add nip34/git-natural-api, using the same approach as https://jsr.io/@fiatjaf/git-natural-api.

nip34/gitnaturalapi/refs.go

@@ -0,0 +1,120 @@
+package gitnaturalapi
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+type InfoRefsUploadPackResponse struct {
+	Refs         map[string]string
+	Capabilities []string
+	Symrefs      map[string]string
+}
+
+var capabilitiesCache sync.Map
+
+func GetCapabilities(url string, existingInfo *InfoRefsUploadPackResponse) ([]string, error) {
+	if existingInfo != nil {
+		capabilitiesCache.Store(url, existingInfo.Capabilities)
+		return existingInfo.Capabilities, nil
+	}
+
+	if cached, ok := capabilitiesCache.Load(url); ok {
+		return cached.([]string), nil
+	}
+
+	info, err := GetInfoRefs(url)
+	if err != nil {
+		return nil, err
+	}
+	capabilitiesCache.Store(url, info.Capabilities)
+	return info.Capabilities, nil
+}
+
+func GetInfoRefs(url string) (*InfoRefsUploadPackResponse, error) {
+	resp, err := http.Get(url + "/info/refs?service=git-upload-pack")
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch info/refs: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read info/refs response: %w", err)
+	}
+	response := string(body)
+
+	result := &InfoRefsUploadPackResponse{
+		Refs:    make(map[string]string),
+		Symrefs: make(map[string]string),
+	}
+
+	lines := strings.Split(response, "\n")
+	firstRef := true
+	for _, line := range lines {
+		if len(line) == 0 {
+			continue
+		}
+
+		if strings.HasPrefix(line, "0000") {
+			line = line[4:]
+		}
+		if len(line) < 4 {
+			continue
+		}
+
+		length, err := strconv.ParseInt(line[:4], 16, 32)
+		if err != nil {
+			continue
+		}
+
+		endIdx := int(length)
+		if endIdx > len(line) {
+			endIdx = len(line)
+		}
+		if endIdx <= 4 {
+			continue
+		}
+		content := line[4:endIdx]
+
+		if firstRef && strings.HasPrefix(content, "# service=") {
+			firstRef = false
+			continue
+		}
+
+		if !strings.Contains(content, " ") {
+			continue
+		}
+
+		parts := strings.SplitN(content, " ", 2)
+		hash := parts[0]
+		refAndCaps := parts[1]
+
+		if strings.Contains(refAndCaps, "\x00") {
+			nulParts := strings.SplitN(refAndCaps, "\x00", 2)
+			ref := strings.TrimSpace(nulParts[0])
+			result.Refs[ref] = hash
+
+			caps := strings.Fields(nulParts[1])
+			result.Capabilities = caps
+
+			for _, cap := range caps {
+				if strings.HasPrefix(cap, "symref=") {
+					symrefData := cap[7:]
+					colonIdx := strings.Index(symrefData, ":")
+					if colonIdx != -1 {
+						result.Symrefs[symrefData[:colonIdx]] = symrefData[colonIdx+1:]
+					}
+				}
+			}
+		} else {
+			result.Refs[strings.TrimSpace(refAndCaps)] = hash
+		}
+	}
+
+	return result, nil
+}