level-parser.zig

// This file simply proceses levels.txt at comptime to turn the
// ascii levels there into something of type [NUMBER_OF_LEVELS] Grid.
const std = @import("std");

const dassert = std.debug.assert;

// Recall that for positive n, the tiles n and -n represent
// fixed and draggable tiles with numeral n respectively.
const Tile = i8;
const Grid = [16] Tile;

const NUMBER_OF_LEVELS = 11;

const LEVEL_FILENAME   = "levels.txt";
const level_string_data = @embedFile(LEVEL_FILENAME);

pub fn parse_levels() [NUMBER_OF_LEVELS] Grid {
    @setEvalBranchQuota(5000);

    var level_data : [NUMBER_OF_LEVELS] Grid = undefined;
    
    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
    const ally = arena.allocator();

    var line_list = std.ArrayList([] const u8).init(ally);
    defer line_list.deinit();

    var grid_row_number     : usize = 0;
    var current_level       : Grid  = undefined;
    var current_level_index : usize = 0;
    
    // NOTE: The \r is needed for windows newlines!!!    
    var line_iter = std.mem.tokenizeAny(u8, level_string_data, "\r\n");
    while (line_iter.next()) |line| {
        const fc = line[0];
        if (fc != '0' and fc != '1' and fc != '2' and fc != '3' and fc != '4') continue;
        // Create the current_level data.
        for (0..4) |i| {
            const tile : i8 = @intCast(line[i] - '0');
            // Check that the tile is one of: 0, 1, 2, 3, 4.
            dassert(0 <= tile and tile <= 4);
            current_level[4 * grid_row_number + i] = tile;
        }

        grid_row_number = grid_row_number + 1;

        if (grid_row_number == 4) {
            grid_row_number = 0;
            level_data[current_level_index] = current_level;
            current_level_index += 1;
        }
    }

    // After all of the lines have been processed, check that the number
    // of levels actually equals NUMBER_OF_LEVELS.
    dassert(current_level_index == NUMBER_OF_LEVELS);
    return level_data;
}