upgrade the script below to properly handle the editing of an iTunes dmg to allow it to run on a newer version of macOS than it is supposed to ru on


#!/bin/bash

# Function to log actions
log_action() {
    echo "$(date '+%Y-%m-%d %H:%M:%S') - $1" >> ~/Desktop/iTunesPatch.log
}

# Function to display messages
show_message() {
    osascript -e "display dialog \"$1\" buttons {\"OK\"} default button \"OK\""
}

# Function to handle errors
handle_error() {
    echo "Error: $1"
    log_action "ERROR: $1"
    show_message "$1"
    exit 1
}

# Backup iTunes if exists
backup_itunes() {
    local backup_dir="$1"
    if [ -d "/Applications/iTunes.app" ]; then
        echo "Backing up existing iTunes app..."
        mv /Applications/iTunes.app "$backup_dir/iTunes_Backup_$(date +'%Y-%m-%d_%H-%M-%S').app" || handle_error "Failed to backup iTunes."
        log_action "Backed up iTunes to $backup_dir."
    fi
}

# Verify if a file exists
verify_file() {
    local file="$1"
    if [ ! -f "$file" ]; then
        handle_error "File not found: $file"
    fi
}

# Ask user to choose iTunes version
choose_version() {
    osascript -e 'choose from list {"12.6.5.3", "12.8.2", "13.6.5.3"} with prompt "Select iTunes version to install:" default items {"12.6.5.3"}' > "$TEMP_DIR/selected_version.txt"
    VERSION=$(cat "$TEMP_DIR/selected_version.txt")
}

# Set the temporary directory and iTunes version
TEMP_DIR="${1:-~/tmp}"
mkdir -p "$TEMP_DIR" || handle_error "Failed to create temporary directory $TEMP_DIR."
choose_version

# Log start of script execution
log_action "Script execution started for iTunes version $VERSION."

# Select the iTunes DMG based on the version chosen
case "$VERSION" in
    "12.6.5.3")
        theDMG="https://support.apple.com/HT208079"
        ;;
    "12.8.2")
        theDMG="https://support.apple.com/kb/dl1977"
        ;;
    "13.6.5.3")
        theDMG="https://support.apple.com/kb/dl1985"
        ;;
    *)
        handle_error "Unsupported iTunes version selected."
        ;;
esac

# Prompt user to download the iTunes version if not already downloaded
if [ ! -f "$TEMP_DIR/iTunes.dmg" ]; then
    osascript -e "display dialog \"Please download iTunes version $VERSION DMG from $theDMG\" buttons {\"OK\"} default button \"OK\""
    exit 0
fi

# Mount the iTunes DMG
hdiutil mount "$TEMP_DIR/iTunes.dmg" || handle_error "Failed to mount the DMG."

# Extract and patch the iTunes application
pkgutil --expand /Volumes/iTunes/Install\\ iTunes.pkg "$TEMP_DIR" || handle_error "Failed to expand iTunes package."

# Unmount the DMG
hdiutil unmount /Volumes/iTunes/ || handle_error "Failed to unmount the DMG."

# Extract iTunes app from the package
cd "$TEMP_DIR/iTunesX.pkg" || handle_error "Failed to change directory to iTunesX.pkg."
cat Payload | gunzip -dc | cpio -i || handle_error "Failed to extract iTunes package."
ditto "$TEMP_DIR/iTunesX.pkg/Applications/iTunes.app" "$TEMP_DIR/iTunes.app" || handle_error "Failed to copy iTunes app."

# Modify version information in the iTunes app
plutil -replace CFBundleGetInfoString -string "iTunes $VERSION" "$TEMP_DIR/iTunes.app/Contents/Info.plist" || handle_error "Failed to update CFBundleGetInfoString."
plutil -replace CFBundleShortVersionString -string "$VERSION" "$TEMP_DIR/iTunes.app/Contents/Info.plist" || handle_error "Failed to update CFBundleShortVersionString."
plutil -replace CFBundleVersion -string "$VERSION" "$TEMP_DIR/iTunes.app/Contents/Info.plist" || handle_error "Failed to update CFBundleVersion."
plutil -replace CFBundleVersion -string "iTunes $VERSION" "$TEMP_DIR/iTunes.app/Contents/version.plist" || handle_error "Failed to update version.plist."
plutil -replace CFBundleShortVersionString -string "$VERSION" "$TEMP_DIR/iTunes.app/Contents/version.plist" || handle_error "Failed to update version.plist."

# Allow user to backup existing iTunes if exists
answer=$(osascript -e 'display dialog "Would you like to backup the existing iTunes app?" buttons {"Yes", "No"} default button "Yes"')
if [[ "$answer" == "Yes" ]]; then
    backup_dir=$(osascript -e 'choose folder with prompt "Select backup location"') || handle_error "Failed to select backup location."
    backup_itunes "$backup_dir"
fi

# Allow user to choose installation path for older version
answer=$(osascript -e 'display dialog "Would you like to install the older iTunes version to /Applications or a custom location?" buttons {"Default /Applications", "Custom Location"} default button "Default /Applications"')
if [[ "$answer" == "Default /Applications" ]]; then
    install_dir="/Applications/iTunes_Old.app"
else
    install_dir=$(osascript -e 'choose folder with prompt "Select custom installation folder"') || handle_error "Failed to select installation folder."
fi

# Copy the patched iTunes to the selected location
ditto "$TEMP_DIR/iTunes.app" "$install_dir" || handle_error "Failed to copy iTunes app to $install_dir."
show_message "Patched iTunes $VERSION was copied to $install_dir."
log_action "Patched iTunes $VERSION copied to $install_dir."

# Optionally create a DMG or PKG for the older iTunes version
answer=$(osascript -e 'display dialog "Save patched iTunes as dmg or pkg?" buttons {"DMG", "PKG", "No"} default button "No"')
if [[ "$answer" == "DMG" ]]; then
    hdiutil create -format UDRO -srcfolder "$TEMP_DIR/iTunes.app" ~/Desktop/iTunes_${VERSION}.dmg || handle_error "Failed to create DMG."
    show_message "iTunes_${VERSION}.dmg was saved on Desktop."
    log_action "Created iTunes_${VERSION}.dmg."
elif [[ "$answer" == "PKG" ]]; then
    pkgbuild --component "$TEMP_DIR/iTunes.app" --install-location /Applications ~/Desktop/iTunes_${VERSION}.pkg || handle_error "Failed to create iTunes PKG."
    show_message "iTunes_${VERSION}.pkg was saved on Desktop."
    log_action "Created iTunes_${VERSION}.pkg."
fi

# Delete temporary folder after installation
answer=$(osascript -e 'display dialog "Delete temporary folder?" buttons {"Yes", "No"} default button "Yes"')
if [[ "$answer" == "Yes" ]]; then
    rm -rf "$TEMP_DIR" || handle_error "Failed to delete temporary files."
    show_message "Temporary files were deleted."
    log_action "Temporary files deleted."
fi

# Log script completion
log_action "Script execution completed for iTunes version $VERSION."