Support rewriting messages from relaybots using ExtractNicks. Fixes #466 (#730)

some examples:
this replaces a message like "Relaybot: <relayeduser> something interesting" to "relayeduser: something interesting"
ExtractNicks=[ [ "Relaybot", "<(.*?)>\\s+" ] ]
you can use multiple entries for multiplebots
this also replaces a message like "otherbot: (relayeduser) something else" to "relayeduser: something else"
ExtractNicks=[ [ "Relaybot", "<(.*?)>\\s+" ],[ "otherbot","\\((.*?)\\)\\s+" ]
OPTIONAL (default empty)
ExtractNicks=[ ["otherbot","<(.*?)>\\s+" ] ]

3 files changed, 116 insertions, 0 deletions

diff --git a/gateway/gateway.go b/gateway/gateway.go
index 0c04a167..2f797734 100644
--- a/gateway/gateway.go
+++ b/gateway/gateway.go
@@ -351,6 +351,8 @@ func (gw *Gateway) modifyMessage(msg *config.Message) {
 		msg.Text = re.ReplaceAllString(msg.Text, replace)
 	}
 
+	gw.handleExtractNicks(msg)
+
 	// messages from api have Gateway specified, don't overwrite
 	if msg.Protocol != apiProtocol {
 		msg.Gateway = gw.Name
diff --git a/gateway/handlers.go b/gateway/handlers.go
index 5af13c14..dfec2ab6 100644
--- a/gateway/handlers.go
+++ b/gateway/handlers.go
@@ -9,6 +9,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"strings"
 	"time"
 
 	"github.com/42wim/matterbridge/bridge"
@@ -225,3 +226,41 @@ func (gw *Gateway) handleMessage(msg config.Message, dest *bridge.Bridge) []*BrM
 	}
 	return brMsgIDs
 }
+
+func (gw *Gateway) handleExtractNicks(msg *config.Message) {
+	var err error
+	br := gw.Bridges[msg.Account]
+	for _, outer := range br.GetStringSlice2D("ExtractNicks") {
+		search := outer[0]
+		replace := outer[1]
+		msg.Username, msg.Text, err = extractNick(search, replace, msg.Username, msg.Text)
+		if err != nil {
+			flog.Errorf("regexp in %s failed: %s", msg.Account, err)
+			break
+		}
+	}
+}
+
+// extractNick searches for a username (based on "search" a regular expression).
+// if this matches it extracts a nick (based on "extract" another regular expression) from text
+// and replaces username with this result.
+// returns error if the regexp doesn't compile.
+func extractNick(search, extract, username, text string) (string, string, error) {
+	re, err := regexp.Compile(search)
+	if err != nil {
+		return username, text, err
+	}
+	if re.MatchString(username) {
+		re, err = regexp.Compile(extract)
+		if err != nil {
+			return username, text, err
+		}
+		res := re.FindAllStringSubmatch(text, 1)
+		// only replace if we have exactly 1 match
+		if len(res) > 0 && len(res[0]) == 2 {
+			username = res[0][1]
+			text = strings.Replace(text, res[0][0], "", 1)
+		}
+	}
+	return username, text, nil
+}
diff --git a/gateway/handlers_test.go b/gateway/handlers_test.go
new file mode 100644
index 00000000..db7988a9
--- /dev/null
+++ b/gateway/handlers_test.go
@@ -0,0 +1,75 @@
+package gateway
+
+import (
+	"github.com/42wim/matterbridge/bridge"
+	"github.com/42wim/matterbridge/bridge/config"
+	"github.com/stretchr/testify/assert"
+
+	"testing"
+)
+
+func TestIgnoreEvent(t *testing.T) {
+	eventTests := map[string]struct {
+		input  string
+		dest   *bridge.Bridge
+		output bool
+	}{
+		"avatar mattermost": {
+			input:  config.EventAvatarDownload,
+			dest:   &bridge.Bridge{Protocol: "mattermost"},
+			output: false,
+		},
+		"avatar slack": {
+			input:  config.EventAvatarDownload,
+			dest:   &bridge.Bridge{Protocol: "slack"},
+			output: true,
+		},
+		"avatar telegram": {
+			input:  config.EventAvatarDownload,
+			dest:   &bridge.Bridge{Protocol: "telegram"},
+			output: false,
+		},
+	}
+	gw := &Gateway{}
+	for testname, testcase := range eventTests {
+		output := gw.ignoreEvent(testcase.input, testcase.dest)
+		assert.Equalf(t, testcase.output, output, "case '%s' failed", testname)
+	}
+
+}
+
+func TestExtractNick(t *testing.T) {
+	eventTests := map[string]struct {
+		search         string
+		extract        string
+		username       string
+		text           string
+		resultUsername string
+		resultText     string
+	}{
+		"test1": {
+			search:         "fromgitter",
+			extract:        "<(.*?)>\\s+",
+			username:       "fromgitter",
+			text:           "<userx> blahblah",
+			resultUsername: "userx",
+			resultText:     "blahblah",
+		},
+		"test2": {
+			search: "<.*?bot>",
+			//extract:        `\((.*?)\)\s+`,
+			extract:        "\\((.*?)\\)\\s+",
+			username:       "<matterbot>",
+			text:           "(userx) blahblah (abc) test",
+			resultUsername: "userx",
+			resultText:     "blahblah (abc) test",
+		},
+	}
+	//	gw := &Gateway{}
+	for testname, testcase := range eventTests {
+		resultUsername, resultText, _ := extractNick(testcase.search, testcase.extract, testcase.username, testcase.text)
+		assert.Equalf(t, testcase.resultUsername, resultUsername, "case '%s' failed", testname)
+		assert.Equalf(t, testcase.resultText, resultText, "case '%s' failed", testname)
+	}
+
+}