Implement real-time invoice payment aggregator with streaming updates, conflict resolution, and rollup snapshots

[Kingsman-99]

Description

Build a PaymentAggregator that maintains a live, incrementally-updated payment summary for an invoice. It must handle out-of-order payment events (from blockchain reorgs or delayed delivery), resolve conflicts via ledger sequence number, produce periodic rollup snapshots to avoid recomputing from scratch, and expose a reactive subscription API.

Acceptance Criteria

• Create src/paymentAggregator.ts exporting PaymentAggregator class
• PaymentAggregator accepts an initial Invoice and maintains internal state: totalFunded: bigint, percentFunded: number, payerBreakdown: Map<string, bigint>, paymentCount: number, lastLedger: number
• applyPayment(payment: Payment & { ledger: number }): void — applies a payment; ignores duplicates (same payer + same ledger); if a payment with lower ledger arrives after a higher one, re-sorts and recomputes (conflict resolution)
• subscribe(cb: (summary: PaymentSummary) => void): () => void — fires callback synchronously on every applyPayment call; returns unsubscribe
• snapshot(): PaymentSnapshot — returns current state serializable to JSON; restore(snapshot: PaymentSnapshot): void — restores state without reprocessing all payments
• getTopPayers(n: number): { address: string, amount: bigint }[] — returns top N payers sorted descending by amount
• percentFunded must never exceed 100 even if totalFunded > invoiceTotal
• All exported from src/index.ts with full types
• Tests: out-of-order payment conflict resolution, duplicate payment ignored, snapshot/restore round-trip, subscriber fires on each apply, unsubscribe works, top payers sorted correctly with tie-breaking by address alphabetically

Context

• Invoice and Payment types are in src/types.ts — Payment may need a ledger: number field added
• src/snapshot.ts already exists — align snapshot format conventions
• bigint arithmetic only — no Number() conversion for amounts

[Smartdevs17]

can I work on this?

[Spycall]

Hi team,
I would love to handle this task.
I will develop a utility to aggregate invoice payment data, calculate funding metrics, and provide payer level payment summaries with corresponding test cases.