1 files changed, 129 insertions, 1 deletions

diff --git a/auction.go b/auction.go
index e4f53b7..32e9758 100644
--- a/auction.go
+++ b/auction.go
@@ -6,7 +6,13 @@ import (
 	"crypto/sha512"
 	"encoding/base32"
 	"encoding/json"
+	"errors"
+	"fmt"
+	"log/slog"
 	"time"
+
+	"kesim.org/seal/nizk/commit"
+	"kesim.org/seal/nizk/stage1"
 )
 
 type Type int
@@ -55,4 +61,126 @@ func (d *Description) Hash() (hash string, e error) {
 	}
 	h := sha512.Sum512(buf.Bytes())
 	return base32.StdEncoding.EncodeToString(h[:]), nil
-}
\ No newline at end of file
+}
+
+func (d *Description) validate() error {
+	if d == nil {
+		return fmt.Errorf("description is nil")
+	}
+	if d.BitLength > MAXBITLENGTH {
+		return fmt.Errorf("invalid BitLength in description: %d", d.BitLength)
+	}
+	return nil
+}
+
+type Auction interface {
+	Start() error
+	Cancel() error
+	Message(msg []byte) error
+}
+
+type Result struct {
+	Price  uint32
+	Winner string
+	Error  error
+}
+
+type auction struct {
+	description *Description
+
+	// non nil if run by an bidder, via Join()
+	bidder Bidder
+	// non nil if run by an observer, via Observe()
+	observer Observer
+
+	// The commitments we received from the bidders.
+	bidders map[string][]*commit.Commitment
+
+	// sorted list of the bidders.
+	bidder_ids []string
+
+	// Stage 1 data per round
+	stage1 []*stage1.Statement
+
+	log *slog.Logger
+}
+
+func (a *auction) Start() error {
+	return errors.New("Start not implemented")
+}
+
+func (a *auction) Cancel() error {
+	return errors.New("Cancel not implemented")
+}
+
+// Message is called by the Bidder or Visitor
+// whenever a message came in for the auction via the dashboard
+// or other means of communication.
+func (a *auction) Message(msg []byte) error {
+	return fmt.Errorf("Auction.Received not implemented")
+}
+
+const MAXBITLENGTH = 64
+
+// Bidder is the interface that the Auction engine uses to interact
+type Bidder interface {
+	Broadcast([]byte) error
+	Result(Result)
+	Start()
+}
+
+func Join(
+	bidder Bidder,
+	description *Description,
+	options ...Option) (Auction, error) {
+
+	if bidder == nil {
+		return nil, fmt.Errorf("missing bidder")
+	}
+	if e := description.validate(); e != nil {
+		return nil, e
+	}
+
+	a := &auction{
+		description: description,
+		bidder:      bidder,
+		log:         slog.Default(),
+	}
+
+	for _, opt := range options {
+		opt(a)
+	}
+
+	return a, nil
+}
+
+// Observer
+type Observer interface {
+	Result(Result)
+	Start()
+}
+
+func Observe(
+	observer Observer,
+	description *Description,
+	options ...Option) (Auction, error) {
+
+	if observer == nil {
+		return nil, fmt.Errorf("missing observer")
+	}
+	if e := description.validate(); e != nil {
+		return nil, e
+	}
+
+	a := &auction{
+		description: description,
+		observer:    observer,
+		log:         slog.Default(),
+	}
+
+	for _, opt := range options {
+		opt(a)
+	}
+
+	return a, nil
+}