feat(stellar): memo-encoded structured metadata schema (#140)

[lockoabosede8-byte]

Summary

Implements #140 — Memo-encoded structured metadata schema for Stellar memos. Partners (Reflector, Soroswap) can now attach reason strings, invoice IDs, or reference bytes to transactions via a compact versioned binary schema that fits within Stellar's 32-byte MEMO_HASH / MEMO_RETURN constraint.

Changes

New files

src/chains/stellar/memo/schema.ts — Encoder + decoder for a structured memo schema:

• Binary layout (32 bytes): version(1) + kind(1) + data_length(1) + data(29)
• MemoKind enum: Reason(0x01), InvoiceId(0x02), Reference(0x03)
• encodeMemoSchema(kind, data) — Encodes a string (UTF-8) or Uint8Array into a 32-byte schema buffer
• decodeMemoSchema(bytes) — Decodes a 32-byte buffer; returns { bytes, schema? }. If the first byte is not the version marker (0x01), returns the buffer as raw bytes for backwards compatibility
• Extension mechanism: kinds 0x04–0xEF reserved for future standardised kinds, 0xF0–0xFF for private/experimental use. Unknown kinds are decoded and forwarded without throwing

test/chains/stellar/memo/schema.test.ts — 33 tests covering:

• Round-trip encode/decode for all 3 kinds
• Backwards compatibility (non-schema-shaped bytes → raw result)
• Data size constraints (max 29 bytes, zero-length, edge cases)
• UTF-8 multi-byte character encoding
• Unknown kind forwarding, private/experimental kind range
• Data length clamping for malformed input
• Determinism and export verification

Modified files

src/chains/stellar/index.ts — Exports the new symbols (encodeMemoSchema, decodeMemoSchema, MemoKind, constants, types)

How it works

import { encodeMemoSchema, decodeMemoSchema, MemoKind } from '@wraith-protocol/sdk/chains/stellar'
import { encodeMemo } from '@wraith-protocol/sdk/chains/stellar'

// Encode a reason string into a 32-byte schema buffer
const schemaBytes = encodeMemoSchema(MemoKind.Reason, 'Payment for order #123')

// Wrap in a Stellar MEMO_HASH
const memo = encodeMemo({ type: 'hash', value: schemaBytes })

// On the receiving side, decode the memo
const decoded = decodeMemoSchema(schemaBytes)
if (decoded.schema) {
  console.log(decoded.schema.kind)  // MemoKind.Reason
  console.log(new TextDecoder().decode(decoded.schema.data))  // 'Payment for order #123'
}

// Backwards compat: raw bytes that don't start with 0x01 are returned as-is
const raw = decodeMemoSchema(new Uint8Array(32).fill(0xab))
// raw.schema === undefined, raw.bytes === the original buffer

Verification

• pnpm build — passes, new types appear in dist/chains/stellar
• pnpm test test/chains/stellar/memo/schema.test.ts — 33/33 pass
• All existing Stellar tests continue to pass (unaffected)

Closes #140

[drips-wave]

@lockoabosede8-byte Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits

[lockoabosede8-byte]

@truthixify, CI is failing on 2 pre-existing issues unrelated to this PR.