# emit_game.ludic — system functions and the frame loop. A system compiles to a
# void function; main() boots (Start systems), then runs the per-frame phases in
# order until the game stops. Runtime hooks (rt_init/poll/running/shutdown) are
# called only when the runtime defines them.

fn emit_system_fn(sys: Node) -> void {
  ll_t = 0;  ll_lbl = 0;  g_term = false;  loc_reset();  nloop = 0;  nself = 0
  ret_ty = "void"
  let fbody = buf_new()
  falloc = buf_new()
  let saved = code
  code = fbody
  emit_block(sys.a)
  if not g_term { emit("  br label %ret\n") }
  emit("ret:\n  ret void\n")
  code = saved
  emit("define void @sys_");  emit(sys.s);  emit("() {\nentry:\n")
  emit(buf_str(falloc))
  emit(buf_str(fbody))
  emit("}\n\n")
}

fn emit_calls_for_phase(phase: ptr) -> void {
  let i = 0
  while i < len(prog) {
    let d = prog[i]
    if d.kind == N_SYS and streq(d.ty, phase) {          # skip a disabled handler
      let he = emit_bind(sconcat("load i32, ptr @HE_", d.s))
      let hc = emit_bind(sconcat("icmp ne i32 ", sconcat(he, ", 0")))
      let run = lbl("hrun");  let skip = lbl("hskip")
      emit("  br i1 ");  emit(hc);  emit(", label %");  emit(run);  emit(", label %");  emit(skip);  emit("\n")
      emit(run);  emit(":\n  call void @sys_");  emit(d.s);  emit("()\n")
      emit("  br label %");  emit(skip);  emit("\n");  emit(skip);  emit(":\n")
    }
    i = i + 1
  }
}

# @OnDespawn(Model) hooks compile to `@on_despawn_<Model>(entity)` functions that
# bind the model's properties and run the body — dispatched by kind at `despawn`.
fn emit_despawn_hooks() -> void {
  let i = 0
  while i < len(g_ondespawn) {
    let hk = g_ondespawn[i]
    let model = find_arch(hk.s)
    ll_t = 0;  ll_lbl = 0;  g_term = false;  loc_reset();  nloop = 0;  nself = 0
    ret_ty = "void"
    let fbody = buf_new()
    falloc = buf_new()
    let saved = code
    code = fbody
    emit_bind_props(model, "%e")
    emit_block(hk.a)
    if not g_term { emit("  br label %ret\n") }
    emit("ret:\n  ret void\n")
    code = saved
    emit("define void @on_despawn_");  emit(hk.s);  emit("(i32 %e) {\nentry:\n")
    emit(buf_str(falloc))
    emit(buf_str(fbody))
    emit("}\n\n")
    i = i + 1
  }
}

fn emit_game_main() -> void {
  # every system becomes a function first
  let i = 0
  while i < len(prog) { if prog[i].kind == N_SYS { emit_system_fn(prog[i]) };  i = i + 1 }
  emit_despawn_hooks()

  emit("define i32 @main(i32 %argc, ptr %argv) {\nentry:\n")
  emit("  store i32 %argc, ptr @L_argc\n")
  emit("  store ptr %argv, ptr @L_argv\n")
  if not ptr_is_null(find_fn("rt_init")) { emit("  call void @fn_rt_init()\n") }
  emit_calls_for_phase("Start")
  emit("  br label %loop\n")
  emit("loop:\n")
  let r = emit_bind("load i32, ptr @L_running")
  let rc = emit_bind(sconcat("icmp ne i32 ", sconcat(r, ", 0")))
  if not ptr_is_null(find_fn("rt_running")) {
    let pr = emit_bind("call i32 @fn_rt_running()")
    let pc = emit_bind(sconcat("icmp ne i32 ", sconcat(pr, ", 0")))
    let go = emit_bind(sconcat("and i1 ", sconcat(rc, sconcat(", ", pc))))
    emit("  br i1 ");  emit(go);  emit(", label %body, label %done\n")
  } else {
    emit("  br i1 ");  emit(rc);  emit(", label %body, label %done\n")
  }
  emit("body:\n")
  if not ptr_is_null(find_fn("rt_poll")) {
    let k = emit_bind("call i32 @fn_rt_poll()")
    emit("  store i32 ");  emit(k);  emit(", ptr @L_key\n")
  }
  emit_calls_for_phase("Input")
  emit_calls_for_phase("FixedUpdate")
  emit_calls_for_phase("Update")
  emit_calls_for_phase("LateUpdate")
  emit_calls_for_phase("Render")
  emit("  br label %loop\n")
  emit("done:\n")
  emit_calls_for_phase("OnQuit")               # @OnQuit shutdown hooks run once, before teardown
  if not ptr_is_null(find_fn("rt_shutdown")) { emit("  call void @fn_rt_shutdown()\n") }
  emit("  ret i32 0\n}\n")
}