# `MPP.DID`
[🔗](https://github.com/ZenHive/mpp/blob/v0.10.0/lib/mpp/did.ex#L1)

Decentralized identifier (DID) helpers for MPP credential sources.

EVM wallet addresses use the `did:pkh:eip155` method per CAIP-10.

## API Functions
| Function | Arity | Description | Param Kinds |
| --- | --- | --- | --- |
| `parse_evm_did` | 1 | Parse a `did:pkh:eip155` credential source into chain ID and address. | `did: value` |
| `evm_did` | 2 | Build a `did:pkh:eip155` identifier for an EVM address and chain. | `address: value`, `chain_id: value` |

# `evm_did`

```elixir
@spec evm_did(String.t(), integer()) :: String.t()
```

Build a `did:pkh:eip155` identifier for an EVM address and chain.

## Parameters

  * `address` - EVM address (e.g., 0x742d35Cc6634c0532925a3b844bC9e7595F8fE00) (value)
  * `chain_id` - EVM chain ID (e.g., 42431 for Tempo Moderato) (value)

## Returns

DID string in `did:pkh:eip155:<chain_id>:<address>` format (`string`)

```elixir
# descripex:contract
%{
  params: %{
    address: %{
      description: "EVM address (e.g., 0x742d35Cc6634c0532925a3b844bC9e7595F8fE00)",
      kind: :value
    },
    chain_id: %{
      description: "EVM chain ID (e.g., 42431 for Tempo Moderato)",
      kind: :value
    }
  },
  returns: %{
    type: :string,
    description: "DID string in `did:pkh:eip155:<chain_id>:<address>` format",
    example: "did:pkh:eip155:42431:0x742d35Cc6634c0532925a3b844bC9e7595F8fE00"
  }
}
```

# `parse_evm_did`

```elixir
@spec parse_evm_did(String.t()) ::
  {:ok, %{chain_id: non_neg_integer(), address: String.t()}}
  | {:error, :invalid_did}
```

Parse a `did:pkh:eip155` credential source into chain ID and address.

## Parameters

  * `did` - DID string (e.g., did:pkh:eip155:42431:0x...) (value)

## Returns

`{:ok, %{chain_id: int, address: string}}` or `{:error, :invalid_did}` (`tagged_tuple`)

## Composes With

  * `evm_did`

```elixir
# descripex:contract
%{
  params: %{
    did: %{
      description: "DID string (e.g., did:pkh:eip155:42431:0x...)",
      kind: :value
    }
  },
  returns: %{
    type: :tagged_tuple,
    description: "`{:ok, %{chain_id: int, address: string}}` or `{:error, :invalid_did}`"
  },
  composes_with: [:evm_did]
}
```

---

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