Merge pull request #175 from edanp/master

Add readFile to JS runtime

Author: Snawoot

README.md

@@ -360,6 +360,8 @@ dumbproxy can select upstream proxy dynamically invoking `getProxy` JS function
 
 Note that this option can be repeated multiple times, same as `-proxy` option for chaining of proxies. These two options can be used together and order of chaining will be as they come in command line. For generalization purposes we can say that `-proxy` option is equivalent to `-js-proxy-router` option with script which returns just one static proxy.
 
+`getProxy` scripts can read helper files using the built-in `readFile(path)` function that returns the file contents as a string.
+
 `getProxy` function is invoked with the [same parameters](#access-filter-by-js-script) as the `access` function. But unlike `access` function it is expected to return proxy URL in string format *scheme://[user:password@]host:port* or empty string `""` if no additional upstream proxy needed (i.e. direct connection if there are no other proxy dialers defined in chain). See [supported upstream proxy schemes](#supported-upstream-proxy-schemes) for details.
 
 Example:

dialer/jsrouter.go

@@ -37,6 +37,10 @@ func NewJSRouter(filename string, instances int, factory func(string) (Dialer, e
 		if err != nil {
 			return nil, errors.New("can't add print function to runtime")
 		}
+		err = jsext.AddFileReader(vm)
+		if err != nil {
+			return nil, errors.New("can't add file reader function to runtime")
+		}
 		vm.SetFieldNameMapper(goja.TagFieldNameMapper("json", true))
 		_, err = vm.RunString(string(script))
 		if err != nil {

jsext/filereader.go

@@ -0,0 +1,23 @@
+package jsext
+
+import (
+	"os"
+
+	"github.com/dop251/goja"
+)
+
+func AddFileReader(vm *goja.Runtime) error {
+	return vm.Set("readFile", func(call goja.FunctionCall) goja.Value {
+		if len(call.Arguments) != 1 {
+			panic(vm.NewTypeError("readFile expects exactly 1 argument"))
+		}
+
+		filename := call.Argument(0).String()
+		content, err := os.ReadFile(filename)
+		if err != nil {
+			panic(vm.NewGoError(err))
+		}
+
+		return vm.ToValue(string(content))
+	})
+}