class Ougai::Logger

def create_formatter
  proc do |severity, time, progname, data|
    JSON.generate({
      name: progname || @app_name,
      hostname: @hostname,
      pid: $$,
      level: to_level(severity),
      time: time.iso8601(3),
      v: 0
    }.merge(data)) + "\n"
  end
end

def debug(message, ex = nil, data = nil)
  super(to_item(message, ex, data))
end

def error(message, ex = nil, data = nil)
  super(to_item(message, ex, data))
end

def fatal(message, ex = nil, data = nil)
  super(to_item(message, ex, data))
end

def info(message, ex = nil, data = nil)
  super(to_item(message, ex, data))
end

def initialize(*args)
  super(*args)
  @default_message = 'No message'
  @app_name = File.basename($0, ".rb")
  @hostname = Socket.gethostname
  @ex_key = :err
  @ex_trace_indent = 2
  @formatter = create_formatter
end

def serialize_ex(ex)
  err = {
    name: ex.class.name,
    message: ex.to_s
  }
  if ex.backtrace
    sp = "\n" + ' ' * @ex_trace_indent
    err[:stack] = ex.backtrace.join(sp)
  end
  err
end

def to_item(msg, ex, data)
  item = {}
  if ex.nil?       # 1 arg
    if msg.is_a?(Exception)
      item[:msg] = msg.to_s
      item[@ex_key] = serialize_ex(msg)
    elsif msg.is_a?(Hash)
      item[:msg] = @default_message unless msg.key?(:msg)
      item.merge!(msg)
    else
      item[:msg] = msg.to_s
    end
  elsif data.nil?  # 2 args
    if ex.is_a?(Exception)
      item[:msg] = msg.to_s
      item[@ex_key] = serialize_ex(ex)
    elsif ex.is_a?(Hash)
      item.merge!(ex)
      if msg.is_a?(Exception)
        item[@ex_key] = serialize_ex(msg)
      else
        item[:msg] = msg.to_s
      end
    end
  elsif msg        # 3 args
    item[@ex_key] = serialize_ex(ex) if ex.is_a?(Exception)
    item.merge!(data) if data.is_a?(Hash)
    item[:msg] = msg.to_s
  else             # No args
    item[:msg] = @default_message
  end
  item
end

def to_level(severity)
  case severity
  when 'INFO'
    30
  when 'WARN'
    40
  when 'ERROR'
    50
  when 'FATAL'
    60
  else # DEBUG
    20
  end
end

def warn(message, ex = nil, data = nil)
  super(to_item(message, ex, data))
end