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terminal/packages/terminal-core/src/session/sessionMachine.ts

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+import type { SessionState } from "../types";
+
+/** 合法状态迁移表 */
+const TRANSITIONS: Record<SessionState, SessionState[]> = {
+  idle:         ["connecting", "disconnected"],
+  connecting:   ["auth_pending", "error", "disconnected"],
+  auth_pending: ["connected", "error", "disconnected"],
+  connected:    ["reconnecting", "disconnected", "error"],
+  reconnecting: ["connected", "error", "disconnected"],
+  disconnected: ["connecting", "idle"],
+  error:        ["connecting", "disconnected"],
+};
+
+export function canTransition(from: SessionState, to: SessionState): boolean {
+  return (TRANSITIONS[from] ?? []).includes(to);
+}
+
+export function assertTransition(from: SessionState, to: SessionState): void {
+  if (!canTransition(from, to)) {
+    throw new Error(`非法状态跳转: ${from} → ${to}`);
+  }
+}
+
+/**
+ * SessionMachine — 会话生命周期状态机。
+ * 纯状态逻辑，无任何副作用，零 DOM 依赖。
+ */
+export class SessionMachine {
+  private _state: SessionState = "idle";
+  private listeners = new Set<(state: SessionState) => void>();
+
+  get state(): SessionState {
+    return this._state;
+  }
+
+  transition(to: SessionState): void {
+    assertTransition(this._state, to);
+    this._state = to;
+    for (const fn of this.listeners) {
+      fn(this._state);
+    }
+  }
+
+  tryTransition(to: SessionState): boolean {
+    if (!canTransition(this._state, to)) return false;
+    this.transition(to);
+    return true;
+  }
+
+  onChange(fn: (state: SessionState) => void): () => void {
+    this.listeners.add(fn);
+    return () => this.listeners.delete(fn);
+  }
+
+  reset(): void {
+    this._state = "idle";
+    for (const fn of this.listeners) {
+      fn(this._state);
+    }
+  }
+}