From 3a1f9fe6800ef5fe7bbf1c0a5976720383ba84fe Mon Sep 17 00:00:00 2001
From: Joel Stålnacke <joel@saker.fi>
Date: Mon, 23 Mar 2026 19:50:18 +0200
Subject: Rewrite native code in Odin and use ECS

---
 lib/simulation.odin | 261 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 261 insertions(+)
 create mode 100644 lib/simulation.odin

(limited to 'lib/simulation.odin')

diff --git a/lib/simulation.odin b/lib/simulation.odin
new file mode 100644
index 0000000..0ac8e89
--- /dev/null
+++ b/lib/simulation.odin
@@ -0,0 +1,261 @@
+package djup
+
+import "base:runtime"
+import "core:log"
+
+#assert(#config(DJUP_CLIENT, false) || #config(DJUP_SERVER, false))
+#assert(!(#config(DJUP_CLIENT, false) && #config(DJUP_SERVER, false)))
+
+SimulationContext :: struct {
+	snapshots:   []Snapshot,
+	ctx:         runtime.Context,
+	assert_func: AssertFunc,
+}
+
+Metadata :: Components
+
+entity_id :: distinct i32
+
+Snapshot :: struct {
+	active:        bool,
+	tick:          u32,
+	metadata:      []Metadata,
+	balls:         []Ball,
+	player_inputs: []PlayerInput,
+	ctx:           ^runtime.Context,
+}
+
+@(export = true)
+sim_create :: proc "c" (snapshots, entities: i32) -> ^SimulationContext {
+	if snapshots <= 0 || entities <= 0 {
+		return nil
+	}
+
+	context = runtime.default_context()
+	context.logger = log.create_console_logger()
+	ctx := new(SimulationContext)
+	ctx.ctx = context
+	ctx.ctx.user_ptr = ctx
+
+	snapshots, err := make([]Snapshot, snapshots)
+	if err != .None {
+		free(ctx)
+		return nil
+	}
+	ctx.snapshots = snapshots
+
+	error := false
+	for &s in ctx.snapshots {
+		s.ctx = &ctx.ctx
+		if !snapshot_init(&s, entities) {
+			error = true
+		}
+	}
+
+	if error {
+		for &s in ctx.snapshots {
+			snapshot_deinit(&s)
+		}
+		delete(ctx.snapshots)
+		free(ctx)
+		return nil
+	}
+
+	log.destroy_console_logger(ctx.ctx.logger)
+	ctx.ctx.logger = log.nil_logger()
+
+	return ctx
+}
+
+@(export = true)
+sim_free :: proc "c" (ctx: ^SimulationContext) {
+	if ctx == nil {
+		return
+	}
+	context = ctx.ctx
+
+	for &s in ctx.snapshots {
+		snapshot_deinit(&s)
+	}
+	delete(ctx.snapshots)
+	free(ctx)
+}
+
+snapshot_init :: proc(s: ^Snapshot, entities: i32) -> bool {
+	make_components :: proc($T: typeid, len: i32, error: ^bool) -> []T {
+		res, err := make([]T, len)
+		if err != .None {
+			log.errorf("Failed to allocate component array: %s", err)
+			error^ = true
+			return nil
+		}
+		return res
+	}
+
+	error := false
+	components: Components = ~{}
+	for c in components {
+		switch c {
+		case .Exists:
+			s.metadata = make_components(Metadata, entities, &error)
+		case .Ball:
+			s.balls = make_components(Ball, entities, &error)
+		case .PlayerInput:
+			s.player_inputs = make_components(PlayerInput, entities, &error)
+		}
+	}
+	return !error
+}
+
+snapshot_deinit :: proc(s: ^Snapshot) -> bool {
+	delete_components :: proc($T: typeid, slice: []T, error: ^bool) {
+		if slice == nil {
+			return
+		}
+		err := delete(slice)
+		if err != .None && error != nil {
+			log.errorf("Failed to delete component array: %s", err)
+			error^ = true
+		}
+	}
+
+	error := false
+	components: Components = ~{}
+	for c in components {
+		switch c {
+		case .Exists:
+			delete_components(Metadata, s.metadata, &error)
+		case .Ball:
+			delete_components(Ball, s.balls, &error)
+		case .PlayerInput:
+			delete_components(PlayerInput, s.player_inputs, &error)
+		}
+	}
+	return !error
+}
+
+@(export = true)
+sim_get_snapshot :: proc "c" (ctx: ^SimulationContext) -> ^Snapshot {
+	if ctx == nil {
+		return nil
+	}
+
+	for &s in ctx.snapshots {
+		if s.active {
+			continue
+		}
+		s.active = true
+		return &s
+	}
+	return nil
+}
+
+@(export = true)
+sim_return_snapshot :: proc "c" (ctx: ^SimulationContext, s: ^Snapshot) {
+	if ctx == nil || s == nil {
+		return
+	}
+
+	s.active = false
+}
+
+@(export = true)
+snapshot_create_entity :: proc "c" (s: ^Snapshot) -> entity_id {
+	if s == nil {
+		return -1
+	}
+	i := 0
+	for i < len(s.metadata) {
+		if .Exists not_in s.metadata[i] {
+			s.metadata[i] = {.Exists}
+			return entity_id(i)
+		}
+	}
+	return -1
+}
+
+ComponentAddError :: enum u32 {
+	None,
+	InvalidArg,
+	InvalidId,
+	EntityNotFound,
+}
+
+@(export = true)
+snapshot_add_component :: proc "c" (
+	s: ^Snapshot,
+	id: entity_id,
+	component: Component,
+	init: rawptr,
+) -> ComponentAddError {
+	if s == nil {
+		return .InvalidArg
+	}
+	if (id < 0 && id >= entity_id(len(s.metadata))) {
+		return .InvalidId
+	}
+
+	if .Exists not_in s.metadata[id] {
+		return .EntityNotFound
+	}
+
+	add :: proc "contextless" (s: ^Snapshot, id: entity_id, c: Components, slice: []$T, init: ^T) {
+		s.metadata[id] += c
+		if init != nil {
+			slice[id] = init^
+		}
+	}
+
+	switch component {
+	case .Exists:
+		add(s, id, {.Exists}, s.metadata, nil)
+	case .Ball:
+		add(s, id, {.Ball}, s.balls, cast(^Ball)init)
+	case .PlayerInput:
+		add(s, id, {.PlayerInput}, s.player_inputs, cast(^PlayerInput)init)
+	}
+	return .None
+}
+
+ComponentRemoveError :: enum u32 {
+	None,
+	InvalidArg,
+	InvalidId,
+	EntityNotFound,
+}
+
+@(export = true)
+snapshot_remove_components :: proc "c" (
+	s: ^Snapshot,
+	id: entity_id,
+	components: Components,
+) -> ComponentRemoveError {
+	if s == nil {
+		return .InvalidArg
+	}
+	if (id < 0 && id >= entity_id(len(s.metadata))) {
+		return .InvalidId
+	}
+
+	if .Exists not_in s.metadata[id] {
+		return .EntityNotFound
+	}
+
+	for c in components {
+		switch c {
+		case .Exists:
+			s.metadata[id] = {}
+		case .Ball:
+			s.balls[id] = Ball{}
+		case .PlayerInput:
+			s.player_inputs[id] = PlayerInput{}
+		}
+	}
+
+	return .None
+}
+
+@(export = true)
+snapshot_reset_entity :: proc "c" (s: ^Snapshot, id: entity_id) -> ComponentRemoveError {
+	return snapshot_remove_components(s, id, ~{})
+}
-- 
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