module ActiveRecord
  module ConnectionAdapters
    module MySQL
      module SchemaStatements # :nodoc:
        # Returns an array of indexes for the given table.
        def indexes(table_name, name = nil)
          if name
            ActiveSupport::Deprecation.warn(<<-MSG.squish)
              Passing name to #indexes is deprecated without replacement.
            MSG
          end

          indexes = []
          current_index = nil
          execute_and_free("SHOW KEYS FROM #{quote_table_name(table_name)}", "SCHEMA") do |result|
            each_hash(result) do |row|
              if current_index != row[:Key_name]
                next if row[:Key_name] == "PRIMARY" # skip the primary key
                current_index = row[:Key_name]

                mysql_index_type = row[:Index_type].downcase.to_sym
                case mysql_index_type
                when :fulltext, :spatial
                  index_type = mysql_index_type
                when :btree, :hash
                  index_using = mysql_index_type
                end

                indexes << IndexDefinition.new(
                  row[:Table],
                  row[:Key_name],
                  row[:Non_unique].to_i == 0,
                  type: index_type,
                  using: index_using,
                  comment: row[:Index_comment].presence
                )
              end

              indexes.last.columns << row[:Column_name]
              indexes.last.lengths.merge!(row[:Column_name] => row[:Sub_part].to_i) if row[:Sub_part]
              indexes.last.orders.merge!(row[:Column_name] => :desc) if row[:Collation] == "D"
            end
          end

          indexes
        end

        def remove_column(table_name, column_name, type = nil, options = {})
          if foreign_key_exists?(table_name, column: column_name)
            remove_foreign_key(table_name, column: column_name)
          end
          super
        end

        def internal_string_options_for_primary_key
          super.tap do |options|
            if CHARSETS_OF_4BYTES_MAXLEN.include?(charset) && (mariadb? || version < "8.0.0")
              options[:collation] = collation.sub(/\A[^_]+/, "utf8")
            end
          end
        end

        private
          CHARSETS_OF_4BYTES_MAXLEN = ["utf8mb4", "utf16", "utf16le", "utf32"]

          def schema_creation
            MySQL::SchemaCreation.new(self)
          end

          def create_table_definition(*args)
            MySQL::TableDefinition.new(*args)
          end

          def new_column_from_field(table_name, field)
            type_metadata = fetch_type_metadata(field[:Type], field[:Extra])
            if type_metadata.type == :datetime && field[:Default] == "CURRENT_TIMESTAMP"
              default, default_function = nil, field[:Default]
            else
              default, default_function = field[:Default], nil
            end

            MySQL::Column.new(
              field[:Field],
              default,
              type_metadata,
              field[:Null] == "YES",
              table_name,
              default_function,
              field[:Collation],
              comment: field[:Comment].presence
            )
          end

          def fetch_type_metadata(sql_type, extra = "")
            MySQL::TypeMetadata.new(super(sql_type), extra: extra)
          end

          def extract_foreign_key_action(specifier)
            super unless specifier == "RESTRICT"
          end

          def data_source_sql(name = nil, type: nil)
            scope = quoted_scope(name, type: type)

            sql = "SELECT table_name FROM information_schema.tables"
            sql << " WHERE table_schema = #{scope[:schema]}"
            sql << " AND table_name = #{scope[:name]}" if scope[:name]
            sql << " AND table_type = #{scope[:type]}" if scope[:type]
            sql
          end

          def quoted_scope(name = nil, type: nil)
            schema, name = extract_schema_qualified_name(name)
            scope = {}
            scope[:schema] = schema ? quote(schema) : "database()"
            scope[:name] = quote(name) if name
            scope[:type] = quote(type) if type
            scope
          end

          def extract_schema_qualified_name(string)
            schema, name = string.to_s.scan(/[^`.\s]+|`[^`]*`/)
            schema, name = nil, schema unless name
            [schema, name]
          end
      end
    end
  end
end