A script for downloading the AWS PHP SDK v3, stripping down to S3 functionality and then applying a custom namespace.

build-as3cf-aws3.sh

#!/usr/bin/env bash

set -e

if [ ! -d src/amazon-s3-and-cloudfront ]; then
    echo 'This script must be run from the repository root.'
    exit 1
fi

for PROG in composer find sed unzip
do
	which ${PROG}
	if [ 0 -ne $? ]
	then
		echo "${PROG} not found in path."
		exit 1
	fi
done

REPO_ROOT=${PWD}
TMP_ROOT="${REPO_ROOT}/aws3-build"
TARGET_DIR="${REPO_ROOT}/src/amazon-s3-and-cloudfront/vendor/Aws3"
SOURCE_ZIP="https://docs.aws.amazon.com/aws-sdk-php/v3/download/aws.zip"

if [ -d "${TMP_ROOT}" ]; then
    rm -rf "${TMP_ROOT}"
fi;

mkdir "${TMP_ROOT}"
cd "${TMP_ROOT}"

function log_step() {
    echo
    echo
    echo ${1}
    echo
    echo
}

log_step "Install the latest v3 of the AWS SDK"
mkdir sdk
(
    cd sdk
    curl -sL ${SOURCE_ZIP} -o aws.zip
    unzip aws.zip
    rm aws.zip

    # Delete everything from the SDK except for S3, CloudFront and Common files.
    find Aws/ -mindepth 1 -maxdepth 1 -type d \
      ! -name S3 \
      ! -name CloudFront \
      ! -name Api \
      ! -name Credentials \
      ! -name Crypto \
      ! -name data \
      ! -name Endpoint \
      ! -name EndpointV2 \
      ! -name EndpointDiscovery \
      ! -name Arn \
      ! -name Exception \
      ! -name Handler \
      ! -name Multipart \
      ! -name Signature \
      ! -name ClientSideMonitoring \
      ! -name Sts \
      ! -name Retry \
      ! -name DefaultsMode \
      ! -name Token \
      -exec rm -rf {} +

    # Delete SDK /data subfolders that are not known to be used by S3 or CloudFront.
    find Aws/data/ -mindepth 1 -maxdepth 1 -type d \
      ! -name s3 \
      ! -name cloudfront \
      ! -name sts \
      -exec rm -rf {} +

    # Remove polyfill, tests & docs
    find . -type d -iname tests -exec rm -rf {} +
    find . -type d -iname docs -exec rm -rf {} +

    # Remove unused classes from the autoloader's classmap.
    cat aws-autoloader.php | grep '__DIR__' | sed "s/^.*__DIR__ . '\///" | cut -d"'" -f1 | while read PHP_FILE_PATH
    do
      if [ ! -f $PHP_FILE_PATH ]
      then
        echo $PHP_FILE_PATH >> remove.list
      fi
    done
    if [ -f remove.list ]
    then
      cat aws-autoloader.php | grep -v -f remove.list > aws-autoloader.new && mv aws-autoloader.new aws-autoloader.php && rm remove.list
    fi
)

log_step "Run the prefixer, adding our namespace prefix" # Prefixed files are written into the ./sdk_prefixed directory.
../vendor/bin/php-scoper add-prefix --config=../scoper.inc.php --prefix="DeliciousBrains\\WP_Offload_Media\\Aws3" --output-dir=sdk_prefixed sdk/
(
    cd sdk_prefixed
    rm -rf composer

    # Set the locale to prevent sed errors from characters with different encoding.
    export LC_ALL=C
    # Perform regex search replace to clean up any missed replacements in string literals (1 literal backslash = 4 in the command)

    OS_NAME=`uname -s`
    if [ "Darwin" = "${OS_NAME}" ]
    then
		find . -type f -name "*.php" -print0 | xargs -0 sed -i '' -E "s:'(Aws|GuzzleHttp|Psr|JmesPath|Symfony)\\\\\\\\:'DeliciousBrains\\\\\\\\WP_Offload_Media\\\\\\\\Aws3\\\\\\\\\1\\\\\\\\:g"
		find . -type f -name "*.php" -print0 | xargs -0 sed -i '' -E "s:'\\\\\\\\(Aws|GuzzleHttp|Psr|JmesPath|Symfony)\\\\\\\\:'DeliciousBrains\\\\\\\\WP_Offload_Media\\\\\\\\Aws3\\\\\\\\\1\\\\\\\\:g"
		find . -type f -name "*.php" -print0 | xargs -0 sed -i '' -E "s:\"(Aws|GuzzleHttp|Psr|JmesPath|Symfony)\\\\\\\\:\"DeliciousBrains\\\\\\\\WP_Offload_Media\\\\\\\\Aws3\\\\\\\\\1\\\\\\\\:g"
    else
		find . -type f -name "*.php" -print0 | xargs -0 sed -i'' -E "s:'(Aws|GuzzleHttp|Psr|JmesPath|Symfony)\\\\\\\\:'DeliciousBrains\\\\\\\\WP_Offload_Media\\\\\\\\Aws3\\\\\\\\\1\\\\\\\\:g"
		find . -type f -name "*.php" -print0 | xargs -0 sed -i'' -E "s:'\\\\\\\\(Aws|GuzzleHttp|Psr|JmesPath|Symfony)\\\\\\\\:'DeliciousBrains\\\\\\\\WP_Offload_Media\\\\\\\\Aws3\\\\\\\\\1\\\\\\\\:g"
		find . -type f -name "*.php" -print0 | xargs -0 sed -i'' -E "s:\"(Aws|GuzzleHttp|Psr|JmesPath|Symfony)\\\\\\\\:\"DeliciousBrains\\\\\\\\WP_Offload_Media\\\\\\\\Aws3\\\\\\\\\1\\\\\\\\:g"
    fi
)

# Delete the target directory if it exists.
if [ -d "${TARGET_DIR}" ]; then
    rm -rf "${TARGET_DIR}"
fi

# Move the prefixed SDK files to the plugin's vendor directory where they are referenced.
mv sdk_prefixed "${TARGET_DIR}"

# Clean up the temporary working directory.
rm -rf "${TMP_ROOT}"

log_step "Done!"

scoper.inc.php

<?php
declare( strict_types=1 );

return [
	// Patch files that have been processed to fix any missed or incorrectly prefixed strings.
	'patchers' => [
		static function ( string $filePath, string $prefix, string $contents ): string {
			if ( false !== strpos( $filePath, 'Aws/Signature/SignatureV4.php' ) ) {
				return str_replace(
					'DeliciousBrains\\\\WP_Offload_Media\\\\Aws3\\\\Ymd\\\\THis\\\\Z',
					'Ymd\\\\THis\\\\Z',
					$contents
				);
			}

			if ( false !== strpos( $filePath, 'gcp-build/sdk/vendor/composer/autoload_real.php' ) ) {
				return str_replace(
					'spl_autoload_unregister(array(\'ComposerAutoloader',
					'spl_autoload_unregister(array(\'DeliciousBrains\\\\WP_Offload_Media\\\\Gcp\\\\ComposerAutoloader',
					$contents
				);
			}

			return $contents;
		},
	],
];