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silverbullet/plugos/system.ts

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import {Hook, Manifest, RuntimeEnvironment} from "./types";
import {EventEmitter} from "../common/event";
import {SandboxFactory} from "./sandbox";
import {Plug} from "./plug";
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export interface SysCallMapping {
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[key: string]: (ctx: SyscallContext, ...args: any) => Promise<any> | any;
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}
export type SystemJSON<HookT> = { [key: string]: Manifest<HookT> };
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export type SystemEvents<HookT> = {
plugLoaded: (name: string, plug: Plug<HookT>) => void;
plugUnloaded: (name: string, plug: Plug<HookT>) => void;
};
export type SyscallContext = {
plug: Plug<any>;
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};
type SyscallSignature = (
ctx: SyscallContext,
...args: any[]
) => Promise<any> | any;
type Syscall = {
requiredPermissions: string[];
callback: SyscallSignature;
};
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export class System<HookT> extends EventEmitter<SystemEvents<HookT>> {
readonly runtimeEnv: RuntimeEnvironment;
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protected plugs = new Map<string, Plug<HookT>>();
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protected registeredSyscalls = new Map<string, Syscall>();
protected enabledHooks = new Set<Hook<HookT>>();
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constructor(env: RuntimeEnvironment) {
super();
this.runtimeEnv = env;
}
get loadedPlugs(): Map<string, Plug<HookT>> {
return this.plugs;
}
addHook(feature: Hook<HookT>) {
this.enabledHooks.add(feature);
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feature.apply(this);
}
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registerSyscalls(
requiredCapabilities: string[],
...registrationObjects: SysCallMapping[]
) {
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for (const registrationObject of registrationObjects) {
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for (let [name, callback] of Object.entries(registrationObject)) {
this.registeredSyscalls.set(name, {
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requiredPermissions: requiredCapabilities,
callback,
});
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}
}
}
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async syscallWithContext(
ctx: SyscallContext,
name: string,
args: any[]
): Promise<any> {
const syscall = this.registeredSyscalls.get(name);
if (!syscall) {
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throw Error(`Unregistered syscall ${name}`);
}
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for (const permission of syscall.requiredPermissions) {
if (!ctx.plug) {
throw Error(`Syscall ${name} requires permission and no plug is set`);
}
if (!ctx.plug.grantedPermissions.includes(permission)) {
throw Error(`Missing permission '${permission}' for syscall ${name}`);
}
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}
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return Promise.resolve(syscall.callback(ctx, ...args));
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}
async load(
name: string,
manifest: Manifest<HookT>,
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sandboxFactory: SandboxFactory<HookT>
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): Promise<Plug<HookT>> {
if (this.plugs.has(name)) {
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console.log("Unloading", name);
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await this.unload(name);
}
// Validate
let errors: string[] = [];
for (const feature of this.enabledHooks) {
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errors = [...errors, ...feature.validateManifest(manifest)];
}
if (errors.length > 0) {
throw new Error(`Invalid manifest: ${errors.join(", ")}`);
}
// Ok, let's load this thing!
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const plug = new Plug(this, name, sandboxFactory);
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await plug.load(manifest);
this.plugs.set(name, plug);
this.emit("plugLoaded", name, plug);
return plug;
}
async unload(name: string) {
const plug = this.plugs.get(name);
if (!plug) {
throw Error(`Plug ${name} not found`);
}
await plug.stop();
this.emit("plugUnloaded", name, plug);
this.plugs.delete(name);
}
toJSON(): SystemJSON<HookT> {
let plugJSON: { [key: string]: Manifest<HookT> } = {};
for (let [name, plug] of this.plugs) {
if (!plug.manifest) {
continue;
}
plugJSON[name] = plug.manifest;
}
return plugJSON;
}
async replaceAllFromJSON(
json: SystemJSON<HookT>,
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sandboxFactory: SandboxFactory<HookT>
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) {
await this.unloadAll();
for (let [name, manifest] of Object.entries(json)) {
console.log("Loading plug", name);
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await this.load(name, manifest, sandboxFactory);
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}
}
async unloadAll(): Promise<void[]> {
return Promise.all(
Array.from(this.plugs.keys()).map(this.unload.bind(this))
);
}
}