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                for my $chunk (@$body) {
                    $writer->write($chunk) or die "failed to write chunk: $!";
                }
            } else {
                # IO::Handle-like object
                local $/ = \4096;
                while (defined(my $chunk = $body->getline)) {
                    $writer->write($chunk) or die "failed to write chunk: $!";
                }
            }
            $writer->close or die "failed to close writer: $!";
            return;
        };
        $response->($psgi_responder);
    };
}

sub _format_response_stream {
    my ($self, $status, $headers) = @_;
    my $headers_hash = {};
    my $cookies = [];

    Plack::Util::header_iter($headers, sub {
        my ($k, $v) = @_;
        $k = lc $k;
        if ($k eq 'set-cookie') {
            push @$cookies, string $v;
        } elsif (exists $headers_hash->{$k}) {
            $headers_hash->{$k} = ", $v";
        } else {
            $headers_hash->{$k} = string $v;
        }
    });

    return +{
        statusCode => number $status,
        headers    => $headers_hash,
        cookies    => $cookies,
    };
}

1;
__END__

=encoding utf-8

=head1 NAME

AWS::Lambda::PSGI - It translates event of Lambda Proxy Integrations in API Gateway and 
Application Load Balancer into L<PSGI>.

=head1 SYNOPSIS

Add the following script into your Lambda code archive.

    use utf8;
    use warnings;
    use strict;
    use AWS::Lambda::PSGI;

    my $app = require "$ENV{'LAMBDA_TASK_ROOT'}/app.psgi";
    my $func = AWS::Lambda::PSGI->wrap($app);

    sub handle {
        return $func->(@_);
    }

    1;

And then, L<Set up Lambda Proxy Integrations in API Gateway|https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html> or
L<Lambda Functions as ALB Targets|https://docs.aws.amazon.com/elasticloadbalancing/latest/application/lambda-functions.html>

=head1 DESCRIPTION

=head2 Streaming Response

L<AWS::Lambda::PSGI> supports L<response streaming|https://docs.aws.amazon.com/lambda/latest/dg/configuration-response-streaming.html>.
The function urls's invoke mode is configured as C<"RESPONSE_STREAM">, and Lambda environment variable "PERL5_LAMBDA_PSGI_INVOKE_MODE" is set to C<"RESPONSE_STREAM">.

    ExampleApi:
        Type: AWS::Serverless::Function
        Properties:
            FunctionUrlConfig:
                AuthType: NONE
                InvokeMode: RESPONSE_STREAM
            Environment:
                Variables:
                PERL5_LAMBDA_PSGI_INVOKE_MODE: RESPONSE_STREAM
            # (snip)

In this mode, the PSGI server accepts L<Delayed Response and Streaming Body|https://metacpan.org/pod/PSGI#Delayed-Response-and-Streaming-Body>.

    my $app = sub {
        my $env = shift;
    
        return sub {
            my $responder = shift;
            $responder->([ 200, ['Content-Type' => 'text/plain'], [ "Hello World" ] ]);
        };
    };

An application MAY omit the third element (the body) when calling the responder.

    my $app = sub {
        my $env = shift;
    
        return sub {
            my $responder = shift;
            my $writer = $responder->([ 200, ['Content-Type' => 'text/plain'] ]);
            $writer->write("Hello World");
            $writer->close;
        };
    };

=head2 Request ID

L<AWS::Lambda::PSGI> injects the request id that compatible with L<Plack::Middleware::RequestId>.

    env->{'psgix.request_id'} # It is same value with $context->aws_request_id

=head1 LICENSE