Untitled

const std = @import("std");

const fname = "input.txt";

const Keypad = struct {
    row: u8 = 2,
    column: u8 = 2,

    pub fn move(self: *Keypad, dir: u8) void {
        switch (dir) {
            'U' => if (self.row > 1) {
                    self.row -= 1;
                },
            'D' => if (self.row < 3) {
                    self.row += 1;
                },
            'L' => if (self.column > 1) {
                    self.column -= 1;
                },
            'R' => if (self.column < 3) {
                    self.column += 1;
                },
            else => unreachable
        }
    }

    pub fn getVal(self: *Keypad) u8 {
        switch (self.row) {
            1 => switch (self.column) {
                1 => return 1,
                2 => return 2,
                3 => return 3,
                else => unreachable
            },
            2 => switch (self.column) {
                1 => return 4,
                2 => return 5,
                3 => return 6,
                else => unreachable
            },
            3 => switch (self.column) {
                1 => return 7,
                2 => return 8,
                3 => return 9,
                else => unreachable
            },
            else => unreachable
        }
    }
};

pub fn main() !void {
    const file = try std.fs.cwd().openFile(fname, .{});

    defer file.close();

    const reader = file.reader();

    var line: [100]u8 = undefined;

    var keypad: Keypad = undefined;

    while (try reader.readUntilDelimiterOrEof(&line, '\n')) |currLine| {
        var atEOL: bool = false;
        for (currLine) |c| {
            if (isValidMove(c)) {
                keypad.move(c);
            }
            else {
                if (!atEOL) {
                    std.debug.print("Key: {}\n", keypad.getVal());
                }
                atEOL = true;
            }
        }
    }
}

fn isValidMove(move: u8) bool {
    switch(move) {
        'U' => return true,
        'D' => return true,
        'L' => return true,
        'R' => return true,
        else => return false
    }
}