module Sequel
  module Schema
    module SQL
      RESTRICT = 'RESTRICT'.freeze
      CASCADE = 'CASCADE'.freeze
      NO_ACTION = 'NO ACTION'.freeze
      SET_NULL = 'SET NULL'.freeze
      SET_DEFAULT = 'SET DEFAULT'.freeze
    
      def on_delete_clause(action)
        case action
        when :restrict: RESTRICT
        when :cascade: CASCADE
        when :set_null: SET_NULL
        when :set_default: SET_DEFAULT
        else NO_ACTION
        end
      end
      
      AUTOINCREMENT = 'AUTOINCREMENT'.freeze

      def auto_increment_sql
        AUTOINCREMENT
      end
      
      COMMA_SEPARATOR = ', '.freeze
      UNIQUE = ' UNIQUE'.freeze
      NOT_NULL = ' NOT NULL'.freeze
      PRIMARY_KEY = ' PRIMARY KEY'.freeze

      TYPES = Hash.new {|h, k| k}
      TYPES[:double] = 'double precision'

      def column_definition_sql(column)
        sql = "#{column[:name]} #{TYPES[column[:type]]}"
        column[:size] ||= 255 if column[:type] == :varchar
        elements = column[:size] || column[:elements]
        sql << "(#{literal(elements)})" if elements
        sql << UNIQUE if column[:unique]
        sql << NOT_NULL if column[:null] == false
        sql << " DEFAULT #{literal(column[:default])}" if column.include?(:default)
        sql << PRIMARY_KEY if column[:primary_key]
        if column[:table]
          sql << " REFERENCES #{column[:table]}"
          sql << "(#{column[:key]})" if column[:key]
        end
        sql << " ON DELETE #{on_delete_clause(column[:on_delete])}" if column[:on_delete]
        sql << " #{auto_increment_sql}" if column[:auto_increment]
        sql
      end
  
      def column_list_sql(columns)
        columns.map {|c| column_definition_sql(c)}.join(COMMA_SEPARATOR)
      end
    
      UNDERSCORE = '_'.freeze

      def default_index_name(table_name, columns)
        "#{table_name}_#{columns.join(UNDERSCORE)}_index"
      end
    
      def index_definition_sql(table_name, index)
        columns = index[:columns].join(COMMA_SEPARATOR)
        index_name = index[:name] || default_index_name(table_name, index[:columns])
        if index[:unique]
          "CREATE UNIQUE INDEX #{index_name} ON #{table_name} (#{columns});"
        else
          "CREATE INDEX #{index_name} ON #{table_name} (#{columns});"
        end
      end
    
      def index_list_sql_list(table_name, indexes)
        indexes.map {|i| index_definition_sql(table_name, i)}
      end
  
      def create_table_sql_list(name, columns, indexes = nil)
        sql = ["CREATE TABLE #{name} (#{column_list_sql(columns)});"]
        if indexes && !indexes.empty?
          sql.concat(index_list_sql_list(name, indexes))
        end
        sql
      end
      
      def drop_table_sql(name)
        "DROP TABLE #{name};"
      end
    end
  end
end