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

nip34/gitnaturalapi/packs.go

@@ -0,0 +1,154 @@
+package gitnaturalapi
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+var NecessaryCapabilities = []string{
+	"multi_ack_detailed",
+	"side-band-64k",
+}
+
+var RequiredCapabilities = []string{
+	"shallow",
+	"object-format=sha1",
+}
+
+var DefaultCapabilities = []string{
+	"ofs-delta",
+	"no-progress",
+}
+
+type MissingRef struct{}
+
+func (e *MissingRef) Error() string { return "missing ref" }
+
+type InvalidCommit struct {
+	Commit string
+}
+
+func (e *InvalidCommit) Error() string {
+	return fmt.Sprintf("invalid commit '%s', must be 20 byte hex", e.Commit)
+}
+
+func FetchPackfile(url string, want string) (*PackfileResult, error) {
+	req, err := http.NewRequest("POST", url+"/git-upload-pack", strings.NewReader(want))
+	if err != nil {
+		return nil, fmt.Errorf("failed to create git-upload-pack request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/x-git-upload-pack-request")
+	req.Header.Set("Accept", "application/x-git-upload-pack-result")
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("failed to call git-upload-pack: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		body, _ := io.ReadAll(resp.Body)
+		return nil, fmt.Errorf("failed to call git-upload-pack: %s", string(body))
+	}
+
+	data, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read git-upload-pack response: %w", err)
+	}
+
+	if len(data) == 0 {
+		return nil, fmt.Errorf("empty response")
+	}
+
+	offset := 0
+	for offset < len(data) {
+		prev := offset
+		if prev+1 >= len(data) {
+			break
+		}
+		nlIdx := bytes.IndexByte(data[prev+1:], '\n')
+		if nlIdx == -1 {
+			if len(data) >= 32 && string(data[4:32]) == "ERR upload-pack: not our ref" {
+				return nil, &MissingRef{}
+			}
+			end := len(data)
+			if end > 63 {
+				end = 63
+			}
+			return nil, fmt.Errorf("unexpected '%s'", string(data[:end]))
+		}
+		offset = prev + nlIdx + 1
+		if offset >= 3 && string(data[offset-3:offset]) == "NAK" {
+			break
+		}
+	}
+	offset++
+
+	var packfileData []byte
+	for offset < len(data) {
+		if offset+5 > len(data) {
+			break
+		}
+		pktLen, err := strconv.ParseInt(string(data[offset:offset+4]), 16, 32)
+		if err != nil {
+			break
+		}
+		length := int(pktLen)
+		if length == 0 {
+			break
+		}
+		if offset+length > len(data) {
+			break
+		}
+		if data[offset+4] == 2 {
+			// progress message, ignore
+		} else if data[offset+4] == 1 {
+			packfileData = append(packfileData, data[offset+5:offset+length]...)
+		}
+		offset += length
+	}
+
+	if len(packfileData) == 0 {
+		return nil, &MissingRef{}
+	}
+
+	return ParsePackfile(packfileData)
+}
+
+func CreateWantRequest(commitSha string, capabilities []string, deepen *int, filter string) (string, error) {
+	if len(commitSha) != 40 {
+		return "", &InvalidCommit{Commit: commitSha}
+	}
+
+	var buf strings.Builder
+
+	wantLine := fmt.Sprintf("want %s %s agent=nsa/1.0.0\n", commitSha, strings.Join(capabilities, " "))
+	buf.WriteString(pktEncode(wantLine))
+
+	if deepen != nil {
+		deepenLine := fmt.Sprintf("deepen %d\n", *deepen)
+		buf.WriteString(pktEncode(deepenLine))
+	}
+
+	if filter != "" {
+		filterLine := fmt.Sprintf("filter %s\n", filter)
+		buf.WriteString(pktEncode(filterLine))
+	}
+
+	buf.WriteString("0000")
+	buf.WriteString(pktEncode("done\n"))
+
+	return buf.String(), nil
+}
+
+func pktEncode(data string) string {
+	if len(data) == 0 {
+		return "0000"
+	}
+	length := len(data) + 4
+	return fmt.Sprintf("%04x%s", length, data)
+}