Disambiguate parsing "Aug 12" and "12 Aug".

This started with just trying to parse the date format:

December 21st, 2013 7:00pm, which was failing with a bad_date error.

The solution involved setting up "Hinted Months", which was just a term
I used to indicate that a month was specified by name (ie "December"),
rather than by number (ie, "12"). Previously, named months were simply
replaced by their respective numbers in the parser.  This tags those
named months so that the parser will unambiguously parse them correctly.

A tagged "Hinted Month" is simply a tuple with the tag `?MONTH_TAG`. For
example: "December" gets converted to `{?MONTH_TAG, 12}`

For example: "Aug 12" and "12 Aug". It's clear to the *reader* what is
meant, but when converted to simply 8 and 12, the parser has no way of
knowing which is which.

Doing this was aided with the addition of some macros to help it
along, since doing just straight comparisons with the hinted months was
yielding unexpected results. For example: `{mon, 1} > 31`  returns
true, so changing that comparison to an ?is_year/1 macro that does:
`is_integer(Y) andalso Y > 31`.

It might not be a bad idea to help the parser be *very* unambiguous by
putting these macros on all comparisons.

Signed-off-by: Jordan Wilberding <diginux@gmail.com>

src/ec_date.erl

@@ -34,10 +34,16 @@
 -define( is_us_sep(X), ( X==$/) ).
 -define( is_world_sep(X), ( X==$-) ).
 
+-define( MONTH_TAG, month ).
+-define( is_year(X), (is_integer(X) andalso X > 31) ).
+-define( is_day(X), (is_integer(X) andalso X =< 31) ).
+-define( is_hinted_month(X), (is_tuple(X) andalso size(X)=:=2 andalso element(1,X)=:=?MONTH_TAG) ).
+-define( is_month(X), ( (is_integer(X) andalso X =< 12) orelse ?is_hinted_month(X) ) ).
+
 -define(GREGORIAN_SECONDS_1970, 62167219200).
 
 -type year() :: non_neg_integer().
--type month() :: 1..12.
+-type month() :: 1..12 | {?MONTH_TAG, 1..12}.
 -type day() :: 1..31.
 -type hour() :: 0..23.
 -type minute() :: 0..59.
@@ -81,7 +87,7 @@ parse(Date, Now) ->
     do_parse(Date, Now, []).
 
 do_parse(Date, Now, Opts) ->
-    case parse(tokenise(string:to_upper(Date), []), Now, Opts) of
+    case filter_hints(parse(tokenise(string:to_upper(Date), []), Now, Opts)) of
         {error, bad_date} ->
             erlang:throw({?MODULE, {bad_date, Date}});
         {D1, T1} = {{Y, M, D}, {H, M1, S}}
@@ -104,6 +110,13 @@ do_parse(Date, Now, Opts) ->
         Unknown -> erlang:throw({?MODULE, {bad_date, Date, Unknown }})
     end.
 
+filter_hints({{Y, {?MONTH_TAG, M}, D}, {H, M1, S}}) ->
+    filter_hints({{Y, M, D}, {H, M1, S}});
+filter_hints({{Y, {?MONTH_TAG, M}, D}, {H, M1, S}, {Ms}}) ->
+    filter_hints({{Y, M, D}, {H, M1, S}, {Ms}});
+filter_hints(Other) ->
+    Other.
+
 -spec nparse(string()) -> now().
 %% @doc parses the datetime from a string into 'now' format
 nparse(Date) ->
@@ -141,40 +154,61 @@ parse([Year, X, Month, X, Day, Hour, $:, Min, $:, Sec, $-, Off | _Rest ], _Now,
 parse([Year,X,Month,X,Day,Hour,$:,Min,$:,Sec,$., Ms | PAM], _Now, _Opts)
   when ?is_meridian(PAM) andalso
        (?is_us_sep(X) orelse ?is_world_sep(X))
-       andalso Year > 31 ->
+       andalso ?is_year(Year) ->
     {{Year, Month, Day}, {hour(Hour, PAM), Min, Sec}, {Ms}};
 parse([Month,X,Day,X,Year,Hour,$:,Min,$:,Sec,$., Ms | PAM], _Now, _Opts)
-  when ?is_meridian(PAM) andalso ?is_us_sep(X) ->
+  when ?is_meridian(PAM) andalso ?is_us_sep(X)
+       andalso ?is_year(Year) ->
     {{Year, Month, Day}, {hour(Hour, PAM), Min, Sec}, {Ms}};
 parse([Day,X,Month,X,Year,Hour,$:,Min,$:,Sec,$., Ms | PAM], _Now, _Opts)
-  when ?is_meridian(PAM) andalso ?is_world_sep(X) ->
+  when ?is_meridian(PAM) andalso ?is_world_sep(X)
+       andalso ?is_year(Year) ->
     {{Year, Month, Day}, {hour(Hour, PAM), Min, Sec}, {Ms}};
 
 parse([Year,X,Month,X,Day,Hour,$:,Min,$:,Sec,$., Ms], _Now, _Opts)
   when  (?is_us_sep(X) orelse ?is_world_sep(X))
-       andalso Year > 31 ->
+       andalso ?is_year(Year) ->
     {{Year, Month, Day}, {hour(Hour,[]), Min, Sec}, {Ms}};
 parse([Month,X,Day,X,Year,Hour,$:,Min,$:,Sec,$., Ms], _Now, _Opts)
-  when ?is_us_sep(X) ->
+  when ?is_us_sep(X) andalso ?is_month(Month) ->
     {{Year, Month, Day}, {hour(Hour, []), Min, Sec}, {Ms}};
 parse([Day,X,Month,X,Year,Hour,$:,Min,$:,Sec,$., Ms ], _Now, _Opts)
-  when ?is_world_sep(X) ->
+  when ?is_world_sep(X) andalso ?is_month(Month) ->
     {{Year, Month, Day}, {hour(Hour, []), Min, Sec}, {Ms}};
 
+%% Date/Times Dec 1st, 2012 6:25 PM
+parse([Month,Day,Year,Hour,$:,Min,$:,Sec | PAM], _Now, _Opts)
+  when ?is_meridian(PAM) andalso ?is_hinted_month(Month) andalso ?is_day(Day) ->
+	{{Year, Month, Day}, {hour(Hour, PAM), Min, Sec}};
+parse([Month,Day,Year,Hour,$:,Min | PAM], _Now, _Opts)
+  when ?is_meridian(PAM) andalso ?is_hinted_month(Month) andalso ?is_day(Day) ->
+	{{Year, Month, Day}, {hour(Hour, PAM), Min, 0}};
+parse([Month,Day,Year,Hour | PAM], _Now, _Opts)
+  when ?is_meridian(PAM) andalso ?is_hinted_month(Month) andalso ?is_day(Day) ->
+	{{Year, Month, Day}, {hour(Hour, PAM), 0, 0}};
+
+%% Date/Times Dec 1st, 2012 18:25:15 (no AM/PM)
+parse([Month,Day,Year,Hour,$:,Min,$:,Sec], _Now, _Opts)
+  when ?is_hinted_month(Month) andalso ?is_day(Day) ->
+	{{Year, Month, Day}, {hour(Hour, []), Min, Sec}};
+parse([Month,Day,Year,Hour,$:,Min], _Now, _Opts)
+  when ?is_hinted_month(Month) andalso ?is_day(Day) ->
+	{{Year, Month, Day}, {hour(Hour, []), Min, 0}};
+
 %% Times - 21:45, 13:45:54, 13:15PM etc
 parse([Hour,$:,Min,$:,Sec | PAM], {Date, _Time}, _O) when ?is_meridian(PAM) ->
     {Date, {hour(Hour, PAM), Min, Sec}};
 parse([Hour,$:,Min | PAM], {Date, _Time}, _Opts) when ?is_meridian(PAM) ->
     {Date, {hour(Hour, PAM), Min, 0}};
 parse([Hour | PAM],{Date,_Time}, _Opts) when ?is_meridian(PAM) ->
-        {Date, {hour(Hour,PAM), 0, 0}};
+    {Date, {hour(Hour,PAM), 0, 0}};
 
 %% Dates 23/april/1963
 parse([Day,Month,Year], {_Date, Time}, _Opts) ->
     {{Year, Month, Day}, Time};
 parse([Year,X,Month,X,Day], {_Date, Time}, _Opts)
   when (?is_us_sep(X) orelse ?is_world_sep(X))
-       andalso Year > 31 ->
+       andalso ?is_year(Year) ->
     {{Year, Month, Day}, Time};
 parse([Month,X,Day,X,Year], {_Date, Time}, _Opts) when ?is_us_sep(X) ->
     {{Year, Month, Day}, Time};
@@ -186,7 +220,7 @@ parse([Day,X,Month,X,Year], {_Date, Time}, _Opts) when ?is_world_sep(X) ->
 parse([Year,X,Month,X,Day,Hour | PAM], _Date, _Opts)
   when ?is_meridian(PAM) andalso
        (?is_us_sep(X) orelse ?is_world_sep(X))
-       andalso Year > 31 ->
+       andalso ?is_year(Year) ->
     {{Year, Month, Day}, {hour(Hour, PAM), 0, 0}};
 parse([Day,X,Month,X,Year,Hour | PAM], _Date, _Opts)
   when ?is_meridian(PAM) andalso ?is_world_sep(X) ->
@@ -200,7 +234,7 @@ parse([Month,X,Day,X,Year,Hour | PAM], _Date, _Opts)
 parse([Year,X,Month,X,Day,Hour,$:,Min | PAM], _Date, _Opts)
   when ?is_meridian(PAM) andalso
        (?is_us_sep(X) orelse ?is_world_sep(X))
-       andalso Year > 31 ->
+       andalso ?is_year(Year) ->
     {{Year, Month, Day}, {hour(Hour, PAM), Min, 0}};
 parse([Day,X,Month,X,Year,Hour,$:,Min | PAM], _Date, _Opts)
   when ?is_meridian(PAM) andalso ?is_world_sep(X) ->
@@ -213,7 +247,7 @@ parse([Month,X,Day,X,Year,Hour,$:,Min | PAM], _Date, _Opts)
 parse([Year,X,Month,X,Day,Hour,$:,Min,$:,Sec | PAM], _Now, _Opts)
   when ?is_meridian(PAM) andalso
        (?is_us_sep(X) orelse ?is_world_sep(X))
-       andalso Year > 31 ->
+       andalso ?is_year(Year) ->
     {{Year, Month, Day}, {hour(Hour, PAM), Min, Sec}};
 parse([Month,X,Day,X,Year,Hour,$:,Min,$:,Sec | PAM], _Now, _Opts)
   when ?is_meridian(PAM) andalso ?is_us_sep(X) ->
@@ -257,32 +291,37 @@ tokenise([N1 | Rest], Acc)
   when ?is_num(N1) ->
     tokenise(Rest, [ ltoi([N1]) | Acc]);
 
-tokenise("JANUARY"++Rest, Acc) -> tokenise(Rest, [1 | Acc]);
+
-tokenise("JAN"++Rest, Acc) -> tokenise(Rest, [1 | Acc]);
+%% Worded Months get tagged with ?MONTH_TAG to let the parser know that these
-tokenise("FEBRUARY"++Rest, Acc) -> tokenise(Rest, [2 | Acc]);
+%% are unambiguously declared to be months. This was there's no confusion
-tokenise("FEB"++Rest, Acc) -> tokenise(Rest, [2 | Acc]);
+%% between, for example: "Aug 12" and "12 Aug"
-tokenise("MARCH"++Rest, Acc) -> tokenise(Rest, [3 | Acc]);
+%% These hint tags are filtered in filter_hints/1 above.
-tokenise("MAR"++Rest, Acc) -> tokenise(Rest, [3 | Acc]);
+tokenise("JANUARY"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,1} | Acc]);
-tokenise("APRIL"++Rest, Acc) -> tokenise(Rest, [4 | Acc]);
+tokenise("JAN"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,1} | Acc]);
-tokenise("APR"++Rest, Acc) -> tokenise(Rest, [4 | Acc]);
+tokenise("FEBRUARY"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,2} | Acc]);
-tokenise("MAY"++Rest, Acc) -> tokenise(Rest, [5 | Acc]);
+tokenise("FEB"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,2} | Acc]);
-tokenise("JUNE"++Rest, Acc) -> tokenise(Rest, [6 | Acc]);
+tokenise("MARCH"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,3} | Acc]);
-tokenise("JUN"++Rest, Acc) -> tokenise(Rest, [6 | Acc]);
+tokenise("MAR"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,3} | Acc]);
-tokenise("JULY"++Rest, Acc) -> tokenise(Rest, [7 | Acc]);
+tokenise("APRIL"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,4} | Acc]);
-tokenise("JUL"++Rest, Acc) -> tokenise(Rest, [7 | Acc]);
+tokenise("APR"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,4} | Acc]);
-tokenise("AUGUST"++Rest, Acc) -> tokenise(Rest, [8 | Acc]);
+tokenise("MAY"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,5} | Acc]);
-tokenise("AUG"++Rest, Acc) -> tokenise(Rest, [8 | Acc]);
+tokenise("JUNE"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,6} | Acc]);
-tokenise("SEPTEMBER"++Rest, Acc) -> tokenise(Rest, [9 | Acc]);
+tokenise("JUN"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,6} | Acc]);
-tokenise("SEPT"++Rest, Acc) -> tokenise(Rest, [9 | Acc]);
+tokenise("JULY"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,7} | Acc]);
-tokenise("SEP"++Rest, Acc) -> tokenise(Rest, [9 | Acc]);
+tokenise("JUL"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,7} | Acc]);
-tokenise("OCTOBER"++Rest, Acc) -> tokenise(Rest, [10 | Acc]);
+tokenise("AUGUST"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,8} | Acc]);
-tokenise("OCT"++Rest, Acc) -> tokenise(Rest, [10 | Acc]);
+tokenise("AUG"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,8} | Acc]);
-tokenise("NOVEMBER"++Rest, Acc) -> tokenise(Rest, [11 | Acc]);
+tokenise("SEPTEMBER"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,9} | Acc]);
-tokenise("NOVEM"++Rest, Acc) -> tokenise(Rest, [11 | Acc]);
+tokenise("SEPT"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,9} | Acc]);
-tokenise("NOV"++Rest, Acc) -> tokenise(Rest, [11 | Acc]);
+tokenise("SEP"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,9} | Acc]);
-tokenise("DECEMBER"++Rest, Acc) -> tokenise(Rest, [12 | Acc]);
+tokenise("OCTOBER"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,10} | Acc]);
-tokenise("DECEM"++Rest, Acc) -> tokenise(Rest, [12 | Acc]);
+tokenise("OCT"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,10} | Acc]);
-tokenise("DEC"++Rest, Acc) -> tokenise(Rest, [12 | Acc]);
+tokenise("NOVEMBER"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,11} | Acc]);
+tokenise("NOVEM"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,11} | Acc]);
+tokenise("NOV"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,11} | Acc]);
+tokenise("DECEMBER"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,12} | Acc]);
+tokenise("DECEM"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,12} | Acc]);
+tokenise("DEC"++Rest, Acc) -> tokenise(Rest, [{?MONTH_TAG,12} | Acc]);
 
 tokenise([$: | Rest], Acc) -> tokenise(Rest, [ $: | Acc]);
 tokenise([$/ | Rest], Acc) -> tokenise(Rest, [ $/ | Acc]);
@@ -505,6 +544,10 @@ to_w(X) -> X.
 suffix(1) -> "st";
 suffix(2) -> "nd";
 suffix(3) -> "rd";
+suffix(21) -> "st";
+suffix(22) -> "nd";
+suffix(23) -> "rd";
+suffix(31) -> "st";
 suffix(_) -> "th".
 
 -spec sdayd(date()) -> string().
@@ -672,6 +715,20 @@ basic_parse_test_() ->
                    parse("22 Aug 2008 6:35 PM", ?DATE)),
      ?_assertEqual({{2008,8,22}, {18,0,0}},
                    parse("22 Aug 2008 6 PM", ?DATE)),
+     ?_assertEqual({{2008,8,22}, {18,0,0}},
+                   parse("Aug 22, 2008 6 PM", ?DATE)),
+     ?_assertEqual({{2008,8,22}, {18,0,0}},
+                   parse("August 22nd, 2008 6:00 PM", ?DATE)),
+     ?_assertEqual({{2008,8,22}, {18,15,15}},
+                   parse("August 22nd 2008, 6:15:15pm", ?DATE)),
+     ?_assertEqual({{2008,8,22}, {18,15,15}},
+                   parse("August 22nd, 2008, 6:15:15pm", ?DATE)),
+     ?_assertEqual({{2008,8,22}, {18,15,0}},
+                   parse("Aug 22nd 2008, 18:15", ?DATE)),
+     ?_assertEqual({{2012,12,10}, {0,0,0}},
+                   parse("Dec 10th, 2012, 12:00 AM", ?DATE)),
+     ?_assertEqual({{2012,12,10}, {0,0,0}},
+                   parse("10 Dec 2012 12:00 AM", ?DATE)),
      ?_assertEqual({{2001,3,10}, {11,15,0}},
                    parse("11:15", ?DATE)),
      ?_assertEqual({{2001,3,10}, {1,15,0}},