Add scripting (tengo) support for every incoming message (#731)

TengoModifyMessage allows you to specify the location of a tengo (https://github.com/d5/tengo/) script.
This script will receive every incoming message and can be used to modify the Username and the Text of that message.
The script will have the following global variables:
to modify: msgUsername and msgText
to read: msgChannel and msgAccount

The script is reloaded on every message, so you can modify the script on the fly.

Example script can be found in https://github.com/42wim/matterbridge/tree/master/gateway/bench.tengo
and https://github.com/42wim/matterbridge/tree/master/contrib/example.tengo

The example below will check if the text contains blah and if so, it'll replace the text and the username of that message.
text := import("text")
if text.re_match("blah",msgText) {
    msgText="replaced by this"
    msgUsername="fakeuser"
}

More information about tengo on: https://github.com/d5/tengo/blob/master/docs/tutorial.md and
https://github.com/d5/tengo/blob/master/docs/stdlib.md

1 files changed, 40 insertions, 0 deletions

diff --git a/vendor/github.com/d5/tengo/compiler/ast/if_stmt.go b/vendor/github.com/d5/tengo/compiler/ast/if_stmt.go
new file mode 100644
index 00000000..b3d65606
--- /dev/null
+++ b/vendor/github.com/d5/tengo/compiler/ast/if_stmt.go
@@ -0,0 +1,40 @@
+package ast
+
+import "github.com/d5/tengo/compiler/source"
+
+// IfStmt represents an if statement.
+type IfStmt struct {
+	IfPos source.Pos
+	Init  Stmt
+	Cond  Expr
+	Body  *BlockStmt
+	Else  Stmt // else branch; or nil
+}
+
+func (s *IfStmt) stmtNode() {}
+
+// Pos returns the position of first character belonging to the node.
+func (s *IfStmt) Pos() source.Pos {
+	return s.IfPos
+}
+
+// End returns the position of first character immediately after the node.
+func (s *IfStmt) End() source.Pos {
+	if s.Else != nil {
+		return s.Else.End()
+	}
+
+	return s.Body.End()
+}
+
+func (s *IfStmt) String() string {
+	var initStmt, elseStmt string
+	if s.Init != nil {
+		initStmt = s.Init.String() + "; "
+	}
+	if s.Else != nil {
+		elseStmt = " else " + s.Else.String()
+	}
+
+	return "if " + initStmt + s.Cond.String() + " " + s.Body.String() + elseStmt
+}