Update ObjC/Swift bridging header

update-bridging-header.rb

#!/usr/bin/ruby

require 'FileUtils'
require 'tempfile'

HEADER_TO_UPDATE = ARGV[0]
FOLDER_TO_SCAN = ARGV[1]
p "Bridging header to update: #{HEADER_TO_UPDATE}"
p "Folder to scan for ObjC headers: #{FOLDER_TO_SCAN}"

TEMP_BRIDGING_HEADER_FILE = "bridging-header.h"
# List of ObjC header files you want to be excluded, 
# Example:
# EXCLUDE_HEADERS = %w(DonWantThisHeader.h DontWantThisHeaderEither.h)
EXCLUDE_HEADERS = %w()

# Find all the ObjC header files 
files = Dir.glob("#{FOLDER_TO_SCAN}/**/*.h")
# Chop off the full path from each ObjC header and leave file name with extension
files.map! { |objc_header_file| File.basename(objc_header_file)}
# Reject all the excluded ObjC header files
files.reject!{ |element| EXCLUDE_HEADERS.include? element}
# Create import statement from each ObjC header file name
files.map! {|objc_header_file| "\#import \"#{objc_header_file}\"\n" }
# Sort the list for easy reading and diffs and merging
files.sort!

# Create temporary file
temp_file = Tempfile.new(TEMP_BRIDGING_HEADER_FILE)
p "Using temp file: #{temp_file.path}"

# This is to allow for custom content in the bridging header
# i.e comments, manualy added imports
#
# The script will read and preserve the bridging header file 
# up to the line saying "FOLLOWING LINES ARE AUTO-GENERATED"
File.open(HEADER_TO_UPDATE, "r") do |file|
  file.each do |line|
    temp_file.write(line)
    break if line.include? "FOLLOWING LINES ARE AUTO-GENERATED"
  end
end

# Append all the import statements for ObjC header files
files.each { |value| temp_file.write(value) }
# All the content is in the temp file
temp_file.close

# See if generated content is any different from the existing bridging header
# This is to prevent from replacing the bridging if there's no change
# thanks to that Xcode will not rebuild the whole project if there is no change 
has_diffs = false
IO.popen("diff --ignore-space-change --side-by-side --suppress-common-lines #{temp_file.path} #{HEADER_TO_UPDATE}") { |io|
  has_diffs = (io.read.length != 0)
}
# Replace the original bridging header only if has changes
FileUtils.mv temp_file.path, HEADER_TO_UPDATE if has_diffs