> For the complete documentation index, see [llms.txt](https://docs.talus.network/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.talus.network/reference/move/nexus_policy/policy.md).

# nexus\_policy::policy

* [Struct `Policy`](#struct-policy)
* [Enum `Symbol`](#enum-symbol)
* [Constants](#constants)
* [Function `witness_symbol`](#function-witness_symbol)
* [Function `uid_symbol_from_uid`](#function-uid_symbol_from_uid)
* [Function `witness_symbol_from_name`](#function-witness_symbol_from_name)
* [Function `new`](#function-new)
* [Function `new_linear`](#function-new_linear)
* [Function `id`](#function-id)
* [Function `data`](#function-data)
* [Function `data_mut`](#function-data_mut)
* [Function `dfa`](#function-dfa)
* [Function `state`](#function-state)
* [Function `state_index`](#function-state_index)
* [Function `configured_dfa`](#function-configured_dfa)
* [Function `is_accepting`](#function-is_accepting)
* [Function `reset`](#function-reset)
* [Function `register`](#function-register)
* [Function `register_uid`](#function-register_uid)
* [Function `register_for_state`](#function-register_for_state)
* [Function `register_uid_for_state`](#function-register_uid_for_state)
* [Function `add_symbol`](#function-add_symbol)
* [Function `add_witness_symbol`](#function-add_witness_symbol)
* [Function `add_uid_symbol`](#function-add_uid_symbol)
* [Function `add_state`](#function-add_state)
* [Function `set_transition`](#function-set_transition)
* [Function `set_accepting`](#function-set_accepting)
* [Function `borrow_config`](#function-borrow_config)
* [Function `borrow_config_for_uid`](#function-borrow_config_for_uid)
* [Function `borrow_mut_config`](#function-borrow_mut_config)
* [Function `borrow_mut_config_for_uid`](#function-borrow_mut_config_for_uid)
* [Function `borrow_state_config`](#function-borrow_state_config)
* [Function `borrow_state_config_for_uid`](#function-borrow_state_config_for_uid)
* [Function `borrow_mut_state_config`](#function-borrow_mut_state_config)
* [Function `borrow_mut_state_config_for_uid`](#function-borrow_mut_state_config_for_uid)
* [Function `advance_with_witness`](#function-advance_with_witness)
* [Function `advance_with_uid`](#function-advance_with_uid)
* [Function `has_witness_symbol`](#function-has_witness_symbol)
* [Function `has_witness_config`](#function-has_witness_config)
* [Function `has_uid_config`](#function-has_uid_config)
* [Function `remove_config`](#function-remove_config)
* [Function `remove_config_for_uid`](#function-remove_config_for_uid)
* [Function `remove_state_config`](#function-remove_state_config)
* [Function `remove_state_config_for_uid`](#function-remove_state_config_for_uid)

### Struct `Policy`

Policy couples a configured DFA with caller defined payload and transition metadata.

```move
public struct Policy<T: store> has key, store
```

<details>

<summary>Fields</summary>

[`id`](#nexus_policy_policy_id)`: sui::object::UID`[`dfa`](#nexus_policy_policy_dfa)`:` [`nexus_policy::automaton::ConfiguredAutomaton`](/reference/move/nexus_policy/automaton.md#nexus_policy_automaton_ConfiguredAutomaton)`<u64,` [`nexus_policy::policy::Symbol`](#nexus_policy_policy_Symbol)`>`[`state_index`](#nexus_policy_policy_state_index)`: u64`[`data`](#nexus_policy_policy_data)`: T`

</details>

#### Enum `Symbol`

DFA alphabet symbol for policies: either a witness TypeName or a concrete sui::object::ID.

```move
public enum Symbol has copy, drop, store
```

<details>

<summary>Variants</summary>

Variant `Witness0: std::type_name::TypeName`Variant `Uid0: sui::object::ID`

</details>

#### Constants

Witness symbol not present in the DFA alphabet.

```move
#[error]
const ESymbolNotInAlphabet: vector<u8> = b"Witness not present in policy alphabet";
```

#### Function `witness_symbol`

Construct a symbol from a witness type.

```move
public fun witness_symbol<W: drop>(): nexus_policy::policy::Symbol
```

#### Function `uid_symbol_from_uid`

Construct a symbol from a specific sui::object::ID.

```move
public fun uid_symbol_from_uid(uid: &sui::object::UID): nexus_policy::policy::Symbol
```

#### Function `witness_symbol_from_name`

Helper to create a witness symbol from a precalculated type name.

```move
public fun witness_symbol_from_name(name: std::type_name::TypeName): nexus_policy::policy::Symbol
```

#### Function `new`

Instantiate a policy with the provided DFA and payload.

```move
public fun new<T: store>(dfa: nexus_policy::automaton::DeterministicAutomaton<u64, nexus_policy::policy::Symbol>, data: T, ctx: &mut sui::tx_context::TxContext): nexus_policy::policy::Policy<T>
```

#### Function `new_linear`

Build a policy that enforces a linear sequence of symbols.

```move
public fun new_linear<T: store>(sequence: &sui::table_vec::TableVec<nexus_policy::policy::Symbol>, data: T, ctx: &mut sui::tx_context::TxContext): nexus_policy::policy::Policy<T>
```

#### Function `id`

Policy object ID.

```move
public fun id<T: store>(policy: &nexus_policy::policy::Policy<T>): &sui::object::UID
```

#### Function `data`

Borrow immutable access to the policy payload.

```move
public fun data<T: store>(policy: &nexus_policy::policy::Policy<T>): &T
```

#### Function `data_mut`

Borrow mutable access to the policy payload.

```move
public fun data_mut<T: store>(policy: &mut nexus_policy::policy::Policy<T>): &mut T
```

#### Function `dfa`

Borrow the underlying DFA.

```move
public fun dfa<T: store>(policy: &nexus_policy::policy::Policy<T>): &nexus_policy::automaton::DeterministicAutomaton<u64, nexus_policy::policy::Symbol>
```

#### Function `state`

Current state as stored in the DFA basis.

```move
public fun state<T: store>(policy: &nexus_policy::policy::Policy<T>): u64
```

#### Function `state_index`

Current state index inside the DFA basis.

```move
public fun state_index<T: store>(policy: &nexus_policy::policy::Policy<T>): u64
```

#### Function `configured_dfa`

Configured DFA with transition metadata.

```move
public fun configured_dfa<T: store>(policy: &nexus_policy::policy::Policy<T>): &nexus_policy::automaton::ConfiguredAutomaton<u64, nexus_policy::policy::Symbol>
```

#### Function `is_accepting`

Check if the DFA is in an accepting state.

```move
public fun is_accepting<T: store>(policy: &nexus_policy::policy::Policy<T>): bool
```

#### Function `reset`

Reset the DFA back to its initial state.

```move
public fun reset<T: store>(policy: &mut nexus_policy::policy::Policy<T>)
```

#### Function `register`

Register a configuration payload keyed by the witness `W`.

```move
public fun register<W: drop, T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>, config: Config)
```

#### Function `register_uid`

Register a configuration payload keyed by object `uid`.

```move
public fun register_uid<T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>, uid: &sui::object::UID, config: Config)
```

#### Function `register_for_state`

Register a configuration scoped to `(`[`state`](#nexus_policy_policy_state)`, W)`.

```move
public fun register_for_state<W: drop, T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>, state: u64, config: Config)
```

#### Function `register_uid_for_state`

Register a configuration scoped to `(`[`state`](#nexus_policy_policy_state)`, uid)`.

```move
public fun register_uid_for_state<T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>, state: u64, uid: &sui::object::UID, config: Config)
```

#### Function `add_symbol`

Add a new symbol to the alphabet with transitions for every state.

```move
public fun add_symbol<T: store>(policy: &mut nexus_policy::policy::Policy<T>, symbol: nexus_policy::policy::Symbol, transitions: &sui::table_vec::TableVec<u64>): u64
```

#### Function `add_witness_symbol`

Add a new witness symbol to the alphabet.

```move
public fun add_witness_symbol<W: drop, T: store>(policy: &mut nexus_policy::policy::Policy<T>, transitions: &sui::table_vec::TableVec<u64>): u64
```

#### Function `add_uid_symbol`

Add a new `sui::object::UID` backed symbol to the alphabet.

```move
public fun add_uid_symbol<T: store>(policy: &mut nexus_policy::policy::Policy<T>, uid: &sui::object::UID, transitions: &sui::table_vec::TableVec<u64>): u64
```

#### Function `add_state`

Add a new DFA state together with its outgoing transitions.

```move
public fun add_state<T: store>(policy: &mut nexus_policy::policy::Policy<T>, state: u64, accepting: bool, transitions: &sui::table_vec::TableVec<u64>, ctx: &mut sui::tx_context::TxContext): u64
```

#### Function `set_transition`

Update a transition `(`[`state`](#nexus_policy_policy_state)`, symbol) → next`.

```move
public fun set_transition<T: store>(policy: &mut nexus_policy::policy::Policy<T>, state: u64, symbol: nexus_policy::policy::Symbol, next: u64)
```

#### Function `set_accepting`

Toggle whether a state is accepting.

```move
public fun set_accepting<T: store>(policy: &mut nexus_policy::policy::Policy<T>, state: u64, accepting: bool)
```

#### Function `borrow_config`

Borrow an immutable reference to the configuration keyed by witness `W`.

```move
public fun borrow_config<W: drop, T: store, Config: store>(policy: &nexus_policy::policy::Policy<T>): &Config
```

#### Function `borrow_config_for_uid`

Borrow an immutable reference to the configuration keyed by object `uid`.

```move
public fun borrow_config_for_uid<T: store, Config: store>(policy: &nexus_policy::policy::Policy<T>, uid: &sui::object::UID): &Config
```

#### Function `borrow_mut_config`

Borrow a mutable reference to the configuration keyed by witness `W`.

```move
public fun borrow_mut_config<W: drop, T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>): &mut Config
```

#### Function `borrow_mut_config_for_uid`

Borrow a mutable reference to the configuration keyed by object `uid`.

```move
public fun borrow_mut_config_for_uid<T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>, uid: &sui::object::UID): &mut Config
```

#### Function `borrow_state_config`

Borrow an immutable reference to a configuration registered for `(`[`state`](#nexus_policy_policy_state)`, W)`.

```move
public fun borrow_state_config<W: drop, T: store, Config: store>(policy: &nexus_policy::policy::Policy<T>, state: u64): &Config
```

#### Function `borrow_state_config_for_uid`

Borrow an immutable reference to a configuration registered for `(`[`state`](#nexus_policy_policy_state)`, uid)`.

```move
public fun borrow_state_config_for_uid<T: store, Config: store>(policy: &nexus_policy::policy::Policy<T>, state: u64, uid: &sui::object::UID): &Config
```

#### Function `borrow_mut_state_config`

Borrow a mutable reference to a configuration registered for `(`[`state`](#nexus_policy_policy_state)`, W)`.

```move
public fun borrow_mut_state_config<W: drop, T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>, state: u64): &mut Config
```

#### Function `borrow_mut_state_config_for_uid`

Borrow a mutable reference to a configuration registered for `(`[`state`](#nexus_policy_policy_state)`, uid)`.

```move
public fun borrow_mut_state_config_for_uid<T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>, state: u64, uid: &sui::object::UID): &mut Config
```

#### Function `advance_with_witness`

Advance the DFA using witness `W` as the symbol. Witness is consumed.

```move
public fun advance_with_witness<W: drop, T: store>(policy: &mut nexus_policy::policy::Policy<T>, witness: W)
```

#### Function `advance_with_uid`

Advance the DFA using an object `uid` as the symbol.

```move
public fun advance_with_uid<T: store>(policy: &mut nexus_policy::policy::Policy<T>, uid: &sui::object::UID)
```

#### Function `has_witness_symbol`

Returns true if the witness symbol exists in the policy alphabet.

```move
public fun has_witness_symbol<W: drop, T: store>(policy: &nexus_policy::policy::Policy<T>): bool
```

#### Function `has_witness_config`

Returns true if a configuration has been registered for witness `W`.

```move
public fun has_witness_config<W: drop, T: store, Config: store>(policy: &nexus_policy::policy::Policy<T>): bool
```

#### Function `has_uid_config`

Returns true if a configuration has been registered for object `uid`.

```move
public fun has_uid_config<T: store, Config: store>(policy: &nexus_policy::policy::Policy<T>, uid: &sui::object::UID): bool
```

#### Function `remove_config`

Removes metadata keyed by witness `W`.

```move
public fun remove_config<W: drop, T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>): Config
```

#### Function `remove_config_for_uid`

Removes metadata keyed by object `uid`.

```move
public fun remove_config_for_uid<T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>, uid: &sui::object::UID): Config
```

#### Function `remove_state_config`

Removes metadata for state [`state`](#nexus_policy_policy_state) and witness `W`.

```move
public fun remove_state_config<W: drop, T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>, state: u64): Config
```

#### Function `remove_state_config_for_uid`

Removes metadata for state [`state`](#nexus_policy_policy_state) and object `uid`.

```move
public fun remove_state_config_for_uid<T: store, Config: store>(policy: &mut nexus_policy::policy::Policy<T>, state: u64, uid: &sui::object::UID): Config
```


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