///- --package .
:# ground_trace static =
    :< testing

:< sm'_operators
:< canary

:== watch = { id : u32; x : i32; y : i32 }

:= emit (line : string) : () = file_system::append_all_text "ground-trace.log" ("ground-trace " ++# line ++# "\n")

:= spot_text (x : i32) (y : i32) : string = "" ++#? x ++# "," ++#? y

:= watch_of (id : u32) (watched : list watch) : option watch =
    listm::fold (\ found (w : watch) =>
        ?= found ?|
        | Some _ => found
        | None => ? w::id = id ?> Some w |: None
        ) None watched

:= holds (id : u32) (ids : list u32) : bool = listm::fold (\ seen i => seen || i = id) !- ids

:= moved_to (id : u32) (x : i32) (y : i32) (watched : list watch) : list watch =
    listm::map (\ (w : watch) => ? w::id = id ?> { id = w::id; x = x; y = y } |: w) watched

:= still_present (present : list u32) (watched : list watch) : list watch =
    listm::fold (\ kept (w : watch) => ? holds w::id present ?> w :: kept |: kept) [] watched |> listm::rev

:= watched_two () : list watch =
    [ { id = 201u32; x = 1950i32; y = 1345i32 }; { id = 202u32; x = 1953i32; y = 1346i32 } ]

:= x_of (id : u32) (watched : list watch) : i32 = ?= watch_of id watched ?| Some w => w::x | None => 0i32

:= watch_facts (moved : list watch) : i32 * bool * bool * i32 =
    x_of 201u32 moved, holds 202u32 [ 202u32 ], holds 7u32 [], listm::length (still_present [ 202u32 ] moved)

///> lua
///> c
:# watches_follow_moves_and_departures =
    watch_facts (moved_to 201u32 1949i32 1344i32 (watched_two ())) |> _assert_eq (1949i32, !+, !-, 1i32)

///> lua
:# spot_text_joins_coordinates =
    spot_text 1949i32 1344i32 |> _assert_eq "1949,1344"

:== ground = { knight_since : mut (option f64); knight_away : mut bool; watched : mut (list watch) }

:== sweep = { present : mut (list u32); knight_present : mut bool }

:= since (g : ground) : i32 =
    ?= *g::knight_since ?|
    | Some t => conv (system_time () - t)
    | None => -1i32

:= emit_at (g : ground) (line : string) : () = emit (line ++# " @knight+" ++#? since g)

:= death_text (c : creature) : string =
    := at = creature_position c
    "death " ++#? creature_id c ++# " " ++# creature_name c ++# " at " ++# spot_text (position_x at) (position_y at)

:= on_ground_death (g : ground) (c : creature) : bool =
    emit_at g (death_text c)
    !+

:= knight_seen_line (x : i32) (y : i32) : string =
    := stamp = date_time::now () |> date_time::format "%Y%m%d-%H%M%S"
    "run " ++# stamp ++# " knight seen at " ++# spot_text x y ++# " @knight+0"

:= saw_knight (g : ground) (x : i32) (y : i32) : () =
    := knight_since = g::knight_since
    ?= *knight_since ?|
    | None =>
        knight_since <- Some (system_time ())
        emit (knight_seen_line x y)
    | Some _ => ()

:= appear_line (c : creature) (id : u32) (x : i32) (y : i32) : string =
    "appear " ++#? id ++# " " ++# creature_name c ++# " at " ++# spot_text x y

:= first_sight (g : ground) (c : creature) (id : u32) (x : i32) (y : i32) : () =
    := watched = g::watched
    creature_register_event c "GroundTraceDeath"
    watched <- { id = id; x = x; y = y } :: *watched
    emit_at g (appear_line c id x y)

:= moved_sight (g : ground) (id : u32) (x : i32) (y : i32) : () =
    := watched = g::watched
    emit_at g ("move " ++#? id ++# " to " ++# spot_text x y)
    watched <- moved_to id x y *watched

:= sighted (g : ground) (c : creature) (id : u32) (x : i32) (y : i32) : () =
    ?= watch_of id *g::watched ?|
    | None => first_sight g c id x y
    | Some seen => ? seen::x <> x || seen::y <> y ?> moved_sight g id x y

:= saw_monster (g : ground) (s : sweep) (c : creature) (x : i32) (y : i32) : () =
    := id, present = creature_id c, s::present
    present <- id :: *present
    sighted g c id x y

:= saw_player (g : ground) (s : sweep) (c : creature) (x : i32) (y : i32) : () =
    := knight_present = s::knight_present
    ? creature_name c = "Knight Sample" ?>
        knight_present <- !+
        saw_knight g x y

:= saw (g : ground) (s : sweep) (c : creature) : () =
    := at = creature_position c
    := x, y = position_x at, position_y at
    ? creature_is_player c ?> saw_player g s c x y
    |? creature_is_monster c ?> saw_monster g s c x y

:= saw_all (g : ground) (s : sweep) (crowd : array creature) : () =
    loop::for' { from = 0i32; nearTo = am'::length crowd } \ i => saw g s (am'::index i crowd)

:= departures (g : ground) (present : list u32) : () =
    := watched = g::watched
    *watched
    |> listm::iter (\ (w : watch) =>
        ? holds w::id present = !- ?> emit_at g ("gone " ++#? w::id)
        )
    watched <- still_present present *watched

:= knight_known (g : ground) : bool = ?= *g::knight_since ?| Some _ => !+ | None => !-

:= flip_view (g : ground) (knight_present : bool) : () =
    := knight_away = g::knight_away
    knight_away <- knight_present = !-
    := view = ? *knight_away ?> "out of view" |: "back in view"
    emit_at g ("knight " ++# view)

:= knight_view (g : ground) (knight_present : bool) : () =
    ? knight_known g && knight_present = *g::knight_away ?> flip_view g knight_present

:= poll_once (g : ground) (centre : position) (reach : i32) : bool =
    := s : sweep = { present = mut []; knight_present = mut !- }
    saw_all g s (spectators centre reach)
    departures g *s::present
    knight_view g *s::knight_present
    !+

:= watch_deaths (g : ground) : () =
    := death = creature_event "GroundTraceDeath"
    on_death death (on_ground_death g)
    register_creature_event death

:= watch_ground (g : ground) : () =
    := centre = position 1947 1345 7
    := poll = global_event "GroundTracePoll"
    on_think poll \ _ => poll_once g centre 16i32
    think_interval poll 250
    register_global_event poll

:= main () : () =
    := g : ground = { knight_since = mut None; knight_away = mut !-; watched = mut [] }
    watch_deaths g
    watch_ground g