1 files changed, 131 insertions, 0 deletions
diff --git a/src/main/otClient.ts b/src/main/otClient.ts
new file mode 100644
index 0000000..7985c66
--- /dev/null
+++ b/src/main/otClient.ts
@@ -0,0 +1,131 @@
+// OT state machine for main process (mirror of renderer otClient)
+import type { OtOp } from './otTypes'
+import { transformOps } from './otTransform'
+
+export type SendFn = (ops: OtOp[], version: number) => void
+export type ApplyFn = (ops: OtOp[]) => void
+
+interface OtState {
+  name: 'synchronized' | 'awaitingConfirm' | 'awaitingWithBuffer'
+  inflight: OtOp[] | null
+  buffer: OtOp[] | null
+  version: number
+}
+
+export class OtClient {
+  private state: OtState
+  private sendFn: SendFn
+  private applyFn: ApplyFn
+
+  constructor(version: number, sendFn: SendFn, applyFn: ApplyFn) {
+    this.state = { name: 'synchronized', inflight: null, buffer: null, version }
+    this.sendFn = sendFn
+    this.applyFn = applyFn
+  }
+
+  get version(): number {
+    return this.state.version
+  }
+
+  get stateName(): string {
+    return this.state.name
+  }
+
+  onLocalOps(ops: OtOp[]) {
+    if (ops.length === 0) return
+
+    switch (this.state.name) {
+      case 'synchronized':
+        this.state = {
+          name: 'awaitingConfirm',
+          inflight: ops,
+          buffer: null,
+          version: this.state.version
+        }
+        this.sendFn(ops, this.state.version)
+        break
+
+      case 'awaitingConfirm':
+        this.state = {
+          name: 'awaitingWithBuffer',
+          inflight: this.state.inflight,
+          buffer: ops,
+          version: this.state.version
+        }
+        break
+
+      case 'awaitingWithBuffer':
+        this.state = {
+          ...this.state,
+          buffer: [...(this.state.buffer || []), ...ops]
+        }
+        break
+    }
+  }
+
+  onAck() {
+    switch (this.state.name) {
+      case 'awaitingConfirm':
+        this.state = {
+          name: 'synchronized',
+          inflight: null,
+          buffer: null,
+          version: this.state.version + 1
+        }
+        break
+
+      case 'awaitingWithBuffer': {
+        const bufferOps = this.state.buffer || []
+        this.state = {
+          name: 'awaitingConfirm',
+          inflight: bufferOps,
+          buffer: null,
+          version: this.state.version + 1
+        }
+        this.sendFn(bufferOps, this.state.version)
+        break
+      }
+
+      case 'synchronized':
+        console.warn('[OtClient:main] unexpected ack in synchronized state')
+        break
+    }
+  }
+
+  onRemoteOps(ops: OtOp[], newVersion: number) {
+    switch (this.state.name) {
+      case 'synchronized':
+        this.state = { ...this.state, version: newVersion }
+        this.applyFn(ops)
+        break
+
+      case 'awaitingConfirm': {
+        const { left: transformedRemote, right: transformedInflight } = transformOps(ops, this.state.inflight || [])
+        this.state = {
+          ...this.state,
+          inflight: transformedInflight,
+          version: newVersion
+        }
+        this.applyFn(transformedRemote)
+        break
+      }
+
+      case 'awaitingWithBuffer': {
+        const { left: remoteAfterInflight, right: inflightAfterRemote } = transformOps(ops, this.state.inflight || [])
+        const { left: remoteAfterBuffer, right: bufferAfterRemote } = transformOps(remoteAfterInflight, this.state.buffer || [])
+        this.state = {
+          ...this.state,
+          inflight: inflightAfterRemote,
+          buffer: bufferAfterRemote,
+          version: newVersion
+        }
+        this.applyFn(remoteAfterBuffer)
+        break
+      }
+    }
+  }
+
+  reset(version: number) {
+    this.state = { name: 'synchronized', inflight: null, buffer: null, version }
+  }
+}