implement getaddressinfo (#53)

* implement getaddressinfo

* fix iswatchonly

---------

Co-authored-by: Stepan Snigirev <stepan@planqc.eu>

Author: stepansnigirev

README.md

@@ -2,7 +2,6 @@
 
 This is a electrum-adapter. It exposes a Bitcoin-Core style API while using an electron API in the backend. It might be useful in specific usecases, e.g. having better performance when connecting to a electrum-server via Tor. In order to do that, it needs a Database. Quite easily you can use a kind of builtin SQLite. Depending on your usecase, you might want to use an external DB.
 
-Note! Requires embit from master branch. (Still true?!)
 ## Modes of usage
 
 This can be used either in standalone mode or as a specter-extension. The second option is probably the main use-case.
@@ -56,4 +55,4 @@ Before your create a PR, make sure to [blackify](https://github.com/psf/black) a
 there is a git [pre-commit hook](https://ljvmiranda921.github.io/notebook/2018/06/21/precommits-using-black-and-flake8/) which you can simply install like this:
 ```
 pre-commit install
-```
+```

src/cryptoadvance/spectrum/spectrum.py

@@ -361,7 +361,6 @@ def sync_script(self, script, state=None):
                 )  # not existing, how can we fix that?
             # new tx
             else:
-
                 tx_details = {
                     "tx_hash": tx_magic,
                     "blockhash": blockheader.get("blockhash"),
@@ -844,6 +843,46 @@ def getrawchangeaddress(self, wallet, address_type=None):
         # TODO: refill keypool, subscribe
         return desc.getscriptpubkey().address(self.network)
 
+    @walletrpc
+    def getaddressinfo(self, wallet, address: str):
+        ismine = False
+        ischange = False
+        iswatchonly = False
+        scriptpubkey = EmbitScript.from_address(address)
+        sc = Script.query.filter_by(
+            script=scriptpubkey.data.hex(), wallet=wallet
+        ).first()
+        if sc:
+            ismine = sc.index is not None
+        if ismine:
+            ischange = sc.descriptor.internal
+            iswatchonly = sc.descriptor.private_descriptor is None
+        obj = {
+            "address": address,
+            "scriptPubKey": scriptpubkey.data.hex(),
+            "ismine": ismine,
+            "ischange": ischange,
+            "solvable": ismine,
+            "iswatchonly": iswatchonly,
+        }
+        if ismine:
+            desc = sc.descriptor.get_descriptor()
+            derived_desc = desc.derive(sc.index).to_public()
+            # convert xpubs to pubs
+            for k in derived_desc.keys:
+                if k.is_extended:
+                    k.key = k.key.key
+            obj.update(
+                {
+                    "desc": add_checksum(str(derived_desc)),
+                    "parent_desc": add_checksum(str(desc.to_public())),
+                }
+            )
+        obj["labels"] = []
+        if sc and sc.label:
+            obj["labels"] = [sc.label]
+        return obj
+
     @walletrpc
     def listlabels(self, wallet, purpose=None):
         return list(