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Diffstat (limited to 'ai.scm')
| -rw-r--r-- | ai.scm | 135 |
1 files changed, 135 insertions, 0 deletions
@@ -0,0 +1,135 @@ +(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)))))) +) |