1 files changed, 140 insertions, 0 deletions
diff --git a/formats/packp/ulreq/encoder.go b/formats/packp/ulreq/encoder.go
new file mode 100644
index 0000000..1e40b63
--- /dev/null
+++ b/formats/packp/ulreq/encoder.go
@@ -0,0 +1,140 @@
+package ulreq
+
+import (
+	"fmt"
+	"io"
+	"sort"
+	"time"
+
+	"gopkg.in/src-d/go-git.v4/core"
+	"gopkg.in/src-d/go-git.v4/formats/packp/pktline"
+)
+
+// An Encoder writes UlReq values to an output stream.
+type Encoder struct {
+	pe          *pktline.Encoder // where to write the encoded data
+	data        *UlReq           // the data to encode
+	sortedWants []string
+	err         error // sticky error
+}
+
+// NewEncoder returns a new encoder that writes to w.
+func NewEncoder(w io.Writer) *Encoder {
+	return &Encoder{
+		pe: pktline.NewEncoder(w),
+	}
+}
+
+// Encode writes the UlReq encoding of v to the stream.
+//
+// All the payloads will end with a newline character.  Wants and
+// shallows are sorted alphabetically.  A depth of 0 means no depth
+// request is sent.
+func (e *Encoder) Encode(v *UlReq) error {
+	if len(v.Wants) == 0 {
+		return fmt.Errorf("empty wants provided")
+	}
+
+	e.data = v
+	e.sortedWants = sortHashes(v.Wants)
+
+	for state := encodeFirstWant; state != nil; {
+		state = state(e)
+	}
+
+	return e.err
+}
+
+type encoderStateFn func(*Encoder) encoderStateFn
+
+func sortHashes(list []core.Hash) []string {
+	sorted := make([]string, len(list))
+	for i, hash := range list {
+		sorted[i] = hash.String()
+	}
+	sort.Strings(sorted)
+
+	return sorted
+}
+
+func encodeFirstWant(e *Encoder) encoderStateFn {
+	var err error
+	if e.data.Capabilities.IsEmpty() {
+		err = e.pe.Encodef("want %s\n", e.sortedWants[0])
+	} else {
+		e.data.Capabilities.Sort()
+		err = e.pe.Encodef(
+			"want %s %s\n",
+			e.sortedWants[0],
+			e.data.Capabilities.String(),
+		)
+	}
+	if err != nil {
+		e.err = fmt.Errorf("encoding first want line: %s", err)
+		return nil
+	}
+
+	return encodeAditionalWants
+}
+
+func encodeAditionalWants(e *Encoder) encoderStateFn {
+	for _, w := range e.sortedWants[1:] {
+		if err := e.pe.Encodef("want %s\n", w); err != nil {
+			e.err = fmt.Errorf("encoding want %q: %s", w, err)
+			return nil
+		}
+	}
+
+	return encodeShallows
+}
+
+func encodeShallows(e *Encoder) encoderStateFn {
+	sorted := sortHashes(e.data.Shallows)
+	for _, s := range sorted {
+		if err := e.pe.Encodef("shallow %s\n", s); err != nil {
+			e.err = fmt.Errorf("encoding shallow %q: %s", s, err)
+			return nil
+		}
+	}
+
+	return encodeDepth
+}
+
+func encodeDepth(e *Encoder) encoderStateFn {
+	switch depth := e.data.Depth.(type) {
+	case DepthCommits:
+		if depth != 0 {
+			commits := int(depth)
+			if err := e.pe.Encodef("deepen %d\n", commits); err != nil {
+				e.err = fmt.Errorf("encoding depth %d: %s", depth, err)
+				return nil
+			}
+		}
+	case DepthSince:
+		when := time.Time(depth).UTC()
+		if err := e.pe.Encodef("deepen-since %d\n", when.Unix()); err != nil {
+			e.err = fmt.Errorf("encoding depth %s: %s", when, err)
+			return nil
+		}
+	case DepthReference:
+		reference := string(depth)
+		if err := e.pe.Encodef("deepen-not %s\n", reference); err != nil {
+			e.err = fmt.Errorf("encoding depth %s: %s", reference, err)
+			return nil
+		}
+	default:
+		e.err = fmt.Errorf("unsupported depth type")
+		return nil
+	}
+
+	return encodeFlush
+}
+
+func encodeFlush(e *Encoder) encoderStateFn {
+	if err := e.pe.Flush(); err != nil {
+		e.err = fmt.Errorf("encoding flush-pkt: %s", err)
+		return nil
+	}
+
+	return nil
+}