class ActiveRecord::ConnectionAdapters::SchemaCache

def self.load_from(filename)
  return unless File.file?(filename)
  read(filename) do |file|
    if filename.include?(".dump")
      Marshal.load(file)
    else
      if YAML.respond_to?(:unsafe_load)
        YAML.unsafe_load(file)
      else
        YAML.load(file)
      end
    end
  end
end

def self.read(filename, &block)
  if File.extname(filename) == ".gz"
    Zlib::GzipReader.open(filename) { |gz|
      yield gz.read
    }
  else
    yield File.read(filename)
  end
end

def add(table_name)
  if data_source_exists?(table_name)
    primary_keys(table_name)
    columns(table_name)
    columns_hash(table_name)
    indexes(table_name)
  end
end

def clear!
  @columns.clear
  @columns_hash.clear
  @primary_keys.clear
  @data_sources.clear
  @indexes.clear
  @version = nil
  @database_version = nil
end

def clear_data_source_cache!(name)
  @columns.delete name
  @columns_hash.delete name
  @primary_keys.delete name
  @data_sources.delete name
  @indexes.delete name
end

def columns(table_name)
  if ignored_table?(table_name)
    raise ActiveRecord::StatementInvalid, "Table '#{table_name}' doesn't exist"
  end
  @columns.fetch(table_name) do
    @columns[deep_deduplicate(table_name)] = deep_deduplicate(connection.columns(table_name))
  end
end

def columns_hash(table_name)
  @columns_hash.fetch(table_name) do
    @columns_hash[deep_deduplicate(table_name)] = columns(table_name).index_by(&:name).freeze
  end
end

def columns_hash?(table_name)
  @columns_hash.key?(table_name)
end

def data_source_exists?(name)
  return if ignored_table?(name)
  prepare_data_sources if @data_sources.empty?
  return @data_sources[name] if @data_sources.key? name
  @data_sources[deep_deduplicate(name)] = connection.data_source_exists?(name)
end

def data_sources(name)
  @data_sources[name]
end

def database_version # :nodoc:
  @database_version ||= connection.get_database_version
end

def deep_deduplicate(value)
  case value
  when Hash
    value.transform_keys { |k| deep_deduplicate(k) }.transform_values { |v| deep_deduplicate(v) }
  when Array
    value.map { |i| deep_deduplicate(i) }
  when String, Deduplicable
    -value
  else
    value
  end
end

def derive_columns_hash_and_deduplicate_values
  @columns      = deep_deduplicate(@columns)
  @columns_hash = @columns.transform_values { |columns| columns.index_by(&:name) }
  @primary_keys = deep_deduplicate(@primary_keys)
  @data_sources = deep_deduplicate(@data_sources)
  @indexes      = deep_deduplicate(@indexes)
end

def dump_to(filename)
  clear!
  tables_to_cache.each { |table| add(table) }
  open(filename) { |f|
    if filename.include?(".dump")
      f.write(Marshal.dump(self))
    else
      f.write(YAML.dump(self))
    end
  }
end

def encode_with(coder)
  reset_version!
  coder["columns"]          = @columns
  coder["primary_keys"]     = @primary_keys
  coder["data_sources"]     = @data_sources
  coder["indexes"]          = @indexes
  coder["version"]          = @version
  coder["database_version"] = database_version
end

def ignored_table?(table_name)
  ActiveRecord.schema_cache_ignored_tables.any? do |ignored|
    ignored === table_name
  end
end

def indexes(table_name)
  @indexes.fetch(table_name) do
    if data_source_exists?(table_name)
      @indexes[deep_deduplicate(table_name)] = deep_deduplicate(connection.indexes(table_name))
    else
      []
    end
  end
end

def init_with(coder)
  @columns          = coder["columns"]
  @primary_keys     = coder["primary_keys"]
  @data_sources     = coder["data_sources"]
  @indexes          = coder["indexes"] || {}
  @version          = coder["version"]
  @database_version = coder["database_version"]
  derive_columns_hash_and_deduplicate_values
end

def initialize(conn)
  @connection = conn
  @columns      = {}
  @columns_hash = {}
  @primary_keys = {}
  @data_sources = {}
  @indexes      = {}
end

def initialize_dup(other)
  super
  @columns      = @columns.dup
  @columns_hash = @columns_hash.dup
  @primary_keys = @primary_keys.dup
  @data_sources = @data_sources.dup
  @indexes      = @indexes.dup
end

def marshal_dump
  reset_version!
  [@version, @columns, {}, @primary_keys, @data_sources, @indexes, database_version]
end

def marshal_load(array)
  @version, @columns, _columns_hash, @primary_keys, @data_sources, @indexes, @database_version = array
  @indexes ||= {}
  derive_columns_hash_and_deduplicate_values
end

def open(filename)
  FileUtils.mkdir_p(File.dirname(filename))
  File.atomic_write(filename) do |file|
    if File.extname(filename) == ".gz"
      zipper = Zlib::GzipWriter.new file
      yield zipper
      zipper.flush
      zipper.close
    else
      yield file
    end
  end
end

def prepare_data_sources
  tables_to_cache.each do |source|
    @data_sources[source] = true
  end
end

def primary_keys(table_name)
  @primary_keys.fetch(table_name) do
    if data_source_exists?(table_name)
      @primary_keys[deep_deduplicate(table_name)] = deep_deduplicate(connection.primary_key(table_name))
    end
  end
end

def reset_version!
  @version = connection.schema_version
end

def size
  [@columns, @columns_hash, @primary_keys, @data_sources].sum(&:size)
end

def tables_to_cache
  connection.data_sources.reject do |table|
    ignored_table?(table)
  end
end