;;-*-Lisp-*-
(in-package goal)

;; name: collide-touch.gc
;; name in dgo: collide-touch
;; dgos: GAME, ENGINE

;; DECOMP BEGINS

;;;;;;;;;;;;;;;;;;;;;
;; Touching List
;;;;;;;;;;;;;;;;;;;;;

;; The idea behind the touching list is to determine which things were touched during collision resolution, then
;; send events to processes based on this.

;; In the end, we want to track pairs of collide-shape-prims, and possibly triangles (if one of the prims has triangles).
;; The logic for this is more confusing than you might expect because they don't count every single intersection that
;; occurs in every single iteration of the collision solve.

;;;;;;;;;;;;;;;;;;;;
;; Entry Pool
;;;;;;;;;;;;;;;;;;;;

;; there's a global shared pool of entries that you can alloc and free from.

(defmethod get-free-node-count touching-prims-entry-pool ((obj touching-prims-entry-pool))
  "Get the number of nodes that are not in use."
  (let ((v0-0 0))
    (let ((v1-0 (-> obj head)))
      (while v1-0
        (+! v0-0 1)
        (set! v1-0 (-> v1-0 next))
        (nop!)
        (nop!)
        (nop!)
        )
      )
    v0-0
    )
  )

(defmethod alloc-node touching-prims-entry-pool ((obj touching-prims-entry-pool))
  "Allocate a node. Will return #f if there are none left."
  (let ((gp-0 (-> obj head)))
    (cond
      (gp-0
        (let ((v1-0 (-> gp-0 next)))
          (set! (-> obj head) v1-0)
          (if v1-0
              (set! (-> v1-0 prev) #f)
              )
          )
        (set! (-> gp-0 allocated?) #t)
        (set! (-> gp-0 next) #f)
        (set! (-> gp-0 prev) #f)
        )
      (else
        (format 0 "ERROR: touching-prims-entry-pool::alloc-node() failed!~%")
        )
      )
    gp-0
    )
  )

(defmethod free-node touching-prims-entry-pool ((obj touching-prims-entry-pool) (arg0 touching-prims-entry))
  "Free a node allocated with alloc-node"
  (when (-> arg0 allocated?)
    (set! (-> arg0 allocated?) #f)
    (let ((v1-1 (-> obj head)))
      (set! (-> arg0 next) v1-1)
      (set! (-> arg0 prev) #f)
      (set! (-> obj head) arg0)
      (if v1-1
        (set! (-> v1-1 prev) arg0)
        )
      )
    )
  )

;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Shapes Entry
;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; a single shape entry represents a pair of shapes that collide.
;; There can be multiple colliding primitives.

(defmethod free-touching-prims-list touching-shapes-entry ((obj touching-shapes-entry))
  "Return all nodes used by this touching-shapes-entry to the touching-prims-entry-pool"
  (when (-> obj cshape1)
    (set! (-> obj cshape1) #f)
    (let ((gp-0 (-> obj head)))
      (when gp-0
        (set! (-> obj head) #f)
        (let ((s5-0 *touching-prims-entry-pool*))
          (while gp-0
            (let ((a1-0 gp-0))
              (set! gp-0 (-> a1-0 next))
              (free-node s5-0 a1-0)
              )
            )
          )
        #f
        )
      )
    )
  )

;;;;;;;;;;;;;;;;;;;;;;
;; Touching List
;;;;;;;;;;;;;;;;;;;;;;

;; A touching list is a list up to TOUCHING_LIST_LENGTH pairs of colliding collide-shapes.

(defmethod free-all-prim-nodes touching-list ((obj touching-list))
  "Free all prim nodes used by all touching shapes in this touching-list."
  (let ((s5-0 (the-as touching-shapes-entry (-> obj touching-shapes))))
    (countdown (s4-0 (-> obj num-touching-shapes))
      (free-touching-prims-list s5-0)
      (&+! s5-0 16)
      )
    )
  (set! (-> obj num-touching-shapes) 0)
  (set! (-> obj resolve-u) 0)
  0
  (none)
  )


(defmethod get-shapes-entry touching-list ((obj touching-list) (arg0 collide-shape) (arg1 collide-shape))
  "Get a touching-shapes-entry for the two shapes. If one exists, it will be returned. Otherwise a new one will be made."
  (let ((v0-0 (the-as touching-shapes-entry (-> obj touching-shapes)))) ;; the candidate
    (let ((v1-0 (the-as touching-shapes-entry #f)))                     ;; a good one
      
      ;; loop over all touching shapes
      (countdown (a3-0 (-> obj num-touching-shapes))
        (let ((t0-0 (-> v0-0 cshape1)))
          (set! v1-0
                (cond
                  (t0-0
                    ;; in use.  If it's match, return it (allows a,b or b,a to match a,b)
                    (if (or (and (= t0-0 arg0) (= (-> v0-0 cshape2) arg1)) (and (= t0-0 arg1) (= (-> v0-0 cshape2) arg0)))
                        (return v0-0)
                        )
                    ;; otherwise bad
                    v1-0
                    )
                  (else
                    ;; not in use. remember it's free and keep looking.
                    v0-0
                    )
                  )
                )
          )
        (&+! v0-0 16)
        )
      
      ;; done looping.
      (cond
        (v1-0 ;; did we find an unused slot? if so return it
          (set! v0-0 v1-0)
          )
        (else
          ;; need to add a new one
          (when (>= (-> obj num-touching-shapes) TOUCHING_LIST_LENGTH)
            ;; but there's no room!
            (format 0 "ERROR: touching-list::get-shapes-entry() failed!~%")
            (return (the-as touching-shapes-entry #f))
            )
          ;; enough room, increase the size
          (+! (-> obj num-touching-shapes) 1)
          )
        )
      )
    
    ;; if we're doing a new one, set it up.
    (set! (-> v0-0 cshape1) arg0)
    (set! (-> v0-0 cshape2) arg1)
    (set! (-> v0-0 head) #f)
    (set! (-> v0-0 resolve-u) 1)
    (set! (-> obj resolve-u) 1)
    (the-as touching-shapes-entry v0-0)
    )
  )

(deftype add-prims-touching-work (structure)
  ((tri1 collide-tri-result  :offset-assert   0)
   (tri2 collide-tri-result  :offset-assert   4)
   )
  :method-count-assert 9
  :size-assert         #x8
  :flag-assert         #x900000008
  )


;;;;;;;;;;;;;;;;;;;;;;;;;
;; Touching List Update
;;;;;;;;;;;;;;;;;;;;;;;;;

;; Note: this code relies a lot on the details of the iterative collision solver they made.
;; Basically, the solver works like this:

;; "What happens if I move forward 1.0 timesteps?"
;;  "You'd hit object A after 0.6 of a step, and object B after 0.3 of a step" (touching list has A and B now)
;; "OK. I will move forward 0.3 then. I will remove A from the touching list because I only went 0.3 of a step, and that's not enough to reach A."
;; ~Move forward 0.3, and handle the collision reaction from hitting B~
;; "I moved forward 0.3, so I now have 0.7 left to move (but potentially in a different direction because I bounced off of B)"
;; "What happens if I move forward 0.7 timesteps?"
;;  .. repeat ..
  



(defmethod add-touching-prims touching-list ((obj touching-list)
                                             (arg0 collide-shape-prim)
                                             (arg1 collide-shape-prim)
                                             (arg2 float)
                                             (arg3 collide-tri-result)
                                             (arg4 collide-tri-result)
                                             )
  "Tell the touching list that if we end taking a step of at least arg2, the prims arg0/arg1 will collide.
   However, you don't have to know for sure if you're going to take this big of a step yet.
   You can provide triangles if you want, but you don't have to.
   The logic for calling this twice for the same prims in between calls to update-from-step-size is a little weird
   so I suspect this never happens (and it's probably cheaper to avoid this duplication in the actual prim collision code)."
  
  ;; I don't know why they made this type, but I'm guessing it's to avoid the compiler spilling to the stack
  (let ((gp-0 (new 'stack-no-clear 'add-prims-touching-work)))
    (set! (-> gp-0 tri1) arg3)
    (set! (-> gp-0 tri2) arg4)
    
    ;; first, grab the entry for the collide-shapes involved.
    (let ((s2-0 (get-shapes-entry obj (-> arg0 cshape) (-> arg1 cshape))))
      (when s2-0
        ;; if we ask for a,b, that function might give us b,a. Detect that, and swap our collide shape prims.
        (when (= (-> s2-0 cshape1) (-> arg1 cshape))
          (let ((v1-4 arg0))
            (set! arg0 arg1)
            (set! arg1 v1-4)
            )
          )
        (let ((s0-0 (-> s2-0 head)))
          ;; loop over all the entries in the shapes
          (while s0-0
            ;; and only look at the ones that match these prims
            (when (and (= (-> s0-0 prim1 cprim) arg0) (= (-> s0-0 prim2 cprim) arg1))
              ;; if we already have an entry for this one, only update if this one is closer.
              (when (< arg2 (-> s0-0 u))
                ;; this value is unused.
                (-> s0-0 u)
                (let ((v1-12 (-> s0-0 prim1))
                      (a1-2 (-> gp-0 tri1))
                      )
                  (cond
                    (a1-2
                      ;; we have a tri, copy it
                      (set! (-> v1-12 has-tri?) #t)
                      (mem-copy! (the-as pointer (-> v1-12 tri)) (the-as pointer a1-2) 84)
                      )
                    (else
                      ;; no tri
                      (set! (-> v1-12 has-tri?) #f)
                      )
                    )
                  )
                ;; same for the other tri.
                (let ((v1-15 (-> s0-0 prim2))
                      (a1-3 (-> gp-0 tri2))
                      )
                  (cond
                    (a1-3
                      (set! (-> v1-15 has-tri?) #t)
                      (mem-copy! (the-as pointer (-> v1-15 tri)) (the-as pointer a1-3) 84)
                      )
                    (else
                      (set! (-> v1-15 has-tri?) #f)
                      )
                    )
                  )
                )
              ;; after we found the matching node for these prims, we're done!
              (return 0)
              )
            (set! s0-0 (-> s0-0 next))
            )
          )
        
        ;; nope, didn't find an entry, so make a new one.
        (let ((s0-1 (alloc-node *touching-prims-entry-pool*)))
          ;; allocate a new node, link it.
          (when s0-1
            (let ((v1-22 (-> s2-0 head)))
              (set! (-> s0-1 next) v1-22)
              (set! (-> s0-1 prev) #f)
              (set! (-> s2-0 head) s0-1)
              (if v1-22
                  (set! (-> v1-22 prev) s0-1)
                  )
              )
            ;; and set it up.
            (set! (-> s0-1 u) arg2)
            (when (>= arg2 0.0)
              ;; if we're >0, we have to move (which we haven't done yet) to actually collide.
              ;; flag us as resolve-u (meaning our u is from the resolve function, which looks at what _would_
              ;; happen if we did it all at once.)
              
              ;; if we're <0, we started in collision (possible, if we didnt' converge on the last frame)
              ;; we should still add, but we don't need to bother with the "did we go far enough" checks.
              (set! (-> s2-0 resolve-u) 1)
              (set! (-> obj resolve-u) 1)
              )
            (let ((v1-26 (-> s0-1 prim1))
                  (a1-4 (-> gp-0 tri1))
                  )
              (set! (-> v1-26 cprim) arg0)
              (cond
                (a1-4
                  (set! (-> v1-26 has-tri?) #t)
                  (mem-copy! (the-as pointer (-> v1-26 tri)) (the-as pointer a1-4) 84)
                  )
                (else
                  (set! (-> v1-26 has-tri?) #f)
                  )
                )
              )
            (let ((v1-29 (-> s0-1 prim2))
                  (a1-5 (-> gp-0 tri2))
                  )
              (set! (-> v1-29 cprim) arg1)
              (cond
                (a1-5
                  (set! (-> v1-29 has-tri?) #t)
                  (mem-copy! (the-as pointer (-> v1-29 tri)) (the-as pointer a1-5) 84)
                  )
                (else
                  (set! (-> v1-29 has-tri?) #f)
                  )
                )
              )
            )
          )
        )
      )
    )
  0
  (none)
  )

(defmethod update-from-step-size touching-list ((obj touching-list) (arg0 float))
  "Given that we actually will take a step size of arg0, remove things we won't actually hit."
  ;; only if we have some un-updated potential collision
  (when (nonzero? (-> obj resolve-u))
    ;; remember we did it
    (set! (-> obj resolve-u) 0)
    
    ;; loop through touching-shape-entries
    (let ((s5-0 (the-as touching-shapes-entry (-> obj touching-shapes))))
      (countdown (s4-0 (-> obj num-touching-shapes))
        ;; only when the entry isn't done yet
        (when (nonzero? (-> s5-0 resolve-u))
          ;; remember we did it
          (set! (-> s5-0 resolve-u) 0)
          ;; we can have empty entries, so check cshape1
          (when (-> s5-0 cshape1)
            ;; loop over nodes (each node is a pair of prims)
            (let ((s3-0 (-> s5-0 head)))
              (while s3-0
                (let ((f0-0 (-> s3-0 u)))
                  (set! s3-0 
                        (cond
                          ((>= f0-0 0.0)
                           ;; we'd have to take a step to hit this one!
                           (cond
                             ((>= arg0 f0-0)
                              ;; our step is big enough!
                              ;; we hit it. To prevent this from being possibly removed later on
                              ;; we set the u to -1.0 to indicate that we're massively intersecting.
                              ;; this will no longer be eligible for removal because we actually hit it.
                              (set! (-> s3-0 u) -1.0)
                              (set! s3-0 (-> s3-0 next))
                              )
                             (else
                               ;; we would have needed to move more than arg0 to hit this one.
                               ;; at least for now, remove by splicing out of the list and freeing.
                               (let ((a1-1 s3-0)) ;; this
                                 (let ((v1-7 (-> s3-0 next))) ;; next
                                   (let ((a0-1 (-> s3-0 prev))) ;; prev
                                     (if a0-1
                                         (set! (-> a0-1 next) v1-7)
                                         (set! (-> s5-0 head) v1-7)
                                         )
                                     (if v1-7
                                         (set! (-> v1-7 prev) a0-1)
                                         )
                                     )
                                   (set! s3-0 v1-7)
                                   )
                                 (free-node *touching-prims-entry-pool* a1-1)
                                 )
                               )
                             )
                           s3-0
                           )
                          (else
                            ;; not touching, advance to the next.
                            (-> s3-0 next)
                            )
                          )
                        )
                  )
                )
              )
            ;; if we removed everything from this, mark it as dead (the allocation function will reuse it now)
            (if (not (-> s5-0 head))
                (set! (-> s5-0 cshape1) #f)
                )
            )
          )
        (&+! s5-0 16)
        )
      )
    )
  0
  (none)
  )

(defmethod send-events-for-touching-shapes touching-list ((obj touching-list))
  "Send all events for touching shapes.
   Note that the order of event sending is basically random.
   (this could explain lava walks's unreliable behavior)"
            
  ;; PC port note : there is a fatal bug here where the processes are NOT SAFE to use without a handle.
  ;; this can lead to crashes if for example target hits 2 things at once, and one of those things kills the other.
  ;; e.g.: target hits eco1 and eco2. eco1 gets processed first and kills eco2 as a result. eco2 is now dead, but
  ;; the touching list will run its logic on it regardless.
  ;; this is fixed here by creating a really large list of 2 handles per collide shape and storing all collided
  ;; process handles there. (process->handle) is then safe to use.
  
  ; (* 2 TOUCHING_LIST_LENGTH) -> 64
  (let ((handles (new 'stack-no-clear 'array 'handle 64)))
  
  (let ((entry (the-as touching-shapes-entry (-> obj touching-shapes))))
    (countdown (i (-> obj num-touching-shapes))
      (let ((c1 (-> entry cshape1)))
        (when c1
          (let ((c2 (-> entry cshape2)))
            
            ;; not quite sure why, but we make it look like cshape1 (s4) is target always.
            ;; I guess this makes it so the target/enemy events are always sent in the same order.
            (when (= (-> c2 process type) target)
              (swap! c1 c2)
              )
              
            (set! (-> handles (+ 0 (* 2 i))) (process->handle (-> c1 process)))
            (set! (-> handles (+ 1 (* 2 i))) (process->handle (-> c2 process)))
            )
          )
        )
      (set! entry (-> (the-as (inline-array touching-shapes-entry) entry) 1))
      )
    )
  
  (let ((entry (the-as touching-shapes-entry (-> obj touching-shapes))))
    (countdown (i (-> obj num-touching-shapes))
      (let ((c1 (-> entry cshape1)))
        (when c1
          (let ((c2 (-> entry cshape2)))
            
            ;; not quite sure why, but we make it look like cshape1 (s4) is target always.
            ;; I guess this makes it so the target/enemy events are always sent in the same order.
            (when (= (-> c2 process type) target)
              (swap! c1 c2)
              )
            
            ;; send events!
            (let (
                  (c1-proc (handle->process (-> handles (+ 0 (* 2 i)))))
                  (c2-proc (handle->process (-> handles (+ 1 (* 2 i)))))
                  )
              (let ((v1-4 (-> c1 event-self)))
                (if v1-4
                    (send-event c1-proc v1-4 :from c2-proc entry)
                    )
                )
              (let ((v1-5 (-> c1 event-other)))
                (if v1-5
                    (send-event c2-proc v1-5 :from c1-proc entry)
                    )
                )
              (let ((v1-6 (-> c2 event-self)))
                (if v1-6
                    (send-event c2-proc v1-6 :from c1-proc entry)
                    )
                )
              (let ((v1-7 (-> c2 event-other)))
                (if v1-7
                    (send-event c1-proc v1-7 :from c2-proc entry)
                    )
                )
              )
            )
          )
        )
      (set! entry (-> (the-as (inline-array touching-shapes-entry) entry) 1))
      )
    )
    
    )
  0
  (none)
  )

(defmethod prims-touching? touching-shapes-entry ((obj touching-shapes-entry) (arg0 collide-shape-moving) (arg1 uint))
  "In a pair of collide shapes, is a prim from the given collide shape with the given prim-id mask touching the other shape?"
  (cond
    ((= (-> obj cshape1) arg0)
     (let ((v1-1 (-> obj head)))
       (while v1-1
         (if (logtest? (-> v1-1 prim1 cprim prim-id) arg1)
             (return v1-1)
             )
         (set! v1-1 (-> v1-1 next))
         )
       )
     )
    ((= (-> obj cshape2) arg0)
     (let ((v1-4 (-> obj head)))
       (while v1-4
         (if (logtest? (-> v1-4 prim2 cprim prim-id) arg1)
             (return v1-4)
             )
         (set! v1-4 (-> v1-4 next))
         )
       )
     )
    (else
      (format 0 "ERROR: touching-shapes-entry::prims-touching? : Bogus cshape value!~%")
      )
    )
  (the-as touching-prims-entry #f)
  )

(defmethod prims-touching-action? touching-shapes-entry ((obj touching-shapes-entry) (arg0 collide-shape) (arg1 collide-action) (arg2 collide-action))
  "In a pair of collide shapes, find a pair of colliding prims where the prim from the given collide shape has at least one of the actions in arg1
   and none of the actions in arg2."
  (cond
    ((= (-> obj cshape1) arg0)
     (let ((v1-1 (-> obj head)))
       (while v1-1
         (let ((a0-1 (-> v1-1 prim1 cprim)))
           (if (and (logtest? arg1 (-> a0-1 prim-core action)) (zero? (logand arg2 (-> a0-1 prim-core action))))
               (return v1-1)
               )
           )
         (set! v1-1 (-> v1-1 next))
         )
       )
     )
    ((= (-> obj cshape2) arg0)
     (let ((v1-4 (-> obj head)))
       (while v1-4
         (let ((a0-5 (-> v1-4 prim2 cprim)))
           (if (and (logtest? arg1 (-> a0-5 prim-core action)) (zero? (logand arg2 (-> a0-5 prim-core action))))
               (return v1-4)
               )
           )
         (set! v1-4 (-> v1-4 next))
         )
       )
     )
    (else
      (format 0 "ERROR: touching-shapes-entry::prims-touching-action? : Bogus cshape value!~%")
      )
    )
  (the-as touching-prims-entry #f)
  )

(defmethod get-touched-shape touching-shapes-entry ((obj touching-shapes-entry) (arg0 collide-shape))
  "Get the other shape in a pair of shapes."
  (cond
    ((= (-> obj cshape1) arg0)
     (return (-> obj cshape2))
     )
    ((= (-> obj cshape2) arg0)
     (return (-> obj cshape1))
     )
    )
  (the-as collide-shape #f)
  )

(defmethod get-touched-prim touching-prims-entry ((obj touching-prims-entry) (arg0 trsqv) (arg1 touching-shapes-entry))
  "Get the primitive belonging to the collide shape that is touching."
  (cond
    ((= (-> arg1 cshape1) arg0)
     (return (-> obj prim1 cprim))
     )
    ((= (-> arg1 cshape2) arg0)
     (return (-> obj prim2 cprim))
     )
    )
  (the-as collide-shape-prim #f)
  )

(defmethod get-touched-tri touching-prims-entry ((obj touching-prims-entry) (arg0 collide-shape) (arg1 touching-shapes-entry))
  "Get the triangle belonging to the the collide shape that is touching (if it has one, otherwise #f)"
  (let ((v0-0 (the-as collide-tri-result #f)))
    (cond
      ((= (-> arg1 cshape1) arg0)
       (let ((v1-2 (-> obj prim1)))
         (if (-> v1-2 has-tri?)
             (set! v0-0 (-> v1-2 tri))
             )
         )
       )
      ((= (-> arg1 cshape2) arg0)
       (let ((v1-5 (-> obj prim2)))
         (if (-> v1-5 has-tri?)
             (set! v0-0 (-> v1-5 tri))
             )
         )
       )
      )
    v0-0
    )
  )

(defmethod get-middle-of-bsphere-overlap touching-prims-entry ((obj touching-prims-entry) (arg0 vector))
  "This is a bit weird...
   But assuming the the bounding spheres overlap, draw a line between their centers, consider the line segment
   that is inside of both spheres, and get the midpoint of that."
  (let* ((s4-0 (-> obj prim1 cprim))
         (s3-0 (-> obj prim2 cprim))
         
         ;; compute the offset between the prim cores.
         (gp-1 (vector-!
                 (new 'stack-no-clear 'vector)
                 (the-as vector (-> s3-0 prim-core))
                 (the-as vector (-> s4-0 prim-core))
                 )
               )
         )
    
    ;; subtract off the two radius. this is now the offset between the "closest" points (and is negative)
    (let ((f1-2 (- (- (vector-length gp-1) (-> s3-0 prim-core world-sphere w)) (-> s4-0 prim-core world-sphere w))))
      ;; this offset is the radius, minus half the overlap distance
      (vector-normalize! gp-1 (+ (-> s4-0 prim-core world-sphere w) (* 0.5 f1-2)))
      )
    ;; so add it to s4's origin to get to the halfway point
    (vector+! arg0 gp-1 (the-as vector (-> s4-0 prim-core)))
    )
  arg0
  )