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: 'localhost',
    dbname: 'leqsikoni',
    user: 'leqsikoni',
    password: 'password',
  ).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, locale: params[:locale] do |context|
    word_id = Integer params[:id]

    word_info = context.word_info(word_id)

    json({
      primary_form: word_info[:primary_form],
      part_of_speech: context.part_of_speech_name(word_id),
      commentary: word_info[:commentary],
      translations: context.translations(word_id),
      inflections: context.inflections(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(locale:)
    self.locale = locale
  end

private

  attr_reader :locale, :locale_id

  def call(db_pool:)
    db_pool.with do |db_conn|
      @locale_id = db_conn.exec_params(
        (
          <<~SQL
            SELECT id
            FROM languages
            WHERE code = $1 OR code = 'en'
            ORDER BY
              (CASE WHEN code != 'en' THEN 1 ELSE 2 END) ASC
            LIMIT 1
          SQL
        ),
        [locale],
      ).values.first&.first

      @db_conn = db_conn
      result = yield self
      @db_conn = nil

      result
    end
  end

  def locale=(locale)
    @locale = String(locale).strip.freeze
  end

public

  ##
  # @return [Hash{Symbol => String}, nil]
  #
  def word_info(word_id)
    word_id = Integer word_id

    row = @db_conn.exec_params(
      'SELECT primary_form, commentary FROM words WHERE id = $1',
      [word_id],
    ).to_a.first

    primary_form = String(row['primary_form']).strip.freeze
    primary_form = nil if primary_form.empty?

    commentary = String(row['commentary']).strip.freeze
    commentary = nil if commentary.empty?

    {
      primary_form: primary_form,
      commentary: commentary,
    }.freeze
  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, locale_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, locale_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

  def inflections(word_id)
    word_id = Integer word_id

    result = @db_conn.exec_params(
      (
        <<~SQL
          SELECT
            inflections.id,
            inflections.descr,
            word_forms.value,
            word_forms.other_word_id
          FROM words
          INNER JOIN parts
          ON parts.id = words.part_id
          INNER JOIN inflections
          ON inflections.part_id = parts.id
          FULL OUTER JOIN word_forms
          ON
            word_forms.inflection_id = inflections.id
            AND
            word_forms.word_id = $1
          WHERE words.id = $1
          ORDER BY inflections.index
        SQL
      ),
      [word_id],
    ).to_a

    result.map do |row|
      inflection_id = Integer row['id']
      inflection_descr = String(row['descr']).strip.freeze

      value = String(row['value']).strip.freeze
      value = nil if value.empty?

      unless row['other_word_id'].nil?
        other_word_id = Integer(row['other_word_id'])
      end

      {
        inflection_id: inflection_id,
        inflection_descr: inflection_descr,
        value: value,
        other_word_id: other_word_id,
      }
    end.freeze
  end

  def examples(word_id)
    word_id = Integer word_id

    left_lang_id  = 5 # Georgian
    right_lang_id = locale_id

    lang_order = left_lang_id < right_lang_id ? 'ASC' : 'DESC'

    result = @db_conn.exec_params(
      (
        <<~SQL
          SELECT
            foo.example_id,
            array_agg(foo.id    ORDER BY foo.language_id #{lang_order})::text[]
              AS ids,
            array_agg(foo.value ORDER BY foo.language_id #{lang_order})::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 = $2 OR language_id = $3)
            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, left_lang_id, right_lang_id],
    ).filter_map do |row|
      example_id = Integer(row['example_id'])

      left_id  = Integer(row['ids'].first) if row['ids'].size > 0
      right_id = Integer(row['ids'].last)  if row['ids'].size > 1

      left  = String(row['values'].first).strip.freeze if row['values'].size > 0
      right = String(row['values'].last).strip.freeze  if row['values'].size > 1

      next if left_id.nil? || left.nil?

      {
        example_id: example_id,
        left_id: left_id,
        right_id: right_id,
        left: left,
        right: right,
        highlights: [],
      }.freeze
    end.freeze

    highlights =
      @db_conn.exec_params(
        (
          <<~SQL
            SELECT
              example_texts.id AS example_text_id,
              array_agg(
                word_form_example_texts.pos
                ORDER BY word_form_example_texts.word_form_id
              ) AS positions,
              array_agg(
                word_forms.len
                ORDER BY word_forms.id
              ) AS lengths
            FROM example_texts
            INNER JOIN word_form_example_texts
            ON word_form_example_texts.example_text_id = example_texts.id
            INNER JOIN word_forms
            ON word_form_example_texts.word_form_id = word_forms.id
            WHERE
              language_id = $1::bigint
              AND
              example_texts.example_id = ANY($2::bigint[])
            GROUP BY example_texts.id
          SQL
        ),
        [
          left_lang_id,
          PG::TextEncoder::Array.new.encode(result.map { |h| h[:example_id] }),
        ],
      )
      .map do |row|
        example_text_id = Integer(row['example_text_id'])

        positions = row['positions'].map { |pos| Integer pos }.freeze
        lengths   = row['lengths'].map   { |len| Integer len }.freeze

        {
          example_text_id: example_text_id,
          data: positions.zip(lengths).map do |pos, len|
            { pos: pos, len: len }.freeze
          end.sort_by { |h| h[:pos] }.freeze,
        }
      end.to_a

    highlights.each do |highlight|
      result
        .find { |item| item[:left_id] == highlight[:example_text_id] }
        &.tap { |item| item[:highlights].replace highlight[:data] }
    end

    result.each { |h| h[:highlights].freeze }
  end
end