feat: tengo http support (#71)

* feat: added support for http module in tengo

* unit test

* removed test

* unit test check

* fixed lint

* fixed lint

* generic with support for headers

* fixed lint

* made the HTTP userfunc modular - resolved comments

* removed redundant line

* check unit test

* fix check unit tests

* fix return values for unit test

* fix timeout unit test

* small typo fix

* fix check tests

* fixed test for header value type

* fixed test for header value type

* httpModule export not required

---------

Co-authored-by: Sumeet Rai <[email protected]>

plugins/internal/tengoutil/secure_script.go

@@ -1,7 +1,12 @@
 package tengoutil
 
 import (
+	"context"
+	"errors"
 	"fmt"
+	"io"
+	"net/http"
+	"time"
 
 	"github.com/d5/tengo/v2"
 	"github.com/d5/tengo/v2/stdlib"
@@ -12,13 +17,23 @@ const (
 	maxConsts = 500
 )
 
+const expectedArgsLength = 2
+
+var defaultTimeout = 5 * time.Second
+
+var httpModule = map[string]tengo.Object{
+	"get": httpGetFunction,
+}
+
 func NewSecureScript(input []byte, globals map[string]interface{}) (*tengo.Script, error) {
 	s := tengo.NewScript(input)
 
-	s.SetImports(stdlib.GetModuleMap(
+	modules := stdlib.GetModuleMap(
 		// `os` is excluded, should *not* be importable from script.
 		"math", "text", "times", "rand", "fmt", "json", "base64", "hex", "enum",
-	))
+	)
+	modules.AddBuiltinModule("http", httpModule)
+	s.SetImports(modules)
 	s.SetMaxAllocs(maxAllocs)
 	s.SetMaxConstObjects(maxConsts)
 
@@ -30,3 +45,81 @@ func NewSecureScript(input []byte, globals map[string]interface{}) (*tengo.Scrip
 
 	return s, nil
 }
+
+var httpGetFunction = &tengo.UserFunction{
+	Name: "get",
+	Value: func(args ...tengo.Object) (tengo.Object, error) {
+		url, err := extractURL(args)
+		if err != nil {
+			return nil, err
+		}
+		headers, err := extractHeaders(args)
+		if err != nil {
+			return nil, err
+		}
+
+		return performGetRequest(url, headers, defaultTimeout)
+	},
+}
+
+func extractURL(args []tengo.Object) (string, error) {
+	if len(args) < 1 {
+		return "", errors.New("expected at least 1 argument (URL)")
+	}
+	url, ok := tengo.ToString(args[0])
+	if !ok {
+		return "", errors.New("expected argument 1 (URL) to be a string")
+	}
+
+	return url, nil
+}
+
+func extractHeaders(args []tengo.Object) (map[string]string, error) {
+	headers := make(map[string]string)
+	if len(args) == expectedArgsLength {
+		headerMap, ok := args[1].(*tengo.Map)
+		if !ok {
+			return nil, fmt.Errorf("expected argument %d (headers) to be a map", expectedArgsLength)
+		}
+		for key, value := range headerMap.Value {
+			strValue, valueOk := tengo.ToString(value)
+			if !valueOk {
+				return nil, fmt.Errorf("header value for key '%s' must be a string, got %T", key, value)
+			}
+			headers[key] = strValue
+		}
+	}
+
+	return headers, nil
+}
+
+func performGetRequest(url string, headers map[string]string, timeout time.Duration) (tengo.Object, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	for key, value := range headers {
+		req.Header.Add(key, value)
+	}
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	return &tengo.Map{
+		Value: map[string]tengo.Object{
+			"body": &tengo.String{Value: string(body)},
+			"code": &tengo.Int{Value: int64(resp.StatusCode)},
+		},
+	}, nil
+}

plugins/internal/tengoutil/secure_script_test.go

@@ -5,6 +5,7 @@ package tengoutil
 
 import (
 	"testing"
+	"time"
 
 	"github.com/MakeNowJust/heredoc"
 	"github.com/stretchr/testify/assert"
@@ -55,4 +56,63 @@ func TestNewSecureScript(t *testing.T) {
 		_, err = s.Compile()
 		assert.NoError(t, err)
 	})
+
+	t.Run("Allows import of custom http module", func(t *testing.T) {
+		s, err := NewSecureScript(([]byte)(heredoc.Doc(`
+			http := import("http")
+			response := http.get("http://example.com")
+			response.body
+		`)), nil)
+		assert.NoError(t, err)
+		_, err = s.Compile()
+		assert.NoError(t, err)
+	})
+
+	t.Run("HTTP GET with headers", func(t *testing.T) {
+		s, err := NewSecureScript(([]byte)(heredoc.Doc(`
+			http := import("http")
+			headers := { "User-Agent": "test-agent", "Accept": "application/json" }
+			response := http.get("http://example.com", headers)
+			response.body
+		`)), nil)
+		assert.NoError(t, err)
+
+		_, err = s.Compile()
+		assert.NoError(t, err)
+	})
+
+	t.Run("HTTP GET with invalid URL argument type", func(t *testing.T) {
+		s, err := NewSecureScript(([]byte)(heredoc.Doc(`
+			http := import("http")
+			http.get(12345)
+		`)), nil)
+		assert.NoError(t, err)
+
+		_, err = s.Compile()
+		assert.NoError(t, err)
+
+		_, err = s.Run()
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "unsupported protocol scheme")
+	})
+
+	t.Run("HTTP GET with timeout", func(t *testing.T) {
+		s, err := NewSecureScript(([]byte)(heredoc.Doc(`
+			http := import("http")
+			response := http.get("http://example.com")
+			response.body
+		`)), nil)
+		assert.NoError(t, err)
+
+		originalTimeout := defaultTimeout
+		defaultTimeout = 1 * time.Millisecond
+		defer func() { defaultTimeout = originalTimeout }()
+
+		_, err = s.Compile()
+		assert.NoError(t, err)
+
+		_, err = s.Run()
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "context deadline exceeded")
+	})
 }