package buildstep

import (
	"bytes"
	"compress/gzip"
	"crypto/sha256"
	"encoding/hex"
	"io"
	"os"
	"path/filepath"
	"testing"
	"time"
)

// fixture writes three files in two directories (modes 0644 and 0755).
func fixture(t *testing.T) string {
	t.Helper()
	root := t.TempDir()
	for _, f := range []struct {
		p    string
		mode os.FileMode
		body string
	}{{"a/x.txt", 0o644, "x\n"}, {"a/run.sh", 0o755, "#!/bin/sh\necho hi\n"}, {"b/c/y.txt", 0o644, "why\n"}} {
		path := filepath.Join(root, f.p)
		if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(path, []byte(f.body), f.mode); err != nil {
			t.Fatal(err)
		}
		if err := os.Chmod(path, f.mode); err != nil {
			t.Fatal(err)
		}
	}
	return root
}

// 1479/AC1: the tar stream inside the archive equals the bytes mesh-controller's pack makes for this tree.
// testdata/pack-golden.tar is the uncompressed stream, made once by running mesh-controller
// internal/builder/builder.go pack (origin/main 073ccc29, :1351-1425) on this fixture (above, modes set by chmod)
// and gunzipping its archive. The gzip layer is not compared byte for byte, since compress/gzip's output differs
// between Go versions; its header is checked to carry no name, no comment and no time.
func TestPackEqualsTheBuildAgentsArchive(t *testing.T) {
	golden, err := os.ReadFile("testdata/pack-golden.tar")
	if err != nil {
		t.Fatal(err)
	}
	archive, digest, err := Pack(fixture(t))
	if err != nil {
		t.Fatal(err)
	}
	zr, err := gzip.NewReader(bytes.NewReader(archive))
	if err != nil {
		t.Fatal(err)
	}
	if zr.Name != "" || zr.Comment != "" || !zr.ModTime.IsZero() {
		t.Errorf("gzip header = name %q, comment %q, time %v; want none", zr.Name, zr.Comment, zr.ModTime)
	}
	tarBytes, err := io.ReadAll(zr)
	if err != nil {
		t.Fatal(err)
	}
	if !bytes.Equal(tarBytes, golden) {
		t.Errorf("the tar stream is %d bytes, the build agent's %d, and they differ", len(tarBytes), len(golden))
	}
	sum := sha256.Sum256(archive)
	if digest != "sha256:"+hex.EncodeToString(sum[:]) {
		t.Errorf("digest = %s, not the sha256 of the archive", digest)
	}
}

// 1479/AC2: touching every file's time changes nothing.
func TestPackDigestIgnoresFileTimes(t *testing.T) {
	root := fixture(t)
	_, first, err := Pack(root)
	if err != nil {
		t.Fatal(err)
	}
	later := time.Now().Add(48 * time.Hour)
	filepath.Walk(root, func(p string, _ os.FileInfo, _ error) error { return os.Chtimes(p, later, later) })
	if _, second, err := Pack(root); err != nil || second != first {
		t.Errorf("digests %s and %s (%v)", first, second, err)
	}
}