From 5e29841717beac083be8f98931cc1e5f8e5bd7ea Mon Sep 17 00:00:00 2001
From: Tangent Wantwight <tangent128@gmail.com>
Date: Sat, 15 Feb 2020 19:52:00 -0500
Subject: [PATCH] Sketch out first pass of lockstep client code

---
 src/Ecs/Lockstep.ts       |  8 ++--
 src/Game/Main.ts          |  1 +
 src/Net/LockstepClient.ts | 85 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 89 insertions(+), 5 deletions(-)
 create mode 100644 src/Net/LockstepClient.ts

diff --git a/src/Ecs/Lockstep.ts b/src/Ecs/Lockstep.ts
index 26e6950..f19d34a 100644
--- a/src/Ecs/Lockstep.ts
+++ b/src/Ecs/Lockstep.ts
@@ -1,4 +1,6 @@
 
+export const INPUT_FREQUENCY = 33; // roughly 30fps
+
 export interface DeepCopy<T> {
     deepCopy(patch: Partial<T>): T;
 }
@@ -17,7 +19,7 @@ function equals<T extends Equals | string | number>(a: T, b: T): boolean {
     return (a as Equals).equals(b as Equals);
 }
 
-interface LockstepProcessor<Input, State> {
+export interface LockstepProcessor<Input, State> {
     compareInput(a: Input, b: Input): boolean;
     cloneState(source: State): State;
     advanceState(state: State, input: Input): void;
@@ -97,7 +99,3 @@ export class Playback<Input, State> {
         return this.state;
     }
 }
-
-export class LockstepLoop<Input, State extends DeepCopy<State>> {
-
-}
diff --git a/src/Game/Main.ts b/src/Game/Main.ts
index da6b48a..6ac5e04 100644
--- a/src/Game/Main.ts
+++ b/src/Game/Main.ts
@@ -1 +1,2 @@
+import {} from "../Ecs/Lockstep";
 import {} from "./GameComponents";
diff --git a/src/Net/LockstepClient.ts b/src/Net/LockstepClient.ts
new file mode 100644
index 0000000..10ebd84
--- /dev/null
+++ b/src/Net/LockstepClient.ts
@@ -0,0 +1,85 @@
+
+import { Callbag } from "callbag";
+
+import { INPUT_FREQUENCY, LockstepProcessor, LockstepState } from "../Ecs/Lockstep";
+
+export const enum MessageTypes {
+    RESET = 0,
+    INPUT = 1,
+}
+
+export type Packet<TypeId, Payload> = { t: TypeId } & Payload;
+
+export type ClientMessage<Input, State> =
+    | Packet<MessageTypes.INPUT, { i: Partial<Input> }>;
+
+export type ServerMessage<Input, State> =
+    | Packet<MessageTypes.RESET, { s: Partial<State> }>
+    | Packet<MessageTypes.INPUT, { i: Input }>;
+
+type Server<Input, State> = Callbag<ClientMessage<Input, State>, ServerMessage<Input, State>>;
+
+export abstract class LockstepClient<Input, State> {
+
+    private state: LockstepState<Input, State>;
+
+    public constructor(
+        public readonly engine: LockstepProcessor<Input, State>,
+    ) {
+        const initialState = this.initState({});
+        this.state = new LockstepState(initialState, engine);
+    }
+
+    public abstract initState(init: Partial<State>): State;
+
+    public abstract gatherInput(): Input;
+
+    /**
+     * Connect to a [perhaps emulated] server and return a disconnect callback
+     */
+    public connect(server: Server<Input, State>): () => void {
+        let serverTalkback: Server<Input, State> | null = null;
+
+        const sampleInput = () => {
+            if (serverTalkback) {
+                const input = this.gatherInput();
+                this.state.addLocalInput(input);
+                serverTalkback(1, {t: MessageTypes.INPUT, i: input});
+                setTimeout(sampleInput, INPUT_FREQUENCY);
+            }
+        };
+
+        // connect to server
+        server(0, (mode: number, data: Server<Input, State> | ServerMessage<Input, State>) => {
+            if (mode == 0) {
+                serverTalkback = data as Server<Input, State>;
+
+                // kickoff input sender
+                setTimeout(sampleInput, INPUT_FREQUENCY);
+            } else if (mode == 1) {
+                // server message
+                const message = data as ServerMessage<Input, State>;
+                switch(message.t) {
+                    case MessageTypes.RESET:
+                        const resetState = this.initState(message.s);
+                        this.state = new LockstepState(resetState, this.engine);
+                        break;
+                    case MessageTypes.INPUT:
+                        this.state.addCanonInput(message.i);
+                        break;
+                }
+            } else if (mode == 2) {
+                // disconnected
+                console.log("Disconnected from server", data);
+                serverTalkback = null;
+            }
+        });
+
+        // disposal
+        return () => {
+            serverTalkback?.(2);
+            serverTalkback = null;
+        };
+    }
+
+}
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