# * Returns a version string from Git
#
# These functions force a re-configure on each git commit so that you can trust the values of the
# variables in your build system.
#
# get_git_head_revision(<refspecvar> <hashvar> [<additional arguments to git describe> ...])
#
# Returns the refspec and sha hash of the current head revision
#
# git_describe(<var> [<additional arguments to git describe> ...])
#
# Returns the results of git describe on the source tree, and adjusting the output so that it tests
# false if an error occurs.
#
# git_get_exact_tag(<var> [<additional arguments to git describe> ...])
#
# Returns the results of git describe --exact-match on the source tree, and adjusting the output so
# that it tests false if there was no exact matching tag.
#
# git_local_changes(<var>)
#
# Returns either "CLEAN" or "DIRTY" with respect to uncommitted changes. Uses the return code of
# "git diff-index --quiet HEAD --". Does not regard untracked files.
#
# git_count_parent_commits(<var>)
#
# Returns number of commits preceeding current commit -1 if git rev-list --count HEAD failed or
# "GIT-NOTFOUND" if git executable was not found or "HEAD-HASH-NOTFOUND" if head hash was not found.
# I don't know if get_git_head_revision() must be called internally or not, as reason of calling it
# is not clear for me also in git_local_changes().
#
# Requires CMake 2.6 or newer (uses the 'function' command)
#
# Original Author: 2009-2010 Ryan Pavlik <rpavlik@iastate.edu> <abiryan@ryand.net>
# http://academic.cleardefinition.com Iowa State University HCI Graduate Program/VRAC
#
# Copyright Iowa State University 2009-2010. Distributed under the Boost Software License, Version
# 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

if(__get_git_revision_description)
  return()
endif()
set(__get_git_revision_description YES)

# We must run the following at "include" time, not at function call time, to find the path to this
# module rather than the path to a calling list file
get_filename_component(_gitdescmoddir ${CMAKE_CURRENT_LIST_FILE} PATH)

function(get_git_head_revision _refspecvar _hashvar)
  set(GIT_PARENT_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
  set(GIT_DIR "${GIT_PARENT_DIR}/.git")
  while(NOT EXISTS "${GIT_DIR}") # .git dir not found, search parent directories
    set(GIT_PREVIOUS_PARENT "${GIT_PARENT_DIR}")
    get_filename_component(GIT_PARENT_DIR ${GIT_PARENT_DIR} PATH)
    if(GIT_PARENT_DIR STREQUAL GIT_PREVIOUS_PARENT)
      # We have reached the root directory, we are not in git
      set(${_refspecvar}
          "GITDIR-NOTFOUND"
          PARENT_SCOPE
          )
      set(${_hashvar}
          "GITDIR-NOTFOUND"
          PARENT_SCOPE
          )
      return()
    endif()
    set(GIT_DIR "${GIT_PARENT_DIR}/.git")
  endwhile()
  # check if this is a submodule
  if(NOT IS_DIRECTORY ${GIT_DIR})
    file(READ ${GIT_DIR} submodule)
    string(REGEX REPLACE "gitdir: (.*)\n$" "\\1" GIT_DIR_RELATIVE ${submodule})
    get_filename_component(SUBMODULE_DIR ${GIT_DIR} PATH)
    get_filename_component(GIT_DIR ${SUBMODULE_DIR}/${GIT_DIR_RELATIVE} ABSOLUTE)
  endif()
  set(GIT_DATA "${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/git-data")
  if(NOT EXISTS "${GIT_DATA}")
    file(MAKE_DIRECTORY "${GIT_DATA}")
  endif()

  if(NOT EXISTS "${GIT_DIR}/HEAD")
    return()
  endif()
  set(HEAD_FILE "${GIT_DATA}/HEAD")
  configure_file("${GIT_DIR}/HEAD" "${HEAD_FILE}" COPYONLY)

  configure_file(
    "${_gitdescmoddir}/GetGitRevisionDescription.cmake.in" "${GIT_DATA}/grabRef.cmake" @ONLY
    )
  include("${GIT_DATA}/grabRef.cmake")

  set(${_refspecvar}
      "${HEAD_REF}"
      PARENT_SCOPE
      )
  set(${_hashvar}
      "${HEAD_HASH}"
      PARENT_SCOPE
      )
endfunction()

function(git_describe _var)
  if(NOT GIT_FOUND)
    find_package(Git QUIET)
  endif()
  get_git_head_revision(refspec hash)
  if(NOT GIT_FOUND)
    set(${_var}
        "GIT-NOTFOUND"
        PARENT_SCOPE
        )
    return()
  endif()
  if(NOT hash)
    set(${_var}
        "HEAD-HASH-NOTFOUND"
        PARENT_SCOPE
        )
    return()
  endif()

  # TODO sanitize if((${ARGN}" MATCHES "&&") OR (ARGN MATCHES "||") OR (ARGN MATCHES "\\;"))
  # message("Please report the following error to the project!") message(FATAL_ERROR "Looks like
  # someone's doing something nefarious with git_describe! Passed arguments ${ARGN}") endif()

  # message(STATUS "Arguments to execute_process: ${ARGN}")

  execute_process(
    COMMAND "${GIT_EXECUTABLE}" describe ${hash} ${ARGN}
    WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
    RESULT_VARIABLE res
    OUTPUT_VARIABLE out
    ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE
    )
  if(NOT res EQUAL 0)
    set(out "${out}-${res}-NOTFOUND")
  endif()

  set(${_var}
      "${out}"
      PARENT_SCOPE
      )
endfunction()

function(git_get_exact_tag _var)
  git_describe(out --exact-match ${ARGN})
  set(${_var}
      "${out}"
      PARENT_SCOPE
      )
endfunction()

function(git_local_changes _var)
  if(NOT GIT_FOUND)
    find_package(Git QUIET)
  endif()
  get_git_head_revision(refspec hash)
  if(NOT GIT_FOUND)
    set(${_var}
        "GIT-NOTFOUND"
        PARENT_SCOPE
        )
    return()
  endif()
  if(NOT hash)
    set(${_var}
        "HEAD-HASH-NOTFOUND"
        PARENT_SCOPE
        )
    return()
  endif()

  execute_process(
    COMMAND "${GIT_EXECUTABLE}" diff-index --quiet HEAD --
    WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
    RESULT_VARIABLE res
    OUTPUT_VARIABLE out
    ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE
    )
  if(res EQUAL 0)
    set(${_var}
        "CLEAN"
        PARENT_SCOPE
        )
  else()
    set(${_var}
        "DIRTY"
        PARENT_SCOPE
        )
  endif()
endfunction()

function(git_count_parent_commits _var)
  if(NOT GIT_FOUND)
    find_package(Git QUIET)
  endif()
  get_git_head_revision(refspec hash)
  if(NOT GIT_FOUND)
    set(${_var}
        "GIT-NOTFOUND"
        PARENT_SCOPE
        )
    return()
  endif()
  if(NOT hash)
    set(${_var}
        "HEAD-HASH-NOTFOUND"
        PARENT_SCOPE
        )
    return()
  endif()

  execute_process(
    COMMAND "${GIT_EXECUTABLE}" rev-list --count HEAD
    WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
    RESULT_VARIABLE res
    OUTPUT_VARIABLE out
    ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE
    )
  if(res EQUAL 0)
    set(${_var}
        "${out}"
        PARENT_SCOPE
        )
  else()
    set(${_var}
        "-1"
        PARENT_SCOPE
        )
  endif()

endfunction()
