-module(ts_json).
-export([encode_record/1, record_to_ejson/1, ejson_to_record/2, ejson_to_record_strict/2]).

-include("ts_db_records.hrl").

encode_record(Record) -> lists:flatten(json:encode(record_to_ejson(Record))).

% User JSON record structure:
% {"id":        "john_doe",
%  "name":      "John Doe",
%  "email":     "john.doe@example.com",
%  "join_date": "2011-01-01T12:00.000Z",
%  "ext_data":  {"last_timeline", "personal"}}

record_to_ejson(Record=#ts_user{}) ->
    {struct, [
        {id, Record#ts_user.username},
        {name, Record#ts_user.name},
        {email, Record#ts_user.email},
        {join_date, encode_datetime(Record#ts_user.join_date)},
        {ext_data, Record#ts_user.ext_data}]};

% Timeline JSON record stucture:
% {"user_id":   "john_doe",
%  "id":        "personal",
%  "created":   "2011-01-01T14:00.000Z",
%  "description:"Personal time-tracking."}

record_to_ejson(Record=#ts_timeline{}) ->
    % pull out the username and timeline id
    {Username, TimelineId} = Record#ts_timeline.ref,

    % create the EJSON struct
    {struct, [
        {user_id, Username},
        {id, TimelineId},
        {created, encode_datetime(Record#ts_timeline.created)},
        {description, Record#ts_timeline.desc}]};

% Entry JSON record structure:
% {"user_id":       "john_doe",
%  "timeline_id":   "personal",
%  "id":            "1",
%   "timestamp":    "2011-01-01T14:01.000Z",
%   "mark":         "Workout.",
%   "notes":        "First workout after a long break."}

record_to_ejson(Record=#ts_entry{}) ->
    % pull out the username, timeline id, and entry id
    {Username, TimelineId, EntryId} = Record#ts_entry.ref,

    % convert the timestamp to a date-time
    DateTime = calendar:gregorian_seconds_to_datetime(Record#ts_entry.timestamp),

    % create the EJSON struct
    {struct, [
        {user_id, Username},
        {timeline_id, TimelineId},
        {id, EntryId},
        {timestamp, encode_datetime(DateTime)},
        {mark, Record#ts_entry.mark},
        {notes, Record#ts_entry.notes}]}.

encode_datetime({{Year, Month, Day}, {Hour, Minute, Second}}) ->
    lists:flatten(io_lib:format("~4.10.0B-~2.10.0B-~2.10.0BT~2.10.0B:~2.10.0B:~2.10.0B.~3.10.0BZ", 
        [Year, Month, Day, Hour, Minute, Second, 000])).

ejson_to_record(Rec=#ts_timeline{}, EJSON) ->
    {struct, Fields} = EJSON,

    Created = case lists:keyfind(created, 1, Fields) of
        false -> undefined;
        {created, CreatedVal} -> decode_datetime(CreatedVal)
    end,

    Desc = case lists:keyfind(description, 1, Fields) of
        false -> undefined;
        {description, DescVal} -> DescVal
    end,

    Rec#ts_timeline{
        created = Created,
        desc = Desc };

ejson_to_record(Rec=#ts_entry{}, EJSON) ->
    {struct, Fields} = EJSON,

    Timestamp = case lists:keyfind(timestamp, 1, Fields) of
        false -> undefined;
        {timestamp, TSVal} -> calendar:datetime_to_gregorian_seconds(
            decode_datetime(TSVal))
    end,

    Mark = case lists:keyfind(mark, 1, Fields) of
        false -> undefined;
        {mark, MarkVal} -> MarkVal
    end,

    Notes = case lists:keyfind(notes, 1, Fields) of
        false -> undefined;
        {notes, NotesVal} -> NotesVal
    end,

    Rec#ts_entry{
        timestamp = Timestamp,
        mark = Mark,
        notes = Notes}.

ejson_to_record_strict(Rec=#ts_timeline{}, EJSON) ->
    {struct, Fields} = EJSON,

    Rec#ts_timeline{
        created = decode_datetime(element(2, lists:keyfind(created, 1, Fields))),
        desc = element(2, lists:keyfind(description, 1, Fields))};

ejson_to_record_strict(Rec=#ts_entry{}, EJSON) ->
    {struct, Fields} = EJSON,

    Rec#ts_entry{
        timestamp = calendar:datetime_to_gregorian_seconds(decode_datetime(
            element(2, lists:keyfind(timestamp, 1, Fields)))),
        mark = element(2, lists:keyfind(mark, 1, Fields)),
        notes = element(2, lists:keyfind(notes, 1, Fields))}.

decode_datetime(DateTimeString) ->
    % TODO: catch badmatch and badarg on whole function

    [DateString, TimeString] = re:split(DateTimeString, "[TZ]",
        [{return, list}, trim]),

    [YearString, MonthString, DayString] =
        re:split(DateString, "-", [{return, list}]),

    [HourString, MinuteString, SecondString] = 
        case re:split(TimeString, "[:\\.]", [{return, list}]) of
            [HS, MS, SS, _MSS] -> [HS, MS, SS];
            [HS, MS, SS] -> [HS, MS, SS]
        end,

    Date = {list_to_integer(YearString), list_to_integer(MonthString),
        list_to_integer(DayString)},

    Time = {list_to_integer(HourString), list_to_integer(MinuteString),
        list_to_integer(SecondString)},

    {Date, Time}.