1 files changed, 133 insertions, 0 deletions
diff --git a/js/js.go b/js/js.go
new file mode 100644
index 0000000..c5b8818
--- /dev/null
+++ b/js/js.go
@@ -0,0 +1,133 @@
+package js
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"math/rand"
+	"os"
+	"path/filepath"
+	"time"
+
+	"flyscrape/js/jsbundle"
+
+	"github.com/evanw/esbuild/pkg/api"
+	v8 "rogchap.com/v8go"
+)
+
+func init() {
+	rand.Seed(time.Now().UnixNano())
+}
+
+type RunOptions struct {
+	HTML string
+}
+
+type RunFunc func(RunOptions) any
+
+type Options struct {
+	URL string `json:"url"`
+}
+
+func Compile(file string) (*Options, RunFunc, error) {
+	src, err := build(file)
+	if err != nil {
+		return nil, nil, err
+	}
+	os.WriteFile("out.js", []byte(src), 0o644)
+	return vm(src)
+}
+
+func build(file string) (string, error) {
+	dir, err := os.MkdirTemp("", "flyscrape")
+	if err != nil {
+		return "", err
+	}
+	defer os.RemoveAll(dir)
+
+	tmpfile := filepath.Join(dir, "flyscrape.js")
+	if err := os.WriteFile(tmpfile, jsbundle.Flyscrape, 0o644); err != nil {
+		return "", err
+	}
+
+	resolve := api.Plugin{
+		Name: "flyscrape",
+		Setup: func(build api.PluginBuild) {
+			build.OnResolve(api.OnResolveOptions{
+				Filter: "^flyscrape$",
+			}, func(ora api.OnResolveArgs) (api.OnResolveResult, error) {
+				return api.OnResolveResult{Path: tmpfile}, nil
+			})
+		},
+	}
+
+	res := api.Build(api.BuildOptions{
+		EntryPoints: []string{file},
+		Bundle:      true,
+		Platform:    api.PlatformNode,
+		Plugins:     []api.Plugin{resolve},
+	})
+
+	var errs []error
+	for _, msg := range res.Errors {
+		errs = append(errs, fmt.Errorf("%s", msg.Text))
+	}
+	if len(res.Errors) > 0 {
+		return "", errors.Join(errs...)
+	}
+
+	out := string(res.OutputFiles[0].Contents)
+	return out, nil
+}
+
+func vm(src string) (*Options, RunFunc, error) {
+	os.WriteFile("out.js", []byte(src), 0o644)
+
+	ctx := v8.NewContext()
+	ctx.RunScript("var module = {}", "main.js")
+	if _, err := ctx.RunScript(src, "main.js"); err != nil {
+		return nil, nil, fmt.Errorf("run bundled js: %w", err)
+	}
+
+	val, err := ctx.RunScript("module.exports.options", "main.js")
+	if err != nil {
+		return nil, nil, fmt.Errorf("export options: %w", err)
+	}
+	options, err := val.AsObject()
+	if err != nil {
+		return nil, nil, fmt.Errorf("cast options as object: %w", err)
+	}
+
+	var opts Options
+	url, err := options.Get("url")
+	if err != nil {
+		return nil, nil, fmt.Errorf("getting url from options: %w", err)
+	}
+	opts.URL = url.String()
+
+	run := func(ro RunOptions) any {
+		suffix := randSeq(10)
+		ctx.Global().Set("html_"+suffix, ro.HTML)
+		data, err := ctx.RunScript(fmt.Sprintf(`JSON.stringify(module.exports.default({html: html_%s}))`, suffix), "main.js")
+		if err != nil {
+			return err.Error()
+		}
+
+		var obj any
+		if err := json.Unmarshal([]byte(data.String()), &obj); err != nil {
+			return err.Error()
+		}
+
+		return obj
+	}
+	return &opts, run, nil
+}
+
+func randSeq(n int) string {
+	letters := []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+	b := make([]rune, n)
+	for i := range b {
+		b[i] = letters[rand.Intn(len(letters))]
+	}
+	return string(b)
+}