Add ffmpegCommand.init to ensure "Begin" command has been used

FlowPluginsTs/CommunityFlowPlugins/ffmpegCommand/ffmpegCommandExecute/1.0.0/index.ts

@@ -180,6 +180,9 @@ const plugin = async (args: IpluginInputArgs): Promise<IpluginOutputArgs> => {
 
   args.logOutcome('tSuc');
 
+  // eslint-disable-next-line no-param-reassign
+  args.variables.ffmpegCommand.init = false;
+
   return {
     outputFileObj: {
       _id: outputFilePath,

FlowPluginsTs/CommunityFlowPlugins/ffmpegCommand/ffmpegCommandStart/1.0.0/index.ts

@@ -40,6 +40,7 @@ const plugin = (args:IpluginInputArgs):IpluginOutputArgs => {
   const container = getContainer(args.inputFileObj._id);
 
   const ffmpegCommand = {
+    init: true,
     inputFiles: [],
     streams: JSON.parse(JSON.stringify(args.inputFileObj.ffProbeData.streams)).map((stream:Istreams) => ({
       ...stream,

FlowPluginsTs/FlowHelpers/1.0.0/interfaces/flowUtils.ts

@@ -0,0 +1,14 @@
+import { IpluginInputArgs } from './interfaces';
+
+// eslint-disable-next-line import/prefer-default-export
+export const checkFfmpegCommandInit = (args: IpluginInputArgs): void => {
+  if (!args?.variables?.ffmpegCommand?.init) {
+    throw new Error(
+      'FFmpeg command plugins not used correctly.'
+      + ' Please use the "Begin Command" plugin before using this plugin.'
+      + ' Afterwards, use the "Execute" plugin to execute the built FFmpeg command.'
+      + ' Once the "Execute" plugin has been used, you need to use a new "Begin Command"'
+      + ' plugin to start a new FFmpeg command.',
+    );
+  }
+};

FlowPluginsTs/FlowHelpers/1.0.0/interfaces/interfaces.ts

@@ -87,6 +87,7 @@ export interface IffmpegCommandStream extends Istreams {
 }
 
 export interface IffmpegCommand {
+    init: boolean,
     inputFiles: string[],
     streams: IffmpegCommandStream[]
     container: string,