write a new nuget download

.gitignore

@@ -2,5 +2,4 @@
 .vscode
 
 openxt
-csproj-to-5
 *.tar.gz

tools/build-and-pack.sh

@@ -15,7 +15,7 @@ function build () {
     rm -rf bin/
 
     GOOS="$os" GOARCH="$arch" go build -o "bin/openxt$bin_tail" . &&
-    GOOS="$os" GOARCH="$arch" go build -o "bin/csproj-to-5$bin_tail" tools/csproj-to-5.go &&
+    GOOS="$os" GOARCH="$arch" go build -o "bin/csproj-to-5$bin_tail" tools/csproj-to-5/main.go &&
     tar cvzf "openxt-$version-$os-$arch.tar.gz" bin
 
     return $?

tools/nuget-download-package/main.go

+package main
+
+import (
+	"github.com/antchfx/xmlquery"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"strings"
+	"sync"
+)
+
+/*
+`dotnet add` has a bug: 
+If my csproj is using net462, and I run
+dotnet add package Microsoft.Azure.Kusto.Cloud.Platform --package-directory ~/tmp/ttt --framework net462
+
+It would say: Package Microsoft.Azure.Kusto.Cloud.Platform 9.1.0 is not compatible with net462
+However, Microsoft.Azure.Kusto.Cloud.Platform 8.1.5 IS compatible with net462. It doesn't download at all!
+
+dotnet add also requires a valid csproj. It's heavy, complex, and slow. It sucks. 
+
+Let's write a simple one!
+*/
+const nugetConfigPath = "~/.nuget/NuGet/NuGet.Config"
+
+func panicErrorIfAny(err error, title string) {
+	if err != nil {
+		panic("[Error] on " + title + ": " + err.Error())
+	}
+}
+func logErrorIfAny(err error, title string) {
+	if err != nil {
+		log.Println("[Error] on " + title + ": " + err.Error())
+	}
+}
+
+func pkgVersionLeftIsGreater(left, right string) bool {
+	// return if left > right
+	return true
+}
+
+var nugetIndexJsonCache []string
+func initNugetIndexJsonCache(pkgName string) {
+	// download index.json from every source, and cache them in global variable.
+	nugetIndexJsonCache = []string{}
+
+	f, err := os.Open(nugetConfigPath)
+	panicErrorIfAny(err, "Open " + nugetConfigPath)
+	parsed, err := xmlquery.Parse(f)
+	panicErrorIfAny(err, "Parse XML " + nugetConfigPath)
+	sources := xmlquery.Find(parsed, "//configuration/packageSources/add")
+
+	var wg sync.WaitGroup
+	nugetIndexJsonCache_wlock := sync.RWMutex{}
+	for _, source := range sources {
+		// Parse xml
+		sname, surl, sauth_username, sauth_password := "", "", "", ""
+		for _, attr := range source.Attr {
+			if attr.Name.Local == "key" {
+				sname = attr.Value
+			} else if attr.Name.Local == "value" {
+				surl = attr.Value
+			}
+		}
+
+		auth_entries := xmlquery.Find(parsed, "//configuration/packageSourceCredentials/" + sname + "/add")
+		for _, auth_entry := range auth_entries {
+			for _, attr := range auth_entry.Attr {
+				if attr.Name.Local == "Username" {
+					sauth_username = attr.Value
+				} else if attr.Name.Local == "ClearTextPassword" {
+					sauth_password = attr.Value
+				}
+			}
+		}
+
+		// Send the HTTP request and download index.json!
+		wg.Add(1)
+		nugetIndexJsonCache = append(nugetIndexJsonCache, "")
+		go func(url, authu, authp string) {
+			defer wg.Done()
+			req, err := http.NewRequest("GET", url, nil)
+			panicErrorIfAny(err, "http.NewRequest")
+			if authu + authp != "" {
+				req.SetBasicAuth(authu, authp)
+			}
+			resp, err := http.DefaultClient.Do(req)
+			logErrorIfAny(err, "download json")
+			defer resp.Body.Close()
+			resp_txt, err := ioutil.ReadAll(resp.Body)
+			logErrorIfAny(err, "download json")
+
+			if len(resp_txt) > 0 {
+				nugetIndexJsonCache_wlock.Lock()
+				nugetIndexJsonCache = append(nugetIndexJsonCache, string(resp_txt))
+				nugetIndexJsonCache_wlock.Unlock()
+			}
+		}(surl, sauth_username, sauth_password)
+	}
+	wg.Wait()
+}
+
+// recursive. If package exists, it exit.
+// One of [pkgVerBegin, pkgVerEnd] would be downloaded.
+func downloadPackageAndDeps(packageName, pkgVerBegin, pkgVerEnd, localRepoDir string) {
+
+}
+
+// [pkgVerBegin, pkgVerEnd] is good for frameworkVersion.
+func decidePackageVersion(packageName, frameworkVersion string) (pkgVerBegin, pkgVerEnd string) {
+	// Generated by curl-to-Go: https://mholt.github.io/curl-to-go
+	// curl -u bensl:xbwejuparq4ighqs4pjq6bqjqmxpzghhtqshql2uy3woi73ew6iq https://o365exchange.pkgs.visualstudio.com/959adb23-f323-4d52-8203-ff34e5cbeefa/_packaging/aacaa93f-61ac-420c-8b20-c17c5d2b52f1/nuget/v3/registrations2-semver2/microsoft.azure.kusto.cloud.platform/index.json
+
+
+	return "1.1.1", "8.8.8"
+}
+
+func main() {
+	if(len(os.Args) < 4) {
+		log.Println("Usage: nuget-download-package <packageName> <packageVersion/frameworkVersion> <localRepoDir>")
+		log.Println("frameworkVersion maybe 'net472', 'netstandard2.0', 'netcoreapp3.1' ...")
+		os.Exit(1)
+	}
+
+    pkgName, pkgVer, localRepoDir := os.Args[1], os.Args[2], os.Args[3]
+    if strings.HasPrefix(pkgVer, "net") {
+    	_, pkgVer = decidePackageVersion(pkgName, pkgVer)
+	}
+
+	downloadPackageAndDeps(pkgName, pkgVer, pkgVer, localRepoDir)
+}
+