fix(contract): use BigInt arithmetic in MeshMarketplaceContract.purchaseAsset
Replaces float-based lovelace arithmetic with BigInt throughout purchaseAsset
to avoid silent precision loss for NFT prices above Number.MAX_SAFE_INTEGER
(~9,007,199 ADA). The previous `as number` casts were TypeScript-only lies
that caused a TypeError at runtime; converting via Number() fixed the crash
but introduced silent rounding errors for large prices.
Changes:
- All fee and seller-payment calculations now use BigInt operators; quantities
are only converted to string at the txOut boundary.
- Ceiling division implemented as (a * b + 9999n) / 10000n instead of
Math.ceil(float), which is exact and matches the on-chain semantics.
- 1-ADA minimum fee floor is now guarded by priceBig > 0n so free listings
(price = 0) no longer incur a spurious mandatory fee.
- lovelaceEntry guard replaces the !.quantity non-null assertion with a
descriptive error instead of an opaque TypeError.
- Constructor validates feePercentageBasisPoint is in [0, 10000] and throws
early rather than silently producing unbalanceable transactions.
Co-Authored-By: Claude Sonnet 4.6 <[email protected]>
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