# frozen_string_literal: true

# transforms "english like" text queries into a where clause with regex
# https://www.postgresql.org/docs/9.5/textsearch-controls.html#TEXTSEARCH-PARSING-QUERIES

class TextToRegexQuery
  def initialize(text, fields, default_field, fields_mappings = {})
    @text = text.to_s.strip
    @fields = fields.map(&:to_sym)
    @default_field = default_field.to_sym
    @fields_mappings = fields_mappings.merge(@fields.reduce({}) do |mappings, field|
      table_name, field_name = field.to_s.split(".")
      mappings[field_name.to_sym] = field
      mappings 
    end)
  end

  def where_clause(query)
    @cleared_text = @text.dup
    @column_chunks = []
    remove_duplicated_spaces
    extract_columns
    escape_special_characters
    generate_where_clause(query)
  end

private

  def remove_duplicated_spaces
    @cleared_text.gsub!(/\s+/, ' ')
  end

  def escape_special_characters
    @cleared_text.gsub!(/\_/, '\_')
    @cleared_text.tr!('\\', '\\')
    @cleared_text.gsub!(/%/, '\%')
  end

  def extract_columns
    column_search_term_pairs = @cleared_text.scan(/([A-Za-z0-9_]+:[\w\_-]+)/)

    @column_chunks = (column_search_term_pairs.flatten.map do |pair|
      column, term = pair.split(':')
      next unless @fields_mappings.include?(column.to_sym) 
      @cleared_text.gsub!(pair, '')
      { @fields_mappings[column.to_sym] => term }
    end).compact
    unless @cleared_text.strip.empty?
      @column_chunks = [{ @default_field.to_s => @cleared_text.strip }] + @column_chunks
    end
    @column_chunks
  end

  def generate_where_clause(query)
    where_clause = ''
    columns = @column_chunks.map { |c| c.keys.first } 
    values = @column_chunks.map { |c| c.values.first }

    columns.each do |column|
      quoted_column = '"' + column.to_s.gsub(".",'"."') + '"'
      where_clause += "#{quoted_column} ILIKE ? OR "
    end
    where_clause += " 1<>1 "
    regexed_values = values.map { |v| "%#{v}%" } 
    query.where([where_clause] + regexed_values) 
  end
end