module ActiveRecord::ConnectionAdapters::MySQL::SchemaStatements

def add_index_length(quoted_columns, **options)
  lengths = options_for_index_columns(options[:length])
  quoted_columns.each do |name, column|
    column << "(#{lengths[name]})" if lengths[name].present?
  end
end

def add_options_for_index_columns(quoted_columns, **options)
  quoted_columns = add_index_length(quoted_columns, **options)
  super
end

def create_schema_dumper(options)
  MySQL::SchemaDumper.create(self, options)
end

def create_table(table_name, options: default_row_format, **)
  super
end

def create_table_definition(name, **options)
  MySQL::TableDefinition.new(self, name, **options)
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]}"
  if scope[:name]
    sql << " AND table_name = #{scope[:name]}"
    sql << " AND table_name IN (SELECT table_name FROM information_schema.tables WHERE table_schema = #{scope[:schema]})"
  end
  sql << " AND table_type = #{scope[:type]}" if scope[:type]
  sql
end

def default_row_format
  return if row_format_dynamic_by_default?
  unless defined?(@default_row_format)
    if query_value("SELECT @@innodb_file_per_table = 1 AND @@innodb_file_format = 'Barracuda'") == 1
      @default_row_format = "ROW_FORMAT=DYNAMIC"
    else
      @default_row_format = nil
    end
  end
  @default_row_format
end

def default_type(table_name, field_name)
  match = create_table_info(table_name)&.match(/`#{field_name}` (.+) DEFAULT ('|\d+|[A-z]+)/)
  default_pre = match[2] if match
  if default_pre == "'"
    :string
  elsif default_pre&.match?(/^\d+$/)
    :integer
  elsif default_pre&.match?(/^[A-z]+$/)
    :function
  end
end

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

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

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

def indexes(table_name)
  indexes = []
  current_index = nil
  internal_exec_query("SHOW KEYS FROM #{quote_table_name(table_name)}", "SCHEMA").each 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 << [
        row["Table"],
        row["Key_name"],
        row["Non_unique"].to_i == 0,
        [],
        lengths: {},
        orders: {},
        type: index_type,
        using: index_using,
        comment: row["Index_comment"].presence
      ]
    end
    if expression = row["Expression"]
      expression = expression.gsub("\\'", "'")
      expression = +"(#{expression})" unless expression.start_with?("(")
      indexes.last[-2] << expression
      indexes.last[-1][:expressions] ||= {}
      indexes.last[-1][:expressions][expression] = expression
      indexes.last[-1][:orders][expression] = :desc if row["Collation"] == "D"
    else
      indexes.last[-2] << row["Column_name"]
      indexes.last[-1][:lengths][row["Column_name"]] = row["Sub_part"].to_i if row["Sub_part"]
      indexes.last[-1][:orders][row["Column_name"]] = :desc if row["Collation"] == "D"
    end
  end
  indexes.map do |index|
    options = index.pop
    if expressions = options.delete(:expressions)
      orders = options.delete(:orders)
      lengths = options.delete(:lengths)
      columns = index[-1].to_h { |name|
        [ name.to_sym, expressions[name] || +quote_column_name(name) ]
      }
      index[-1] = add_options_for_index_columns(
        columns, order: orders, length: lengths
      ).values.join(", ")
    end
    IndexDefinition.new(*index, **options)
  end
rescue StatementInvalid => e
  if e.message.match?(/Table '.+' doesn't exist/)
    []
  else
    raise
  end
end

def integer_to_sql(limit)
  case limit
  when 1; "tinyint"
  when 2; "smallint"
  when 3; "mediumint"
  when nil, 4; "int"
  when 5..8; "bigint"
  else raise ArgumentError, "No integer type has byte size #{limit}. Use a decimal with scale 0 instead."
  end
end

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

def limit_to_size(limit, type)
  case type.to_s
  when "text", "blob", "binary"
    case limit
    when 0..0xff;               "tiny"
    when nil, 0x100..0xffff;    nil
    when 0x10000..0xffffff;     "medium"
    when 0x1000000..0xffffffff; "long"
    else raise ArgumentError, "No #{type} type has byte size #{limit}"
    end
  end
end

def new_column_from_field(table_name, field, _definitions)
  field_name = field.fetch("Field")
  type_metadata = fetch_type_metadata(field["Type"], field["Extra"])
  default, default_function = field["Default"], nil
  if type_metadata.type == :datetime && /\ACURRENT_TIMESTAMP(?:\([0-6]?\))?\z/i.match?(default)
    default = "#{default} ON UPDATE #{default}" if /on update CURRENT_TIMESTAMP/i.match?(field["Extra"])
    default, default_function = nil, default
  elsif type_metadata.extra == "DEFAULT_GENERATED"
    default = +"(#{default})" unless default.start_with?("(")
    default = default.gsub("\\'", "'")
    default, default_function = nil, default
  elsif type_metadata.type == :text && default&.start_with?("'")
    # strip and unescape quotes
    default = default[1...-1].gsub("\\'", "'")
  elsif default&.match?(/\A\d/)
    # Its a number so we can skip the query to check if it is a function
  elsif default && default_type(table_name, field_name) == :function
    default, default_function = nil, default
  end
  MySQL::Column.new(
    field["Field"],
    default,
    type_metadata,
    field["Null"] == "YES",
    default_function,
    collation: field["Collation"],
    comment: field["Comment"].presence
  )
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 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 remove_foreign_key(from_table, to_table = nil, **options)
  # RESTRICT is by default in MySQL.
  options.delete(:on_update) if options[:on_update] == :restrict
  options.delete(:on_delete) if options[:on_delete] == :restrict
  super
end

def row_format_dynamic_by_default?
  if mariadb?
    database_version >= "10.2.2"
  else
    database_version >= "5.7.9"
  end
end

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

def table_alias_length
  256 # https://dev.mysql.com/doc/refman/en/identifiers.html
end

def type_to_sql(type, limit: nil, precision: nil, scale: nil, size: limit_to_size(limit, type), unsigned: nil, **)
  sql =
    case type.to_s
    when "integer"
      integer_to_sql(limit)
    when "text"
      type_with_size_to_sql("text", size)
    when "blob"
      type_with_size_to_sql("blob", size)
    when "binary"
      if (0..0xfff) === limit
        "varbinary(#{limit})"
      else
        type_with_size_to_sql("blob", size)
      end
    else
      super
    end
  sql = "#{sql} unsigned" if unsigned && type != :primary_key
  sql
end

def type_with_size_to_sql(type, size)
  case size&.to_s
  when nil, "tiny", "medium", "long"
    "#{size}#{type}"
  else
    raise ArgumentError,
      "#{size.inspect} is invalid :size value. Only :tiny, :medium, and :long are allowed."
  end
end

def update_table_definition(table_name, base)
  MySQL::Table.new(table_name, base)
end

def valid_primary_key_options
  super + [:unsigned, :auto_increment]
end