Simple database: Difference between revisions

=={{header|Erlang}}==

<lang Erlang>

#! /usr/bin/env escript

-compile({no_auto_import,[date/0]}).

main( ["add", Tag | Descriptions] ) -> add( date(), Tag, Descriptions );

main( ["add_date", Date, Tag | Descriptions] ) -> add( date_internal(string:tokens(Date, "-")), Tag, Descriptions );

main( ["print_latest"] ) -> print_latest( contents() );

main( ["print_latest_for_each"] ) -> print_latest_for_each( contents() );

main( ["print_all_date", Date] ) -> print_all_date( date_internal(string:tokens(Date, "-")), contents() );

main( _Error ) -> usage().

add( Date, Tag, Descriptions ) ->

Contents = contents(),

file:write_file( file(), io_lib:format("simple_database_v1.~n~p.~n", [[{Date, Tag, Descriptions} | Contents]]) ).

date() ->

{{Date, _Time}} = calendar:local_time(),

Date.

date_external( {Year, Month, Day} ) -> string:join( [erlang:integer_to_list(Year), erlang:integer_to_list(Month), erlang:integer_to_list(Day)], "-" );

date_external( _Error ) -> usage().

date_internal( [Year, Month, Day] ) -> {erlang:list_to_integer(Year), erlang:list_to_integer(Month), erlang:list_to_integer(Day)};

date_internal( _Error ) -> usage().

file() -> "simple_database_contents".

contents() -> contents( file:consult(file()) ).

contents( {ok, [simple_database_v1, Contents]} ) -> Contents;

contents( {error, Error} ) when is_atom(Error) -> [];

contents( {error, _Error} ) ->

io:fwrite( "Error: ~p corrupt. Starting from scratch~n", [file()] ),

[].

print_all_date( _Date, [] ) -> ok;

print_all_date( Date, Contents ) -> [print_latest([{D, Tag, Descriptions}]) || {D, Tag, Descriptions} <- Contents, D =:= Date].

print_latest( [] ) -> ok;

print_latest( [{Date, Tag, Descriptions} | _T] ) -> io:fwrite( "~s~n", [string:join( [date_external(Date), Tag | Descriptions], " ")] ).

print_latest_for_each( [] ) -> ok;

print_latest_for_each( Contents ) ->

Tags = lists:usort( [Tag || {_Date, Tag, _Descriptions} <- Contents] ),

[print_latest([lists:keyfind(X, 2, Contents)]) || X <- Tags].

usage() ->

io:fwrite( "Usage: ~p [add | add_date <date>] tag description ...~n", [escript:script_name()] ),

io:fwrite( "Or: ~p [print_latest | print_latest_for_each | print_all_date <date>]~n", [escript:script_name()] ),

io:fwrite( "Date format is YYYY-MM-DD~n" ),

io:fwrite( "Data stored in ~p~n", [file()] ),

init:stop().

</lang>

Command line session started with these file contents as database:

<pre>

simple_database_v1.

[{{2013,9,16},"comic",["hobbe"]},

{{2013,9,16},"comic",["gustaf"]}].

</pre>

Command line session:

<pre>

./simple_database add num 1 2 3

./simple_database add_date 1991-01-01 num 999 888

./simple_database print_latest

1991-1-1 num 999 888

./simple_database print_latest_for_each

2013-9-16 comic hobbe

1991-1-1 num 999 888

./simple_database print_all_date 2013-09-16

2013-9-16 num 1 2 3

2013-9-16 comic hobbe

2013-9-16 comic gustaf

</pre>