feat: add fingerprinted asset generator

web/assetsgen/generator.go

@@ -0,0 +1,114 @@
+package assetsgen
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+type Manifest map[string]string
+
+type Options struct {
+	SourceDir string
+	OutputDir string
+	HashLen   int
+}
+
+func Generate(opts Options) (Manifest, error) {
+	if opts.HashLen <= 0 {
+		opts.HashLen = 8
+	}
+	if opts.HashLen > sha256.Size*2 {
+		opts.HashLen = sha256.Size * 2
+	}
+
+	manifest := make(Manifest)
+	if err := os.MkdirAll(opts.OutputDir, 0o755); err != nil {
+		return nil, err
+	}
+
+	err := filepath.WalkDir(opts.SourceDir, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() {
+			return nil
+		}
+
+		rel, err := filepath.Rel(opts.SourceDir, path)
+		if err != nil {
+			return err
+		}
+		rel = filepath.ToSlash(rel)
+
+		raw, err := os.ReadFile(path)
+		if err != nil {
+			return err
+		}
+
+		sum := sha256.Sum256(raw)
+		hash := hex.EncodeToString(sum[:])[:opts.HashLen]
+		target := fingerprint(rel, hash)
+		targetPath := filepath.Join(opts.OutputDir, filepath.FromSlash(target))
+
+		if err := os.MkdirAll(filepath.Dir(targetPath), 0o755); err != nil {
+			return err
+		}
+		if err := os.WriteFile(targetPath, raw, 0o644); err != nil {
+			return err
+		}
+
+		manifest[rel] = target
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return manifest, nil
+}
+
+func WriteManifest(path string, manifest Manifest) error {
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		return err
+	}
+
+	raw, err := json.MarshalIndent(manifest, "", "  ")
+	if err != nil {
+		return err
+	}
+	raw = append(raw, '\n')
+	return os.WriteFile(path, raw, 0o644)
+}
+
+func fingerprint(rel, hash string) string {
+	name := filepath.Base(rel)
+	if strings.HasPrefix(name, ".") && strings.Count(name, ".") == 1 {
+		return rel + "." + hash
+	}
+
+	ext := filepath.Ext(rel)
+	base := strings.TrimSuffix(rel, ext)
+	if ext == "" {
+		return rel + "." + hash
+	}
+	return base + "." + hash + ext
+}
+
+func CopyFile(dst string, src io.Reader) error {
+	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
+		return err
+	}
+	f, err := os.Create(dst)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = io.Copy(f, src)
+	return err
+}

web/assetsgen/generator_test.go

@@ -0,0 +1,165 @@
+package assetsgen
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestGenerateProducesFingerprintManifestAndFiles(t *testing.T) {
+	src := t.TempDir()
+	dst := t.TempDir()
+
+	if err := os.MkdirAll(filepath.Join(src, "js"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(src, "js", "app.js"), []byte("console.log('v1')\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	manifest, err := Generate(Options{
+		SourceDir: src,
+		OutputDir: filepath.Join(dst, "assets"),
+		HashLen:   8,
+	})
+	if err != nil {
+		t.Fatalf("Generate returned error: %v", err)
+	}
+
+	got, ok := manifest["js/app.js"]
+	if !ok {
+		t.Fatalf("manifest missing logical path: %#v", manifest)
+	}
+
+	sum := sha256.Sum256([]byte("console.log('v1')\n"))
+	wantHash := hex.EncodeToString(sum[:])[:8]
+	want := "js/app." + wantHash + ".js"
+	if got != want {
+		t.Fatalf("unexpected hashed filename: got %q want %q", got, want)
+	}
+
+	if _, err := os.Stat(filepath.Join(dst, "assets", got)); err != nil {
+		t.Fatalf("hashed output missing: %v", err)
+	}
+
+	defaultManifest, err := Generate(Options{
+		SourceDir: src,
+		OutputDir: filepath.Join(dst, "default-assets"),
+	})
+	if err != nil {
+		t.Fatalf("Generate with default hash length returned error: %v", err)
+	}
+
+	if gotDefault := defaultManifest["js/app.js"]; gotDefault != want {
+		t.Fatalf("default HashLen mismatch: got %q want %q", gotDefault, want)
+	}
+
+	if _, err := os.Stat(filepath.Join(dst, "default-assets", want)); err != nil {
+		t.Fatalf("default hashed output missing: %v", err)
+	}
+}
+
+func TestGenerateClampsHashLenToSha256HexLength(t *testing.T) {
+	src := t.TempDir()
+	dst := t.TempDir()
+
+	if err := os.WriteFile(filepath.Join(src, "main.css"), []byte("body{}\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	manifest, err := Generate(Options{
+		SourceDir: src,
+		OutputDir: filepath.Join(dst, "assets"),
+		HashLen:   65,
+	})
+	if err != nil {
+		t.Fatalf("Generate returned error: %v", err)
+	}
+
+	sum := sha256.Sum256([]byte("body{}\n"))
+	wantHash := hex.EncodeToString(sum[:])
+	want := "main." + wantHash + ".css"
+	if got := manifest["main.css"]; got != want {
+		t.Fatalf("unexpected hashed filename: got %q want %q", got, want)
+	}
+
+	if _, err := os.Stat(filepath.Join(dst, "assets", want)); err != nil {
+		t.Fatalf("clamped hashed output missing: %v", err)
+	}
+}
+
+func TestGenerateFingerprintsDotfilesWithoutLeadingExtension(t *testing.T) {
+	src := t.TempDir()
+	dst := t.TempDir()
+
+	if err := os.MkdirAll(filepath.Join(src, "dir"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(src, ".env"), []byte("ROOT=1\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(src, "dir", ".env"), []byte("NESTED=1\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	manifest, err := Generate(Options{
+		SourceDir: src,
+		OutputDir: filepath.Join(dst, "assets"),
+		HashLen:   8,
+	})
+	if err != nil {
+		t.Fatalf("Generate returned error: %v", err)
+	}
+
+	rootSum := sha256.Sum256([]byte("ROOT=1\n"))
+	rootWant := ".env." + hex.EncodeToString(rootSum[:])[:8]
+	if got := manifest[".env"]; got != rootWant {
+		t.Fatalf("unexpected root dotfile fingerprint: got %q want %q", got, rootWant)
+	}
+	if _, err := os.Stat(filepath.Join(dst, "assets", rootWant)); err != nil {
+		t.Fatalf("root dotfile output missing: %v", err)
+	}
+
+	nestedSum := sha256.Sum256([]byte("NESTED=1\n"))
+	nestedWant := filepath.ToSlash(filepath.Join("dir", ".env.")) + hex.EncodeToString(nestedSum[:])[:8]
+	if got := manifest["dir/.env"]; got != nestedWant {
+		t.Fatalf("unexpected nested dotfile fingerprint: got %q want %q", got, nestedWant)
+	}
+	if _, err := os.Stat(filepath.Join(dst, "assets", filepath.FromSlash(nestedWant))); err != nil {
+		t.Fatalf("nested dotfile output missing: %v", err)
+	}
+}
+
+func TestWriteManifestSerializesStableJson(t *testing.T) {
+	dst := t.TempDir()
+	path := filepath.Join(dst, "assets-manifest.json")
+	manifest := Manifest{
+		"css/a.css": "css/a.11111111.css",
+		"js/b.js":   "js/b.22222222.js",
+	}
+
+	if err := WriteManifest(path, manifest); err != nil {
+		t.Fatalf("WriteManifest returned error: %v", err)
+	}
+
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := "{\n  \"css/a.css\": \"css/a.11111111.css\",\n  \"js/b.js\": \"js/b.22222222.js\"\n}\n"
+	if string(raw) != want {
+		t.Fatalf("unexpected manifest json:\n got: %q\nwant: %q", string(raw), want)
+	}
+
+	var decoded map[string]string
+	if err := json.Unmarshal(raw, &decoded); err != nil {
+		t.Fatalf("manifest json invalid: %v", err)
+	}
+	if decoded["js/b.js"] != "js/b.22222222.js" {
+		t.Fatalf("unexpected manifest entry: %#v", decoded)
+	}
+}