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% 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.
-module(couch_key_tree).
-export([merge/2, find_missing/2, get_key_leafs/2, get_full_key_paths/2, get/2]).
-export([map/2, get_all_leafs/1, get_leaf_keys/1, count_leafs/1, remove_leafs/2]).
% a key tree looks like this:
% Tree -> [] or [{Key, Value, ChildTree} | SiblingTree]
% ChildTree -> Tree
% SiblingTree -> [] or [{SiblingKey, Value, Tree} | Tree]
% And each Key < SiblingKey
% key tree functions
% When the same key is found in the trees, the value in tree B is discarded.
merge([], B) ->
B;
merge(A, []) ->
A;
merge([ATree | ANextTree], [BTree | BNextTree]) ->
{AKey, AValue, ASubTree} = ATree,
{BKey, _BValue, BSubTree} = BTree,
if
AKey == BKey ->
%same key
MergedSubTree = merge(ASubTree, BSubTree),
MergedNextTree = merge(ANextTree, BNextTree),
[{AKey, AValue, MergedSubTree} | MergedNextTree];
AKey < BKey ->
[ATree | merge(ANextTree, [BTree | BNextTree])];
true ->
[BTree | merge([ATree | ANextTree], BNextTree)]
end.
find_missing(_Tree, []) ->
[];
find_missing([], Keys) ->
Keys;
find_missing([{Key, _, SubTree} | RestTree], Keys) ->
SrcKeys2 = Keys -- [Key],
SrcKeys3 = find_missing(SubTree, SrcKeys2),
find_missing(RestTree, SrcKeys3).
get_all_key_paths_rev([], KeyPathAcc) ->
KeyPathAcc;
get_all_key_paths_rev([{Key, Value, SubTree} | RestTree], KeyPathAcc) ->
get_all_key_paths_rev(SubTree, [{Key, Value} | KeyPathAcc]) ++
get_all_key_paths_rev(RestTree, KeyPathAcc).
% Removes any branches from the tree whose leaf node(s) are in the Keys
remove_leafs(Tree, Keys) ->
% flatten each branch in a tree into a tree path
Paths = get_all_key_paths_rev(Tree, []),
% filter out any that are in the keys list.
{FoundKeys, FilteredPaths} = lists:mapfoldl(
fun(Key, PathsAcc) ->
case [Path || [{LeafKey,_}|_]=Path <- PathsAcc, LeafKey /= Key] of
PathsAcc ->
{nil, PathsAcc};
PathsAcc2 ->
{Key, PathsAcc2}
end
end, Paths, Keys),
% convert paths back to trees
NewTree = lists:foldl(
fun(Path,TreeAcc) ->
SingleTree = lists:foldl(
fun({K,V},NewTreeAcc) -> [{K,V,NewTreeAcc}] end, [], Path),
merge(TreeAcc, SingleTree)
end, [], FilteredPaths),
{NewTree, FoundKeys}.
% get the leafs in the tree matching the keys. The matching key nodes can be
% leafs or an inner nodes. If an inner node, then the leafs for that node
% are returned.
get_key_leafs(Tree, Keys) ->
get_key_leafs(Tree, Keys, []).
get_key_leafs(_Tree, [], _KeyPathAcc) ->
{[], []};
get_key_leafs([], KeysToGet, _KeyPathAcc) ->
{[], KeysToGet};
get_key_leafs([{Key, _Value, SubTree}=Tree | RestTree], KeysToGet, KeyPathAcc) ->
case KeysToGet -- [Key] of
KeysToGet -> % same list, key not found
{LeafsFound, KeysToGet2} = get_key_leafs(SubTree, KeysToGet, [Key | KeyPathAcc]),
{RestLeafsFound, KeysRemaining} = get_key_leafs(RestTree, KeysToGet2, KeyPathAcc),
{LeafsFound ++ RestLeafsFound, KeysRemaining};
KeysToGet2 ->
LeafsFound = get_all_leafs([Tree], KeyPathAcc),
LeafKeysFound = [LeafKeyFound || {LeafKeyFound, _, _} <- LeafsFound],
KeysToGet2 = KeysToGet2 -- LeafKeysFound,
{RestLeafsFound, KeysRemaining} = get_key_leafs(RestTree, KeysToGet2, KeyPathAcc),
{LeafsFound ++ RestLeafsFound, KeysRemaining}
end.
get(Tree, KeysToGet) ->
{KeyPaths, KeysNotFound} = get_full_key_paths(Tree, KeysToGet),
FixedResults = [ {Key, Value, [Key0 || {Key0, _} <- Path]} || [{Key, Value}|_] = Path <- KeyPaths],
{FixedResults, KeysNotFound}.
get_full_key_paths(Tree, Keys) ->
get_full_key_paths(Tree, Keys, []).
get_full_key_paths(_Tree, [], _KeyPathAcc) ->
{[], []};
get_full_key_paths([], KeysToGet, _KeyPathAcc) ->
{[], KeysToGet};
get_full_key_paths([{KeyId, Value, SubTree} | RestTree], KeysToGet, KeyPathAcc) ->
KeysToGet2 = KeysToGet -- [KeyId],
CurrentNodeResult =
case length(KeysToGet2) == length(KeysToGet) of
true -> % not in the key list.
[];
false -> % this node is the key list. return it
[[{KeyId, Value} | KeyPathAcc]]
end,
{KeysGotten, KeysRemaining} = get_full_key_paths(SubTree, KeysToGet2, [{KeyId, Value} | KeyPathAcc]),
{KeysGotten2, KeysRemaining2} = get_full_key_paths(RestTree, KeysRemaining, KeyPathAcc),
{CurrentNodeResult ++ KeysGotten ++ KeysGotten2, KeysRemaining2}.
get_all_leafs(Tree) ->
get_all_leafs(Tree, []).
get_all_leafs([], _KeyPathAcc) ->
[];
get_all_leafs([{KeyId, Value, []} | RestTree], KeyPathAcc) ->
[{KeyId, Value, [KeyId | KeyPathAcc]} | get_all_leafs(RestTree, KeyPathAcc)];
get_all_leafs([{KeyId, _Value, SubTree} | RestTree], KeyPathAcc) ->
get_all_leafs(SubTree, [KeyId | KeyPathAcc]) ++ get_all_leafs(RestTree, KeyPathAcc).
get_leaf_keys([]) ->
[];
get_leaf_keys([{Key, _Value, []} | RestTree]) ->
[Key | get_leaf_keys(RestTree)];
get_leaf_keys([{_Key, _Value, SubTree} | RestTree]) ->
get_leaf_keys(SubTree) ++ get_leaf_keys(RestTree).
count_leafs([]) ->
0;
count_leafs([{_Key, _Value, []} | RestTree]) ->
1 + count_leafs(RestTree);
count_leafs([{_Key, _Value, SubTree} | RestTree]) ->
count_leafs(SubTree) + count_leafs(RestTree).
map(_Fun, []) ->
[];
map(Fun, [{Key, Value, SubTree} | RestTree]) ->
Value2 = Fun(Key, Value),
[{Key, Value2, map(Fun, SubTree)} | map(Fun, RestTree)].
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