Build payment method management with fallback chains

[Smartdevs17]

Context

Implement build payment method management with fallback chains for the platform.

Current Limitation

This functionality is currently missing or needs improvement.

Expected Outcome

• Production-ready implementation
• Comprehensive test coverage
• Documentation and examples
• Performance benchmarks where applicable

Acceptance Criteria

• Feature implemented with full functionality
• Unit tests added with >80% coverage
• Integration tests for critical paths
• No regression introduced
• Documentation updated
• Code review approved
• Performance benchmarks met

Technical Scope

src/services/walletService.ts, src/store/walletStore.ts

Labels

• drips-wave
• high
• 200-points

[progress-caleb]

@progress-caleb has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Kindly issues this to me

ℹ️ Repo Maintainers: To accept this application, review their application or assign @progress-caleb to this issue.

[retkatmun]

@retkatmun has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi Maintainer,

I’m a smart contract and full-stack developer and would love to contribute to this issue. I’m an experienced contributor with hands-on expertise in Rust, Soroban, Cairo, and TypeScript.

I’m passionate about building secure, scalable blockchain solutions, with a strong emphasis on writing clean and maintainable code. Based on the scope of this issue, I’m confident I can deliver a complete solution within 24 hours of assignment.

I’d greatly appreciate the opportunity to contribute and help move this forward.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @retkatmun to this issue.

[drips-wave]

Congratulations, @retkatmun! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @retkatmun: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊

[retkatmun]

Fix implemented — PR raised

PR #1035 implements this feature: #1035

What was built

• PaymentMethodService — full CRUD, fallback chain logic (processPaymentWithChain), expiry tracking, analytics (computeAnalytics), and payment method sharing
• FallbackChainEngine — 6 pluggable ordering strategies: priority, weighted, sticky, priority-burst, geo-aware, round-robin
• PaymentMethodManager — circuit breaker (opens after 3 failures), health scoring (0–100), rate limiting per method
• useWalletStore — full Zustand slice: addPaymentMethod, removePaymentMethod, createFallbackChain, reorderFallbackChain, processPaymentWithChain, expiryAlerts, deactivateExpiredMethods, paymentAnalytics, sharePaymentMethod, and more
• PaymentMethodManager.tsx — full-screen UI with 4 tabs (Methods / Chains / Analytics / Alerts), fully accessible
• src/types/paymentMethod.ts — dedicated type module
• Removed duplicate PaymentMethodService class from walletService.ts; unified import source

Tests

• 40+ unit tests for PaymentMethodService
• 35+ unit tests for useWalletStore
• 11 integration tests covering: sequential fallback, full chain failure, stopOnHardDecline, maxAttempts, gas price spike, sticky/geo-aware strategies, circuit breaker, default chain, validate→process round-trip, analytics

Docs

docs/payment-method-management.md — architecture, API reference, error codes, execution flow

Closes #951