# This is called by cmake as an extermal process from
# ./source/creator/CMakeLists.txt to write ./source/creator/buildinfo.h

# Extract working copy information for SOURCE_DIR into MY_XXX variables
# with a default in case anything fails, for examble when using git-svn
set(MY_WC_HASH "unknown")
set(MY_WC_BRANCH "unknown")
set(MY_WC_COMMIT_TIMESTAMP 0)

# Guess if this is a SVN working copy and then look up the revision
if(EXISTS ${SOURCE_DIR}/.git)
	# The FindGit.cmake module is part of the standard distribution
	include(FindGit)
	if(GIT_FOUND)
		message(STATUS "-- Found Git: ${GIT_EXECUTABLE}")

		execute_process(COMMAND git rev-parse --abbrev-ref HEAD
		                WORKING_DIRECTORY ${SOURCE_DIR}
		                OUTPUT_VARIABLE MY_WC_BRANCH
		                OUTPUT_STRIP_TRAILING_WHITESPACE)

		if(MY_WC_BRANCH STREQUAL "HEAD")
			# Detached HEAD, check whether commit hash is reachable
			# in the master branch
			execute_process(COMMAND git rev-parse --short HEAD
			                WORKING_DIRECTORY ${SOURCE_DIR}
			                OUTPUT_VARIABLE MY_WC_HASH
			                OUTPUT_STRIP_TRAILING_WHITESPACE)

			execute_process(COMMAND git branch --list master --contains ${MY_WC_HASH}
			                WORKING_DIRECTORY ${SOURCE_DIR}
			                OUTPUT_VARIABLE _git_contains_check
			                OUTPUT_STRIP_TRAILING_WHITESPACE)

			STRING(REGEX REPLACE "^[ \t]+" "" _git_contains_check "${_git_contains_check}")
			if(_git_contains_check STREQUAL "master")
				set(MY_WC_BRANCH "master")
			else()
				execute_process(COMMAND git show-ref --tags -d
				                WORKING_DIRECTORY ${SOURCE_DIR}
				                OUTPUT_VARIABLE _git_tag_hashes
				                OUTPUT_STRIP_TRAILING_WHITESPACE)

				execute_process(COMMAND git rev-parse HEAD
				                WORKING_DIRECTORY ${SOURCE_DIR}
				                OUTPUT_VARIABLE _git_head_hash
				                OUTPUT_STRIP_TRAILING_WHITESPACE)

				if(_git_tag_hashes MATCHES "${_git_head_hash}")
					set(MY_WC_BRANCH "master")
				endif()

				unset(_git_tag_hashes)
				unset(_git_head_hashs)
			endif()


			unset(_git_contains_check)
		else()
			execute_process(COMMAND git log HEAD..@{u}
			                WORKING_DIRECTORY ${SOURCE_DIR}
			                OUTPUT_VARIABLE _git_below_check
			                OUTPUT_STRIP_TRAILING_WHITESPACE)
			if(NOT _git_below_check STREQUAL "")
				# If there're commits between HEAD and upstream this means
				# that we're reset-ed to older revision. Use it's hash then.
				execute_process(COMMAND git rev-parse --short HEAD
				                WORKING_DIRECTORY ${SOURCE_DIR}
				                OUTPUT_VARIABLE MY_WC_HASH
				                OUTPUT_STRIP_TRAILING_WHITESPACE)
			else()
				execute_process(COMMAND git rev-parse --short @{u}
				                WORKING_DIRECTORY ${SOURCE_DIR}
				                OUTPUT_VARIABLE MY_WC_HASH
				                OUTPUT_STRIP_TRAILING_WHITESPACE
				                ERROR_QUIET)

				if(MY_WC_HASH STREQUAL "")
					# Local branch, not set to upstream.
					# Well, let's use HEAD for now
					execute_process(COMMAND git rev-parse --short HEAD
					                WORKING_DIRECTORY ${SOURCE_DIR}
					                OUTPUT_VARIABLE MY_WC_HASH
					                OUTPUT_STRIP_TRAILING_WHITESPACE)
				endif()
			endif()

			unset(_git_below_check)
		endif()

		execute_process(COMMAND git log -1 --format=%ct
		                WORKING_DIRECTORY ${SOURCE_DIR}
		                OUTPUT_VARIABLE MY_WC_COMMIT_TIMESTAMP
		                OUTPUT_STRIP_TRAILING_WHITESPACE)

		# Update GIT index before getting dirty files
		execute_process(COMMAND git update-index -q --refresh
		                WORKING_DIRECTORY ${SOURCE_DIR}
		                OUTPUT_STRIP_TRAILING_WHITESPACE)

		execute_process(COMMAND git diff-index --name-only HEAD --
		                WORKING_DIRECTORY ${SOURCE_DIR}
		                OUTPUT_VARIABLE _git_changed_files
		                OUTPUT_STRIP_TRAILING_WHITESPACE)

		if(NOT _git_changed_files STREQUAL "")
			set(MY_WC_BRANCH "${MY_WC_BRANCH} (modified)")
		else()
			# Unpushed commits are also considered local odifications
			execute_process(COMMAND git log @{u}..
			                WORKING_DIRECTORY ${SOURCE_DIR}
			                OUTPUT_VARIABLE _git_unpushed_log
			                OUTPUT_STRIP_TRAILING_WHITESPACE
			                ERROR_QUIET)
			if(NOT _git_unpushed_log STREQUAL "")
				set(MY_WC_BRANCH "${MY_WC_BRANCH} (modified)")
			endif()
			unset(_git_unpushed_log)
		endif()

		unset(_git_changed_files)
	endif()
endif()

# BUILD_PLATFORM and BUILD_PLATFORM are taken from CMake
# but BUILD_DATE and BUILD_TIME are plataform dependant
if(UNIX)
	execute_process(COMMAND date "+%Y-%m-%d" OUTPUT_VARIABLE BUILD_DATE OUTPUT_STRIP_TRAILING_WHITESPACE)
	execute_process(COMMAND date "+%H:%M:%S" OUTPUT_VARIABLE BUILD_TIME OUTPUT_STRIP_TRAILING_WHITESPACE)
endif()
if(WIN32)
	execute_process(COMMAND cmd /c date /t OUTPUT_VARIABLE BUILD_DATE OUTPUT_STRIP_TRAILING_WHITESPACE)
	execute_process(COMMAND cmd /c time /t OUTPUT_VARIABLE BUILD_TIME OUTPUT_STRIP_TRAILING_WHITESPACE)
endif()

# Write a file with the SVNVERSION define
file(WRITE buildinfo.h.txt
	"#define BUILD_HASH \"${MY_WC_HASH}\"\n"
	"#define BUILD_COMMIT_TIMESTAMP ${MY_WC_COMMIT_TIMESTAMP}\n"
	"#define BUILD_BRANCH \"${MY_WC_BRANCH}\"\n"
	"#define BUILD_DATE \"${BUILD_DATE}\"\n"
	"#define BUILD_TIME \"${BUILD_TIME}\"\n"
)

# Copy the file to the final header only if the version changes
# and avoid needless rebuilds
# TODO: verify this comment is true, as BUILD_TIME probably changes
execute_process(COMMAND ${CMAKE_COMMAND} -E copy_if_different
                        buildinfo.h.txt buildinfo.h)