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 '/words/:id' do
  Context.call db_pool: $DB_POOL, user_lang_id: 2 do |context|
    word_id = Integer params[:id]

    json({
      primary_form: context.primary_form(word_id),
      part_of_speech: context.part_of_speech_name(word_id),
      translations: context.translations(word_id),
      examples: context.examples(word_id),
    })
  end
end

class Context
  private_class_method :new

  def self.call(db_pool:, **kwargs, &block)
    new(**kwargs).send :call, db_pool: db_pool, &block
  end

  def initialize(user_lang_id:)
    self.user_lang_id = user_lang_id
  end

private

  attr_reader :user_lang_id

  def call(db_pool:)
    db_pool.with do |db_conn|
      @db_conn = db_conn
      result = yield self
      @db_conn = nil
      result
    end
  end

  def user_lang_id=(user_lang_id)
    return @user_lang_id = nil if user_lang_id.nil?

    user_lang_id = Integer user_lang_id
    raise unless user_lang_id.positive?

    @user_lang_id = user_lang_id
  end

public

  ##
  # @return [String, nil]
  #
  def primary_form(word_id)
    word_id = Integer word_id

    column = @db_conn.exec_params(
      'SELECT primary_form FROM words WHERE id = $1',
      [word_id],
    ).values.first&.first

    str = String(column).strip.freeze
    str unless str.empty?
  end

  ##
  # @return [String, nil]
  #
  def part_of_speech_name(word_id)
    word_id = Integer word_id

    column = @db_conn.exec_params(
      (
        <<~SQL
          SELECT part_names.value
          FROM words
          INNER JOIN parts
          ON words.part_id = parts.id
          INNER JOIN part_names
          ON part_names.part_id = parts.id
          WHERE
            words.id = $1
            AND (
              part_names.name_lang_id = $2
              OR
              $2 IS NULL
            )
          LIMIT 1
        SQL
      ),
      [word_id, user_lang_id],
    ).values.first&.first

    str = String(column).strip.freeze
    str unless str.empty?
  end

  def translations(word_id)
    word_id = Integer word_id

    values = @db_conn.exec_params(
      (
        <<~SQL
          SELECT
            translation_texts.value,
            translation_texts.commentary
          FROM words
          INNER JOIN translations
          ON translations.word_id = words.id
          INNER JOIN translation_texts
          ON translation_texts.translation_id = translations.id
          WHERE
            word_id = $1
            AND
            translation_texts.lang_id = $2
          ORDER BY translations.index ASC
        SQL
      ),
      [word_id, user_lang_id],
    ).to_a

    values.map.with_index do |row, index|
      commentary = String(row['commentary']).strip.freeze
      commentary = nil if commentary.empty?

      {
        index: index + 1,
        translation: String(row['value']).strip.freeze,
        commentary: commentary,
      }.freeze
    end.freeze
  end

  ##
  # @return [Array<Array(String, String)>]
  #
  def examples(word_id)
    word_id = Integer word_id

    result = @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(
                SELECT example_texts.example_id
                FROM words
                INNER JOIN word_forms
                ON word_forms.word_id = words.id
                INNER JOIN word_form_example_texts
                ON word_form_example_texts.word_form_id = word_forms.id
                INNER JOIN example_texts
                ON example_texts.id = word_form_example_texts.example_text_id
                WHERE words.id = $1
                GROUP BY example_texts.example_id
              )
              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
      ),
      [word_id],
    ).map { |row| row['values'] }

    result.map { |pair| pair.map(&:freeze).freeze }.freeze
  end
end