From 96b341fde50052785f296e969c658d010c2c037c Mon Sep 17 00:00:00 2001
From: Gilbert <gilbertw@emqx.io>
Date: Wed, 7 Aug 2019 09:24:03 +0800
Subject: [PATCH] Add proper tests for base62 (#2761)

* Add proper tests for base62

* Delete useless comment
---
 .travis.yml          |  1 +
 Makefile             |  7 ++++++
 rebar.config         |  6 +++---
 src/emqx_base62.erl  | 13 +----------
 src/emqx_guid.erl    |  3 +--
 test/prop_base62.erl | 51 ++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 64 insertions(+), 17 deletions(-)
 create mode 100644 test/prop_base62.erl

diff --git a/.travis.yml b/.travis.yml
index abe6f7a6a..c0b7bf5b9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,6 +11,7 @@ script:
   - make xref
   - make eunit
   - make ct
+  - make proper
   - make cover
 
 after_success:
diff --git a/Makefile b/Makefile
index 202046e60..b0a1dce16 100644
--- a/Makefile
+++ b/Makefile
@@ -14,6 +14,13 @@ RUN_NODE_NAME = emqxdebug@127.0.0.1
 .PHONY: all
 all: compile
 
+.PHONY: tests
+tests: eunit ct proper
+
+.PHONY: proper
+proper:
+	@rebar3 proper
+
 .PHONY: run
 run: run_setup unlock
 	@rebar3 as test get-deps
diff --git a/rebar.config b/rebar.config
index 3d0971cdf..fff6954c9 100644
--- a/rebar.config
+++ b/rebar.config
@@ -21,15 +21,15 @@
 {cover_opts, [verbose]}.
 {cover_export_enabled, true}.
 
-{plugins, [coveralls]}.
+{plugins, [coveralls,
+           rebar3_proper]}.
 
 {erl_first_files, ["src/emqx_logger.erl"]}.
 
 {profiles,
     [{test,
         [{deps,
-            [{meck, "0.8.13"}, % hex
-             {bbmustache, "1.7.0"}, % hex
+            [{bbmustache, "1.7.0"}, % hex
              {emqtt, {git, "https://github.com/emqx/emqtt", {tag, "v1.0.1"}}},
              {emqx_ct_helpers, {git, "https://github.com/emqx/emqx-ct-helpers", {branch, "develop"}}}
             ]}
diff --git a/src/emqx_base62.erl b/src/emqx_base62.erl
index 6d1f5a882..979821d06 100644
--- a/src/emqx_base62.erl
+++ b/src/emqx_base62.erl
@@ -18,9 +18,7 @@
 
 %% APIs
 -export([ encode/1
-        , encode/2
         , decode/1
-        , decode/2
         ]).
 
 %%--------------------------------------------------------------------
@@ -32,7 +30,7 @@
 encode(I) when is_integer(I) ->
     encode(integer_to_binary(I));
 encode(S) when is_list(S)->
-    encode(list_to_binary(S));
+    encode(unicode:characters_to_binary(S));
 encode(B) when is_binary(B) ->
     encode(B, <<>>).
 
@@ -40,8 +38,6 @@ encode(B) when is_binary(B) ->
 %%     binary_to_list(encode(D)).
 
 %% @doc Decode base62 binary to origin data binary
-decode(L) when is_list(L) ->
-    decode(list_to_binary(L));
 decode(B) when is_binary(B) ->
     decode(B, <<>>).
 
@@ -49,8 +45,6 @@ decode(B) when is_binary(B) ->
 %% Interval Functions
 %%--------------------------------------------------------------------
 
-encode(D, string) ->
-    binary_to_list(encode(D));
 encode(<<Index1:6, Index2:6, Index3:6, Index4:6, Rest/binary>>, Acc) ->
     CharList = [encode_char(Index1), encode_char(Index2), encode_char(Index3), encode_char(Index4)],
     NewAcc = <<Acc/binary,(iolist_to_binary(CharList))/binary>>,
@@ -66,10 +60,6 @@ encode(<<Index1:6, Index2:2>>, Acc) ->
 encode(<<>>, Acc) ->
     Acc.
 
-decode(D, integer) ->
-    binary_to_integer(decode(D));
-decode(D, string) ->
-    binary_to_list(decode(D));
 decode(<<Head:8, Rest/binary>>, Acc)
   when bit_size(Rest) >= 8->
     case Head == $9 of
@@ -114,4 +104,3 @@ decode_char(I) when I >= $A andalso I =< $Z->
 
 decode_char(9, I) ->
     I + 61 - $A.
-
diff --git a/src/emqx_guid.erl b/src/emqx_guid.erl
index 2a3715b9e..c9368ca1c 100644
--- a/src/emqx_guid.erl
+++ b/src/emqx_guid.erl
@@ -138,6 +138,5 @@ to_base62(<<I:128>>) ->
     emqx_base62:encode(I).
 
 from_base62(S) ->
-    I = emqx_base62:decode(S, integer),
+    I = binary_to_integer( emqx_base62:decode(S)),
     <<I:128>>.
-
diff --git a/test/prop_base62.erl b/test/prop_base62.erl
new file mode 100644
index 000000000..a660012db
--- /dev/null
+++ b/test/prop_base62.erl
@@ -0,0 +1,51 @@
+-module(prop_base62).
+-include_lib("proper/include/proper.hrl").
+
+%%%%%%%%%%%%%%%%%%
+%%% Properties %%%
+%%%%%%%%%%%%%%%%%%
+prop_symmetric() ->
+    ?FORALL(Data, raw_data(),
+        begin
+            Encoded = emqx_base62:encode(Data),
+            to_binary(Data) =:= emqx_base62:decode(Encoded)
+        end).
+
+prop_size() ->
+    ?FORALL(Data, binary(),
+         begin
+             Encoded = emqx_base62:encode(Data),
+             base62_size(Data, Encoded)
+         end).
+
+%%%%%%%%%%%%%%%
+%%% Helpers %%%
+%%%%%%%%%%%%%%%
+to_binary(Data) when is_list(Data) ->
+    unicode:characters_to_binary(Data);
+to_binary(Data) when is_integer(Data) ->
+    integer_to_binary(Data);
+to_binary(Data) when is_binary(Data) ->
+    Data.
+
+base62_size(Data, Encoded) ->
+    DataSize = erlang:size(Data),
+    EncodedSize = erlang:size(Encoded),
+    case (DataSize * 8 rem 6) of
+        0 ->
+            %% Due to the particularity of base 62, 3 bytes data maybe encoded
+            %% as 4 bytes data or 5 bytes data, the encode size maybe in the
+            %% range between DataSize*4/3 and DataSize*8/3
+            RangeStart = DataSize div 3 * 4,
+            RangeEnd = DataSize div 3 * 8,
+            EncodedSize >= RangeStart andalso EncodedSize =< RangeEnd;
+        _Rem ->
+            RangeStart = DataSize * 8 div 6  + 1,
+            RangeEnd = DataSize * 8 div 6 * 2 + 1,
+            EncodedSize >= RangeStart andalso EncodedSize =< RangeEnd
+    end.
+
+%%%%%%%%%%%%%%%%%%
+%%% Generators %%%
+%%%%%%%%%%%%%%%%%%
+raw_data() -> oneof([integer(), string(), binary()]).