add zaps.fetchZappedReceipts + examples for receipts

packages/ndk/example/zaps/receipts_for_event.dart

@@ -0,0 +1,36 @@
+// ignore_for_file: avoid_print
+
+import 'package:ndk/ndk.dart';
+
+void main() async {
+  final ndk = Ndk.defaultConfig();
+
+  print("fetching zap receipts for single event ");
+  final receipts = await ndk.zaps.fetchZappedReceipts(
+      pubKey:
+          "30782a8323b7c98b172c5a2af7206bb8283c655be6ddce11133611a03d5f1177",
+      eventId:
+          "d7bc29fa3c55ac525a3d5f2021211edb672b58565225dec423479a0875feea9d");
+
+  // Sort eventReceipts by amountSats in descending order
+  receipts
+      .sort((a, b) => (b.amountSats ?? 0).compareTo(a.amountSats ?? 0));
+
+  // Sort profileReceipts by amountSats in descending order
+  receipts
+      .sort((a, b) => (b.amountSats ?? 0).compareTo(a.amountSats ?? 0));
+
+  int eventSum = 0;
+  for (var receipt in receipts) {
+    String? sender;
+    if (receipt.sender!=null) {
+      Metadata? metadata = await ndk.metadata.loadMetadata(receipt.sender!);
+      sender = metadata?.name;
+    }
+    print("${sender!=null?"from ${sender} ":""} ${receipt.amountSats} sats ${receipt.comment}");
+    eventSum += receipt.amountSats ?? 0;
+  }
+  print("${receipts.length} receipts, total of $eventSum sats");
+
+  await ndk.destroy();
+}

packages/ndk/example/zaps/receipts_for_profile.dart

@@ -0,0 +1,30 @@
+// ignore_for_file: avoid_print
+
+import 'package:ndk/ndk.dart';
+
+void main() async {
+  final ndk = Ndk.defaultConfig();
+
+  print("fetching zap receipts for profile ");
+  final profileReceipts = await ndk.zaps.fetchZappedReceipts(
+    pubKey: "30782a8323b7c98b172c5a2af7206bb8283c655be6ddce11133611a03d5f1177",
+  );
+
+  // Sort profileReceipts by amountSats in descending order
+  profileReceipts
+      .sort((a, b) => (b.amountSats ?? 0).compareTo(a.amountSats ?? 0));
+
+  int profileSum = 0;
+  for (var receipt in profileReceipts) {
+    String? sender;
+    if (receipt.sender!=null) {
+      Metadata? metadata = await ndk.metadata.loadMetadata(receipt.sender!);
+      sender = metadata?.name;
+    }
+    print("${sender!=null?"from ${sender} ":""} ${receipt.amountSats} sats ${receipt.comment}");
+    profileSum += receipt.amountSats ?? 0;
+  }
+  print("${profileReceipts.length} receipts, total of $profileSum sats");
+
+  await ndk.destroy();
+}

packages/ndk/lib/domain_layer/entities/nip_01_event.dart

@@ -131,17 +131,7 @@ class Nip01Event {
 
   /// return first `e` tag found
   String? getEId() {
-    for (var tag in tags) {
-      if (tag.length > 1) {
-        var key = tag[0];
-        var value = tag[1];
-
-        if (key == "e") {
-          return value;
-        }
-      }
-    }
-    return null;
+    return getFirstTag("e");
   }
 
   /// return all tags that match given `tag`
@@ -189,12 +179,17 @@ class Nip01Event {
 
   /// return first found `d` tag
   String? getDtag() {
+    return getFirstTag("d");
+  }
+
+  /// Get first tag matching given name
+  String? getFirstTag(String name) {
     for (var tag in tags) {
       if (tag.length > 1) {
         var key = tag[0];
         var value = tag[1];
 
-        if (key == "d") {
+        if (key == name) {
           return value;
         }
       }

packages/ndk/lib/domain_layer/usecases/lnurl/lnurl.dart

@@ -142,4 +142,46 @@ abstract class Lnurl {
     await signer.sign(event);
     return event;
   }
+
+  /// extract amount from bolt11 in sats
+  static int getAmountFromBolt11(String bolt11) {
+    final numStr = subUntil(bolt11, "lnbc", "1p");
+    if (numStr.isNotEmpty) {
+      var numStrLength = numStr.length;
+      if (numStrLength > 1) {
+        var lastStr = numStr.substring(numStr.length - 1);
+        var pureNumStr = numStr.substring(0, numStr.length - 1);
+        var pureNum = int.tryParse(pureNumStr);
+        if (pureNum != null) {
+          if (lastStr == "p") {
+            return (pureNum * 0.0001).round();
+          } else if (lastStr == "n") {
+            return (pureNum * 0.1).round();
+          } else if (lastStr == "u") {
+            return (pureNum * 100).round();
+          } else if (lastStr == "m") {
+            return (pureNum * 100000).round();
+          }
+        }
+      }
+    }
+
+    return 0;
+  }
+
+  static String subUntil(String content, String before, String end) {
+    var beforeLength = before.length;
+    var index = content.indexOf(before);
+    if (index < 0) {
+      return "";
+    }
+
+    var index2 = content.indexOf(end, index + beforeLength);
+    if (index2 <= 0) {
+      return "";
+    }
+
+    return content.substring(index + beforeLength, index2);
+  }
+
 }

packages/ndk/lib/domain_layer/usecases/zaps/zap_receipt.dart

@@ -1,33 +1,27 @@
 import 'dart:convert';
 
 import 'package:ndk/domain_layer/entities/nip_01_event.dart';
+import 'package:ndk/domain_layer/usecases/lnurl/lnurl.dart';
+import 'package:ndk/domain_layer/usecases/zaps/zap_request.dart';
+
+import '../../../shared/logger/logger.dart';
 
 class ZapReceipt {
   static const KIND = 9735;
 
   int? paidAt;
+  int? amountSats;
   String? pubKey;
   String? bolt11;
   String? preimage;
-  String? zapRequestJson;
   String? recipient;
   String? eventId;
-  String? zapContent;
+  String? comment;
   String? sender;
   String? anon;
 
-  ZapReceipt(
-      this.paidAt,
-      this.pubKey,
-      this.bolt11,
-      this.preimage,
-      this.zapRequestJson,
-      this.recipient,
-      this.eventId,
-      this.zapContent,
-      this.sender);
-
   ZapReceipt.fromEvent(Nip01Event event) {
+    String? zapRequestJson;
     if (event.kind == 9735) {
       for (var tag in event.tags) {
         if (tag[0] == 'bolt11') bolt11 = tag[1];
@@ -39,15 +33,25 @@ class ZapReceipt {
         if (tag[0] == 'P') sender = tag[1];
       }
       paidAt = event.createdAt;
-      if (zapRequestJson != null) {
-        try {
-          Map map = jsonDecode(zapRequestJson!);
-          zapContent = map['content'];
-          sender = map['pubkey'];
-        } catch (_) {
-          zapContent = '';
+      if (zapRequestJson != null && zapRequestJson.isNotEmpty) {
+        Nip01Event event = Nip01Event.fromJson(jsonDecode(zapRequestJson));
+        comment = event.content;
+        sender = event.pubKey;
+        String? amountString = event.getFirstTag('amount');
+        if (amountString != null && amountString.isNotEmpty) {
+          try {
+            double? amount = double.tryParse(amountString);
+            if (amount != null) {
+              amountSats = (amount / 1000).round();
+            }
+          } catch (e) {
+            Logger.log.w(e);
+          }
         }
       }
+      if (amountSats == null && bolt11 != null) {
+        amountSats = Lnurl.getAmountFromBolt11(bolt11!);
+      }
       List<String>? splitStrings = anon?.split('_');
       if (splitStrings != null && splitStrings.length == 2) {
         // /// recipient decrypt
@@ -94,11 +98,10 @@ class ZapReceipt {
     //  - The zap receipt event's pubkey MUST be the same as the recipient's lnurl provider's nostrPubkey (retrieved in step 1 of the protocol flow).
     //  - The invoiceAmount contained in the bolt11 tag of the zap receipt MUST equal the amount tag of the zap request (if present).
     //  - The lnurl tag of the zap request (if present) SHOULD equal the recipient's lnurl.
-    //  - SHA256(description) MUST match the description hash in the bolt11 invoice.
   }
 
   @override
   String toString() {
-    return 'ZapReceipt(paidAt: $paidAt, pubKey: $pubKey, bolt11: $bolt11, preimage: $preimage, description: $zapRequestJson, recipient: $recipient, eventId: $eventId, zapContent: $zapContent, sender: $sender, anon: $anon)';
+    return 'ZapReceipt(paidAt: $paidAt, pubKey: $pubKey, bolt11: $bolt11, preimage: $preimage, amount: $amountSats, recipient: $recipient, eventId: $eventId, comment: $comment, sender: $sender, anon: $anon)';
   }
 }

packages/ndk/lib/domain_layer/usecases/zaps/zap_request.dart

@@ -1,8 +1,10 @@
 import 'package:ndk/domain_layer/entities/nip_01_event.dart';
 
+/// Zap Request
 class ZapRequest extends Nip01Event {
   static const int KIND = 9734;
 
+  /// Zap Request
   ZapRequest(
       {required super.pubKey, required super.tags, required super.content})
       : super(kind: KIND);

packages/ndk/lib/domain_layer/usecases/zaps/zaps.dart

@@ -105,6 +105,23 @@ class Zaps {
       return ZapResponse(error: e.toString());
     }
   }
+
+  /// fetch all zap receipts matching given pubKey and optional event id, in sats
+  Future<List<ZapReceipt>> fetchZappedReceipts({required String pubKey, String? eventId, Duration? timeout} ) async {
+    NdkResponse? response = _requests.query(filters: [
+      eventId!=null?
+      Filter(
+          kinds: [ZapReceipt.KIND],
+          eTags: [eventId],
+          pTags: [pubKey])
+          :
+      Filter(
+          kinds: [ZapReceipt.KIND],
+          pTags: [pubKey])
+    ], timeout: timeout?? Duration(seconds: 20));
+    List<Nip01Event> events = await response.future;
+    return events.map((event) => ZapReceipt.fromEvent(event)).toList();
+  }
 }
 
 /// zap response