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Zhongwei Li
335
templates/workflow-with-events.ts
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335
templates/workflow-with-events.ts
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/**
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* Event-Driven Workflow Example
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*
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* Demonstrates:
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* - step.waitForEvent() for external events
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* - instance.sendEvent() to trigger waiting workflows
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* - Timeout handling
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* - Human-in-the-loop patterns
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*/
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import { WorkflowEntrypoint, WorkflowStep, WorkflowEvent } from 'cloudflare:workers';
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type Env = {
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APPROVAL_WORKFLOW: Workflow;
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DB: D1Database;
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};
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type ApprovalParams = {
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requestId: string;
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requesterId: string;
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amount: number;
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description: string;
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};
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type ApprovalEvent = {
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approved: boolean;
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approverId: string;
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comments?: string;
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};
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/**
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* Approval Workflow with Event Waiting
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*
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* Flow:
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* 1. Create approval request
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* 2. Notify approvers
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* 3. Wait for approval decision (max 7 days)
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* 4. Process decision
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* 5. Execute approved action or reject
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*/
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export class ApprovalWorkflow extends WorkflowEntrypoint<Env, ApprovalParams> {
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async run(event: WorkflowEvent<ApprovalParams>, step: WorkflowStep) {
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const { requestId, requesterId, amount, description } = event.payload;
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// Step 1: Create approval request in database
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await step.do('create approval request', async () => {
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await this.env.DB.prepare(`
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INSERT INTO approval_requests
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(id, requester_id, amount, description, status, created_at)
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VALUES (?, ?, ?, ?, ?, ?)
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`).bind(
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requestId,
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requesterId,
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amount,
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description,
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'pending',
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new Date().toISOString()
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).run();
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return { created: true };
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});
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// Step 2: Send notification to approvers
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await step.do('notify approvers', async () => {
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// Get list of approvers based on amount
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const approvers = amount > 10000
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? ['senior-manager@example.com', 'finance@example.com']
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: ['manager@example.com'];
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// Send notification to each approver
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await fetch('https://api.example.com/send-notifications', {
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method: 'POST',
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headers: { 'Content-Type': 'application/json' },
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body: JSON.stringify({
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recipients: approvers,
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subject: `Approval Required: ${description}`,
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body: `
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Request ID: ${requestId}
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Amount: $${amount}
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Description: ${description}
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Requester: ${requesterId}
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Please review and approve/reject at:
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https://app.example.com/approvals/${requestId}
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`,
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data: {
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requestId,
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workflowInstanceId: event.instanceId // Store for sending event later
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}
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})
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});
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return { notified: true, approvers };
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});
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// Step 3: Wait for approval decision (max 7 days)
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let approvalEvent: ApprovalEvent;
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try {
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approvalEvent = await step.waitForEvent<ApprovalEvent>(
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'wait for approval decision',
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{
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type: 'approval-decision',
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timeout: '7 days' // Auto-reject after 7 days
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}
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);
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console.log('Approval decision received:', approvalEvent);
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} catch (error) {
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// Timeout occurred - auto-reject
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console.log('Approval timeout - auto-rejecting');
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await step.do('auto-reject due to timeout', async () => {
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await this.env.DB.prepare(`
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UPDATE approval_requests
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SET status = ?, updated_at = ?, rejection_reason = ?
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WHERE id = ?
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`).bind(
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'rejected',
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new Date().toISOString(),
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'Approval timeout - no response within 7 days',
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requestId
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).run();
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// Notify requester
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await this.notifyRequester(requesterId, requestId, false, 'Approval timeout');
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return { rejected: true, reason: 'timeout' };
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});
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return {
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requestId,
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status: 'rejected',
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reason: 'timeout'
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};
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}
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// Step 4: Process approval decision
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await step.do('process approval decision', async () => {
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await this.env.DB.prepare(`
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UPDATE approval_requests
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SET status = ?, approver_id = ?, comments = ?, updated_at = ?
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WHERE id = ?
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`).bind(
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approvalEvent.approved ? 'approved' : 'rejected',
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approvalEvent.approverId,
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approvalEvent.comments || null,
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new Date().toISOString(),
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requestId
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).run();
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return { processed: true };
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});
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// Step 5: Notify requester
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await step.do('notify requester', async () => {
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await this.notifyRequester(
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requesterId,
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requestId,
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approvalEvent.approved,
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approvalEvent.comments
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);
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return { notified: true };
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});
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// Step 6: Execute approved action if approved
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if (approvalEvent.approved) {
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await step.do('execute approved action', async () => {
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// Execute the action that was approved
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console.log(`Executing approved action for request ${requestId}`);
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// Example: Process payment, create resource, etc.
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await fetch('https://api.example.com/execute-action', {
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method: 'POST',
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headers: { 'Content-Type': 'application/json' },
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body: JSON.stringify({
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requestId,
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amount,
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description
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})
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});
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return { executed: true };
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});
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}
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return {
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requestId,
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status: approvalEvent.approved ? 'approved' : 'rejected',
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approver: approvalEvent.approverId
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};
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}
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/**
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* Send notification to requester
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*/
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private async notifyRequester(
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requesterId: string,
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requestId: string,
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approved: boolean,
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comments?: string
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) {
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await fetch('https://api.example.com/send-notification', {
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method: 'POST',
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headers: { 'Content-Type': 'application/json' },
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body: JSON.stringify({
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recipient: requesterId,
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subject: `Request ${requestId} ${approved ? 'Approved' : 'Rejected'}`,
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body: `
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Your request ${requestId} has been ${approved ? 'approved' : 'rejected'}.
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${comments ? `\n\nComments: ${comments}` : ''}
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`
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})
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});
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}
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}
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/**
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* Worker that handles:
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* 1. Creating approval workflows
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* 2. Receiving approval decisions via webhook
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* 3. Sending events to waiting workflows
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*/
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export default {
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async fetch(req: Request, env: Env): Promise<Response> {
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const url = new URL(req.url);
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if (url.pathname.startsWith('/favicon')) {
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return Response.json({}, { status: 404 });
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}
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// Endpoint: Create new approval request
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if (url.pathname === '/approvals/create' && req.method === 'POST') {
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const body = await req.json<ApprovalParams>();
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// Create workflow instance
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const instance = await env.APPROVAL_WORKFLOW.create({
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params: body
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});
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// Store instance ID for later (when approval decision comes in)
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// In production, store this in DB/KV
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await env.DB.prepare(`
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UPDATE approval_requests
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SET workflow_instance_id = ?
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WHERE id = ?
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`).bind(instance.id, body.requestId).run();
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return Response.json({
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id: instance.id,
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requestId: body.requestId,
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status: await instance.status()
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});
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}
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// Endpoint: Submit approval decision (webhook from approval UI)
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if (url.pathname === '/approvals/decide' && req.method === 'POST') {
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const body = await req.json<{
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requestId: string;
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approved: boolean;
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approverId: string;
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comments?: string;
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}>();
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// Get workflow instance ID from database
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const result = await env.DB.prepare(`
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SELECT workflow_instance_id
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FROM approval_requests
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WHERE id = ?
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`).bind(body.requestId).first<{ workflow_instance_id: string }>();
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if (!result) {
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return Response.json(
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{ error: 'Request not found' },
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{ status: 404 }
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);
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}
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// Get workflow instance
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const instance = await env.APPROVAL_WORKFLOW.get(result.workflow_instance_id);
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// Send event to waiting workflow
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await instance.sendEvent({
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type: 'approval-decision',
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payload: {
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approved: body.approved,
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approverId: body.approverId,
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comments: body.comments
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}
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});
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return Response.json({
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success: true,
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message: 'Approval decision sent to workflow'
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});
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}
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// Endpoint: Get approval status
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if (url.pathname.startsWith('/approvals/') && req.method === 'GET') {
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const requestId = url.pathname.split('/')[2];
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const result = await env.DB.prepare(`
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SELECT workflow_instance_id, status
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FROM approval_requests
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WHERE id = ?
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`).bind(requestId).first<{ workflow_instance_id: string; status: string }>();
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if (!result) {
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return Response.json(
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{ error: 'Request not found' },
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{ status: 404 }
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);
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}
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const instance = await env.APPROVAL_WORKFLOW.get(result.workflow_instance_id);
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const workflowStatus = await instance.status();
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return Response.json({
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requestId,
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dbStatus: result.status,
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workflowStatus
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});
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}
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// Default: Show usage
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return Response.json({
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endpoints: {
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'POST /approvals/create': 'Create approval request',
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'POST /approvals/decide': 'Submit approval decision',
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'GET /approvals/:id': 'Get approval status'
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}
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});
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}
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};
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