    // Set the address of the device to our public address.
    await deps.request({
      url: deps.OAUTH3.url.normalize(directives.api)+'/api/com.daplie.domains/acl/devices/' + conf.device.hostname
    , method: 'POST'
    , headers: {
        'Authorization': 'Bearer ' + session.refresh_token
      , 'Accept': 'application/json; charset=utf-8'
      }
    , json: {
        addresses: [
          { value: addr, type:  dnsType(addr) }
        ]
      }
    });

    // Then update all of the records attached to our hostname, first removing the old records
    // to remove the reference to the old address, then creating new records for the same domains
    // using our new address.
    var allDns = await deps.OAUTH3.api(directives.api, {session: session, api: 'dns.list'});
    var ourDns = allDns.filter(function (record) {
      if (record.device !== conf.device.hostname) {
        return false;
      }
      if ([ 'A', 'AAAA' ].indexOf(record.type) < 0) {
        return false;
      }
      return domains.indexOf(record.host) !== -1;
    });

    // Of all the DNS records referring to our device and the current list of domains determine
    // which domains have records with outdated address, and which ones we can just leave be
    // without updating them.
    var badAddrDomains = ourDns.filter(function (record) {
      return record.value !== addr;
    }).map(record => record.host);
    var goodAddrDomains = ourDns.filter(function (record) {
      return record.value === addr && badAddrDomains.indexOf(record.host) < 0;
    }).map(record => record.host);
    var requiredUpdates = domains.filter(function (domain) {
      return goodAddrDomains.indexOf(domain) < 0;
    });

    var oldDns = await splitDomains(directives.api, badAddrDomains);
    var common = {
      api: 'devices.detach'
    , session: session
    , device: conf.device.hostname
    };
    await deps.PromiseA.all(oldDns.map(function (record) {
      return deps.OAUTH3.api(directives.api, Object.assign({}, common, record));
    }));
    if (conf.debug && badAddrDomains.length) {
      console.log('removed bad DNS records for ' + badAddrDomains.join(', '));
    }

    var newDns = await splitDomains(directives.api, requiredUpdates);
    common = {
      api: 'devices.attach'
    , session: session
    , device: conf.device.hostname
    , ip: addr
    , ttl: 300
    };
    await deps.PromiseA.all(newDns.map(function (record) {
      return deps.OAUTH3.api(directives.api, Object.assign({}, common, record));
    }));
    if (conf.debug && requiredUpdates.length) {
      console.log('set new DNS records for ' + requiredUpdates.join(', '));
    }
  }

  async function getDeviceAddresses(session) {
    var directives = await deps.OAUTH3.discover(session.token.aud);

    var result = await deps.request({
      url: deps.OAUTH3.url.normalize(directives.api)+'/api/org.oauth3.dns/acl/devices'
    , method: 'GET'
    , headers: {
        'Authorization': 'Bearer ' + session.refresh_token
      , 'Accept': 'application/json; charset=utf-8'
      }
    , json: true
    });

    if (!result.body) {
      throw new Error('No response body in request for device addresses');
    }
    if (result.body.error) {
      throw Object.assign(new Error('error getting device list'), result.body.error);
    }

    var dev = result.body.devices.filter(function (dev) {
      return dev.name === conf.device.hostname;
    })[0];
    return (dev || {}).addresses || [];
  }

  async function removeDomains(session, domains) {
    var directives = await deps.OAUTH3.discover(session.token.aud);

    var oldDns = await splitDomains(directives.api, domains);
    var common = {
      api: 'devices.detach'
    , session: session
    , device: conf.device.hostname
    };
    await deps.PromiseA.all(oldDns.map(function (record) {
      return deps.OAUTH3.api(directives.api, Object.assign({}, common, record));
    }));
  }

  return {
    getDeviceAddresses
  , setDeviceAddress
  , removeDomains
  };
};