Migration wizard skeleton setup (#11758)

extensions/sql-migration/src/models/stateMachine.ts

@@ -3,7 +3,11 @@
  *  Licensed under the Source EULA. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
+import * as azdata from 'azdata';
+import * as vscode from 'vscode';
+
 export enum State {
+	INIT,
 	COLLECTING_SOURCE_INFO,
 	COLLECTION_SOURCE_INFO_ERROR,
 	TARGET_SELECTION,
@@ -20,3 +24,45 @@ export enum State {
 	EXIT,
 }
 
+export interface Model {
+	readonly sourceConnection: azdata.IConnectionProfile;
+	readonly currentState: State;
+}
+
+export interface StateChangeEvent {
+	oldState: State;
+	newState: State;
+}
+
+export class MigrationStateModel implements Model, vscode.Disposable {
+	private _stateChangeEventEmitter = new vscode.EventEmitter<StateChangeEvent>();
+	private _currentState: State;
+
+	constructor(private readonly _sourceConnection: azdata.IConnectionProfile) {
+		this._currentState = State.INIT;
+	}
+
+	public get sourceConnection(): azdata.IConnectionProfile {
+		return this._sourceConnection;
+	}
+
+	public get currentState(): State {
+		return this._currentState;
+	}
+
+	public set currentState(newState: State) {
+		const oldState = this.currentState;
+
+		this._currentState = newState;
+
+		this._stateChangeEventEmitter.fire({ oldState, newState: this.currentState });
+	}
+
+	public get stateChangeEvent(): vscode.Event<StateChangeEvent> {
+		return this._stateChangeEventEmitter.event;
+	}
+
+	dispose() {
+		this._stateChangeEventEmitter.dispose();
+	}
+}