added scripts and 2020 folder

scripts/fetchers/cmd-prompts/prompts.go

@@ -0,0 +1,87 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"path/filepath"
+	"strings"
+
+	"golang.org/x/net/html"
+
+	"github.com/alexchao26/advent-of-code-go/scripts/fetchers"
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	// determine day to fetch
+	day, year, cookie := fetchers.ParseFlags()
+	fmt.Println("fetching for day", day)
+
+	// make the request
+	url := fmt.Sprintf("https://adventofcode.com/%d/day/%d", year, day)
+	body := fetchers.GetWithAOCCookie(url, cookie)
+
+	// parse the dang html
+	prompt := parseHTML(body)
+
+	// write to file
+	filename := filepath.Join(util.Dirname(), "../../../", fmt.Sprintf("%d/day%02d-prompt.md", year, day))
+	fetchers.WriteToFile(filename, []byte(prompt))
+
+	fmt.Println("Wrote prompt to file: ", filename)
+
+	fmt.Println("Done!")
+}
+
+// uses dfsHTML function once to get the class=day-desc html nodes, then parse
+// the text inside of them
+func parseHTML(htmlIn []byte) (promptOnly string) {
+	strBuilder := strings.Builder{}
+	node, _ := html.Parse(bytes.NewReader(htmlIn))
+
+	dayDescNodes := dfsHTML(node, cbFindDayDescClass)
+	dayDescNodesMap := map[*html.Node]bool{}
+
+	for _, ddNode := range dayDescNodes {
+		dayDescNodesMap[ddNode.(*html.Node)] = true
+		dfsHTML(ddNode.(*html.Node), cbParseHTMLText(&strBuilder, dayDescNodesMap))
+	}
+
+	return strBuilder.String()
+}
+
+// function takes in a node and a callback that is run on each node
+// callback returns a slice of interfaces which are returned by dfs
+func dfsHTML(node *html.Node, cb func(*html.Node) []interface{}) []interface{} {
+	var sli []interface{}
+	for child := node.FirstChild; child != nil; child = child.NextSibling {
+		if cb(child) != nil {
+			sli = append(sli, child)
+		}
+		sli = append(sli, dfsHTML(child, cb)...)
+	}
+	return sli
+}
+
+func cbFindDayDescClass(node *html.Node) []interface{} {
+	for _, attr := range node.Attr {
+		if attr.Key == "class" && attr.Val == "day-desc" {
+			fmt.Println("day-desc node found!")
+			return []interface{}{node}
+		}
+	}
+
+	return nil
+}
+
+func cbParseHTMLText(builder *strings.Builder, dayDescNodesMap map[*html.Node]bool) func(*html.Node) []interface{} {
+	return func(node *html.Node) []interface{} {
+		if node.Type == html.TextNode {
+			builder.WriteString(node.Data)
+		}
+		if node.Parent != nil && dayDescNodesMap[node.Parent] {
+			builder.WriteString("\n")
+		}
+		return nil
+	}
+}