add backend

dot/parachain/dispute/backend.go

@@ -2,24 +2,32 @@ package dispute
 
 import (
 	"bytes"
-	"fmt"
+	"github.com/ChainSafe/gossamer/dot/parachain/dispute/types"
 	"github.com/ChainSafe/gossamer/lib/common"
 	"github.com/ChainSafe/gossamer/lib/parachain"
-	"github.com/ChainSafe/gossamer/pkg/scale"
 	"github.com/emirpasic/gods/maps/treemap"
 	"github.com/google/btree"
 	"time"
 )
 
+// CandidateHash represents a candidate hash.
 type CandidateHash common.Hash
 
+// Comparator for ordering of disputes for candidate.
 type Comparator struct {
 	SessionIndex  parachain.SessionIndex
 	CandidateHash CandidateHash
 }
 
-// Less returns true if the current item is less than the other item
-// it uses the Key to determine the order
+// CandidateVotes tracked votes for a candidate, for the purpose of dispute resolution.
+type CandidateVotes struct {
+	candidateReceipt parachain.CandidateReceipt
+	valid            *treemap.Map
+	invalid          *treemap.Map
+}
+
+// Less returns true if the current dispute item is less than the other item
+// it uses the Comparator to determine the order
 func (d Dispute) Less(than btree.Item) bool {
 	other := than.(*Dispute)
 
@@ -30,100 +38,14 @@ func (d Dispute) Less(than btree.Item) bool {
 	return d.comparator.SessionIndex < other.comparator.SessionIndex
 }
 
-type CandidateVotes struct {
-	candidateReceipt parachain.CandidateReceipt
-	valid            *treemap.Map
-	invalid          *treemap.Map
-}
-
+// Dispute is a dispute for a candidate.
+// It is used as an item in the btree.BTree ordered by session index and candidate hash.
 type Dispute struct {
 	comparator    *Comparator
-	disputeStatus *Status
-}
-
-func NewCandidateVotes() *CandidateVotes {
-	return &CandidateVotes{
-		valid:   treemap.NewWithIntComparator(),
-		invalid: treemap.NewWithIntComparator(),
-	}
-}
-
-type Active struct{}
-
-func (Active) Index() uint {
-	return 0
-}
-
-type ConcludedFor struct {
-	Since uint64
-}
-
-func (ConcludedFor) Index() uint {
-	return 1
-}
-
-type ConcludedAgainst struct {
-	Since uint64
-}
-
-func (ConcludedAgainst) Index() uint {
-	return 2
-}
-
-type Confirmed struct{}
-
-func (Confirmed) Index() uint {
-	return 3
-}
-
-type Status scale.VaryingDataType
-
-// Set will set a VaryingDataTypeValue using the underlying VaryingDataType
-func (ds *Status) Set(val scale.VaryingDataTypeValue) (err error) {
-	vdt := scale.VaryingDataType(*ds)
-	err = vdt.Set(val)
-	if err != nil {
-		return fmt.Errorf("setting value to varying data type: %w", err)
-	}
-	*ds = Status(vdt)
-	return nil
-}
-
-// Value returns the value from the underlying VaryingDataType
-func (ds *Status) Value() (scale.VaryingDataTypeValue, error) {
-	vdt := scale.VaryingDataType(*ds)
-	return vdt.Value()
-}
-
-// TODO: check if we can avoid using pointers
-func (ds *Status) ConcludedAt() (*uint64, error) {
-	vdt := scale.VaryingDataType(*ds)
-	val, err := vdt.Value()
-	if err != nil {
-		return nil, fmt.Errorf("getting value from DisputeStatus vdt: %w", err)
-	}
-
-	switch v := val.(type) {
-	case Active, Confirmed:
-		return nil, nil
-	case ConcludedFor:
-		return &v.Since, nil
-	case ConcludedAgainst:
-		return &v.Since, nil
-	default:
-		return nil, fmt.Errorf("invalid dispute status type")
-	}
-}
-
-func NewDisputeStatus() (Status, error) {
-	vdt, err := scale.NewVaryingDataType(Active{}, ConcludedFor{}, ConcludedAgainst{}, Confirmed{})
-	if err != nil {
-		return Status{}, fmt.Errorf("creating new dispute status vdt: %w", err)
-	}
-
-	return Status(vdt), nil
+	disputeStatus *types.DisputeStatus
 }
 
+// Backend is the backend for the dispute coordinator module.
 type Backend interface {
 	// GetEarliestSession returns the earliest session index, if any.
 	GetEarliestSession() (*parachain.SessionIndex, error)
@@ -133,14 +55,15 @@ type Backend interface {
 	GetCandidateVotes(session parachain.SessionIndex, candidateHash CandidateHash) (*CandidateVotes, error)
 
 	// GetActiveDisputes returns the active disputes, if any.
-	GetActiveDisputes() (*btree.BTree, error)
+	GetActiveDisputes(now int64) (*btree.BTree, error)
 
 	// TODO: need to explore further to see if we need these
 	SetEarliestSession(session parachain.SessionIndex)
 	SetRecentDisputes(recentDisputes *btree.BTree)
 	SetCandidateVotes(session parachain.SessionIndex, candidateHash CandidateHash, votes *CandidateVotes)
 }
 
+// backend implements Backend.
 type backend struct {
 	// TODO: db
 	earliestSession *parachain.SessionIndex
@@ -200,23 +123,29 @@ func (b backend) SetCandidateVotes(session parachain.SessionIndex, candidateHash
 	b.candidateVotes[key] = votes
 }
 
+// ActiveDuration an arbitrary duration for how long a dispute is considered active.
 const ActiveDuration = 180 * time.Second
 
-func (b backend) GetActiveDisputes() (*btree.BTree, error) {
+func (b backend) GetActiveDisputes(now int64) (*btree.BTree, error) {
 	activeDisputes := btree.New(32)
 
 	b.recentDisputes.Ascend(func(i btree.Item) bool {
-		d := i.(*Dispute)
-		concludedAt, err := d.disputeStatus.ConcludedAt()
-		if err == nil && concludedAt != nil && *concludedAt+uint64(ActiveDuration.Seconds()) > uint64(time.Now().Unix()) {
-			activeDisputes.ReplaceOrInsert(d)
+		dispute, ok := i.(*Dispute)
+		if !ok {
+			// TODO: do we want to panic here?
+			panic("invalid dispute type")
+		}
+		concludedAt, err := dispute.disputeStatus.ConcludedAt()
+		if err == nil && concludedAt != nil && *concludedAt+uint64(ActiveDuration.Seconds()) > uint64(now) {
+			activeDisputes.ReplaceOrInsert(dispute)
 		}
 		return true
 	})
 
 	return activeDisputes, nil
 }
 
+// NewBackend creates a new backend.
 func NewBackend() Backend {
 	return &backend{
 		recentDisputes: btree.New(32),