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(module downstroke/ai *
(import scheme
(chicken base)
(chicken keyword)
(only srfi-1 find)
states
downstroke/entity
downstroke/world)
;; Patrol speed in pixels per frame
(define *patrol-speed* 1)
;; Chase behavior constants
(define *chase-speed* 2)
(define *detect-range-x* 80)
(define *detect-range-y* 16)
(define *chase-max-distance* 96)
(define *blind-spot-x* 16)
(define *attack-range-x* 20)
(define *attack-duration* 10)
;; ---- Geometry helpers ----
(define (entity-center-x e)
(+ (entity-ref e #:x 0) (/ (entity-ref e #:width 0) 2)))
(define (entity-center-y e)
(+ (entity-ref e #:y 0) (/ (entity-ref e #:height 0) 2)))
(define (direction-to entity target)
(if (>= (entity-center-x target) (entity-center-x entity)) 1 -1))
;; ---- Entity update helpers ----
;; Find player by #:tags list (tag-based lookup, Milestone 10)
(define (find-player entities)
(find (lambda (e) (member 'player (entity-ref e #:tags '()))) entities))
;; Set both facing fields in the same direction
(define (face-toward entity dir)
(entity-set (entity-set entity #:ai-facing dir) #:facing dir))
;; Face a direction and set horizontal velocity
(define (move-toward entity dir speed)
(entity-set (face-toward entity dir) #:vx (* speed dir)))
;; ---- Detection predicates ----
(define (player-in-range? entity entities)
(let ((player (find-player entities)))
(and player
(let ((dx (abs (- (entity-center-x player) (entity-center-x entity))))
(dy (abs (- (entity-center-y player) (entity-center-y entity)))))
(and (<= dx *detect-range-x*)
(<= dy *detect-range-y*)
(not (and (< (entity-center-y player) (entity-center-y entity))
(<= dx *blind-spot-x*))))))))
(define (player-in-attack-range? entity entities)
(let ((player (find-player entities)))
(and player
(<= (abs (- (entity-center-x player) (entity-center-x entity))) *attack-range-x*)
(<= (abs (- (entity-center-y player) (entity-center-y entity))) *detect-range-y*))))
;; ---- State machine ----
(define (idle-trigger) #f)
(define (patrol-trigger) #f)
(define (chase-trigger) #f)
(define (make-enemy-ai-machine)
(state-machine idle
(idle-trigger ! idle -> patrol)
(patrol-trigger ! patrol -> chase)
(chase-trigger ! chase -> patrol)))
;; ---- Per-state handlers ----
(define (ai-state-idle entity sm)
(%make-transition sm 'patrol)
(entity-set entity #:vx (* *patrol-speed* (entity-ref entity #:ai-facing 1))))
(define (patrol-wall-flip entity)
(let ((new-facing (- (entity-ref entity #:ai-facing 1))))
(move-toward entity new-facing *patrol-speed*)))
(define (ai-state-patrol entity entities sm)
(if (player-in-range? entity entities)
(let* ((player (find-player entities))
(dir (direction-to entity player)))
(%make-transition sm 'chase)
(move-toward (entity-set entity #:chase-origin-x (entity-ref entity #:x 0))
dir *chase-speed*))
(if (zero? (entity-ref entity #:vx 0))
(patrol-wall-flip entity)
entity)))
(define (chase-give-up? entity entities)
(let ((distance-chased (abs (- (entity-ref entity #:x 0)
(entity-ref entity #:chase-origin-x 0)))))
(or (not (player-in-range? entity entities))
(> distance-chased *chase-max-distance*))))
(define (ai-state-chase entity entities sm)
(if (player-in-attack-range? entity entities)
(let* ((player (find-player entities))
(dir (direction-to entity player))
(stopped (entity-set (face-toward entity dir) #:vx 0)))
(if (= (entity-ref stopped #:attack-timer 0) 0)
(entity-set stopped #:attack-timer *attack-duration*)
stopped))
(if (chase-give-up? entity entities)
(begin
(%make-transition sm 'patrol)
(entity-set entity #:vx (* *patrol-speed* (entity-ref entity #:ai-facing 1))))
(move-toward entity
(direction-to entity (find-player entities))
*chase-speed*))))
;; ---- Top-level dispatcher ----
;; Update AI for a single enemy entity.
;; entities: all entities in the current scene (used for player detection).
(define (update-enemy-ai entity entities)
(if (entity-ref entity #:disabled #f)
entity
(let ((sm (entity-ref entity #:ai-machine #f)))
(if (not sm)
entity
(case (machine-state sm)
((idle) (ai-state-idle entity sm))
((patrol) (ai-state-patrol entity entities sm))
((chase) (ai-state-chase entity entities sm))
(else entity))))))
)
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