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Mar 26, 2026
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notifications service creation with all the relevant methods #653

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306 changes: 306 additions & 0 deletions backend/src/notifications/notifications.service.ts
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import { Injectable, Logger } from '@nestjs/common';
import { OnEvent } from '@nestjs/event-emitter';
import { MailerService } from '@nestjs-modules/mailer';
import {
SHIPMENT_ACCEPTED,
SHIPMENT_IN_TRANSIT,
SHIPMENT_DELIVERED,
SHIPMENT_COMPLETED,
SHIPMENT_CANCELLED,
SHIPMENT_DISPUTED,
SHIPMENT_DISPUTE_RESOLVED,
ShipmentEvent,
} from '../shipments/events/shipment.events';
import { Shipment } from '../shipments/entities/shipment.entity';

@Injectable()
export class NotificationsService {
private readonly logger = new Logger(NotificationsService.name);

constructor(private readonly mailerService: MailerService) {}

// ── Helpers ─────────────────────────────────────────────────────────────────

private async sendSafe(
to: string,
subject: string,
html: string,
): Promise<void> {
try {
await this.mailerService.sendMail({ to, subject, html });
} catch (err: unknown) {
const msg = err instanceof Error ? err.message : String(err);
this.logger.warn(`Failed to send email to ${to}: ${msg}`);
}
}

private shipmentSummary(s: Shipment): string {
return `
<table style="border-collapse:collapse;width:100%;font-size:14px;">
<tr><td style="padding:6px 0;color:#6b7280;">Tracking #</td><td style="padding:6px 0;font-weight:600;">${s.trackingNumber}</td></tr>
<tr><td style="padding:6px 0;color:#6b7280;">Route</td><td style="padding:6px 0;">${s.origin} → ${s.destination}</td></tr>
<tr><td style="padding:6px 0;color:#6b7280;">Cargo</td><td style="padding:6px 0;">${s.cargoDescription}</td></tr>
<tr><td style="padding:6px 0;color:#6b7280;">Weight</td><td style="padding:6px 0;">${s.weightKg} kg</td></tr>
<tr><td style="padding:6px 0;color:#6b7280;">Value</td><td style="padding:6px 0;">${s.currency} ${Number(s.price).toLocaleString()}</td></tr>
</table>
`;
}

private baseTemplate(title: string, body: string): string {
return `
<div style="font-family:sans-serif;max-width:600px;margin:0 auto;padding:24px;">
<h2 style="color:#1e40af;margin-bottom:16px;">${title}</h2>
${body}
<hr style="margin:24px 0;border:none;border-top:1px solid #e5e7eb;" />
<p style="color:#9ca3af;font-size:12px;">FreightFlow — Decentralized Freight Management</p>
</div>
`;
}

// ── Event Handlers ───────────────────────────────────────────────────────────

@OnEvent(SHIPMENT_ACCEPTED)
async onShipmentAccepted({ shipment }: ShipmentEvent): Promise<void> {
const { shipper, carrier } = shipment;
if (!shipper || !carrier) return;

// Notify shipper: a carrier accepted their shipment
await this.sendSafe(
shipper.email,
`✅ Carrier found for your shipment ${shipment.trackingNumber}`,
this.baseTemplate(
'Your shipment has been accepted!',
`
<p>Hi ${shipper.firstName},</p>
<p>Great news! <strong>${carrier.firstName} ${carrier.lastName}</strong> has accepted your shipment and will be handling the delivery.</p>
${this.shipmentSummary(shipment)}
<p style="margin-top:16px;">You will receive another update when your cargo is picked up.</p>
`,
),
);

// Notify carrier: confirm they accepted
await this.sendSafe(
carrier.email,
`📦 You accepted shipment ${shipment.trackingNumber}`,
this.baseTemplate(
'Shipment accepted — pickup next',
`
<p>Hi ${carrier.firstName},</p>
<p>You have successfully accepted a shipment. Please proceed to pick up the cargo.</p>
${this.shipmentSummary(shipment)}
<p style="margin-top:16px;"><strong>Pickup location:</strong> ${shipment.origin}</p>
`,
),
);
}

@OnEvent(SHIPMENT_IN_TRANSIT)
async onShipmentInTransit({ shipment }: ShipmentEvent): Promise<void> {
const { shipper, carrier } = shipment;
if (!shipper || !carrier) return;

await this.sendSafe(
shipper.email,
`🚚 Your shipment ${shipment.trackingNumber} is on the way`,
this.baseTemplate(
'Shipment picked up — in transit',
`
<p>Hi ${shipper.firstName},</p>
<p>Your cargo has been picked up by <strong>${carrier.firstName} ${carrier.lastName}</strong> and is now in transit.</p>
${this.shipmentSummary(shipment)}
${shipment.estimatedDeliveryDate ? `<p style="margin-top:16px;"><strong>Estimated delivery:</strong> ${new Date(shipment.estimatedDeliveryDate).toDateString()}</p>` : ''}
`,
),
);
}

@OnEvent(SHIPMENT_DELIVERED)
async onShipmentDelivered({ shipment }: ShipmentEvent): Promise<void> {
const { shipper, carrier } = shipment;
if (!shipper || !carrier) return;

// Notify shipper: please confirm delivery
await this.sendSafe(
shipper.email,
`📬 Your shipment ${shipment.trackingNumber} has been delivered — action required`,
this.baseTemplate(
'Delivery reported — please confirm',
`
<p>Hi ${shipper.firstName},</p>
<p><strong>${carrier.firstName} ${carrier.lastName}</strong> has marked your shipment as delivered on <strong>${new Date().toDateString()}</strong>.</p>
${this.shipmentSummary(shipment)}
<p style="margin-top:16px;">Please log in to FreightFlow to <strong>confirm delivery</strong> and complete the transaction, or raise a dispute if there is an issue.</p>
`,
),
);

// Notify carrier: delivery marked, waiting for shipper confirmation
await this.sendSafe(
carrier.email,
`✔️ Delivery marked for ${shipment.trackingNumber} — awaiting confirmation`,
this.baseTemplate(
'Delivery marked — awaiting shipper confirmation',
`
<p>Hi ${carrier.firstName},</p>
<p>You have successfully marked shipment <strong>${shipment.trackingNumber}</strong> as delivered. The shipper has been notified and will confirm receipt shortly.</p>
${this.shipmentSummary(shipment)}
`,
),
);
}

@OnEvent(SHIPMENT_COMPLETED)
async onShipmentCompleted({ shipment }: ShipmentEvent): Promise<void> {
const { shipper, carrier } = shipment;
if (!shipper || !carrier) return;

// Notify carrier: delivery confirmed, job done
await this.sendSafe(
carrier.email,
`🎉 Shipment ${shipment.trackingNumber} completed — delivery confirmed`,
this.baseTemplate(
'Job complete — delivery confirmed by shipper',
`
<p>Hi ${carrier.firstName},</p>
<p>The shipper has confirmed receipt of shipment <strong>${shipment.trackingNumber}</strong>. This job is now complete.</p>
${this.shipmentSummary(shipment)}
<p style="margin-top:16px;">Thank you for your service on FreightFlow!</p>
`,
),
);

// Notify shipper: transaction complete
await this.sendSafe(
shipper.email,
`✅ Shipment ${shipment.trackingNumber} completed successfully`,
this.baseTemplate(
'Shipment completed',
`
<p>Hi ${shipper.firstName},</p>
<p>Your shipment <strong>${shipment.trackingNumber}</strong> has been completed successfully. Thank you for using FreightFlow!</p>
${this.shipmentSummary(shipment)}
`,
),
);
}

@OnEvent(SHIPMENT_CANCELLED)
async onShipmentCancelled({
shipment,
reason,
}: ShipmentEvent): Promise<void> {
const { shipper, carrier } = shipment;
const reasonNote = reason
? `<p><strong>Reason:</strong> ${reason}</p>`
: '';

if (shipper) {
await this.sendSafe(
shipper.email,
`❌ Shipment ${shipment.trackingNumber} has been cancelled`,
this.baseTemplate(
'Shipment cancelled',
`
<p>Hi ${shipper.firstName},</p>
<p>Shipment <strong>${shipment.trackingNumber}</strong> has been cancelled.</p>
${reasonNote}
${this.shipmentSummary(shipment)}
`,
),
);
}

if (carrier) {
await this.sendSafe(
carrier.email,
`❌ Shipment ${shipment.trackingNumber} has been cancelled`,
this.baseTemplate(
'Shipment cancelled',
`
<p>Hi ${carrier.firstName},</p>
<p>Shipment <strong>${shipment.trackingNumber}</strong> that you were assigned to has been cancelled.</p>
${reasonNote}
${this.shipmentSummary(shipment)}
`,
),
);
}
}

@OnEvent(SHIPMENT_DISPUTED)
async onShipmentDisputed({ shipment, reason }: ShipmentEvent): Promise<void> {
const { shipper, carrier } = shipment;
const reasonNote = reason
? `<p><strong>Reason for dispute:</strong> ${reason}</p>`
: '';

if (shipper) {
await this.sendSafe(
shipper.email,
`⚠️ Dispute raised on shipment ${shipment.trackingNumber}`,
this.baseTemplate(
'A dispute has been raised',
`
<p>Hi ${shipper.firstName},</p>
<p>A dispute has been raised on shipment <strong>${shipment.trackingNumber}</strong>. Our team will review and resolve it.</p>
${reasonNote}
${this.shipmentSummary(shipment)}
`,
),
);
}

if (carrier) {
await this.sendSafe(
carrier.email,
`⚠️ Dispute raised on shipment ${shipment.trackingNumber}`,
this.baseTemplate(
'A dispute has been raised',
`
<p>Hi ${carrier.firstName},</p>
<p>A dispute has been raised on shipment <strong>${shipment.trackingNumber}</strong>. Our team will review and resolve it.</p>
${reasonNote}
${this.shipmentSummary(shipment)}
`,
),
);
}
}

@OnEvent(SHIPMENT_DISPUTE_RESOLVED)
async onDisputeResolved({ shipment, reason }: ShipmentEvent): Promise<void> {
const { shipper, carrier } = shipment;
const outcome = shipment.status.toUpperCase();
const reasonNote = reason
? `<p><strong>Resolution note:</strong> ${reason}</p>`
: '';

const body = (firstName: string) =>
this.baseTemplate(
`Dispute resolved — ${outcome}`,
`
<p>Hi ${firstName},</p>
<p>The dispute on shipment <strong>${shipment.trackingNumber}</strong> has been reviewed and resolved by our admin team.</p>
<p><strong>Outcome:</strong> ${outcome}</p>
${reasonNote}
${this.shipmentSummary(shipment)}
`,
);

if (shipper) {
await this.sendSafe(
shipper.email,
`🔔 Dispute resolved for shipment ${shipment.trackingNumber}`,
body(shipper.firstName),
);
}
if (carrier) {
await this.sendSafe(
carrier.email,
`🔔 Dispute resolved for shipment ${shipment.trackingNumber}`,
body(carrier.firstName),
);
}
}
}
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