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#
# Helper functions for managing more complex options
#

# Creates a string cache variable with multiple choices
#
# Usage:
#   gmx_option_multichoice(VAR "Description" DEFAULT_VALUE
#                          Value1 Value2 ... ValueN)
# Output:
#   VAR is set in the cache and in the caller's scope. The caller can assume
#   that it is always one of the provided values, converted to uppercase.
#
# Main benefit is that the list of allowed values only needs to be provided
# once, and gets used in multiple contexts:
#   1. It is automatically added to the description.
#   2. It is set as the STRINGS property of the created cache variable for use
#      with CMake GUIs.
#   3. The user-provided value is checked against the list, and a fatal error
#      is produced if the value is not known.  The caller does not need to
#      produce good error messages in cases where it may be necessary to check
#      for the validity again.
# As a special case, any "[built-in]" string in the allowed values is ignored
# when checking the user-provided value, but is added to all user-visible
# messages.
#
# It appears that ccmake does not use the STRINGS property, but perhaps some
# day...
#
function(GMX_OPTION_MULTICHOICE NAME DESCRIPTION DEFAULT)
    # Some processing of the input values
    string(REPLACE ";" ", " _allowed_comma_separated "${ARGN}")
    set(_description "${DESCRIPTION}. Pick one of: ${_allowed_comma_separated}")
    string(REPLACE "[built-in]" "" _allowed "${ARGN}")

    # Set the cache properties
    set(${NAME} ${DEFAULT} CACHE STRING ${_description})
    set_property(CACHE ${NAME} PROPERTY STRINGS ${_allowed})

    # Check that the value is one of the allowed
    set(_org_value "${${NAME}}")
    string(TOUPPER "${${NAME}}" ${NAME})
    string(TOUPPER "${_allowed}" _allowed_as_upper)
    list(FIND _allowed_as_upper "${${NAME}}" _found_index)
    if (_found_index EQUAL -1)
        message(FATAL_ERROR "Invalid value for ${NAME}: ${_org_value}.  "
                            "Pick one of: ${_allowed_comma_separated}")
    endif ()
    # Always provide the upper-case value to the caller
    set(${NAME} "${${NAME}}" PARENT_SCOPE)
endfunction()

# Convenience function for reporting a fatal error for an invalid input value
function(GMX_INVALID_OPTION_VALUE NAME)
    message(FATAL_ERROR "Invalid value for ${NAME}: ${${NAME}}")
endfunction()