///- --package .

walk_pace (test)

///- --test static --symbol

:< testing

:< sm'_operators

:== straight_step = { direction : i32; after_straight : bool; interval : i32 }

:== bands = { formula_ms : i32; formula_slack_ms : i32; base_ms : i32; base_slack_ms : i32 }

:= pc4_bands () : bands = { formula_ms = 486; formula_slack_ms = 60; base_ms = 702; base_slack_ms = 30 }

:= sign (n : i32) : i32 = ? n > 0 ?> 1 |? n < 0 ?> -1 |: 0

:= coordinate (text : string) (at : i32) : option i32 =
    convert::try_convert (am'::index at (text |> sm'::split "," |> array))

:= heading (from : string) (onto : string) : option i32 =
    ?= coordinate from 0, coordinate from 1, coordinate onto 0, coordinate onto 1 ?|
    | Some x, Some y, Some x', Some y' => Some (sign (x' - x) + 10 * sign (y' - y))
    | _ => None

:= tokens_after (marker : string) (line : string) : array string =
    := at : i32 = sm'::index_of marker line
    := start = at + sm'::length marker
    := rest = ? at < 0i32 ?> "" |: sm'::substring start (sm'::length line - start) line
    rest |> sm'::split " " |> array

:= straight_from (t : array string) (d : i32) (ms : i32) : straight_step =
    { direction = d; after_straight = am'::index 6 t = "knight-straight"; interval = ms }

:= step_of_tokens (t : array string) : option straight_step =
    := onto = sm'::replace ";" "" (am'::index 2 t)
    ?= heading (am'::index 0 t) onto, convert::try_convert (am'::index 8 t) ?|
    | Some d, Some ms => Some (straight_from t d ms)
    | _ => None

:= step_of (line : string) : option straight_step =
    := t = tokens_after " knight-straight step " line
    ? am'::length t < 10 ?> None |: step_of_tokens t

:== pace = { previous : i32; kept : list i32; turns : i32 }

:= paced (p : pace) (s : straight_step) : pace =
    := kept = s::after_straight && s::direction = p::previous
    := turns = ? kept ?> p::turns |: p::turns + 1
    { previous = s::direction; kept = (? kept ?> s::interval :: p::kept |: p::kept); turns = turns }

:= pace_of_log (p : pace) (lines : list string) : pace =
    listm::fold paced { p ?| previous = 0 } (listm'::choose step_of lines)

:~ ^ inserted (n : i32) (sorted : list i32) : list i32 =
    ?= sorted ?|
    | [] => [ n ]
    | head :: rest => ? n < head ?> n :: sorted |: head :: inserted n rest

:~ ^ item_at (i : i32) (xs : list i32) : i32 =
    ?= xs ?|
    | [] => 0
    | x :: rest => ? i = 0 ?> x |: item_at (i - 1) rest

:= doubled_median (xs : list i32) : i32 =
    := sorted = listm::fold (\ acc x => inserted x acc) [] xs
    := n : i32 = listm::length sorted
    ? n % 2 = 1 ?> 2 * item_at (n / 2) sorted |: item_at (n / 2 - 1) sorted + item_at (n / 2) sorted

:| pace_verdict =
    | FormulaSpeed
    | BaseSpeed
    | NeitherBand

:= within (low : i32) (high : i32) (x : i32) : bool = x >= low && x <= high

:= formula_pace (b : bands) (twice : i32) : bool =
    within (2 * b::formula_ms) (2 * (b::formula_ms + b::formula_slack_ms)) twice

:= base_pace (b : bands) (twice : i32) : bool =
    within (2 * (b::base_ms - b::base_slack_ms)) (2 * (b::base_ms + b::base_slack_ms)) twice

:= verdict_of (b : bands) (twice : i32) : pace_verdict =
    ? formula_pace b twice ?> FormulaSpeed |? base_pace b twice ?> BaseSpeed |: NeitherBand

:= step_line (x : i32) (y : i32) (kind : string) (ms : i32) : string =
    := onto = "" ++#? x ++# "," ++#? y ++# ",7"
    " knight-straight step 0,0,7 -> " ++# onto ++# "; interval after its " ++# kind ++# " step " ++#? ms ++# " ms"

:= walk_lines () : list string =
    [ step_line 1 0 "knight-straight" 500; step_line 1 0 "knight-straight" 490; step_line 0 1 "knight-straight" 900 ]

:= walk_facts (lines : list string) : i32 * i32 * pace_verdict =
    := p = pace_of_log { previous = 0; kept = []; turns = 0 } lines
    listm::length p::kept, p::turns, verdict_of (pc4_bands ()) (doubled_median p::kept)

a_turn_is_excluded_and_the_straight_run_is_kept (test)

///- --test --symbol
///> lua
///> rust

:= ~lines = walk_lines ()
walk_facts lines |> _assert_eq (1i32, 2i32, FormulaSpeed)

__assert_eq { expected = (1, 2, FormulaSpeed) }
lua: unavailable on this machine (`spiral lua --lua-path /tmp/spiral_cells/1793693032914-9122/main.lua` was not found)

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