From 062b36fe5725d1267c66db2e506b4131d78ce772 Mon Sep 17 00:00:00 2001
From: Philipp Tanlak <philipp.tanlak@gmail.com>
Date: Fri, 11 Aug 2023 18:31:20 +0200
Subject: simplify project structure

---
 js.go | 107 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 js.go

(limited to 'js.go')

diff --git a/js.go b/js.go
new file mode 100644
index 0000000..526f27b
--- /dev/null
+++ b/js.go
@@ -0,0 +1,107 @@
+package flyscrape
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"math/rand"
+	"strings"
+	"time"
+
+	"flyscrape/js"
+
+	"github.com/evanw/esbuild/pkg/api"
+	v8 "rogchap.com/v8go"
+)
+
+func init() {
+	rand.Seed(time.Now().UnixNano())
+}
+
+func Compile(src string) (ScrapeOptions, ScrapeFunc, error) {
+	src, err := build(src)
+	if err != nil {
+		return ScrapeOptions{}, nil, err
+	}
+	return vm(src)
+}
+
+func build(src string) (string, error) {
+	res := api.Transform(src, api.TransformOptions{
+		Platform: api.PlatformBrowser,
+		Format:   api.FormatIIFE,
+	})
+
+	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...)
+	}
+
+	return string(res.Code), nil
+}
+
+func vm(src string) (ScrapeOptions, ScrapeFunc, error) {
+	ctx := v8.NewContext()
+	ctx.RunScript("var module = {}", "main.js")
+
+	if _, err := ctx.RunScript(removeIIFE(js.Flyscrape), "main.js"); err != nil {
+		return ScrapeOptions{}, nil, fmt.Errorf("running flyscrape bundle: %w", err)
+	}
+	if _, err := ctx.RunScript(`const require = () => require_flyscrape();`, "main.js"); err != nil {
+		return ScrapeOptions{}, nil, fmt.Errorf("creating require function: %w", err)
+	}
+	if _, err := ctx.RunScript(removeIIFE(src), "main.js"); err != nil {
+		return ScrapeOptions{}, nil, fmt.Errorf("running user script: %w", err)
+	}
+
+	var opts ScrapeOptions
+
+	url, err := ctx.RunScript("options.url", "main.js")
+	if err != nil {
+		return ScrapeOptions{}, nil, fmt.Errorf("reading options.url: %w", err)
+	}
+	opts.URL = url.String()
+
+	depth, err := ctx.RunScript("options.depth", "main.js")
+	if err != nil {
+		return ScrapeOptions{}, nil, fmt.Errorf("reading options.depth: %w", err)
+	}
+	opts.Depth = int(depth.Integer())
+
+	scrape := func(params ScrapeParams) (any, error) {
+		suffix := randSeq(10)
+		ctx.Global().Set("html_"+suffix, params.HTML)
+		ctx.Global().Set("url_"+suffix, params.URL)
+		data, err := ctx.RunScript(fmt.Sprintf(`JSON.stringify(stdin_default({html: html_%s, url: url_%s}))`, suffix, suffix), "main.js")
+		if err != nil {
+			return nil, err
+		}
+
+		var obj any
+		if err := json.Unmarshal([]byte(data.String()), &obj); err != nil {
+			return nil, err
+		}
+
+		return obj, nil
+	}
+
+	return opts, scrape, 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)
+}
+
+func removeIIFE(s string) string {
+	s = strings.TrimPrefix(s, "(() => {\n")
+	s = strings.TrimSuffix(s, "})();\n")
+	return s
+}
-- 
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