Completed minimal Ledger implementation, first tests in chron-cli

core/interfaces.go

@@ -13,6 +13,6 @@ type EntryStore interface {
 
 type ReferenceStore interface {
 	Set(ctx context.Context, name string, entryID EntryID) error
-	Get(ctx context.Context, name string) (EntryID, error)
+	Get(ctx context.Context, name string) (EntryID, bool, error)
 	Delete(ctx context.Context, name string) error
 }

core/ledger.go

@@ -1,6 +1,10 @@
 package core
 
-import ()
+import (
+	"context"
+	"errors"
+	"time"
+)
 
 type Ledger struct {
 	entryStore     EntryStore
@@ -14,10 +18,111 @@ func NewLedger(entryStore EntryStore, referenceStore ReferenceStore) (*Ledger, e
 	}, nil
 }
 
-func (l *Ledger) Append()            {}
-func (l *Ledger) AppendToReference() {}
-func (l *Ledger) Get()               {}
-func (l *Ledger) GetFromReference()  {}
-func (l *Ledger) SetHead()           {}
-func (l *Ledger) SetReference()      {}
-func (l *Ledger) RemoveReference()   {}
+func (l *Ledger) Append(ctx context.Context, payload []byte) error {
+	currentHeadEntryID, ok, err := l.referenceStore.Get(ctx, "HEAD")
+	if err != nil {
+		return err
+	}
+
+	if !ok {
+		l.referenceStore.Set(ctx, "HEAD", EntryID{})
+		currentHeadEntryID = EntryID{}
+	}
+
+	entryTime := time.Now()
+	entryID := ComputeEntryID(currentHeadEntryID, entryTime, payload)
+
+	entry := Entry{
+		EntryID:   entryID,
+		Previous:  currentHeadEntryID,
+		Timestamp: entryTime,
+		Payload:   payload,
+	}
+
+	if ComputeEntryID(entry.Previous, entry.Timestamp, entry.Payload) != entryID {
+		panic("EntryID hash mismatch fuckup")
+	}
+
+	err = l.entryStore.Store(ctx, entry)
+	if err != nil {
+		return err
+	}
+
+	err = l.referenceStore.Set(ctx, "HEAD", entry.EntryID)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (l *Ledger) AppendTo(ctx context.Context, prevEntryID EntryID, payload []byte) error {
+	entryTime := time.Now()
+	entryID := ComputeEntryID(prevEntryID, entryTime, payload)
+
+	entry := Entry{
+		EntryID:   entryID,
+		Previous:  prevEntryID,
+		Timestamp: entryTime,
+		Payload:   payload,
+	}
+
+	if ComputeEntryID(entry.Previous, entry.Timestamp, entry.Payload) != entryID {
+		panic("EntryID hash mismatch fuckup")
+	}
+
+	err := l.entryStore.Store(ctx, entry)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (l *Ledger) Get(ctx context.Context) (Entry, error) {
+	headEntryID, ok, err := l.referenceStore.Get(ctx, "HEAD")
+	if err != nil {
+		return Entry{}, err
+	}
+
+	if !ok {
+		return Entry{}, errors.New("HEAD not set")
+	}
+
+	entry, err := l.entryStore.Load(ctx, headEntryID)
+	if err != nil {
+		return Entry{}, err
+	}
+
+	return entry, nil
+}
+
+func (l *Ledger) GetFromReference(ctx context.Context, reference string) (Entry, error) {
+	referenceEntryID, ok, err := l.referenceStore.Get(ctx, reference)
+	if err != nil {
+		return Entry{}, err
+	}
+
+	if !ok {
+		return Entry{}, errors.New("HEAD not set")
+	}
+
+	entry, err := l.entryStore.Load(ctx, referenceEntryID)
+	if err != nil {
+		return Entry{}, err
+	}
+
+	return entry, nil
+}
+
+func (l *Ledger) SetHead(ctx context.Context, entryID EntryID) error {
+	return l.referenceStore.Set(ctx, "HEAD", entryID)
+}
+
+func (l *Ledger) SetReference(ctx context.Context, reference string, entryID EntryID) error {
+	return l.referenceStore.Set(ctx, reference, entryID)
+}
+
+func (l *Ledger) RemoveReference(ctx context.Context, reference string) error {
+	return l.referenceStore.Delete(ctx, reference)
+}