:- use_module(library(pio)).
:- use_module(library(clpfd)).
:- initialization(main, main).

main([FileName|_]) :-
    input(FileName, Input),
    concurrent_maplist(row_weight, Rocks, Weights),
    sum_list(Weights, W),
    writef('%t\n', [W]).

row_weight(Row, Weight) :-
    phrase(rock_counts(Rocks), Row),
    convlist([N-z-_, N]>>(true), Rocks, RockCounts),
    sum_list(RockCounts, Weight).

% North is to the left
roll(Map, NewMap) :-
    concurrent_maplist(collapse, Map, NorthCollapsed),
    rotate(NorthCollapsed, West),
    concurrent_maplist(collapse, West, WestCollapsed),
    rotate(WestCollapsed, South),
    concurrent_maplist(collapse, South, SouthCollapsed),
    rotate(SouthCollapsed, East),
    concurrent_maplist(collapse, East, EastCollapsed),
    rotate(EastCollapsed, NewMap).

rotate(Map, NewMap) :-
    transpose(Map, X),
    concurrent_maplist(reverse, X, NewMap).

print(Map) :-
    rotate(Map, RotMap),
    append([[_|RealMap], [_]], RotMap),
    maplist([X]>>(
        append([_|Y], [_], X),
        atomics_to_string(Y, S),
        writef('%t\n', [S])), RealMap),
    write('\n').

collapse(Row, NewRow) :-
    % abolish_private_tables,
    % table(rock_counts/3), table(condense/3), table(reexpand/3),
    phrase(rock_counts(Counts), Row),
    phrase(condense(Zs), Counts),
    phrase(reexpand(Zs), NewRow),
    % NewRow = Zs,
    true.

reexpand([]) --> eos.
reexpand([N-Next|Rocks]) --> ['#'], stack(N, Next), reexpand(Rocks).

stack(0, 0) --> [], !.
stack(0, Z) --> {NextZ is Z - 1}, ['.'], stack(0, NextZ), !.
stack(N, Z) --> {NextZ is Z - 1, NextN is N - 1}, ['O'], stack(NextN, NextZ).

condense([]) --> [0-0-0].
condense([N-Next|Rocks]) --> [0-I-I, N-z-Next], condense(Rocks), !.
condense(Rocks) --> [_-_-_], condense(Rocks).

rock_counts([0-0-0]) --> [].
rock_counts([LastN-I-LastZ, LastN-LastI-LastZ|Rocks]) -->
    ['.'], rock_counts([LastN-LastI-LastZ|Rocks]),
    {I is LastI + 1}.
rock_counts([N-I-LastZ, LastN-LastI-LastZ|Rocks]) -->
    ['O'], rock_counts([LastN-LastI-LastZ|Rocks]),
    {I is LastI + 1, N is LastN + 1}.
rock_counts([0-I-I, LastN-z-Len, LastN-LastI-LastZ|Rocks]) -->
    ['#'], rock_counts([LastN-LastI-LastZ|Rocks]),
    {I is LastI + 1, Len is I - LastZ - 1}.

% North is to the left
input(FileName, Input) :-
    phrase_from_file(lines(Raw), FileName),
    concurrent_maplist(pad, Raw, PaddedInput),
    concurrent_maplist(reverse, PaddedInput, Reversed),
    transpose(Reversed, Rotated),
    concurrent_maplist(pad, Rotated, Input).

pad(Row, Rowx) :- append(['#'|Row], ['#'], Rowx).

lines([]) --> eos, !.
lines([Line|Lines]) --> line(Line), lines(Lines).

line([]) --> "\n"; eos.
line(['O'|Chars]) --> "O", line(Chars).
line(['.'|Chars]) --> ".", line(Chars).
line(['#'|Chars]) --> "#", line(Chars).

eos([], []).