module RedhillonrailsCore::ActiveRecord::ConnectionAdapters
  module MysqlAdapter
    def self.included(base)
      base.class_eval do
        alias_method_chain :remove_column, :redhillonrails_core
        alias_method_chain :remove_columns, :redhillonrails_core
      end
    end

    def set_table_comment(table_name, comment)
      execute "ALTER TABLE #{table_name} COMMENT='#{quote_string(comment)}'"
    end
    
    def clear_table_comment(table_name)
      execute "ALTER TABLE #{table_name} COMMENT=''"
    end

    def remove_foreign_key(table_name, foreign_key_name)
      execute "ALTER TABLE #{table_name} DROP FOREIGN KEY #{foreign_key_name}"
    end

    def remove_column_with_redhillonrails_core(table_name, *column_names)
      raise ArgumentError.new("You must specify at least one column name.  Example: remove_column(:people, :first_name)") if column_names.empty?
      column_names.flatten.each do |column_name|
        foreign_keys(table_name).select { |foreign_key| foreign_key.column_names.include?(column_name.to_s) }.each do |foreign_key|
          remove_foreign_key(table_name, foreign_key.name)
        end
        remove_column_without_redhillonrails_core(table_name, column_name)
      end
    end
    alias :remove_columns_with_redhillonrails_core :remove_column_with_redhillonrails_core

    def foreign_keys(table_name, name = nil)
      results = execute("SHOW CREATE TABLE #{quote_table_name(table_name)}", name)

      foreign_keys = []

      results.each do |row|
        row[1].each_line do |line|
          if line =~ /^  CONSTRAINT [`"](.+?)[`"] FOREIGN KEY \([`"](.+?)[`"]\) REFERENCES [`"](.+?)[`"] \((.+?)\)( ON DELETE (.+?))?( ON UPDATE (.+?))?,?$/
            name = $1
            column_names = $2
            references_table_name = $3
            references_column_names = $4
            on_update = $8
            on_delete = $6
            on_update = on_update.downcase.gsub(' ', '_').to_sym if on_update
            on_delete = on_delete.downcase.gsub(' ', '_').to_sym if on_delete

            foreign_keys << ForeignKeyDefinition.new(name,
                                                     table_name, column_names.gsub('`', '').split(', '),
                                                     references_table_name, references_column_names.gsub('`', '').split(', '),
                                                     on_update, on_delete)
          end
        end
      end

      foreign_keys
    end

#    def reverse_foreign_keys(table_name, name = nil)
#      results = execute(<<-SQL, name)
#      SELECT constraint_name, table_name, column_name, referenced_table_name, referenced_column_name
#        FROM information_schema.key_column_usage
#        WHERE table_schema = SCHEMA()
#          AND referenced_table_schema = table_schema
#        ORDER BY constraint_name, ordinal_position;
#      SQL
#      current_foreign_key = nil
#      foreign_keys = []
#
#      results.each do |row|
#        next unless table_name.casecmp(row[3]) == 0
#        if current_foreign_key != row[0]
#          foreign_keys << ForeignKeyDefinition.new(row[0], row[1], [], row[3], [])
#          current_foreign_key = row[0]
#        end
#
#        foreign_keys.last.column_names << row[2]
#        foreign_keys.last.references_column_names << row[4]
#      end
#
#      foreign_keys
#    end

    def reverse_foreign_keys(table_name, name = nil)
#      @@schema ||= nil
#      @@schema_version ||= 0
#      current_version = ActiveRecord::Migrator.current_version
#      if @@schema.nil? || @@schema_version != current_version
#        @@schema_version = current_version
#        ans = execute(<<-SQL, name)
#        SELECT constraint_name, table_name, column_name, referenced_table_name, referenced_column_name
#          FROM information_schema.key_column_usage
#         WHERE table_schema = SCHEMA()
#           AND referenced_table_schema = table_schema
#         ORDER BY constraint_name, ordinal_position;
#        SQL
#        @@schema = []
#        ans.each do | row |
#          @@schema << [row[0], row[1], row[2], row[3], row[4]]
#        end
#      end
#      results = @@schema

      results = execute(<<-SQL, name)
      SELECT constraint_name, table_name, column_name, referenced_table_name, referenced_column_name
        FROM information_schema.key_column_usage
        WHERE table_schema = SCHEMA()
          AND referenced_table_schema = table_schema
        ORDER BY constraint_name, ordinal_position;
      SQL

      current_foreign_key = nil
      foreign_keys = []

      results.each do |row|
        next if row[3] != table_name
        if current_foreign_key != row[0]
          foreign_keys << ForeignKeyDefinition.new(row[0], row[1], [], row[3], [])
          current_foreign_key = row[0]
        end

        foreign_keys.last.column_names << row[2]
        foreign_keys.last.references_column_names << row[4]
      end

      foreign_keys
    end
  end
end