refactor of channel persistence to use UUIDs

irc/datastore/datastore.go

@@ -0,0 +1,45 @@
+// Copyright (c) 2022 Shivaram Lingamneni <slingamn@cs.stanford.edu>
+// released under the MIT license
+
+package datastore
+
+import (
+	"time"
+
+	"github.com/ergochat/ergo/irc/utils"
+)
+
+type Table uint16
+
+// XXX these are persisted and must remain stable;
+// do not reorder, when deleting use _ to ensure that the deleted value is skipped
+const (
+	TableMetadata Table = iota
+	TableChannels
+	TableChannelPurges
+)
+
+type KV struct {
+	UUID  utils.UUID
+	Value []byte
+}
+
+// A Datastore provides the following abstraction:
+// 1. Tables, each keyed on a UUID (the implementation is free to merge
+// the table name and the UUID into a single key as long as the rest of
+// the contract can be satisfied). Table names are [a-z0-9_]+
+// 2. The ability to efficiently enumerate all uuid-value pairs in a table
+// 3. Gets, sets, and deletes for individual (table, uuid) keys
+type Datastore interface {
+	Backoff() time.Duration
+
+	GetAll(table Table) ([]KV, error)
+
+	// This is rarely used because it would typically lead to TOCTOU races
+	Get(table Table, key utils.UUID) (value []byte, err error)
+
+	Set(table Table, key utils.UUID, value []byte, expiration time.Time) error
+
+	// Note that deleting a nonexistent key is not considered an error
+	Delete(table Table, key utils.UUID) error
+}