Implement draft-to-submitted transition with line total evaluation
epic-expense-approval-workflow-core-logic-task-002 — Implement the submitClaim() method on ApprovalWorkflowService. On call, the service must aggregate all ExpenseLine totals for the claim, invoke ThresholdEvaluationService to determine the approval path (auto vs. manual), persist the new submitted state via ExpenseClaimStatusRepository, and return the computed path to the caller.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Implementation Notes
Create ApprovalWorkflowServiceImpl in lib/src/approval_workflow/approval_workflow_service_impl.dart implementing the abstract interface. Use constructor injection for all dependencies (ThresholdEvaluationService, ExpenseClaimStatusRepository, ClaimAuditEventRepository) — never use service locators inside the class. For line total aggregation, add an aggregateLineTotals(claimId) method to ExpenseClaimStatusRepository that delegates to a Supabase RPC or a SELECT SUM query. Wrap the entire submitClaim() body in a try-catch that maps exceptions to ClaimTransitionFailure — use specific exception types if the repository layer throws them.
The threshold evaluation and status update should happen in sequence (not parallel) because the approval path must be known before persisting state. Do not start the auto-approval transition inside submitClaim() — that is the responsibility of the caller (task-003).
Testing Requirements
Unit tests (flutter_test): mock ThresholdEvaluationService, ExpenseClaimStatusRepository, ClaimAuditEventRepository. Test cases: (1) draft claim below threshold → returns autoApproval path; (2) draft claim above threshold → returns manualReview path; (3) non-draft claim → returns invalidState failure; (4) claim not found → returns claimNotFound failure; (5) repository throws on updateStatus → returns repositoryError failure; (6) audit event is recorded with correct fields in success case; (7) actor is not claim owner → returns insufficientPermissions. Use verify() to assert repository methods are called the expected number of times.
The ThresholdEvaluationService is described as shared Dart logic used both client-side and in the Edge Function. Supabase Edge Functions run Deno/TypeScript, not Dart, meaning the threshold logic must be maintained in two languages and can diverge, causing the server to reject legitimate client submissions.
Mitigation & Contingency
Mitigation: Implement the threshold logic as a single TypeScript module in the Edge Function and call it via a thin Dart HTTP client wrapper for client-side preview feedback only. The server is always authoritative; the client version is purely for UX (showing the user whether their claim will auto-approve before they submit).
Contingency: If dual-language maintenance is unavoidable, create a shared golden test file (JSON fixtures with inputs and expected outputs) that is run against both implementations in CI to detect divergence immediately.
A peer mentor could double-tap the submit button or a network retry could trigger a duplicate submission, causing the ApprovalWorkflowService to attempt two concurrent state transitions from draft→submitted for the same claim, potentially resulting in two audit events or conflicting statuses.
Mitigation & Contingency
Mitigation: Implement idempotency in the ApprovalWorkflowService using a database-level unique constraint on (claim_id, from_status, to_status) per transition, combined with a UI-level submission lock (disable button after first tap until response returns).
Contingency: Add a deduplication check at the start of every state transition method that returns the existing state if an identical transition is already in progress or completed within the last 10 seconds.
Claims with multiple expense lines (e.g., mileage + parking) must have their combined total evaluated against the threshold. If individual lines are added asynchronously or the evaluation runs before all lines are persisted, the auto-approval decision may be computed on an incomplete set of expense lines.
Mitigation & Contingency
Mitigation: The Edge Function always fetches all expense lines from the database (not from the client payload) before computing the threshold decision. Define a clear claim submission contract that requires all expense lines to be persisted before the submit action is called.
Contingency: Add a validation step in ApprovalWorkflowService that counts expected vs. persisted expense lines before allowing the transition, returning a validation error if lines are missing.