mina_tree::scan_state::transaction_logic

Module transaction_union_payload

Expand description

Unified transaction representation for SNARK circuits

This module provides a single, unified structure (TransactionUnion) that can represent all transaction types (payments, stake delegations, fee transfers, coinbase) for SNARK circuit processing. This enables efficient proof generation by using a single circuit design regardless of the specific transaction type.

§Transaction Union

The TransactionUnion type encodes all transaction variants using a tagged union approach:

Common: Fields present in all transactions (fee, nonce, memo, etc.)
Body: Transaction-specific fields with interpretation based on Tag
Tag: Discriminates between Payment, StakeDelegation, FeeTransfer, and Coinbase

§Field Interpretation

Fields in Body are interpreted differently based on the Tag value:

Payment: source_pk and receiver_pk are sender and recipient
Stake Delegation: receiver_pk is the new delegate
Fee Transfer: receiver_pk is the fee recipient, amount is the fee
Coinbase: receiver_pk is the block producer, amount is the reward

§Receipt Chain Hash

This module also provides functions for computing receipt chain hashes, which commit to the sequence of transactions applied to an account:

cons_signed_command_payload: Updates receipt chain hash for signed commands
cons_zkapp_command_commitment: Updates receipt chain hash for zkApp commands
checked_cons_signed_command_payload: Checked version for use in circuits

§Timing and Vesting

The module implements timing validation for timed (vested) accounts:

validate_timing: Ensures timing constraints are met for an account deduction
validate_nonces: Validates transaction nonce matches account nonce
account_check_timing: Checks timing status for an account
timing_error_to_user_command_status: Converts timing errors to transaction failures

Timed accounts have a minimum balance that decreases over time according to a vesting schedule. When the minimum balance reaches zero, the account automatically becomes untimed.

§Account Helpers

Utility functions for account operations:

get_with_location: Retrieves an account or creates a placeholder for new accounts
ExistingOrNew: Indicates whether an account exists or is newly created
add_amount/sub_amount: Safe balance arithmetic with overflow/underflow checking