feat: add snjs package

packages/snjs/lib/Migrations/Migration.ts

@@ -0,0 +1,60 @@
+import { Challenge } from '../Services/Challenge'
+import { MigrationServices } from './MigrationServices'
+import { ApplicationStage, ChallengeValidation, ChallengeReason, ChallengePrompt } from '@standardnotes/services'
+
+type StageHandler = () => Promise<void>
+
+export abstract class Migration {
+  private stageHandlers: Partial<Record<ApplicationStage, StageHandler>> = {}
+  private onDoneHandler?: () => void
+
+  constructor(protected services: MigrationServices) {
+    this.registerStageHandlers()
+  }
+
+  public static version(): string {
+    throw 'Must override migration version'
+  }
+
+  protected abstract registerStageHandlers(): void
+
+  protected registerStageHandler(stage: ApplicationStage, handler: StageHandler) {
+    this.stageHandlers[stage] = handler
+  }
+
+  protected markDone() {
+    this.onDoneHandler?.()
+    this.onDoneHandler = undefined
+  }
+
+  protected async promptForPasscodeUntilCorrect(validationCallback: (passcode: string) => Promise<boolean>) {
+    const challenge = new Challenge([new ChallengePrompt(ChallengeValidation.None)], ChallengeReason.Migration, false)
+    return new Promise((resolve) => {
+      this.services.challengeService.addChallengeObserver(challenge, {
+        onNonvalidatedSubmit: async (challengeResponse) => {
+          const value = challengeResponse.values[0]
+          const passcode = value.value as string
+          const valid = await validationCallback(passcode)
+          if (valid) {
+            this.services.challengeService.completeChallenge(challenge)
+            resolve(passcode)
+          } else {
+            this.services.challengeService.setValidationStatusForChallenge(challenge, value, false)
+          }
+        },
+      })
+      void this.services.challengeService.promptForChallengeResponse(challenge)
+    })
+  }
+
+  onDone(callback: () => void) {
+    this.onDoneHandler = callback
+  }
+
+  async handleStage(stage: ApplicationStage): Promise<void> {
+    const handler = this.stageHandlers[stage]
+    if (handler) {
+      await handler()
+    }
+  }
+}