Onchain

Shared Ethereum/blockchain library for Elixir. Provides read (eth_call) and write (transaction signing) capabilities using signet as the sole Ethereum dependency.

Installation

Add onchain to your list of dependencies in mix.exs:

def deps do
  [
    {:onchain, "~> 0.3"}
  ]
end

Requires an Ethereum JSON-RPC endpoint. Configure via:

# config/config.exs
config :signet, :rpc_url, "https://eth-mainnet.g.alchemy.com/v2/YOUR_KEY"

Or pass the URL per-call to Onchain.RPC functions.

Modules

Core

Module	Purpose
`Onchain.Hex`	Hex encoding/decoding (hex<->binary, hex<->integer, 0x prefix)
`Onchain.ABI`	ABI encoding/decoding for contract calls
`Onchain.Address`	Address validation, EIP-55 checksum, normalization
`Onchain.Decimal`	Decimal precision helpers (to_decimal, div_pow10, to_basis_points)
`Onchain.RPC`	Ethereum JSON-RPC wrapper (eth_call, eth_getLogs, receipts, nonces, balances)
`Onchain.RPC.Helpers`	Shared RPC helper functions (hex normalization, block tags, tx hash validation)
`Onchain.Block`	Block fetching with parsed fields, timestamp-based binary search
`Onchain.Contract`	Generic contract call (encode -> eth_call -> decode in one function)
`Onchain.Multicall`	Batch multiple eth_call via Multicall3
`Onchain.Log`	Event log parsing against ABI signatures
`Onchain.Signer`	Key management and transaction signing
`Onchain.ERC20`	ERC-20 read (balanceOf, allowance) and write (transfer, approve)

Chain Intelligence

Module	Purpose
`Onchain.Wallet`	Classify address (EOA/contract), native ETH balance
`Onchain.Transfer`	Parse ERC-20/721/1155 Transfer events into normalized structs
`Onchain.ENS`	ENS name resolution (forward, reverse, text records, contenthash)

Contract Codegen

Module	Purpose
`Onchain.Solidity`	Rustler NIF: Alloy-powered Solidity ABI parser
`Onchain.Contract.Generator`	Macro: `.sol` file -> typed Elixir module at compile time

Local EVM Simulation

Module	Purpose
`Onchain.EVM`	Rustler NIF: revm local EVM execution (fork mainnet, simulate transactions)
`Onchain.Trace`	Debug/trace APIs (trace_transaction, trace_call, storage_at)

Aave v3

Module	Purpose
`Onchain.Aave.Pool`	Pool read + write calls (getUserAccountData, supply, borrow, repay)
`Onchain.Aave.Oracle`	Asset price oracle + Chainlink
`Onchain.Aave.Math`	USD conversion, LTV, health factor, ray math
`Onchain.Aave.Contracts`	Verified address registry (mainnet + multi-chain)
`Onchain.Aave.UIPoolDataProvider`	Reserves and user reserves data
`Onchain.Aave.Faucet`	Testnet faucet interactions (mint test tokens)

Discovery

All modules use descripex for self-describing APIs:

Onchain.describe()                  # Module overview
Onchain.describe(:hex)              # Function list
Onchain.describe(:hex, :decode)     # Full function details

Testing

mix test.json --quiet                          # Unit tests (no RPC needed)
mix test.json --quiet --include integration    # Integration tests (requires RPC)

Integration tests require an Ethereum RPC endpoint:

export ETHEREUM_API_URL="https://eth-mainnet.g.alchemy.com/v2/YOUR_KEY"

Sepolia write tests additionally require SIGNER_PRIVATE_KEY.

License

MIT