app [main!] { pf: platform "https://github.com/lukewilliamboswell/roc-platform-template-zig/releases/download/0.3/98T93wthPgoBRLYtPTT4RBBsQunrfDG94gihPf1zYYmE.tar.zst" }

import pf.Stdout

data =
    \\L50
    \\L12
    \\R13
    \\L1
    \\L5
    \\R5


parse_instruction: List(U8) -> Try(I32, _)
parse_instruction = |chars| {
    match chars {
        [] => Err(ParsingError)
        [c, ..rest] => {
            num_str = Str.from_utf8(rest)?
            num = I32.from_str(num_str)?
            if c == 'L' { Ok(-num) } else { Ok(num) }
        }
    }
}

count_zeroes: List(I32), I32, U32 -> U32
count_zeroes = |instructions, pos, count| {
    match instructions {
        [] => count
        [inst, ..rest] => {
            new_pos = pos + inst
            new_count =
                if new_pos % 100 == 0
                    count + 1
                else
                    count
            rest->count_zeroes(new_pos, new_count)
        }
    }
}

split_on: List(a), a -> List(List(a)) where [a.is_eq : a, a -> Bool]
split_on = |elements, delimiter| {
    help = |remaining, chunks, current_chunk| {
        match remaining {
            [] => chunks.append(current_chunk)
            [x, ..rest] => {
                if x == delimiter {
                    help(rest, chunks.append(current_chunk), [])
                } else {
                    help(rest, chunks, current_chunk.append(x))
                }
            }
        }
    }
    help(elements, [], [])
}

map_try: List(a), (a -> Try(b, c)) -> Try(List(b), c)
map_try = |list, to_result_fun| {
    list->walk_try(
        [],
        |state, elem| {
            match to_result_fun(elem) {
                Ok(ok) => Ok(state->List.append(ok))
                Err(b) => Err(b)
            }
        }
    )
}

walk_try: List(a), s, (s, a -> Try(s, c)) -> Try(s, c)
walk_try = |list, init, func| {
    match list {
        [] => { Ok(init) }
        [val, ..rest] => {
            maybe_state = func(init, val)
            match maybe_state {
                Ok(state) => walk_try(rest, state, func)
                Err(b) => Err(b)
            }
        }
    }
}

main!: List Str -> Try({}, Exit)
main! = |_args| {
    maybe_instructions = data.to_utf8()->split_on('\n')->map_try(parse_instruction)
    match maybe_instructions {
        Ok(instructions) => {
            result1 = instructions->count_zeroes(50, 0)
            Stdout.line!(result1.to_str())
            Ok({})
        }
        _ => Err(Exit(1))
    }
}

error: Child process /Users/ageron/Library/Caches/roc/e59c636351ad64c25ba81dca340f7248/temp/roc-tmp-9Tj9smFRS15c5UvOO30epYt9BZ2CYQ9G/roc_run_994723065 killed by signal: 11
error: Child process crashed with segmentation fault (SIGSEGV)

main! : List(Str) => Try({}, [Exit(I32)])

-- BAD LIST REST PATTERN SYNTAX ------------------

List rest patterns should use the `.. as name` syntax, not `..name`.
For example, use `[first, .. as rest]` instead of `[first, ..rest]`.

   ┌─ /Users/ageron/dev/roc/aoc2025-roc/day01.roc:18:13
   │
18 │         [c, ..rest] => {
   │             ^^^^^^

-- BAD LIST REST PATTERN SYNTAX ------------------

List rest patterns should use the `.. as name` syntax, not `..name`.
For example, use `[first, .. as rest]` instead of `[first, ..rest]`.

   ┌─ /Users/ageron/dev/roc/aoc2025-roc/day01.roc:30:16
   │
30 │         [inst, ..rest] => {
   │                ^^^^^^

-- BAD LIST REST PATTERN SYNTAX ------------------

List rest patterns should use the `.. as name` syntax, not `..name`.
For example, use `[first, .. as rest]` instead of `[first, ..rest]`.

   ┌─ /Users/ageron/dev/roc/aoc2025-roc/day01.roc:47:17
   │
47 │             [x, ..rest] => {
   │                 ^^^^^^

-- BAD LIST REST PATTERN SYNTAX ------------------

List rest patterns should use the `.. as name` syntax, not `..name`.
For example, use `[first, .. as rest]` instead of `[first, ..rest]`.

   ┌─ /Users/ageron/dev/roc/aoc2025-roc/day01.roc:76:15
   │
76 │         [val, ..rest] => {
   │               ^^^^^^

zsh: segmentation fault  roc2 test day01.roc

[REFCOUNT] INCREF list (copyToPtr) ptr=0x101460018 len=1 rc=1 slice=0 elems_rc=1
error: Child process /Users/ageron/Library/Caches/roc/e59c636351ad64c25ba81dca340f7248/temp/roc-tmp-2q9ZB7TrXASkuFMITQ3Xqvx7AXG5qNWK/roc_run_994723065 killed by signal: 11
error: Child process crashed with segmentation fault (SIGSEGV)