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, 95 insertions, 0 deletions

diff --git a/vendor/github.com/d5/tengo/objects/string.go b/vendor/github.com/d5/tengo/objects/string.go
new file mode 100644
index 00000000..6a53b44d
--- /dev/null
+++ b/vendor/github.com/d5/tengo/objects/string.go
@@ -0,0 +1,95 @@
+package objects
+
+import (
+	"strconv"
+
+	"github.com/d5/tengo/compiler/token"
+)
+
+// String represents a string value.
+type String struct {
+	Value   string
+	runeStr []rune
+}
+
+// TypeName returns the name of the type.
+func (o *String) TypeName() string {
+	return "string"
+}
+
+func (o *String) String() string {
+	return strconv.Quote(o.Value)
+}
+
+// BinaryOp returns another object that is the result of
+// a given binary operator and a right-hand side object.
+func (o *String) BinaryOp(op token.Token, rhs Object) (Object, error) {
+	switch op {
+	case token.Add:
+		switch rhs := rhs.(type) {
+		case *String:
+			return &String{Value: o.Value + rhs.Value}, nil
+		default:
+			return &String{Value: o.Value + rhs.String()}, nil
+		}
+	}
+
+	return nil, ErrInvalidOperator
+}
+
+// IsFalsy returns true if the value of the type is falsy.
+func (o *String) IsFalsy() bool {
+	return len(o.Value) == 0
+}
+
+// Copy returns a copy of the type.
+func (o *String) Copy() Object {
+	return &String{Value: o.Value}
+}
+
+// Equals returns true if the value of the type
+// is equal to the value of another object.
+func (o *String) Equals(x Object) bool {
+	t, ok := x.(*String)
+	if !ok {
+		return false
+	}
+
+	return o.Value == t.Value
+}
+
+// IndexGet returns a character at a given index.
+func (o *String) IndexGet(index Object) (res Object, err error) {
+	intIdx, ok := index.(*Int)
+	if !ok {
+		err = ErrInvalidIndexType
+		return
+	}
+
+	idxVal := int(intIdx.Value)
+
+	if o.runeStr == nil {
+		o.runeStr = []rune(o.Value)
+	}
+
+	if idxVal < 0 || idxVal >= len(o.runeStr) {
+		res = UndefinedValue
+		return
+	}
+
+	res = &Char{Value: o.runeStr[idxVal]}
+
+	return
+}
+
+// Iterate creates a string iterator.
+func (o *String) Iterate() Iterator {
+	if o.runeStr == nil {
+		o.runeStr = []rune(o.Value)
+	}
+
+	return &StringIterator{
+		v: o.runeStr,
+		l: len(o.runeStr),
+	}
+}