1 files changed, 192 insertions, 0 deletions
diff --git a/network/protocol/v0v1/server/receivepack/capabilities.go b/network/protocol/v0v1/server/receivepack/capabilities.go
new file mode 100644
index 00000000..e0ff51a3
--- /dev/null
+++ b/network/protocol/v0v1/server/receivepack/capabilities.go
@@ -0,0 +1,192 @@
+package receivepack
+
+import (
+	"fmt"
+	"slices"
+	"strings"
+
+	objectid "codeberg.org/lindenii/furgit/object/id"
+)
+
+// Capabilities describes one receive-pack capability set.
+type Capabilities struct {
+	ReportStatus   bool
+	ReportStatusV2 bool
+	DeleteRefs     bool
+	SideBand64K    bool
+	Quiet          bool
+	Atomic         bool
+	OfsDelta       bool
+	PushOptions    bool
+	PushCertNonce  string
+	ObjectFormat   objectid.Algorithm
+	SessionID      string
+	Agent          string
+}
+
+// Normalize returns one normalized copy of caps.
+func (caps Capabilities) Normalize(defaultAlgorithm objectid.Algorithm) Capabilities {
+	if caps.ObjectFormat == objectid.AlgorithmUnknown {
+		caps.ObjectFormat = defaultAlgorithm
+	}
+
+	return caps
+}
+
+// Tokens returns capabilities in Git advertisement order.
+func (caps Capabilities) Tokens(defaultAlgorithm objectid.Algorithm) []string {
+	caps = caps.Normalize(defaultAlgorithm)
+
+	tokens := make([]string, 0, 11)
+	if caps.ReportStatus {
+		tokens = append(tokens, "report-status")
+	}
+
+	if caps.ReportStatusV2 {
+		tokens = append(tokens, "report-status-v2")
+	}
+
+	if caps.DeleteRefs {
+		tokens = append(tokens, "delete-refs")
+	}
+
+	if caps.SideBand64K {
+		tokens = append(tokens, "side-band-64k")
+	}
+
+	if caps.Quiet {
+		tokens = append(tokens, "quiet")
+	}
+
+	if caps.Atomic {
+		tokens = append(tokens, "atomic")
+	}
+
+	if caps.OfsDelta {
+		tokens = append(tokens, "ofs-delta")
+	}
+
+	if caps.PushCertNonce != "" {
+		tokens = append(tokens, "push-cert="+caps.PushCertNonce)
+	}
+
+	if caps.PushOptions {
+		tokens = append(tokens, "push-options")
+	}
+
+	if caps.SessionID != "" {
+		tokens = append(tokens, "session-id="+caps.SessionID)
+	}
+
+	if caps.ObjectFormat != objectid.AlgorithmUnknown {
+		tokens = append(tokens, "object-format="+caps.ObjectFormat.String())
+	}
+
+	if caps.Agent != "" {
+		tokens = append(tokens, "agent="+caps.Agent)
+	}
+
+	return tokens
+}
+
+func (caps Capabilities) supportsToken(token string, defaultAlgorithm objectid.Algorithm) bool {
+	name, value, _ := strings.Cut(token, "=")
+
+	switch name {
+	case "report-status":
+		return caps.ReportStatus && value == ""
+	case "report-status-v2":
+		return caps.ReportStatusV2 && value == ""
+	case "delete-refs":
+		return caps.DeleteRefs && value == ""
+	case "side-band-64k":
+		return caps.SideBand64K && value == ""
+	case "quiet":
+		return caps.Quiet && value == ""
+	case "atomic":
+		return caps.Atomic && value == ""
+	case "ofs-delta":
+		return caps.OfsDelta && value == ""
+	case "push-options":
+		return caps.PushOptions && value == ""
+	case "push-cert":
+		return caps.PushCertNonce != "" && value != ""
+	case "object-format":
+		if value == "" {
+			return false
+		}
+
+		algo, ok := objectid.ParseAlgorithm(value)
+
+		return ok && algo == caps.Normalize(defaultAlgorithm).ObjectFormat
+	case "session-id":
+		return caps.SessionID != "" && value != ""
+	case "agent":
+		return caps.Agent != "" && value != ""
+	default:
+		return false
+	}
+}
+
+func parseCapabilityList(s string) ([]string, error) {
+	s = strings.TrimSuffix(s, "\n")
+	if s == "" {
+		return nil, nil
+	}
+
+	tokens := strings.Fields(s)
+	if slices.Contains(tokens, "") {
+		return nil, &ProtocolError{Reason: "empty capability token"}
+	}
+
+	return tokens, nil
+}
+
+func parseRequestedCapabilities(
+	tokens []string,
+	supported Capabilities,
+	defaultAlgorithm objectid.Algorithm,
+) (Capabilities, error) {
+	var requested Capabilities
+
+	requested.ObjectFormat = defaultAlgorithm
+
+	for _, token := range tokens {
+		if !supported.supportsToken(token, defaultAlgorithm) {
+			return Capabilities{}, &ProtocolError{
+				Reason: fmt.Sprintf("unsupported capability %q", token),
+			}
+		}
+
+		name, value, _ := strings.Cut(token, "=")
+		switch name {
+		case "report-status":
+			requested.ReportStatus = true
+		case "report-status-v2":
+			requested.ReportStatusV2 = true
+		case "delete-refs":
+			requested.DeleteRefs = true
+		case "side-band-64k":
+			requested.SideBand64K = true
+		case "quiet":
+			requested.Quiet = true
+		case "atomic":
+			requested.Atomic = true
+		case "ofs-delta":
+			requested.OfsDelta = true
+		case "push-options":
+			requested.PushOptions = true
+		case "push-cert":
+			requested.PushCertNonce = value
+		case "object-format":
+			algo, _ := objectid.ParseAlgorithm(value)
+			requested.ObjectFormat = algo
+		case "session-id":
+			requested.SessionID = value
+		case "agent":
+			requested.Agent = value
+		}
+	}
+
+	return requested, nil
+}