Implement cache migrations

internal/cache/cache_migrations.go

@@ -0,0 +1,57 @@
+package cache
+
+import (
+	"errors"
+	"fmt"
+
+	"golang.org/x/mod/semver"
+)
+
+type migrationFunc func(c *Cache) error
+
+// Registry of migrations by version
+var migrations = map[string]map[string]migrationFunc{
+	"v0.1.0": {
+		"Make Aliases Unique": v010_aliases,
+	},
+}
+
+// Performs any required updates based on version
+// of cache read from disk.
+// Does not check to ensure migrations were successful,
+// only checks if a version has been achieved
+func (c *Cache) DoMigrations() error {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	return c.doMigrations()
+}
+
+func (c *Cache) doMigrations() error {
+	var errs error
+	for version, migrationFuncs := range migrations {
+		if semver.Compare(c.CacheVersion, version) < 0 {
+			for name, migration := range migrationFuncs {
+				err := migration(c)
+				if err != nil {
+					errs = errors.Join(
+						errs,
+						fmt.Errorf("%s - %s: %w", version, name, err),
+					)
+				}
+			}
+
+			// We've reached a cache version, update the CacheVersion
+			// and write to disk
+			if errs == nil {
+				c.CacheVersion = version
+				c.write()
+			}
+		}
+	}
+
+	return errs
+}
+
+func v010_aliases(c *Cache) error {
+	return errors.New("unimplemented migration")
+}