docs: add docs for ScriptSigner

core/src/main/java/org/nervos/ckb/sign/ScriptSigner.java

@@ -2,6 +2,27 @@
 
 import org.nervos.ckb.type.Transaction;
 
+/**
+ * ScriptSigner implements the signing logic for various scripts.
+ *
+ * These signers should be registered in {@link TransactionSigner}.
+ */
 public interface ScriptSigner {
+  /**
+   * Sign the transaction for the script.
+   *
+   * This function is called by {@link TransactionSigner}
+   * for each context and each matched script group.
+   *
+   * @param transaction The transaction to be signed.
+   * @param scriptGroup TransactionSigner selects the corresponding ScriptSigner for each script group.
+   *     This selection is based on the registered ScriptSigner's provided script type and hash.
+   * @param context This is passed from {@code TransactionSigner.signTransaction}
+   * @return {@code true} when the script handler has modified the transaction.
+   *
+   * @see TransactionSigner#signTransaction(TransactionWithScriptGroups, Context...)
+   * @see TransactionSigner#signTransaction(TransactionWithScriptGroups, Set<Context>)
+   * @see TransactionSigner#signTransaction(TransactionWithScriptGroups, String...)
+   */
   boolean signTransaction(Transaction transaction, ScriptGroup scriptGroup, Context context);
 }

core/src/main/java/org/nervos/ckb/sign/TransactionSigner.java

@@ -87,12 +87,25 @@ public TransactionSigner registerLockScriptSigner(String codeHash, ScriptSigner
     return registerLockScriptSigner(Numeric.hexStringToByteArray(codeHash), scriptSigner);
   }
 
-
+  /**
+   * signTransaction signs the transaction using registered ScriptSigners.
+   *
+   * @param transaction Transaction to be signed.
+   * @param contexts Contexts for {@link org.nervos.ckb.sign.ScriptSigner}.
+   * @return signed groups indices.
+   */
   public Set<Integer> signTransaction(
       TransactionWithScriptGroups transaction, Context... contexts) {
     return signTransaction(transaction, new HashSet<>(Arrays.asList(contexts)));
   }
 
+  /**
+   * signTransaction signs the transaction using registered ScriptSigners.
+   *
+   * @param transaction Transaction to be signed.
+   * @param contexts Contexts for {@link org.nervos.ckb.sign.ScriptSigner}.
+   * @return signed groups indices.
+   */
   public Set<Integer> signTransaction(
       TransactionWithScriptGroups transaction, Set<Context> contexts) {
     Set<Integer> signedGroupsIndices = new HashSet<>();
@@ -122,6 +135,13 @@ public Set<Integer> signTransaction(
     return signedGroupsIndices;
   }
 
+  /**
+   * signTransaction signs the transaction using registered ScriptSigners.
+   *
+   * @param transaction Transaction to be signed.
+   * @param privateKeys Each private key is wrapped in one {@link Context}. These contexts will be passed to ScriptSigners.
+   * @return signed groups indices.
+   */
   public Set<Integer> signTransaction(
       TransactionWithScriptGroups transaction, String... privateKeys) {
     Contexts contexts = new Contexts();