const _ = require('lodash');
const elasticsearch = require('elasticsearch');

var TypeMapping = function(){

  // A list of all sources
  this.sources = [];

  // A list of alternate names for sources, mostly used to save typing
  this.source_aliases = {};

  // A list of all layers
  this.layers = [];

  /*
   * A list of all layers in each source. This is used for convenience elswhere
   * and to determine when a combination of source and layer parameters is
   * not going to match any records and will return no results.
   */
  this.layers_by_source = {};

  /*
   * A list of layer aliases that can be used to support specific use cases
   * (like coarse geocoding) * or work around the fact that different sources
   * may have layers that mean the same thing but have a different name
   */
  this.layer_aliases = {};

  /*
   * A list of the canonical sources included in the default Pelias configuration
   */
  this.canonical_sources = [];

  /*
   * An object that contains all sources or aliases. The key is the source or alias,
   * the value is either that source, or the canonical name for that alias if it's an alias.
   */
  this.source_mapping = {};

  /*
   * An object that has a key for each possible layer or alias,
   * and returns either that layer, or gall the layers in the alias
   */
  this.layer_mapping = {};
};

TypeMapping.addStandardTargetsToAliases = function(standard, aliases) {
  var combined = _.extend({}, aliases);
  standard.forEach(function(target) {
    if (combined[target] === undefined) {
      combined[target] = [target];
    }
  });

  return combined;
};

// source alias setter
TypeMapping.prototype.setSourceAliases = function( aliases ){
  this.source_aliases = aliases;
};

// layers-by-source alias setter
TypeMapping.prototype.setLayersBySource = function( lbs ){
  this.layers_by_source = lbs;
};

// layer alias setter
TypeMapping.prototype.setLayerAliases = function( aliases ){
  this.layer_aliases = aliases;
};

// canonical sources setter
TypeMapping.prototype.setCanonicalSources = function( sources ){
  this.canonical_sources = sources;
};

// generate mappings after setters have been run
TypeMapping.prototype.generateMappings = function(){
  this.sources = Object.keys( this.layers_by_source );
  this.source_mapping = TypeMapping.addStandardTargetsToAliases(this.sources, this.source_aliases);
  this.layers = _.uniq(Object.keys(this.layers_by_source).reduce(function(acc, key) {
    return acc.concat(this.layers_by_source[key]);
  }.bind(this), []));
  this.layer_mapping = TypeMapping.addStandardTargetsToAliases(this.layers, this.layer_aliases);
};

// generate a list of all layers which are part of the canonical Pelias configuration
TypeMapping.prototype.getCanonicalLayers = function(){
  var canonicalLayers = [];
  for( var source in this.layers_by_source ){
    if( _.includes( this.canonical_sources, source ) ){
      canonicalLayers = _.uniq( canonicalLayers.concat( this.layers_by_source[source] ) );
    }
  }
  return canonicalLayers;
};

// load values from targets block
TypeMapping.prototype.loadTargets = function( targetsBlock ){

  if( !_.isObject(targetsBlock) ){ return; }

  // set values from targets block
  this.setSourceAliases( targetsBlock.source_aliases || {} );
  this.setLayersBySource( targetsBlock.layers_by_source || {} );
  this.setLayerAliases( targetsBlock.layer_aliases || {} );
  this.setCanonicalSources( targetsBlock.canonical_sources || [] );

  // generate the mappings
  this.generateMappings();
};

// load values from either pelias config file or from elasticsearch
TypeMapping.prototype.load = function( done ){

  // load pelias config
  const peliasConfigTargets = _.get(
    require('pelias-config').generate(require('../schema')),
    'api.targets', {}
  );

  // load targets from config file
  this.loadTargets( peliasConfigTargets );

  // do not load values from elasticsearch
  if( true !== peliasConfigTargets.auto_discover ){
    if( 'function' === typeof done ){ done(); }
    return;
  }

  if( 'function' === typeof done ){ done(); }
  return;

  // load values from elasticsearch

  // create connection to elasticsearch
  // const esclient = elasticsearch.Client(peliasConfig.esclient);

  // const query = {
  //   requestCache: true,
  //   preference: '_replica_first',
  //   timeout: '10s',
  //   body: {
  //     aggs: {
  //       sources: {
  //         terms: {
  //           field: 'source',
  //           size: 100
  //         }
  //       },
  //       layers: {
  //         terms: {
  //           field: 'layer',
  //           size: 100
  //         }
  //       }
  //     },
  //     size: 0
  //   }
  // };

  // esclient.search( query, ( err, res ) => {
  //   console.error( err, res );
  // });
};

module.exports = TypeMapping;