1 files changed, 126 insertions, 0 deletions
diff --git a/src/fields/Proxy.ts b/src/fields/Proxy.ts
new file mode 100644
index 000000000..555faaad0
--- /dev/null
+++ b/src/fields/Proxy.ts
@@ -0,0 +1,126 @@
+import { Deserializable } from "../client/util/SerializationHelper";
+import { FieldWaiting } from "./Doc";
+import { primitive, serializable } from "serializr";
+import { observable, action, runInAction } from "mobx";
+import { DocServer } from "../client/DocServer";
+import { RefField } from "./RefField";
+import { ObjectField } from "./ObjectField";
+import { Id, Copy, ToScriptString, ToString } from "./FieldSymbols";
+import { scriptingGlobal } from "../client/util/Scripting";
+import { Plugins } from "./util";
+
+@Deserializable("proxy")
+export class ProxyField<T extends RefField> extends ObjectField {
+    constructor();
+    constructor(value: T);
+    constructor(fieldId: string);
+    constructor(value?: T | string) {
+        super();
+        if (typeof value === "string") {
+            this.fieldId = value;
+        } else if (value) {
+            this.cache = value;
+            this.fieldId = value[Id];
+        }
+    }
+
+    [Copy]() {
+        if (this.cache) return new ProxyField<T>(this.cache);
+        return new ProxyField<T>(this.fieldId);
+    }
+
+    [ToScriptString]() {
+        return "invalid";
+    }
+    [ToString]() {
+        return "ProxyField";
+    }
+
+    @serializable(primitive())
+    readonly fieldId: string = "";
+
+    // This getter/setter and nested object thing is 
+    // because mobx doesn't play well with observable proxies
+    @observable.ref
+    private _cache: { readonly field: T | undefined } = { field: undefined };
+    private get cache(): T | undefined {
+        return this._cache.field;
+    }
+    private set cache(field: T | undefined) {
+        this._cache = { field };
+    }
+
+    private failed = false;
+    private promise?: Promise<any>;
+
+    value(): T | undefined | FieldWaiting<T> {
+        if (this.cache) {
+            return this.cache;
+        }
+        if (this.failed) {
+            return undefined;
+        }
+        if (!this.promise) {
+            const cached = DocServer.GetCachedRefField(this.fieldId);
+            if (cached !== undefined) {
+                runInAction(() => this.cache = cached as any);
+                return cached as any;
+            }
+            this.promise = DocServer.GetRefField(this.fieldId).then(action((field: any) => {
+                this.promise = undefined;
+                this.cache = field;
+                if (field === undefined) this.failed = true;
+                return field;
+            }));
+        }
+        return this.promise as any;
+    }
+    promisedValue(): string { return !this.cache && !this.failed && !this.promise ? this.fieldId : ""; }
+    setPromise(promise: any) {
+        this.promise = promise;
+    }
+    @action
+    setValue(field: any) {
+        this.promise = undefined;
+        this.cache = field;
+        if (field === undefined) this.failed = true;
+        return field;
+    }
+}
+
+export namespace ProxyField {
+    let useProxy = true;
+    export function DisableProxyFields() {
+        useProxy = false;
+    }
+
+    export function EnableProxyFields() {
+        useProxy = true;
+    }
+
+    export function WithoutProxy<T>(fn: () => T) {
+        DisableProxyFields();
+        try {
+            return fn();
+        } finally {
+            EnableProxyFields();
+        }
+    }
+
+    export function initPlugin() {
+        Plugins.addGetterPlugin((doc, _, value) => {
+            if (useProxy && value instanceof ProxyField) {
+                return { value: value.value() };
+            }
+        });
+    }
+}
+
+function prefetchValue(proxy: PrefetchProxy<RefField>) {
+    return proxy.value() as any;
+}
+
+@scriptingGlobal
+@Deserializable("prefetch_proxy", prefetchValue)
+export class PrefetchProxy<T extends RefField> extends ProxyField<T> {
+}