///
/// Copyright © 2016-2026 The Thingsboard Authors
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///     http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///

import vm, { Script } from 'vm';
import { _logger } from '../config/logger';

export type TbScript = Script | Function;

export class JsExecutor {
    useSandbox: boolean;
    private logger = _logger('JsExecutor');

    constructor(useSandbox: boolean) {
        this.useSandbox = useSandbox;
        if (!useSandbox) {
            this.logger.warn(
                'script.use_sandbox=false: dangerous by design — user-supplied scripts run in the host realm with no isolation. ' +
                'Use only as a performance trade-off in trusted, non-public clusters.'
            );
        }
    }

    compileScript(code: string): Promise<TbScript> {
        if (this.useSandbox) {
            return this.createScript(code);
        } else {
            return this.createFunction(code);
        }
    }

    executeScript(script: TbScript, args: string[], timeout?: number): Promise<any> {
        if (this.useSandbox) {
            return this.invokeScript(script as Script, args, timeout);
        } else {
            return this.invokeFunction(script as Function, args);
        }
    }

    private createScript(code: string): Promise<Script> {
        return new Promise((resolve, reject) => {
            try {
                code = "("+code+")(...args)";
                const script = new vm.Script(code);
                resolve(script);
            } catch (err) {
                reject(err);
            }
        });
    }

    private invokeScript(script: Script, args: string[], timeout: number | undefined): Promise<any> {
        return new Promise((resolve, reject) => {
            try {
                const sandbox = vm.createContext(Object.create(null));
                // Construct args inside the sandbox context so it inherits sandbox-realm
                // prototypes; prevents prototype-based escapes from the host realm.
                const ctxArgs = vm.runInContext('[]', sandbox) as string[];
                for (let i = 0; i < args.length; i++) {
                    ctxArgs[i] = String(args[i]);
                }
                sandbox.args = ctxArgs;
                const result = script.runInContext(sandbox, {timeout: timeout});
                resolve(result);
            } catch (err) {
                reject(err);
            }
        });
    }


    // DANGEROUS BY DESIGN: the non-sandbox path. vm.compileFunction's
    // parsingContext only isolates *parsing*, not *execution* — the resulting
    // function runs in the host realm with full access to host globals
    // (process, require, etc.). Enabled only via script.use_sandbox=false as
    // a performance trade-off in trusted clusters.
    private createFunction(code: string): Promise<Function> {
        return new Promise((resolve, reject) => {
            try {
                code = "return ("+code+")(...args)";
                const parsingContext = vm.createContext({});
                const func = vm.compileFunction(code, ['args'], {parsingContext: parsingContext});
                resolve(func);
            } catch (err) {
                reject(err);
            }
        });
    }

    private invokeFunction(func: Function, args: string[]): Promise<any> {
        return new Promise((resolve, reject) => {
            try {
                const result = func(args);
                resolve(result);
            } catch (err) {
                reject(err);
            }
        });
    }
}