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open Id
open Range
let err_empty_input = "input is empty"
(** [input_to_lines input] is a list of strings that have been split on ','.
Example: [input_to_lines "12-34,56-78,90-100"] becomes the list \[ "12-34"; "56-78"; "90-100" \].
Requires: [input] to be a string in the format "12-34,56-78,90-100". *)
let input_to_lines input = input |> String.trim |> String.split_on_char ','
let pp_lines = Seq.iter (fun l -> Logs.debug (fun m -> m "line=%s" l))
(** [lines_to_ranges line] is a list of [Range]s found on [line]. *)
let lines_to_ranges =
Seq.map (fun line ->
Scanf.sscanf line "%d-%d" (fun id1 id2 -> Range.create (id1, id2)) )
let pp_ranges = Seq.iter (fun r -> Logs.debug (fun m -> m "%s" (Range.pp r)))
(** [collect_all ranges] is an unsorted list of [ID]s within the [ranges] (inclusive). *)
let collect_all =
Seq.concat_map (fun range -> List.to_seq (Range.collect range))
let pp_collection = Seq.iter (fun c -> Logs.debug (fun m -> m "%s" (ID.pp c)))
(** [rules] is a list of rules that [ID]s must pass to be considered invalid. *)
let rules =
[ (fun id -> String.length (ID.to_string id) mod 2 = 0)
; (fun id ->
let id' = ID.to_string id in
let id_len = String.length id' in
let left = String.sub id' 0 (id_len / 2) in
let right = String.sub id' (id_len / 2) (id_len / 2) in
String.equal left right ) ]
(** [is_invalid id] is [true] for an [id] that passes all of the rules and is considered invalid. *)
let is_invalid = ID.validate rules
(** [passthrough_with_logs logger lst] is [lst] with the side-effects caused by calling [logger] on [lst]. *)
let passthrough_with_logs logger lst = logger lst ; lst
let solve input () =
if input = "" then Error err_empty_input
else
let answer =
input |> input_to_lines |> List.to_seq
|> passthrough_with_logs pp_lines
|> lines_to_ranges
|> passthrough_with_logs pp_ranges
|> collect_all
|> passthrough_with_logs pp_collection
|> Seq.filter is_invalid
|> Seq.fold_left (fun acc id -> acc + ID.to_int id) 0
in
Ok answer
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