Your First Loop

1SUBMITTED -> UNDER_REVIEW -> APPROVED
2                        \-> REJECTED

1import { aggregateId, transitionId } from '@loop-engine/core'
2import { LoopBuilder, createLoopSystem } from '@loop-engine/sdk'
3 
4const approval = LoopBuilder
5  .create('expense.approval', 'finance')
6  .description('Expense report approval')
7  .state('SUBMITTED')
8  .state('UNDER_REVIEW')
9  .state('APPROVED', { isTerminal: true })
10  .state('REJECTED', { isTerminal: true })
11  .initialState('SUBMITTED')
12  .transition({
13    id: 'start_review',
14    from: 'SUBMITTED',
15    to: 'UNDER_REVIEW',
16    actors: ['automation']
17  })
18  .transition({
19    id: 'approve',
20    from: 'UNDER_REVIEW',
21    to: 'APPROVED',
22    actors: ['human'],
23    guards: [
24      {
25        id: 'approval_obtained',
26        severity: 'hard',
27        evaluatedBy: 'runtime',
28        description: 'Approval must be present',
29        failureMessage: 'Approval not obtained'
30      }
31    ]
32  })
33  .transition({
34    id: 'reject',
35    from: 'UNDER_REVIEW',
36    to: 'REJECTED',
37    actors: ['human']
38  })
39  .outcome({
40    id: 'expense_approved',
41    description: 'Expense report approved',
42    valueUnit: 'expense_approved'
43  })
44  .build()
45 
46const aggregate = aggregateId('EXP-2026-001')
47const { engine } = createLoopSystem({ loops: [approval] })
48 
49await engine.start({
50  loopId: 'expense.approval',
51  aggregateId: aggregate,
52  orgId: 'acme',
53  actor: { type: 'system', id: 'system:intake' }, "cmt">// StartOptions.actor
54  metadata: { source: 'expense_form' } "cmt">// optional StartOptions.metadata
55})
56 
57const reviewResult = await engine.transition({
58  aggregateId: aggregate,
59  transitionId: transitionId('start_review'),
60  actor: { type: 'automation', id: 'system:router' }
61})
62 
63const approveResult = await engine.transition({
64  aggregateId: aggregate,
65  transitionId: transitionId('approve'),
66  actor: { type: 'human', id: 'manager@acme.com' },
67  evidence: { approved: true, comment: 'Within policy' }
68})