Onchain

Pure Elixir Ethereum library. Provides read (eth_call) and write (transaction signing) capabilities using signet as the sole Ethereum dependency. No native deps, no Rustler.

Package Family

Package	Purpose	Deps
onchain (this)	Core Ethereum primitives, RPC, ABI, signing	signet
onchain_aave	Aave V3 protocol wrappers	onchain
onchain_evm	Rust NIFs: revm simulation, Solidity parsing, codegen	onchain + rustler

Pick what you need — consumers who only need eth_call never compile Rust.

Installation

def deps do
  [
    {:onchain, "~> 0.4"},
    # Add if you need Aave:
    {:onchain_aave, "~> 0.1"},
    # Add if you need EVM simulation / Solidity parsing:
    {:onchain_evm, "~> 0.1"}
  ]
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)

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