Foundation: config, schema/migrations, auth, stable IDs, metadata probing

internal/idgen/idgen.go

@@ -0,0 +1,34 @@
+// Package idgen generates stable, opaque, URL-safe identifiers for domain
+// entities (users, folders, artists, albums, songs, ...).
+//
+// IDs are random and assigned once, then persisted. They are never derived
+// from filesystem position or recomputed on rescan: the scanner looks up
+// existing rows by natural key (e.g. a song's path within its music
+// folder) and only calls NewID for rows it has never seen before, so IDs
+// stay stable across restarts and normal rescans.
+package idgen
+
+import (
+	"crypto/rand"
+	"encoding/base32"
+	"strings"
+)
+
+// enc is unpadded base32 using Crockford's alphabet-like lowercase set,
+// which is URL-safe and avoids ambiguous characters better than base64url
+// for anything a human might need to read back (log lines, debugging).
+var enc = base32.NewEncoding("0123456789abcdefghjkmnpqrstvwxyz").WithPadding(base32.NoPadding)
+
+// New returns a new opaque ID with the given short type prefix, e.g.
+// New("us") -> "us_1a2b3c4d5e6f7g8h9j0k1m2n".
+func New(prefix string) string {
+	b := make([]byte, 16)
+	if _, err := rand.Read(b); err != nil {
+		panic(err) // crypto/rand failing means the system is broken
+	}
+	id := strings.ToLower(enc.EncodeToString(b))
+	if prefix == "" {
+		return id
+	}
+	return prefix + "_" + id
+}

internal/idgen/idgen_test.go

@@ -0,0 +1,39 @@
+package idgen
+
+import (
+	"net/url"
+	"strings"
+	"testing"
+)
+
+func TestNewHasPrefix(t *testing.T) {
+	id := New("sg")
+	if !strings.HasPrefix(id, "sg_") {
+		t.Fatalf("New(%q) = %q, want prefix sg_", "sg", id)
+	}
+}
+
+func TestNewIsUnique(t *testing.T) {
+	seen := make(map[string]bool)
+	for i := 0; i < 1000; i++ {
+		id := New("sg")
+		if seen[id] {
+			t.Fatalf("duplicate ID generated: %s", id)
+		}
+		seen[id] = true
+	}
+}
+
+func TestNewIsURLSafe(t *testing.T) {
+	id := New("al")
+	if url.PathEscape(id) != id {
+		t.Fatalf("New() = %q is not URL-safe when path-escaped: %q", id, url.PathEscape(id))
+	}
+}
+
+func TestNewNoPrefix(t *testing.T) {
+	id := New("")
+	if strings.Contains(id, "_") {
+		t.Fatalf("New(\"\") = %q should not contain an underscore", id)
+	}
+}