#---------------------------------------------------------------------
## Checks the current return code from the previous command and prints
## an error message if that return code is an error code.
##
## @param error_message_to_print_if_error
##
## @return current_return_code (gives back the same return code the
##           function starts with)
#---------------------------------------------------------------------
_buildsys_chkerr() {
  local rc="$?"
  [ "$rc" -eq 0 ] && return 0
  message "${PROBLEM_COLOR}$*${DEFAULT_COLOR}"
  return "$rc"
}

#---------------------------------------------------------------------
## Maps build system names and aliases to unique build system names.
## Outputs the unique name if there is a match on the input.
##
## @param build_system (the build system name to map from)
#---------------------------------------------------------------------
buildsys_mapping() {
  local buildsys="$1"
  case "$buildsys" in
    autotools|configure)
      echo autotools
      ;;
    cmake)
      echo cmake
      ;;
    meson)
      echo meson
      ;;
  esac
}

#---------------------------------------------------------------------
## Routes requests for default option values to the matching build
## system function, if available.
##
## @param active_build_system (the currently active build system)
## @param setting_value (required, must be either enabled or disabled)
## @param setting_name (name of the option to set)
##
## @return 1 on invalid parameters
## @return 2 on unknown build system (no matching defaults)
#---------------------------------------------------------------------
buildsys_defaults() {
  local buildsys="$1"
  [ -n "$buildsys" ]
  _buildsys_chkerr "build system not defined" || return 1
  shift 1
  local func="$(buildsys_mapping "$buildsys")"
  [ -n func ]
  _buildsys_chkerr "no matching defaults function for $buildsys" || return 2
  func="buildsys_${func}_default"
  local func_check="$(command -v "$func")"
  case "$func_check" in
    "$func") ;;
    *) unset func ;;
  esac
  [ -n "$func" ]
  _buildsys_chkerr "$buildsys defaults function not defined: $func" || return 2
  "$func" "$@"
}

#---------------------------------------------------------------------
## Outputs the default enabled or default disabled, depending on the
## first parameter, for the given setting/option name.
##
## @param setting_value (required, must be either enabled or disabled)
## @param setting_name (name of the option to set)
##
## @return 1 on invalid parameters
#---------------------------------------------------------------------
buildsys_autotools_default() {
  [ "$#" -eq 2 ]
  _buildsys_chkerr "invalid parameters" || return 1
  local value="$1"
  local name="$2"
  printf -- '--%s-%s\n' "${value%d}" "$name"
}

#---------------------------------------------------------------------
## Outputs the default enabled or default disabled, depending on the
## first parameter, for the given setting/option name.
##
## @param setting_value (required, must be either enabled or disabled)
## @param setting_name (name of the option to set)
##
## @return 1 on invalid parameters
#---------------------------------------------------------------------
buildsys_cmake_default() {
  [ "$#" -eq 2 ]
  _buildsys_chkerr "invalid parameters" || return 1
  local value="$1"
  local name="$2"
  case "$value" in
    enabled) value=ON ;;
    disabled) value=OFF ;;
  esac
  printf -- '-D%s=%s\n' "$name" "$value"
}

#---------------------------------------------------------------------
## Outputs the default enabled or default disabled, depending on the
## first parameter, for the given setting/option name.
##
## @param setting_value (required, must be either enabled or disabled)
## @param setting_name (name of the option to set)
##
## @return 1 on invalid parameters
#---------------------------------------------------------------------
buildsys_meson_default() {
  [ "$#" -eq 2 ]
  _buildsys_chkerr "invalid parameters" || return 1
  local value="$1"
  local name="$2"
  printf -- '%s=%s\n' "$name" "$value"
}

#---------------------------------------------------------------------
## A wrapper over the usual depends and optional_depends functions.
## Translates dependencies in a DEPENDS file into the formats required
## for processing by the relevant build system(s) currently enabled.
##
## @param dependency_type (must be one of depends or optional_depends)
## @param -a active_build_system (optional, flag to specify the
##             currently active build system, overrides the build
##             system set in $SPELL_BUILD_SYSTEM)
## @param -g grimoire (optional, flag to specify the grimoire to use)
## @param -o global_optname (optional, flag to give the default option
##             name to use across all build systems)
## @param -sub sub_dependency (optional, flag to give the
##              sub-dependencies)
## @param spell_name (the name of the actual dependency as a spell)
## @param [-b] build_system (the build system to define options for,
##               e.g. cmake, meson, autotools, etc.)
## @param -o local_optname (optional, flag to override the
##             global_optname)
## @param message (message to the user explaining this option)
## @param enabled (the option or setting for when the dependency is
##          enabled)
## @param disabled (the option or setting for when the dependency is
##          disabled)
##
## The syntax for the parameters is as follows:
##
## buildsys_depends[_optional] \
##                             [-a active_build_system] \
##                             [-g grimoire] \
##                             [-o global_optname] \
##                             [-sub subdependency_feature] \
##                             spell_name \
##                               ...
##                               [-b] build_systemN \
##                                 [-o local_optname] \
##                                 message \
##                                 [enabled] \
##                                 [disabled]
##                               [-b] build_systemN+1 \
##                                 [-o local_optname] \
##                                 message \
##                                 [enabled] \
##                                 [disabled] \
##                               ...
##
## @return 1 on parameter error
## @return 2 if the active build system does not have a matching build
##           system block defined
## @return 3 when defaults are needed but not defined for the currently
##           active build system
## @return return code of the wrapped depends or optional_depends
##           function otherwise
#---------------------------------------------------------------------
_buildsys_transform_depends() {
  [ "$#" -gt 0 ]
  _buildsys_chkerr "invalid parameters" || return 1
  local buildsys
  local disabled
  local enabled
  local global_optname
  local grimoire
  local match
  local next
  local optname
  local spell
  local subdeps
  local targetsys
  depends_func="$1" &&
  shift 1 &&
  case "$1" in
    -a) targetsys="$2" && shift 2 ;;
  esac &&
  : "${targetsys:=$(buildsys_mapping "$SPELL_BUILD_SYSTEM")}" &&
  [ -n "$targetsys" ]
  _buildsys_chkerr "SPELL_BUILD_SYSTEM not defined" || return 1
  while [ "$#" -gt 0 ] ;do
    case "$1" in
      -g) grimoire="$2" && shift 2 ;;
      -o) global_optname="$2" && shift 2 ;;
      -sub) subdeps="$2" && shift 2 ;;
      *) break ;;
    esac
  done &&
  spell="$1" &&
  shift 1 &&
  match=true &&
  while [ "$#" -gt 0 ] ;do
    match=false &&
    buildsys="$targetsys"
    case "$1" in
      -b) buildsys="$2" && shift 2 ;;
    esac &&
    match=false &&
    case "$(buildsys_mapping "$buildsys")" in
      "$targetsys") match=true ;;
    esac &&
    unset optname &&
    for arg in msg enabled disabled ;do
      [ "$#" -eq 0 ] && break
      if ! "$match" ;then
        case "$1" in
          -b) break ;;
        esac
      fi &&
      case "$1" in
        -b)
          if [ -n "${msg+1}" ] ;then
            break
          else
            _buildsys_chkerr "invalid parameters: empty build system block"
	    return 1
          fi
          ;;
        -o)
          optname="$2" &&
          shift 2
          ;;
      esac &&
      case "$arg" in
        msg) msg="$1" ;;
        enabled) enabled="$1" ;;
        disabled) disabled="$1" ;;
      esac &&
      shift 1
    done &&
    if ! "$match" ;then
      continue
    fi &&
    : "${optname=$global_optname}" &&
    : "${optname=$spell}" &&
    if [ -n "$optname" ] ;then
      : "${enabled:=$(buildsys_defaults "$buildsys" enabled "$optname")}"
      [ -n "$enabled" ]
      _buildsys_chkerr "$enabled" || return 3
      : "${disabled:=$(buildsys_defaults "$buildsys" disabled "$optname")}"
      [ -n "$disabled" ]
      _buildsys_chkerr "$disabled" || return 3
    fi &&
    "$match" && break
  done &&
  "$match"
  _buildsys_chkerr "no matching build system found" || return 2
  if [ -n "$global_optname" ] ;then
    # provide a last-resort fallback value for enabled settings
    : "${enabled:=$(buildsys_defaults "$targetsys" enabled "$global_optname")}"
  fi
  case "$depends_func" in
    depends)
      "$depends_func" ${subdeps:+-sub "$subdeps"} "$spell" \
        "$enabled" \
        "$msg" \
        "$grimoire"
      ;;
    optional_depends)
      "$depends_func" ${subdeps:+-sub "$subdeps"} "$spell" \
        "$enabled" \
        "$disabled" \
        "$msg" \
        "$grimoire"
      ;;
  esac
}

#---------------------------------------------------------------------
## A wrapper over the _buildsys_transform_depends function.
## Calls _buildsys_transform_depends with the dependency type set to
## "depends". See _buildsys_optional_depends for further details of
## the parameters.
##
## @param -g grimoire (optional, flag to specify the grimoire to use)
## @param -o global_optname (optional, flag to give the default option
##             name to use across all build systems)
## @param spell_name (the name of the actual dependency as a spell)
## @param [-b] build_system (the build system to define options for,
##               e.g. cmake, meson, autotools, etc.)
## @param -o local_optname (optional, flag to override the
##             global_optname)
## @param -sub subdependency_feature (optional, flag to give required
##               subdepedency feature names, one per flag, can be specified
##               more than once)
## @param message (message to the user explaining this option)
## @param enabled (the option or setting for when the dependency is
##          enabled)
## @param disabled (the option or setting for when the dependency is
##          disabled)
##
## @return the return value of _buildsys_transform_depends
#---------------------------------------------------------------------
buildsys_depends() {
  _buildsys_transform_depends "depends" "$@"
}

#---------------------------------------------------------------------
## A wrapper over the _buildsys_transform_depends function.
## Calls _buildsys_transform_depends with the dependency type set to
## "optional_depends". See _buildsys_optional_depends for details of
## the parameters.
##
## @param -g grimoire (optional, flag to specify the grimoire to use)
## @param -o global_optname (optional, flag to give the default option
##             name to use across all build systems)
## @param spell_name (the name of the actual dependency as a spell)
## @param [-b] build_system (the build system to define options for,
##               e.g. cmake, meson, autotools, etc.)
## @param -o local_optname (optional, flag to override the
##             global_optname)
## @param message (message to the user explaining this option)
## @param enabled (the option or setting for when the dependency is
##          enabled)
## @param disabled (the option or setting for when the dependency is
##          disabled)
##
## @return the return value of _buildsys_transform_depends
#---------------------------------------------------------------------
buildsys_optional_depends() {
  _buildsys_transform_depends "optional_depends" "$@"
}

.