#!/bin/bash
#Following the the spec set here https://semver.org/ (2.0.0)
#we have three parts to a version number:
major=0
minor=0
patch_level=0
#And there is a fourth additional label for the build metadata.
#These labels are for pre-release and build metadata.
meta=0

file_contents=""
#Looping code from
#https://stackoverflow.com/questions/10929453/read-a-file-line-by-line-assigning-the-value-to-a-variable
#Adding numbers in bash:
#https://stackoverflow.com/questions/6348902/how-can-i-add-numbers-in-a-bash-script
while IFS=' ' read -ra line; do
	if [[ $line != \#define* ]] 
	then
		continue
	fi
	#Lob off the quotes surrounding the version number.
	#After lobbing off the quotes, replace all instances of '-' with a period.
	version_number=($(echo ${line[2]:1:-1} | tr "-" "."))
	#The symbol name that #define was setting (i.e. KERNEL_VERSION_NUMBER).
	symbol=${line[1]}
	#Read in the version number and split it on all periods.
	IFS='.' read -a chunks <<<$version_number
	
	version_part_counter=0
	
	for i in "${chunks[@]}"; do
		
		case "$version_part_counter" in
		"0")
			major=$i
			;;
		"1")
			minor=$i
			;;
		"2")
			patch_level=$i
			;;
		"3")
			#Check to see if a second parameter has been passed.
			#It doesn't matter what its value is only that one is present.
			#If there isn't a second parameter set, then we increment the meta build
			#number, otherwise we decrement.
			if [ "$2" != "reset" ]
			then
				echo "Incrementing meta build number."
				meta=$(($i + 1))
			else
				echo "Resetting meta build number."
				meta=0
			fi
			;;
		esac
		
		version_part_counter=$(($version_part_counter + 1))
	done
	
	ver="$major.$minor.$patch_level-$meta"

	file_contents="$file_contents#ifndef ${symbol}\n#define ${symbol} \"$ver\"\n#endif\n"
done < "$1"

printf "$file_contents" > "$1"