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Type safe coercion for typescript
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@galeaspablo
galeaspablo committed Jan 6, 2025
1 parent 1862d0c commit 445ddf5
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Showing 5 changed files with 101 additions and 67 deletions.
12 changes: 11 additions & 1 deletion application/backend-credit-card-enrollment/backend-typescript/package-lock.json
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3 changes: 2 additions & 1 deletion application/backend-credit-card-enrollment/backend-typescript/package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,8 @@
"pg": "^8.8.0",
"reflect-metadata": "^0.2.2",
"tsyringe": "^4.8.0",
"winston": "^3.8.2"
"winston": "^3.8.2",
"zod": "^3.24.1"
},
"devDependencies": {
"@types/express": "^4.17.21",
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144 changes: 80 additions & 64 deletions ...kend-credit-card-enrollment/backend-typescript/src/common/serializedEvent/Deserializer.ts
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Original file line number Diff line number Diff line change
@@ -1,12 +1,13 @@
import { Event } from '../event/Event';
import { SerializedEvent } from './SerializedEvent';
import {EnrollmentRequested} from "../../creditCard/enrollment/event/EnrollmentRequested";
import {EnrollmentAccepted} from "../../creditCard/enrollment/event/EnrollmentAccepted";
import {EnrollmentDeclined} from "../../creditCard/enrollment/event/EnrollmentDeclined";
import {ProductActivated} from "../../creditCard/product/event/ProductActivated";
import {ProductDeactivated} from "../../creditCard/product/event/ProductDeactivated";
import {ProductDefined} from "../../creditCard/product/event/ProductDefined";
import {injectable} from "tsyringe";
import { EnrollmentRequested } from "../../creditCard/enrollment/event/EnrollmentRequested";
import { EnrollmentAccepted } from "../../creditCard/enrollment/event/EnrollmentAccepted";
import { EnrollmentDeclined } from "../../creditCard/enrollment/event/EnrollmentDeclined";
import { ProductActivated } from "../../creditCard/product/event/ProductActivated";
import { ProductDeactivated } from "../../creditCard/product/event/ProductDeactivated";
import { ProductDefined } from "../../creditCard/product/event/ProductDefined";
import { injectable } from "tsyringe";
import { typeSafeCoercion } from "../util/TypeSafeCoercion";

@injectable()
export class Deserializer {
Expand All @@ -16,79 +17,79 @@ export class Deserializer {

switch (serializedEvent.event_name) {
case 'CreditCard_Enrollment_EnrollmentRequested':
return new EnrollmentRequested(
serializedEvent.event_id,
serializedEvent.aggregate_id,
serializedEvent.aggregate_version,
serializedEvent.correlation_id,
serializedEvent.causation_id,
return typeSafeCoercion<EnrollmentRequested>(new EnrollmentRequested(
this.parseString(serializedEvent.event_id),
this.parseString(serializedEvent.aggregate_id),
this.parseNumber(serializedEvent.aggregate_version),
this.parseString(serializedEvent.correlation_id),
this.parseString(serializedEvent.causation_id),
recordedOn,
payload.userId,
payload.productId,
payload.annualIncomeInCents
);
this.parseString(payload.userId),
this.parseString(payload.productId),
this.parseNumber(payload.annualIncomeInCents)
));

case 'CreditCard_Enrollment_EnrollmentAccepted':
return new EnrollmentAccepted(
serializedEvent.event_id,
serializedEvent.aggregate_id,
serializedEvent.aggregate_version,
serializedEvent.correlation_id,
serializedEvent.causation_id,
return typeSafeCoercion<EnrollmentAccepted>(new EnrollmentAccepted(
this.parseString(serializedEvent.event_id),
this.parseString(serializedEvent.aggregate_id),
this.parseNumber(serializedEvent.aggregate_version),
this.parseString(serializedEvent.correlation_id),
this.parseString(serializedEvent.causation_id),
recordedOn,
payload.reasonCode,
payload.reasonDescription
);
this.parseString(payload.reasonCode),
this.parseString(payload.reasonDescription)
));

case 'CreditCard_Enrollment_EnrollmentDeclined':
return new EnrollmentDeclined(
serializedEvent.event_id,
serializedEvent.aggregate_id,
serializedEvent.aggregate_version,
serializedEvent.correlation_id,
serializedEvent.causation_id,
return typeSafeCoercion<EnrollmentDeclined>(new EnrollmentDeclined(
this.parseString(serializedEvent.event_id),
this.parseString(serializedEvent.aggregate_id),
this.parseNumber(serializedEvent.aggregate_version),
this.parseString(serializedEvent.correlation_id),
this.parseString(serializedEvent.causation_id),
recordedOn,
payload.reasonCode,
payload.reasonDescription
);
this.parseString(payload.reasonCode),
this.parseString(payload.reasonDescription)
));

case 'CreditCard_Product_ProductActivated':
return new ProductActivated(
serializedEvent.event_id,
serializedEvent.aggregate_id,
serializedEvent.aggregate_version,
serializedEvent.correlation_id,
serializedEvent.causation_id,
return typeSafeCoercion<ProductActivated>(new ProductActivated(
this.parseString(serializedEvent.event_id),
this.parseString(serializedEvent.aggregate_id),
this.parseNumber(serializedEvent.aggregate_version),
this.parseString(serializedEvent.correlation_id),
this.parseString(serializedEvent.causation_id),
recordedOn
);
));

case 'CreditCard_Product_ProductDeactivated':
return new ProductDeactivated(
serializedEvent.event_id,
serializedEvent.aggregate_id,
serializedEvent.aggregate_version,
serializedEvent.correlation_id,
serializedEvent.causation_id,
return typeSafeCoercion<ProductDeactivated>(new ProductDeactivated(
this.parseString(serializedEvent.event_id),
this.parseString(serializedEvent.aggregate_id),
this.parseNumber(serializedEvent.aggregate_version),
this.parseString(serializedEvent.correlation_id),
this.parseString(serializedEvent.causation_id),
recordedOn
);
));

case 'CreditCard_Product_ProductDefined':
return new ProductDefined(
serializedEvent.event_id,
serializedEvent.aggregate_id,
serializedEvent.aggregate_version,
serializedEvent.correlation_id,
serializedEvent.causation_id,
return typeSafeCoercion<ProductDefined>(new ProductDefined(
this.parseString(serializedEvent.event_id),
this.parseString(serializedEvent.aggregate_id),
this.parseNumber(serializedEvent.aggregate_version),
this.parseString(serializedEvent.correlation_id),
this.parseString(serializedEvent.causation_id),
recordedOn,
payload.name,
payload.interestInBasisPoints,
payload.annualFeeInCents,
payload.paymentCycle,
payload.creditLimitInCents,
payload.maxBalanceTransferAllowedInCents,
payload.reward,
payload.cardBackgroundHex
);
this.parseString(payload.name),
this.parseNumber(payload.interestInBasisPoints),
this.parseNumber(payload.annualFeeInCents),
this.parseString(payload.paymentCycle),
this.parseNumber(payload.creditLimitInCents),
this.parseNumber(payload.maxBalanceTransferAllowedInCents),
this.parseString(payload.reward),
this.parseString(payload.cardBackgroundHex)
));

default:
throw new Error(`Unknown event type: ${serializedEvent.event_name}`);
Expand All @@ -105,4 +106,19 @@ export class Deserializer {
}
return parsed;
}

private parseString(value: any): string {
if (typeof value !== 'string') {
throw new Error(`Expected string but got ${typeof value}`);
}
return value;
}

private parseNumber(value: any): number {
const parsed = Number(value);
if (isNaN(parsed)) {
throw new Error(`Expected number but got ${typeof value}`);
}
return parsed;
}
}
6 changes: 6 additions & 0 deletions ...ion/backend-credit-card-enrollment/backend-typescript/src/common/util/TypeSafeCoercion.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
import { z } from 'zod';

export function typeSafeCoercion<T>(data: unknown): T {
const schema = z.custom<T>().transform((val) => val as T);
return schema.parse(data);
}
3 changes: 2 additions & 1 deletion ...lment/backend-typescript/src/creditCard/enrollment/command/EnrollmentCommandController.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ import { RequestEnrollmentCommandHandler } from './RequestEnrollmentCommandHandl
import { RequestEnrollmentCommand } from './RequestEnrollmentCommand';
import { RequestEnrollmentHttpRequest } from './RequestEnrollmentHttpRequest';
import {inject, injectable} from "tsyringe";
import {typeSafeCoercion} from "../../../common/util/TypeSafeCoercion";

@injectable()
export class EnrollmentCommandController extends CommandController {
Expand All @@ -31,7 +32,7 @@ export class EnrollmentCommandController extends CommandController {
return;
}

const requestBody: RequestEnrollmentHttpRequest = req.body;
const requestBody = typeSafeCoercion<RequestEnrollmentHttpRequest>(req.body);
const command = new RequestEnrollmentCommand(
sessionToken,
requestBody.productId,
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