feat: extension support (#78)

pkg/download/engine/engine.go

@@ -0,0 +1,125 @@
+package engine
+
+import (
+	_ "embed"
+	"errors"
+	"fmt"
+	"github.com/GopeedLab/gopeed/pkg/download/engine/inject/file"
+	"github.com/GopeedLab/gopeed/pkg/download/engine/inject/formdata"
+	"github.com/GopeedLab/gopeed/pkg/download/engine/inject/xhr"
+	"github.com/dop251/goja"
+	"github.com/dop251/goja_nodejs/eventloop"
+	"github.com/dop251/goja_nodejs/process"
+	"github.com/dop251/goja_nodejs/url"
+)
+
+//go:embed polyfill/out/index.js
+var polyfillScript string
+
+type Engine struct {
+	loop *eventloop.EventLoop
+
+	Runtime *goja.Runtime
+}
+
+// RunString executes the script and returns the go type value
+// if script result is promise, it will be resolved
+func (e *Engine) RunString(script string) (value any, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("%v", r)
+		}
+	}()
+	var result goja.Value
+	e.loop.Run(func(runtime *goja.Runtime) {
+		result, err = runtime.RunString(script)
+	})
+	if err != nil {
+		return
+	}
+	return resolveResult(result)
+}
+
+// CallFunction calls the function and returns the go type value
+// if function result is promise, it will be resolved
+func (e *Engine) CallFunction(fn goja.Callable, args ...any) (value any, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("%v", r)
+		}
+	}()
+	var result goja.Value
+	e.loop.Run(func(runtime *goja.Runtime) {
+		if args == nil {
+			result, err = fn(nil)
+		} else {
+			var jsArgs []goja.Value
+			for _, arg := range args {
+				jsArgs = append(jsArgs, runtime.ToValue(arg))
+			}
+			result, err = fn(nil, jsArgs...)
+		}
+	})
+	if err != nil {
+		return nil, err
+	}
+	return resolveResult(result)
+}
+
+func (e *Engine) Close() {
+	e.loop.Stop()
+}
+
+func NewEngine() *Engine {
+	loop := eventloop.NewEventLoop()
+	engine := &Engine{
+		loop: loop,
+	}
+	loop.Run(func(runtime *goja.Runtime) {
+		engine.Runtime = runtime
+		runtime.SetFieldNameMapper(goja.TagFieldNameMapper("json", true))
+		url.Enable(runtime)
+		process.Enable(runtime)
+		if err := file.Enable(runtime); err != nil {
+			return
+		}
+		if err := formdata.Enable(runtime); err != nil {
+			return
+		}
+		if err := xhr.Enable(runtime); err != nil {
+			return
+		}
+		if _, err := runtime.RunString(polyfillScript); err != nil {
+			return
+		}
+		// polyfill global
+		if err := runtime.Set("global", runtime.GlobalObject()); err != nil {
+			return
+		}
+		return
+	})
+	return engine
+}
+
+func Run(script string) (value any, err error) {
+	engine := NewEngine()
+	return engine.RunString(script)
+}
+
+// if the value is Promise, it will be resolved and return the result.
+func resolveResult(value goja.Value) (any, error) {
+	export := value.Export()
+	switch export.(type) {
+	case *goja.Promise:
+		p := export.(*goja.Promise)
+		switch p.State() {
+		case goja.PromiseStatePending:
+			return nil, nil
+		case goja.PromiseStateFulfilled:
+			return p.Result().Export(), nil
+		case goja.PromiseStateRejected:
+			return nil, errors.New(p.Result().String())
+		}
+	}
+	return export, nil
+}