# `Bourse.Signing.EIP712`
[🔗](https://github.com/ZenHive/bourse/blob/main/lib/bourse/signing/eip712.ex#L1)

Minimal EIP-712 typed-data encoder for the custom DEX signing modules
(`Bourse.Signing.Hyperliquid`).

Implements canonical EIP-712 encoding for the atomic-field message types
Hyperliquid uses (`Agent`, `HyperliquidTransaction:*`). The
result is the EIP-712 digest preimage `0x1901 ‖ domainSeparator ‖ hashStruct`,
as defined by EIP-712.

## Scope

Only **atomic** field types are supported (`string`, `bytes`, `bytes32`,
`address`, `bool`, `uint*`, `int*`). Struct-typed fields (nested custom types)
raise — none of the supported Hyperliquid message types use them, so a nested
type is a programming error rather than a silent wrong signature.

The `EIP712Domain` type is rendered in ethers' canonical field order
(`name`, `version`, `chainId`, `verifyingContract`, `salt`), including only the
fields present in the supplied domain.

# `domain`

```elixir
@type domain() :: %{optional(String.t()) => term()}
```

# `field`

```elixir
@type field() :: %{required(String.t()) => String.t()}
```

# `domain_separator`

```elixir
@spec domain_separator(domain()) :: binary()
```

Computes the 32-byte EIP-712 domain separator for `domain`.

# `encode`

```elixir
@spec encode(domain(), %{required(String.t()) => [field()]}, String.t(), map()) ::
  binary()
```

Encodes typed data into the EIP-712 digest preimage
`0x1901 ‖ domainSeparator ‖ hashStruct(primaryType, message)`.

# `hash_struct`

```elixir
@spec hash_struct(String.t(), %{required(String.t()) => [field()]}, map()) :: binary()
```

Computes `hashStruct(primaryType) = keccak256(typeHash ‖ encodeData)`.

---

*Consult [api-reference.md](api-reference.md) for complete listing*