[PHASE-7] Add encoding and decoding for client

internal/protocol/encoder.go

@@ -0,0 +1,41 @@
+package protocol
+
+import (
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"io"
+)
+
+// encode is a helper function that encodes any message with the given message type
+func encode(w io.Writer, msgType MessageType, payload interface{}) error {
+	var payloadBytes []byte
+	var err error
+
+	// Only marshal if payload is not nil
+	if payload != nil {
+		payloadBytes, err = json.Marshal(payload)
+		if err != nil {
+			return fmt.Errorf("failed to encode payload: %w", err)
+		}
+	}
+
+	// Write message type (1 byte)
+	if err := binary.Write(w, binary.BigEndian, msgType); err != nil {
+		return fmt.Errorf("failed to write message type: %w", err)
+	}
+
+	// Write payload length (4 bytes, big-endian)
+	if err := binary.Write(w, binary.BigEndian, uint32(len(payloadBytes))); err != nil {
+		return fmt.Errorf("failed to write payload length: %w", err)
+	}
+
+	// Write JSON payload if we have one
+	if len(payloadBytes) > 0 {
+		if _, err := w.Write(payloadBytes); err != nil {
+			return fmt.Errorf("failed to write payload: %w", err)
+		}
+	}
+
+	return nil
+}

internal/protocol/requests.go

@@ -7,6 +7,7 @@ import (
 	"hash-of-wisdom/internal/pow/challenge"
 )
 
+
 // ChallengeRequest is empty (no payload for challenge requests)
 type ChallengeRequest struct{}
 
@@ -16,6 +17,11 @@ func (r *ChallengeRequest) Decode(stream io.Reader) error {
 	return nil
 }
 
+// Encode writes a challenge request to the writer
+func (r *ChallengeRequest) Encode(w io.Writer) error {
+	return encode(w, ChallengeRequestType, nil)
+}
+
 // SolutionRequest contains the client's solution attempt
 type SolutionRequest struct {
 	Challenge challenge.Challenge `json:"challenge"`
@@ -33,3 +39,8 @@ func (r *SolutionRequest) Decode(stream io.Reader) error {
 	decoder := json.NewDecoder(stream)
 	return decoder.Decode(r)
 }
+
+// Encode writes a solution request to the writer
+func (r *SolutionRequest) Encode(w io.Writer) error {
+	return encode(w, SolutionRequestType, r)
+}

internal/protocol/responses.go

@@ -1,63 +1,46 @@
 package protocol
 
 import (
-	"encoding/binary"
 	"encoding/json"
-	"fmt"
 	"io"
 
 	"hash-of-wisdom/internal/pow/challenge"
 	"hash-of-wisdom/internal/quotes"
 )
 
-// writeHeader writes the message type and payload length to the writer
-func writeHeader(w io.Writer, msgType MessageType, payloadLength uint32) error {
-	// Write message type (1 byte)
-	if err := binary.Write(w, binary.BigEndian, msgType); err != nil {
-		return fmt.Errorf("failed to write message type: %w", err)
-	}
-
-	// Write payload length (4 bytes, big-endian)
-	if err := binary.Write(w, binary.BigEndian, payloadLength); err != nil {
-		return fmt.Errorf("failed to write payload length: %w", err)
-	}
-
-	return nil
-}
-
-// encodeResponse is a helper function that encodes any response with the given message type
-func encodeResponse(w io.Writer, msgType MessageType, payload interface{}) error {
-	// Marshal to get exact payload size
-	payloadBytes, err := json.Marshal(payload)
-	if err != nil {
-		return fmt.Errorf("failed to encode payload: %w", err)
-	}
-
-	// Write header
-	if err := writeHeader(w, msgType, uint32(len(payloadBytes))); err != nil {
-		return err
-	}
-
-	// Write JSON payload directly to stream
-	if len(payloadBytes) > 0 {
-		if _, err := w.Write(payloadBytes); err != nil {
-			return fmt.Errorf("failed to write payload: %w", err)
-		}
-	}
-
-	return nil
-}
 
 // ChallengeResponse represents a challenge response
 type ChallengeResponse struct {
 	Challenge *challenge.Challenge
 }
 
+// Decode reads a challenge response from the payload stream
+func (r *ChallengeResponse) Decode(stream io.Reader) error {
+	if stream == nil {
+		return io.EOF
+	}
+
+	// Parse JSON directly from stream
+	decoder := json.NewDecoder(stream)
+	return decoder.Decode(&r.Challenge)
+}
+
 // SolutionResponse represents a successful solution response (contains quote)
 type SolutionResponse struct {
 	Quote *quotes.Quote
 }
 
+// Decode reads a solution response from the payload stream
+func (r *SolutionResponse) Decode(stream io.Reader) error {
+	if stream == nil {
+		return io.EOF
+	}
+
+	// Parse JSON directly from stream
+	decoder := json.NewDecoder(stream)
+	return decoder.Decode(&r.Quote)
+}
+
 // ErrorResponse represents an error response
 type ErrorResponse struct {
 	Code       string            `json:"code"`
@@ -66,17 +49,28 @@ type ErrorResponse struct {
 	Details    map[string]string `json:"details,omitempty"`
 }
 
+// Decode reads an error response from the payload stream
+func (r *ErrorResponse) Decode(stream io.Reader) error {
+	if stream == nil {
+		return io.EOF
+	}
+
+	// Parse JSON directly from stream
+	decoder := json.NewDecoder(stream)
+	return decoder.Decode(r)
+}
+
 // Encode writes the challenge response to the writer
 func (r *ChallengeResponse) Encode(w io.Writer) error {
-	return encodeResponse(w, ChallengeResponseType, r.Challenge)
+	return encode(w, ChallengeResponseType, r.Challenge)
 }
 
 // Encode writes the solution response to the writer
 func (r *SolutionResponse) Encode(w io.Writer) error {
-	return encodeResponse(w, QuoteResponseType, r.Quote)
+	return encode(w, QuoteResponseType, r.Quote)
 }
 
 // Encode writes the error response to the writer
 func (r *ErrorResponse) Encode(w io.Writer) error {
-	return encodeResponse(w, ErrorResponseType, r)
+	return encode(w, ErrorResponseType, r)
 }