usg/src/movement.zig

const Grid = @import("grid.zig");
const Piece = @import("piece.zig");

pub fn moveRight(grid: Grid, piece: Piece) Piece {
    var new_piece = piece;
    new_piece.col += 1;
    for (new_piece.structure) |_, y| {
        for (new_piece.structure[y]) |_, x| {
            if (new_piece.structure[y][x] and
                @intCast(i32, x) + new_piece.col > Grid.ncolumns - 1)
            {
                return piece;
            }
            if (new_piece.structure[y][x] and
                !grid.cells[@intCast(usize, new_piece.row + @intCast(i32, y))][@intCast(usize, new_piece.col + @intCast(i32, x))].free)
            {
                return piece;
            }
        }
    }
    return new_piece;
}

pub fn moveLeft(grid: Grid, piece: Piece) Piece {
    var new_piece = piece;
    new_piece.col -= 1;
    for (new_piece.structure) |_, y| {
        for (new_piece.structure[y]) |_, x| {
            if (new_piece.structure[y][x] and
                @intCast(i32, x) + new_piece.col < 0)
            {
                return piece;
            }
            if (new_piece.structure[y][x] and
                !grid.cells[@intCast(usize, new_piece.row + @intCast(i32, y))][@intCast(usize, new_piece.col + @intCast(i32, x))].free)
            {
                return piece;
            }
        }
    }
    return new_piece;
}

pub fn moveDown(grid: Grid, piece: Piece) Piece {
    var new_piece = piece;
    new_piece.row += 1;
    for (new_piece.structure) |_, y| {
        for (new_piece.structure[y]) |_, x| {
            if (new_piece.structure[y][x] and
                @intCast(i32, y) + new_piece.row > Grid.nrows - 1)
            {
                new_piece.row -= 1;
                new_piece.dropped = true;
                return new_piece;
            }
            if (new_piece.structure[y][x] and
                !grid.cells[@intCast(usize, new_piece.row + @intCast(i32, y))][@intCast(usize, new_piece.col + @intCast(i32, x))].free)
            {
                new_piece.row -= 1;
                new_piece.dropped = true;
                return new_piece;
            }
        }
    }
    return new_piece;
}

pub fn drop(grid: Grid, piece: Piece) Grid {
    var new_grid = grid;

    for (piece.structure) |_, y| {
        for (piece.structure[y]) |_, x| {
            if (piece.structure[y][x]) {
                new_grid.cells[@intCast(usize, piece.row + @intCast(i32, y))][@intCast(usize, piece.col + @intCast(i32, x))].free = false;
                new_grid.cells[@intCast(usize, piece.row + @intCast(i32, y))][@intCast(usize, piece.col + @intCast(i32, x))].color = piece.color;
            }
        }
    }

    return new_grid;
}