feat: add offline api docs

docs/pages/client.md

@@ -11,9 +11,9 @@ interface PolkadotClient {
   getChainSpecData: () => Promise<ChainSpecData>
 
   /**
-   * Observable that emits `BlockInfo` from the latest known finalized block.
-   * It's a multicast and stateful observable, that will synchronously replay
-   * its latest known state.
+   * Observable that emits `BlockInfo` for every new finalized block. It's a
+   * multicast and stateful observable, that will synchronously replay its
+   * latest known state.
    */
   finalizedBlock$: Observable<BlockInfo>
   /**
@@ -29,9 +29,8 @@ interface PolkadotClient {
    * i.e. a new array is emitted at every event but the reference to its
    * children are stable if the children didn't change.
    *
-   * Note that subscribing to this observable already supersedes the need of
-   * subscribing to `finalizedBlock$`, since the last element of the array will
-   * be the latest known finalized block.
+   * Note that some blocks might not get reported, e.g. if they become finalized
+   * immediately without being part of the best block chain.
    */
   bestBlocks$: Observable<BlockInfo[]>
   /**
@@ -67,37 +66,38 @@ interface PolkadotClient {
   getBlockHeader: (hash?: string) => Promise<BlockHeader>
 
   /**
-   * Broadcast a transaction (Promise-based)
+   * Broadcasts a transaction (Promise-based). The promise will resolve when the
+   * transaction is found in a finalized block; and will reject if the
+   * transaction is invalid and can't be broadcasted, or if it is deemed invalid
+   * later on.
    *
    * @param transaction  SCALE-encoded tx to broadcast.
    * @param at           It can be a block hash, `"finalized"`, or `"best"`.
    *                     That block will be used to verify the validity of
-   *                     the tx, retrieve the next nonce,
-   *                     and create the mortality taking that block into
-   *                     account.
+   *                     the tx.
    */
   submit: (
     transaction: HexString,
     at?: HexString,
   ) => Promise<TxFinalizedPayload>
   /**
-   * Broadcast a transaction and returns an Observable. The observable will
-   * complete as soon as the transaction is in a finalized block.
+   * Broadcasts a transaction and returns an Observable. The observable will
+   * complete as soon as the transaction is in a finalized block. See
+   * https://papi.how/typed/tx#signsubmitandwatch to learn about all possible
+   * events.
    *
    * @param transaction  SCALE-encoded tx to broadcast.
    * @param at           It can be a block hash, `"finalized"`, or `"best"`.
    *                     That block will be used to verify the validity of
-   *                     the tx, retrieve the next nonce,
-   *                     and create the mortality taking that block into
-   *                     account.
+   *                     the tx.
    */
   submitAndWatch: (
     transaction: HexString,
     at?: HexString,
   ) => Observable<TxBroadcastEvent>
 
   /**
-   * Returns an instance of a `TypedApi`
+   * Returns an instance of a `TypedApi`.
    *
    * @param descriptors  Pass descriptors from `@polkadot-api/descriptors`
    *                     generated by `papi` CLI.

docs/pages/offline.md

@@ -0,0 +1,62 @@
+# Offline API
+
+The rationale behind the offline api is to allow consumers to do certain actions with PAPI without the need of a provider. As expected, this client is more limited than the regular [`PolkadotClient`](/client).
+
+Let's see an example first of all:
+
+```typescript
+import { getOfflineApi } from "polkadot-api"
+import { dotDescriptors } from "@polkadot-api/descriptors" // you'll need them!
+
+const offline = await getOfflineApi(dotDescriptors) // it is async!
+
+// metadata constants can be easily accessed
+const prefix = api.constants.System.SS58Prefix // directly the value; e.g. `0`
+const { spec_name, spec_version } = api.constants.System.Version
+
+// transactions can be created and signed
+const tx = api.tx.Balances.transfer_keep_alive({
+  dest: MultiAddress.Id(myAddr),
+  value: amount,
+})
+
+tx.encodedData // we have the encoded callData
+tx.decodedCall // and the decodedCall
+
+const tx2 = offline.tx.Utility.batch({
+  calls: [
+    offline.tx.System.remark({ remark: Binary.fromText("HELLO!") }).decodedCall,
+    tx.decodedCall,
+  ],
+})
+
+// we can sign txs, but we need to add more stuff than usual!
+const signedTx = await tx2.sign(signer, {
+  nonce: 24, // nonce is always compulsory
+  mortality: { mortal: false }, // and mortality!
+})
+```
+
+## Constants
+
+Constants can be accessed easily having the metadata. `api.constants.Pallet.Entry` already gives the decoded value.
+
+## Transactions
+
+This is the main usecase of offline api. It allows to create and encode transactions, and even sign them.
+The transactions are created in the exact same way as in the regular API ([see docs](/typed/tx)). Nevertheless, only a subset of the fields are exposed:
+
+- `decodedCall`: it enables to get the _PAPI decoded_ transaction. It is helpful to create other txs that require them as a parameter (e.g. `Utility.batch`).
+- `encodedData`: a `Binary` with the encoded call data.
+- `sign`: it takes the same arguments as the regular API, but there are two compulsory signed extensions:
+  - `nonce`: nonce cannot be retrieved anymore from the chain, and therefore has to be passed
+  - `mortality`: transactions can be signed either mortal or immortal. In case the tx were to be mortal, the block information has to be passed as well.
+  ```typescript
+  type Mortality =
+    | { mortal: false }
+    | {
+        mortal: true
+        period: number
+        startAtBlock: { height: number; hash: HexString }
+      }
+  ```

docs/pages/requirements.md

@@ -6,7 +6,7 @@ PAPI is designed to work flawlessly with almost any Polkadot-like chain. Even th
 
 ### NodeJS
 
-PAPI is developed using the latest NodeJS LTS (currently `20.x`). The minimum required version is `20.6.0`, while we recommend the latest available release.
+PAPI is developed using the latest NodeJS LTS (currently `22.x`). The minimum required version is `20.6.0`, while we recommend the latest available release.
 
 ### Bun
 
@@ -70,10 +70,6 @@ Besides that, Polkadot-API requires runtimes to implement some basic runtime cal
 - In order to get the metadata, it needs `Metadata_metadata_versions` and `Metadata_metadata_at_version`. If they are not present, then `Metadata_metadata` needs to be there and answer a `v14` Metadata.
 - To create and broadcast transactions, Polkadot-API needs `AccountNonceApi_account_nonce` and `TaggedTransactionQueue_validate_transaction`. To estimate the fees, it also requires `TransactionPaymentApi_query_info`.
 
-In order to create transactions as well, the following storage entry is required for obtaining the genesis block-hash:
-
-- `System.BlockHash`
-
-And the following constant:
+In order to create transactions as well, the following constant is required:
 
 - `System.Version`, having `spec_version` and `transaction_version` fields.

vocs.config.tsx

@@ -95,6 +95,10 @@ export default defineConfig({
         },
       ],
     },
+    {
+      text: "Offline API",
+      link: "/offline",
+    },
     {
       text: "PAPI SDKs",
       link: "/sdks/intro",