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, 180 insertions, 0 deletions

diff --git a/vendor/github.com/d5/tengo/script/script.go b/vendor/github.com/d5/tengo/script/script.go
new file mode 100644
index 00000000..0b810278
--- /dev/null
+++ b/vendor/github.com/d5/tengo/script/script.go
@@ -0,0 +1,180 @@
+package script
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/d5/tengo/compiler"
+	"github.com/d5/tengo/compiler/parser"
+	"github.com/d5/tengo/compiler/source"
+	"github.com/d5/tengo/objects"
+	"github.com/d5/tengo/runtime"
+	"github.com/d5/tengo/stdlib"
+)
+
+// Script can simplify compilation and execution of embedded scripts.
+type Script struct {
+	variables         map[string]*Variable
+	removedBuiltins   map[string]bool
+	removedStdModules map[string]bool
+	userModuleLoader  compiler.ModuleLoader
+	input             []byte
+}
+
+// New creates a Script instance with an input script.
+func New(input []byte) *Script {
+	return &Script{
+		variables: make(map[string]*Variable),
+		input:     input,
+	}
+}
+
+// Add adds a new variable or updates an existing variable to the script.
+func (s *Script) Add(name string, value interface{}) error {
+	obj, err := objects.FromInterface(value)
+	if err != nil {
+		return err
+	}
+
+	s.variables[name] = &Variable{
+		name:  name,
+		value: &obj,
+	}
+
+	return nil
+}
+
+// Remove removes (undefines) an existing variable for the script.
+// It returns false if the variable name is not defined.
+func (s *Script) Remove(name string) bool {
+	if _, ok := s.variables[name]; !ok {
+		return false
+	}
+
+	delete(s.variables, name)
+
+	return true
+}
+
+// DisableBuiltinFunction disables a builtin function.
+func (s *Script) DisableBuiltinFunction(name string) {
+	if s.removedBuiltins == nil {
+		s.removedBuiltins = make(map[string]bool)
+	}
+
+	s.removedBuiltins[name] = true
+}
+
+// DisableStdModule disables a standard library module.
+func (s *Script) DisableStdModule(name string) {
+	if s.removedStdModules == nil {
+		s.removedStdModules = make(map[string]bool)
+	}
+
+	s.removedStdModules[name] = true
+}
+
+// SetUserModuleLoader sets the user module loader for the compiler.
+func (s *Script) SetUserModuleLoader(loader compiler.ModuleLoader) {
+	s.userModuleLoader = loader
+}
+
+// Compile compiles the script with all the defined variables, and, returns Compiled object.
+func (s *Script) Compile() (*Compiled, error) {
+	symbolTable, stdModules, globals, err := s.prepCompile()
+	if err != nil {
+		return nil, err
+	}
+
+	fileSet := source.NewFileSet()
+	srcFile := fileSet.AddFile("(main)", -1, len(s.input))
+
+	p := parser.NewParser(srcFile, s.input, nil)
+	file, err := p.ParseFile()
+	if err != nil {
+		return nil, fmt.Errorf("parse error: %s", err.Error())
+	}
+
+	c := compiler.NewCompiler(srcFile, symbolTable, nil, stdModules, nil)
+
+	if s.userModuleLoader != nil {
+		c.SetModuleLoader(s.userModuleLoader)
+	}
+
+	if err := c.Compile(file); err != nil {
+		return nil, err
+	}
+
+	return &Compiled{
+		symbolTable: symbolTable,
+		machine:     runtime.NewVM(c.Bytecode(), globals, nil),
+	}, nil
+}
+
+// Run compiles and runs the scripts.
+// Use returned compiled object to access global variables.
+func (s *Script) Run() (compiled *Compiled, err error) {
+	compiled, err = s.Compile()
+	if err != nil {
+		return
+	}
+
+	err = compiled.Run()
+
+	return
+}
+
+// RunContext is like Run but includes a context.
+func (s *Script) RunContext(ctx context.Context) (compiled *Compiled, err error) {
+	compiled, err = s.Compile()
+	if err != nil {
+		return
+	}
+
+	err = compiled.RunContext(ctx)
+
+	return
+}
+
+func (s *Script) prepCompile() (symbolTable *compiler.SymbolTable, stdModules map[string]bool, globals []*objects.Object, err error) {
+	var names []string
+	for name := range s.variables {
+		names = append(names, name)
+	}
+
+	symbolTable = compiler.NewSymbolTable()
+	for idx, fn := range objects.Builtins {
+		if !s.removedBuiltins[fn.Name] {
+			symbolTable.DefineBuiltin(idx, fn.Name)
+		}
+	}
+
+	stdModules = make(map[string]bool)
+	for name := range stdlib.Modules {
+		if !s.removedStdModules[name] {
+			stdModules[name] = true
+		}
+	}
+
+	globals = make([]*objects.Object, runtime.GlobalsSize, runtime.GlobalsSize)
+
+	for idx, name := range names {
+		symbol := symbolTable.Define(name)
+		if symbol.Index != idx {
+			panic(fmt.Errorf("wrong symbol index: %d != %d", idx, symbol.Index))
+		}
+
+		globals[symbol.Index] = s.variables[name].value
+	}
+
+	return
+}
+
+func (s *Script) copyVariables() map[string]*Variable {
+	vars := make(map[string]*Variable)
+	for n, v := range s.variables {
+		vars[n] = v
+	}
+
+	return vars
+}