some more fixes

internal/store/interface.go

@@ -0,0 +1,89 @@
+package store
+
+import (
+	"context"
+)
+
+// KV represents a key-value pair from the store.
+type KV struct {
+	Key     string
+	Value   []byte
+	Version int64 // etcd ModRevision or similar versioning
+}
+
+// EventType defines the type of change observed by a Watch.
+type EventType int
+
+const (
+	// EventTypePut indicates a key was created or updated.
+	EventTypePut EventType = iota
+	// EventTypeDelete indicates a key was deleted.
+	EventTypeDelete
+)
+
+// WatchEvent represents a single event from a Watch operation.
+type WatchEvent struct {
+	Type   EventType
+	KV     KV
+	PrevKV *KV // Previous KV, if available and applicable (e.g., for updates)
+}
+
+// Compare is used in transactions to check a key's version.
+type Compare struct {
+	Key             string
+	ExpectedVersion int64 // 0 means key should not exist. >0 means key must have this version.
+}
+
+// OpType defines the type of operation in a transaction.
+type OpType int
+
+const (
+	// OpPut represents a put operation.
+	OpPut OpType = iota
+	// OpDelete represents a delete operation.
+	OpDelete
+	// OpGet is not typically used in Txn success/fail ops but included for completeness if needed.
+	OpGet
+)
+
+// Op represents an operation to be performed within a transaction.
+type Op struct {
+	Type  OpType
+	Key   string
+	Value []byte // Used for OpPut
+}
+
+// StateStore defines the interface for interacting with the underlying key-value store.
+// It's designed based on RFC 5.1.
+type StateStore interface {
+	// Put stores a key-value pair.
+	Put(ctx context.Context, key string, value []byte) error
+	// Get retrieves a key-value pair. Returns an error if key not found.
+	Get(ctx context.Context, key string) (*KV, error)
+	// Delete removes a key.
+	Delete(ctx context.Context, key string) error
+	// List retrieves all key-value pairs matching a prefix.
+	List(ctx context.Context, prefix string) ([]KV, error)
+	// Watch observes changes to a key or prefix, starting from a given revision.
+	// startRevision = 0 means watch from current.
+	Watch(ctx context.Context, keyOrPrefix string, startRevision int64) (<-chan WatchEvent, error)
+	// Close releases any resources held by the store client.
+	Close() error
+
+	// Campaign attempts to acquire leadership for the given leaderID.
+	// It returns a leadershipCtx that is cancelled when leadership is lost or Resign is called.
+	// leaseTTLSeconds specifies the TTL for the leader's lease.
+	Campaign(ctx context.Context, leaderID string, leaseTTLSeconds int64) (leadershipCtx context.Context, err error)
+	// Resign relinquishes leadership if currently held.
+	// The context passed should ideally be the one associated with the current leadership term or a parent.
+	Resign(ctx context.Context) error
+	// GetLeader retrieves the ID of the current leader.
+	GetLeader(ctx context.Context) (leaderID string, err error)
+
+	// DoTransaction executes a list of operations atomically if all checks pass.
+	// checks are conditions that must be true.
+	// onSuccess operations are performed if checks pass.
+	// onFailure operations are performed if checks fail (not typically supported by etcd Txn else).
+	// Returns true if the transaction was committed (onSuccess ops were applied).
+	DoTransaction(ctx context.Context, checks []Compare, onSuccess []Op, onFailure []Op) (committed bool, err error)
+}