@spec build_exact_authorization(map(), String.t()) ::
  {:ok, authorization()} | {:error, :invalid_requirements}

Builds an exact PermitWitnessTransferFrom authorization in wire shape.

permitted carries the requirements' asset and exact amount; the spender is the x402ExactPermit2Proxy; the nonce is a fresh random uint256; the deadline is now plus maxTimeoutSeconds; and the witness binds payTo (to) with validAfter "0" (immediately valid), mirroring the reference SDKs.

Field values are validated when the digest is computed, not here.

@spec build_upto_authorization(map(), String.t()) ::
  {:ok, authorization()} | {:error, authorization_error()}

Builds an upto PermitWitnessTransferFrom authorization in wire shape.

permitted carries the requirements' asset and maximum amount; the spender is the x402UptoPermit2Proxy; the nonce is a fresh random uint256; the deadline is now plus maxTimeoutSeconds; and the witness binds payTo (to), extra.facilitatorAddress (facilitator), and validAfter "0" (immediately valid), mirroring the reference SDKs.

Field values are validated when the digest is computed, not here.

@spec digest(map(), map()) :: {:ok, <<_::256>>} | {:error, encode_error()}

Computes the EIP-712 digest of a PermitWitnessTransferFrom.

Returns keccak256(0x19 0x01 || domainSeparator || structHash) as a 32-byte binary — the value the client signs and the value to recover the payer address from (X402.EIP3009.recover_signer/2). The witness shape selects the type string: a witness with a facilitator field hashes as the upto Witness(address to,address facilitator,uint256 validAfter), otherwise as the exact Witness(address to,uint256 validAfter). domain and authorization accept both the internal snake-case atom keys and the wire-style string keys; the authorization's from is not part of the signed struct (Permit2 recovers the owner from the signature).

@spec domain(map()) :: {:ok, X402.EIP712.domain()} | {:error, domain_error()}

Derives the canonical Permit2 EIP-712 domain from v2 payment requirements.

The domain is name: "Permit2", the chain id from the CAIP-2 network, and the canonical Permit2 contract as the verifying contract. Permit2 declares no domain version, so the returned map carries no :version key and X402.EIP712.domain_separator/1 hashes the three-field EIP712Domain type. The same domain serves the exact and upto flows.

Examples

iex> X402.Permit2.domain(%{"network" => "eip155:84532"})
{:ok,
 %{
   name: "Permit2",
   chain_id: 84532,
   verifying_contract: "0x000000000022D473030F116dDEE9F6B43aC78BA3"
 }}

iex> X402.Permit2.domain(%{"network" => "solana:mainnet"})
{:error, :unsupported_network}

@spec exact_proxy_address() :: String.t()

Returns the x402ExactPermit2Proxy contract address — the spender of exact payments using the Permit2 transfer method.

Deployed at the same address on every supported EVM chain via CREATE2.

Examples

iex> X402.Permit2.exact_proxy_address()
"0x402085c248EeA27D92E8b30b2C58ed07f9E20001"

@spec facilitator_address(map()) ::
  {:ok, String.t()} | {:error, {:missing_extra, String.t()}}

Fetches the facilitator address from the requirements' extra.

The upto scheme requires extra.facilitatorAddress — the facilitator announces it via GET /supported (X402.Facilitator.supported/1) and the resource server forwards it in each upto requirements entry; the client binds it into the signed witness.

Examples

iex> X402.Permit2.facilitator_address(%{
...>   "extra" => %{"facilitatorAddress" => "0x2222222222222222222222222222222222222222"}
...> })
{:ok, "0x2222222222222222222222222222222222222222"}

iex> X402.Permit2.facilitator_address(%{"extra" => %{}})
{:error, {:missing_extra, "facilitatorAddress"}}

@spec permit2_address() :: String.t()

Returns the canonical Permit2 contract address.

Examples

iex> X402.Permit2.permit2_address()
"0x000000000022D473030F116dDEE9F6B43aC78BA3"

@spec random_nonce() :: String.t()

Returns a fresh random uint256 nonce as a decimal string.

Permit2 uses unordered nonces; the reference SDKs draw 32 random bytes per authorization, making collisions negligible.

Examples

iex> nonce = X402.Permit2.random_nonce()
iex> String.match?(nonce, ~r/^[0-9]+$/)
true

@spec sign_authorization(X402.Signer.t(), map(), map()) ::
  {:ok, String.t()} | {:error, encode_error() | term()}

Signs an authorization's EIP-712 digest with a signer.

The witness shape selects the exact or upto typed data (see the module documentation). Returns the 0x-prefixed 65-byte r || s || v signature.

@spec sign_exact(map(), X402.Signer.t()) ::
  {:ok, payload()}
  | {:error, domain_error() | authorization_error() | encode_error() | term()}

Signs the exact Permit2 scheme payload for the given requirements.

Derives the canonical Permit2 domain from the requirements' network, builds a fresh authorization from the signer's address (from), the requirements' asset/amount (permitted), payTo (the witness), and maxTimeoutSeconds (the deadline), computes the EIP-712 digest, and signs it through signer.

Examples

{:ok, signer} = X402.Signer.LocalKey.new(private_key)

{:ok, %{"signature" => _, "permit2Authorization" => _}} =
  X402.Permit2.sign_exact(
    %{
      "scheme" => "exact",
      "network" => "eip155:84532",
      "amount" => "10000",
      "asset" => "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
      "payTo" => "0x209693Bc6afc0C5328bA36FaF03C514EF312287C",
      "maxTimeoutSeconds" => 60,
      "extra" => %{"assetTransferMethod" => "permit2", "name" => "USDC", "version" => "2"}
    },
    signer
  )

@spec sign_upto(map(), X402.Signer.t()) ::
  {:ok, payload()}
  | {:error, domain_error() | authorization_error() | encode_error() | term()}

Signs the upto Permit2 scheme payload for the given requirements.

Derives the canonical Permit2 domain from the requirements' network, builds a fresh authorization from the signer's address (from), the requirements' asset/amount (permitted), payTo and extra.facilitatorAddress (the witness), and maxTimeoutSeconds (the deadline), computes the EIP-712 digest, and signs it through signer.

Requirements without extra.facilitatorAddress return {:error, {:missing_extra, "facilitatorAddress"}} — the facilitator address is required so the witness can bind settlement to it.

Examples

{:ok, signer} = X402.Signer.LocalKey.new(private_key)

{:ok, %{"signature" => _, "permit2Authorization" => _}} =
  X402.Permit2.sign_upto(
    %{
      "scheme" => "upto",
      "network" => "eip155:84532",
      "amount" => "5000000",
      "asset" => "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
      "payTo" => "0x209693Bc6afc0C5328bA36FaF03C514EF312287C",
      "maxTimeoutSeconds" => 300,
      "extra" => %{
        "name" => "USDC",
        "version" => "2",
        "facilitatorAddress" => "0x2222222222222222222222222222222222222222"
      }
    },
    signer
  )

@spec upto_digest(map(), map()) :: {:ok, <<_::256>>} | {:error, encode_error()}

Computes the EIP-712 digest of a PermitWitnessTransferFrom — same as digest/2.

@spec upto_domain(map()) :: {:ok, X402.EIP712.domain()} | {:error, domain_error()}

Derives the canonical Permit2 EIP-712 domain — same as domain/1.

Examples

iex> X402.Permit2.upto_domain(%{"network" => "eip155:84532"})
{:ok,
 %{
   name: "Permit2",
   chain_id: 84532,
   verifying_contract: "0x000000000022D473030F116dDEE9F6B43aC78BA3"
 }}

iex> X402.Permit2.upto_domain(%{"network" => "solana:mainnet"})
{:error, :unsupported_network}

@spec upto_proxy_address() :: String.t()

Returns the x402UptoPermit2Proxy contract address — the upto spender.

Deployed at the same address on every supported EVM chain via CREATE2.

Examples

iex> X402.Permit2.upto_proxy_address()
"0x4020A4f3b7b90ccA423B9fabCc0CE57C6C240002"