//nolint:testpackage // white-box tests exercise unexported internals
package cli

import (
	"bytes"
	"context"
	"os"
	"testing"
	"time"

	"github.com/spf13/afero"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/mfer/mfer"
)

// stubFileInfo is a minimal fs.FileInfo for exercising recordEntry
// without touching a filesystem.
type stubFileInfo struct {
	size  int64
	mtime time.Time
}

func (s stubFileInfo) Name() string       { return "stub" }
func (s stubFileInfo) Size() int64        { return s.size }
func (s stubFileInfo) Mode() os.FileMode  { return 0 }
func (s stubFileInfo) ModTime() time.Time { return s.mtime }
func (s stubFileInfo) IsDir() bool        { return false }
func (s stubFileInfo) Sys() any           { return nil }

// setupFreshenDir populates /testdir with two files, scans it, and
// writes the resulting manifest to /testdir/.index.mf.
func setupFreshenDir(t *testing.T, fs afero.Fs) {
	t.Helper()

	require.NoError(t, fs.MkdirAll(testDir, 0o755))
	writeTestFile(t, fs, testFile1, "content1")
	writeTestFile(t, fs, "/testdir/file2.txt", "content2")

	// Generate initial manifest
	opts := &mfer.ScannerOptions{Fs: fs}
	s := mfer.NewScannerWithOptions(opts)
	require.NoError(t, s.EnumeratePath(testDir, nil))

	var manifestBuf bytes.Buffer

	require.NoError(t, s.ToManifest(context.Background(), &manifestBuf, nil))

	// Write manifest to filesystem
	require.NoError(t,
		afero.WriteFile(fs, "/testdir/.index.mf", manifestBuf.Bytes(), 0o644))
}

func TestFreshenUnchanged(t *testing.T) {
	t.Parallel()

	fs := afero.NewMemMapFs()
	setupFreshenDir(t, fs)

	// Parse manifest to verify
	manifest, err := mfer.NewManifestFromFile(fs, "/testdir/.index.mf")
	require.NoError(t, err)
	assert.Len(t, manifest.Files(), 2)
}

func TestFreshenWithChanges(t *testing.T) {
	t.Parallel()

	fs := afero.NewMemMapFs()
	setupFreshenDir(t, fs)

	// Verify initial manifest has 2 files
	manifest, err := mfer.NewManifestFromFile(fs, "/testdir/.index.mf")
	require.NoError(t, err)
	assert.Len(t, manifest.Files(), 2)

	// Add a new file
	writeTestFile(t, fs, "/testdir/file3.txt", "content3")

	// Modify file2 (change content and size)
	writeTestFile(t, fs, "/testdir/file2.txt", "modified content2")

	// Remove file1
	require.NoError(t, fs.Remove(testFile1))

	// Note: The freshen operation would need to be run here
	// For now, we just verify the test setup is correct
	exists, _ := afero.Exists(fs, testFile1)
	assert.False(t, exists)

	exists, _ = afero.Exists(fs, "/testdir/file3.txt")
	assert.True(t, exists)

	content, _ := afero.ReadFile(fs, "/testdir/file2.txt")
	assert.Equal(t, "modified content2", string(content))
}

// TestFreshenRecordEntryMtimePresence pins the behavior of recordEntry
// with respect to MFFilePath.Mtime, which is a message pointer with
// proto3 field presence and may legitimately be absent.
//
// An absent mtime must never be read as time.Unix(0, 0): that value
// never equals a real modification time, so every entry would be
// classified as changed, re-hashed, and the manifest rewritten
// unconditionally - the exact inverse of what freshen is for, and
// silent. An entry with no mtime is therefore "changed" because it
// cannot be compared, not because it looks like it dates from 1970.
func TestFreshenRecordEntryMtimePresence(t *testing.T) {
	t.Parallel()

	const relPath = "file1.txt"

	mtime := time.Unix(1_700_000_000, 0)
	info := stubFileInfo{size: 8, mtime: mtime}

	for _, tc := range []struct {
		name      string
		entry     *mfer.MFFilePath
		needsHash bool
		changed   int64
		unchanged int64
	}{
		{
			name: "matching mtime and size is unchanged",
			entry: &mfer.MFFilePath{
				Path:  relPath,
				Size:  8,
				Mtime: &mfer.Timestamp{Seconds: mtime.Unix()},
			},
			needsHash: false,
			changed:   0,
			unchanged: 1,
		},
		{
			name: "absent mtime is changed, not epoch",
			entry: &mfer.MFFilePath{
				Path:  relPath,
				Size:  8,
				Mtime: nil,
			},
			needsHash: true,
			changed:   1,
			unchanged: 0,
		},
	} {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			s := &freshenScanner{
				existingByPath: map[string]*mfer.MFFilePath{relPath: tc.entry},
			}
			s.recordEntry(relPath, info)

			require.Len(t, s.entries, 1)
			assert.Equal(t, tc.needsHash, s.entries[0].needsHash)
			assert.Equal(t, tc.changed, s.changed)
			assert.Equal(t, tc.unchanged, s.unchanged)
			assert.Zero(t, s.added)
		})
	}
}

// TestFreshenAddExistingRejectsMissingMtime pins that an entry with no
// mtime is never carried forward into a rebuilt manifest with a
// fabricated epoch timestamp.
func TestFreshenAddExistingRejectsMissingMtime(t *testing.T) {
	t.Parallel()

	b := mfer.NewBuilder()
	entry := &mfer.MFFilePath{
		Path:  "file1.txt",
		Size:  8,
		Mtime: nil,
		Hashes: []*mfer.MFFileChecksum{
			{MultiHash: []byte{0x12, 0x20}},
		},
	}

	err := addExistingToBuilder(b, entry)
	require.ErrorIs(t, err, errEntryMissingMtime)
	assert.Contains(t, err.Error(), "file1.txt")
}

// TestEntryMtime pins the presence semantics the callers depend on.
func TestEntryMtime(t *testing.T) {
	t.Parallel()

	got, ok := entryMtime(&mfer.MFFilePath{Mtime: nil})
	assert.False(t, ok)
	assert.True(t, got.IsZero())

	got, ok = entryMtime(&mfer.MFFilePath{
		Mtime: &mfer.Timestamp{Seconds: 1_700_000_000, Nanos: 500},
	})
	assert.True(t, ok)
	assert.Equal(t, time.Unix(1_700_000_000, 500), got)
}