support --jq flag on fetch and event commands.

event.go

@@ -90,6 +90,11 @@ example:
 			Usage:    "print the event enveloped in a [\"EVENT\", ...] message ready to be sent to a relay",
 			Category: CATEGORY_EXTRAS,
 		},
+		&cli.StringFlag{
+			Name:     "jq",
+			Usage:    "filter returned events with jq expression",
+			Category: CATEGORY_EXTRAS,
+		},
 		&cli.BoolFlag{
 			Name:     "nevent",
 			Usage:    "print the nevent code (to stderr) after the event is published",
@@ -182,6 +187,11 @@ example:
 			return err
 		}
 
+		jq, err := jqPrepare(c.String("jq"))
+		if err != nil {
+			return err
+		}
+
 		// then process input and generate events:
 
 		// will reuse this
@@ -401,15 +411,26 @@ example:
 			}
 
 			// print event as json
-			var result string
-			if c.Bool("envelope") {
-				j, _ := json.Marshal(nostr.EventEnvelope{Event: evt})
-				result = string(j)
+			if jq == nil {
+				var result string
+				if c.Bool("envelope") {
+					j, _ := json.Marshal(nostr.EventEnvelope{Event: evt})
+					result = string(j)
+				} else {
+					j, _ := easyjson.Marshal(&evt)
+					result = string(j)
+				}
+				stdout(result)
 			} else {
-				j, _ := easyjson.Marshal(&evt)
-				result = string(j)
+				v, matches, err := jq(evt)
+				if err != nil {
+					return fmt.Errorf("jq filter failed: %w", err)
+				}
+				if matches {
+					out, _ := json.MarshalToString(v)
+					stdout(out)
+				}
 			}
-			stdout(result)
 
 			return publishFlow(ctx, c, kr, evt, relays)
 		}

fetch.go

@@ -24,9 +24,18 @@ var fetch = &cli.Command{
 			Aliases: []string{"r"},
 			Usage:   "also use these relays to fetch from",
 		},
+		&cli.StringFlag{
+			Name:  "jq",
+			Usage: "filter returned events with jq expression",
+		},
 	),
 	ArgsUsage: "[nip05_or_nip19_code]",
 	Action: func(ctx context.Context, c *cli.Command) error {
+		jq, err := jqPrepare(c.String("jq"))
+		if err != nil {
+			return err
+		}
+
 		for code := range getStdinLinesOrArguments(c.Args()) {
 			filter := nostr.Filter{}
 			var authorHint nostr.PubKey
@@ -111,7 +120,20 @@ var fetch = &cli.Command{
 				Label: "nak-fetch",
 			}) {
 				found = true
-				stdout(ie.Event)
+				var out string
+				if jq == nil {
+					out = ie.Event.String()
+				} else {
+					v, matches, err := jq(ie.Event)
+					if err != nil {
+						return fmt.Errorf("jq filter failed: %w", err)
+					}
+					if !matches {
+						continue
+					}
+					out, _ = json.MarshalToString(v)
+				}
+				stdout(out)
 			}
 
 			if !found {