backend/main.rb

#!/usr/bin/env ruby
# frozen_string_literal: true

require 'connection_pool'
require 'pg'
require 'sinatra'
require 'sinatra/json'

$DB_POOL = ConnectionPool.new size: 5, timeout: 5 do
  PG.connect(
    host: 'pg.causa-arcana.com',
    dbname: 'leqsikoni',
    user: 'leqsikoni',
    password: 'ggeucene3ou7mqh2upehhm52tfp5bkcj',
  ).tap do |conn|
    conn.type_map_for_results = PG::BasicTypeMapForResults.new conn
  end
end

before do
  headers 'Access-Control-Allow-Origin' => '*'
end

get '/examples' do
  $DB_POOL.with do |db_conn|
    ids =
      case params[:ids]
      when Array then params[:ids]
      when String then params[:ids].split(',')
      else raise 'Invalid param "ids"'
      end.map { |id| Integer id }

    examples = db_conn.exec_params(
      (
        <<~SQL
          SELECT
            array_agg(foo.value ORDER BY foo.language_id DESC)::text[] AS values
          FROM example_texts foo
          INNER JOIN (
            SELECT example_id, language_id, MIN(index) as min_index
            FROM example_texts
            WHERE
              example_id = ANY($1)
              AND
              (language_id = 5 OR language_id = 2)
            GROUP BY example_id, language_id
          ) bar
          ON
            foo.example_id  = bar.example_id  AND
            foo.language_id = bar.language_id AND
            foo.index       = bar.min_index
          GROUP BY foo.example_id
        SQL
      ),
      [PG::TextEncoder::Array.new.encode(ids)],
    ).map { |row| row['values'] }

    json examples
  end
end