#
# Copyright (C) 2007 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

#
# Clears a list of variables using ":=".
#
# E.g.,
#   $(call clear-var-list,A B C)
# would be the same as:
#   A :=
#   B :=
#   C :=
#
# $(1): list of variable names to clear
#
define clear-var-list
$(foreach v,$(1),$(eval $(v):=))
endef

#
# Copies a list of variables into another list of variables.
# The target list is the same as the source list, but has
# a dotted prefix affixed to it.
#
# E.g.,
#   $(call copy-var-list, PREFIX, A B)
# would be the same as:
#   PREFIX.A := $(A)
#   PREFIX.B := $(B)
#
# $(1): destination prefix
# $(2): list of variable names to copy
#
define copy-var-list
$(foreach v,$(2),$(eval $(strip $(1)).$(v):=$($(v))))
endef

#
# Moves a list of variables into another list of variables.
# The variable names differ by a prefix.  After moving, the
# source variable is cleared.
#
# NOTE: Spaces are not allowed around the prefixes.
#
# E.g.,
#   $(call move-var-list,SRC,DST,A B)
# would be the same as:
#   DST.A := $(SRC.A)
#   SRC.A :=
#   DST.B := $(SRC.B)
#   SRC.B :=
#
# $(1): source prefix
# $(2): destination prefix
# $(3): list of variable names to move
#
define move-var-list
$(foreach v,$(3), \
  $(eval $(2).$(v) := $($(1).$(v))) \
  $(eval $(1).$(v) :=) \
 )
endef

#
# $(1): haystack
# $(2): needle
#
# Guarantees that needle appears at most once in haystack,
# without changing the order of other elements in haystack.
# If needle appears multiple times, only the first occurrance
# will survive.
#
# How it works:
#
# - Stick everything in haystack into a single word,
#   with "|||" separating the words.
# - Replace occurrances of "|||$(needle)|||" with "||| |||",
#   breaking haystack back into multiple words, with spaces
#   where needle appeared.
# - Add needle between the first and second words of haystack.
# - Replace "|||" with spaces, breaking haystack back into
#   individual words.
#
empty :=
space := $(empty) $(empty)
define uniq-word
$(strip \
  $(if $(filter $(2),$(1)), \
    $(eval h := |||$(subst $(space),|||,$(strip $(1)))|||) \
    $(eval h := $(subst |||$(strip $(2))|||,|||$(space)|||,$(h))) \
    $(eval h := $(word 1,$(h)) $(2) $(wordlist 2,9999,$(h))) \
    $(subst |||,$(space),$(h)) \
   , \
    $(1) \
 ))
endef

INHERIT_TAG := @inherit:

#
# Walks through the list of variables, each qualified by the prefix,
# and finds instances of words beginning with INHERIT_TAG.  Scrape
# off INHERIT_TAG from each matching word, and return the sorted,
# unique set of those words.
#
# E.g., given
#   PREFIX.A := A $(INHERIT_TAG)aaa B C
#   PREFIX.B := B $(INHERIT_TAG)aaa C $(INHERIT_TAG)bbb D E
# Then
#   $(call get-inherited-nodes,PREFIX,A B)
# returns
#   aaa bbb
#
# $(1): variable prefix
# $(2): list of variables to check
#
define get-inherited-nodes
$(sort \
  $(subst $(INHERIT_TAG),, \
    $(filter $(INHERIT_TAG)%, \
      $(foreach v,$(2),$($(1).$(v))) \
 )))
endef

#
# for each variable ( (prefix + name) * vars ):
#   get list of inherited words; if not empty:
#     for each inherit:
#       replace the first occurrence with (prefix + inherited + var)
#       clear the source var so we can't inherit the value twice
#
# $(1): context prefix
# $(2): name of this node
# $(3): list of variable names
#
define _expand-inherited-values
  $(foreach v,$(3), \
    $(eval ### "Shorthand for the name of the target variable") \
    $(eval _eiv_tv := $(1).$(2).$(v)) \
    $(eval ### "Get the list of nodes that this variable inherits") \
    $(eval _eiv_i := \
        $(sort \
            $(patsubst $(INHERIT_TAG)%,%, \
                $(filter $(INHERIT_TAG)%, $($(_eiv_tv)) \
     )))) \
    $(foreach i,$(_eiv_i), \
      $(eval ### "Make sure that this inherit appears only once") \
      $(eval $(_eiv_tv) := \
          $(call uniq-word,$($(_eiv_tv)),$(INHERIT_TAG)$(i))) \
      $(eval ### "Expand the inherit tag") \
      $(eval $(_eiv_tv) := \
          $(patsubst $(INHERIT_TAG)$(i),$($(1).$(i).$(v)), \
              $($(_eiv_tv)))) \
      $(eval ### "Clear the child so DAGs don't create duplicate entries" ) \
      $(eval $(1).$(i).$(v) :=) \
      $(eval ### "If we just inherited ourselves, it's a cycle.") \
      $(if $(filter $(INHERIT_TAG)$(2),$($(_eiv_tv))), \
        $(warning Cycle detected between "$(2)" and "$(i)" for context "$(1)") \
        $(error import of "$(2)" failed) \
      ) \
     ) \
   ) \
   $(eval _eiv_tv :=) \
   $(eval _eiv_i :=)
endef

#
# $(1): context prefix
# $(2): makefile representing this node
# $(3): list of node variable names
#
#TODO: keep a debug stack to make error messages more helpful
define _import-node
  $(call clear-var-list, $(3))
  $(eval include $(2))
  $(call copy-var-list, $(1).$(2), $(3))
  $(call clear-var-list, $(3))

  $(eval $(1).$(2).inherited := \
      $(call get-inherited-nodes,$(1).$(2),$(3)))
  $(call _import-nodes-inner,$(1),$($(1).$(2).inherited),$(3))

  $(call _expand-inherited-values,$(1),$(2),$(3))

  $(eval $(1).$(2).inherited :=)
endef

#
# $(1): context prefix
# $(2): list of makefiles representing nodes to import
# $(3): list of node variable names
#
#TODO: Make the "does not exist" message more helpful;
#      should print out the name of the file trying to include it.
define _import-nodes-inner
  $(foreach _in,$(2), \
    $(if $(wildcard $(_in)), \
      $(if $($(1).$(_in).seen), \
        $(eval ### "skipping already-imported $(_in)") \
       , \
        $(eval $(1).$(_in).seen := true) \
        $(call _import-node,$(1),$(strip $(_in)),$(3)) \
       ) \
     , \
      $(error $(1): "$(_in)" does not exist) \
     ) \
   )
endef

#
# $(1): output list variable name, like "PRODUCTS" or "DEVICES"
# $(2): list of makefiles representing nodes to import
# $(3): list of node variable names
#
define import-nodes
$(if \
  $(foreach _in,$(2), \
    $(eval _node_import_context := _nic.$(1).[[$(_in)]]) \
    $(call _import-nodes-inner,$(_node_import_context),$(_in),$(3)) \
    $(call move-var-list,$(_node_import_context).$(_in),$(1).$(_in),$(3)) \
    $(eval _node_import_context :=) \
    $(eval $(1) := $($(1)) $(_in)) \
   ) \
,)
endef