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, 59 insertions, 0 deletions

diff --git a/vendor/github.com/d5/tengo/compiler/instructions.go b/vendor/github.com/d5/tengo/compiler/instructions.go
new file mode 100644
index 00000000..b04b2826
--- /dev/null
+++ b/vendor/github.com/d5/tengo/compiler/instructions.go
@@ -0,0 +1,59 @@
+package compiler
+
+import (
+	"fmt"
+)
+
+// MakeInstruction returns a bytecode for an opcode and the operands.
+func MakeInstruction(opcode Opcode, operands ...int) []byte {
+	numOperands := OpcodeOperands[opcode]
+
+	totalLen := 1
+	for _, w := range numOperands {
+		totalLen += w
+	}
+
+	instruction := make([]byte, totalLen, totalLen)
+	instruction[0] = byte(opcode)
+
+	offset := 1
+	for i, o := range operands {
+		width := numOperands[i]
+		switch width {
+		case 1:
+			instruction[offset] = byte(o)
+		case 2:
+			n := uint16(o)
+			instruction[offset] = byte(n >> 8)
+			instruction[offset+1] = byte(n)
+		}
+		offset += width
+	}
+
+	return instruction
+}
+
+// FormatInstructions returns string representation of
+// bytecode instructions.
+func FormatInstructions(b []byte, posOffset int) []string {
+	var out []string
+
+	i := 0
+	for i < len(b) {
+		numOperands := OpcodeOperands[Opcode(b[i])]
+		operands, read := ReadOperands(numOperands, b[i+1:])
+
+		switch len(numOperands) {
+		case 0:
+			out = append(out, fmt.Sprintf("%04d %-7s", posOffset+i, OpcodeNames[Opcode(b[i])]))
+		case 1:
+			out = append(out, fmt.Sprintf("%04d %-7s %-5d", posOffset+i, OpcodeNames[Opcode(b[i])], operands[0]))
+		case 2:
+			out = append(out, fmt.Sprintf("%04d %-7s %-5d %-5d", posOffset+i, OpcodeNames[Opcode(b[i])], operands[0], operands[1]))
+		}
+
+		i += 1 + read
+	}
+
+	return out
+}