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

import (
	"crypto/sha256"
	"maps"
	"os"
	"path/filepath"
	"slices"
	"testing"
	"time"

	"github.com/multiformats/go-multihash"
	"github.com/spf13/afero"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"google.golang.org/protobuf/proto"
	"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 writes files, by path and content, into a fresh temp
// dir and runs gen on it. It returns the temp dir and the path of the
// manifest gen wrote there.
func setupFreshenDir(
	t *testing.T, fs afero.Fs, files map[string]string,
) (string, string) {
	t.Helper()

	root := t.TempDir()
	manifestPath := filepath.Join(root, defaultManifestName)

	for path, content := range files {
		require.NoError(t, fs.MkdirAll(filepath.Dir(filepath.Join(root, path)), 0o750))
		writeTestFile(t, fs, filepath.Join(root, path), content)
	}

	opts := testOpts([]string{testApp, cmdGenerate, "-q", "-o", manifestPath, root}, fs)
	require.Equal(t, 0, runCLI(opts), "stderr: %s", testStderr(t, opts))

	return root, manifestPath
}

// runFreshen runs freshen on the manifest at manifestPath for the tree
// at root and requires it to succeed.
func runFreshen(t *testing.T, fs afero.Fs, root, manifestPath string) {
	t.Helper()

	opts := testOpts([]string{
		testApp, cmdFreshen, "-q", testFlagBase, root, manifestPath,
	}, fs)
	require.Equal(t, 0, runCLI(opts), "stderr: %s", testStderr(t, opts))
}

// manifestFiles returns the file entries of the manifest at path.
func manifestFiles(t *testing.T, fs afero.Fs, path string) []*mfer.MFFilePath {
	t.Helper()

	manifest, err := mfer.NewManifestFromFile(&mfer.ManifestFromFileOptions{
		Path: path,
		Fs:   fs,
	})
	require.NoError(t, err)

	return manifest.Files()
}

// TestFreshenUnchanged freshens a tree that has not changed since gen
// made its manifest: the manifest must list the same entries as before.
func TestFreshenUnchanged(t *testing.T) {
	t.Parallel()

	fs := afero.NewOsFs()
	root, manifestPath := setupFreshenDir(t, fs,
		map[string]string{testFileTxt: "content1", testDirFile: "content2"})
	before := manifestFiles(t, fs, manifestPath)

	runFreshen(t, fs, root, manifestPath)

	after := manifestFiles(t, fs, manifestPath)
	require.Len(t, after, len(before))

	for i := range before {
		assert.True(t, proto.Equal(before[i], after[i]),
			"entry for %s changed", before[i].GetPath())
	}
}

// assertManifestLists asserts that the manifest at manifestPath lists
// exactly the files in want, each with the size and SHA-256 hash of its
// content in want and the mtime of the file of that name under root.
func assertManifestLists(
	t *testing.T, fs afero.Fs, root, manifestPath string, want map[string]string,
) {
	t.Helper()

	files := manifestFiles(t, fs, manifestPath)
	listed := make([]string, 0, len(files))

	for _, f := range files {
		listed = append(listed, f.GetPath())

		content, ok := want[f.GetPath()]
		if !ok {
			continue // reported by the ElementsMatch below
		}

		digest := sha256.Sum256([]byte(content))
		hash, err := multihash.Encode(digest[:], multihash.SHA2_256)
		require.NoError(t, err)

		assert.Equal(t, int64(len(content)), f.GetSize(), f.GetPath())
		require.NotEmpty(t, f.GetHashes(), f.GetPath())
		assert.Equal(t, hash, f.GetHashes()[0].GetMultiHash(), f.GetPath())

		info, err := fs.Stat(filepath.Join(root, f.GetPath()))
		require.NoError(t, err)

		mtime, ok := entryMtime(f)
		assert.True(t, ok && mtime.Equal(info.ModTime()),
			"%s: manifest has mtime %v, file has %v",
			f.GetPath(), mtime, info.ModTime())
	}

	assert.ElementsMatch(t, slices.Collect(maps.Keys(want)), listed)
}

// TestFreshenWithChanges makes one change to a tree after gen made its
// manifest, then freshens the manifest. The rewritten manifest must list
// exactly the files now in the tree, and check must pass on the tree.
func TestFreshenWithChanges(t *testing.T) {
	t.Parallel()

	tree := map[string]string{testFileTxt: "content1", testDirFile: "content2"}

	// Every file a case writes gets this mtime, which differs from the one
	// gen recorded, so an edit that keeps the size is told apart by its
	// mtime whatever the filesystem's clock resolution.
	writtenMtime := time.Unix(1_700_000_000, 0)

	for _, tc := range []struct {
		name   string
		write  map[string]string // files to write, by path and content
		remove string            // file to delete, if any
	}{
		{
			name:  "modified file",
			write: map[string]string{testDirFile: "modified content2"},
		},
		{
			name:  "modified file, same size",
			write: map[string]string{testDirFile: "CONTENT2"},
		},
		{
			name:  "new file",
			write: map[string]string{"dir/new.txt": "content3"},
		},
		{
			name:   "deleted file",
			remove: testFileTxt,
		},
	} {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			fs := afero.NewOsFs()
			root, manifestPath := setupFreshenDir(t, fs, tree)

			// want is the tree as it is after the change.
			want := maps.Clone(tree)

			for path, content := range tc.write {
				writeTestFile(t, fs, filepath.Join(root, path), content)
				require.NoError(t, fs.Chtimes(
					filepath.Join(root, path), writtenMtime, writtenMtime))
				want[path] = content
			}

			if tc.remove != "" {
				require.NoError(t, fs.Remove(filepath.Join(root, tc.remove)))
				delete(want, tc.remove)
			}

			runFreshen(t, fs, root, manifestPath)

			assertManifestLists(t, fs, root, manifestPath, want)

			opts := testOpts([]string{
				testApp, cmdCheck, "-q", testFlagNoExtra, testFlagBase, root, manifestPath,
			}, fs)
			assert.Equal(t, 0, runCLI(opts), "stderr: %s", testStderr(t, opts))
		})
	}
}

// TestFreshenLeavesManifestOutOfListing freshens a manifest kept in a
// subdirectory of the tree it lists: the manifest is not listed, while an
// ordinary file of the same name at the top of the tree is. The manifest
// is recognized by file identity, which needs the real filesystem.
func TestFreshenLeavesManifestOutOfListing(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	manifestPath := filepath.Join(root, "sub", "listing.mf")

	fs := afero.NewOsFs()
	require.NoError(t, fs.MkdirAll(filepath.Join(root, "sub"), 0o750))
	writeTestFile(t, fs, filepath.Join(root, testFileTxt), "hello")
	writeTestFile(t, fs, filepath.Join(root, "listing.mf"), "an ordinary file")

	opts := testOpts([]string{testApp, cmdGenerate, "-q", "-o", manifestPath, root}, fs)
	require.Equal(t, 0, runCLI(opts), "stderr: %s", testStderr(t, opts))

	// A new file gives freshen something to write.
	writeTestFile(t, fs, filepath.Join(root, "added.txt"), "added")

	opts = testOpts([]string{
		testApp, "freshen", "-q", testFlagBase, root, manifestPath,
	}, fs)
	require.Equal(t, 0, runCLI(opts), "stderr: %s", testStderr(t, opts))

	assert.ElementsMatch(t, []string{testFileTxt, "listing.mf", "added.txt"},
		manifestPaths(t, fs, manifestPath))
}

// TestFreshenLeavesLeftoverTempFileOutOfListing freshens a manifest where
// an interrupted run left its temp file beside it: the leftover is not
// listed.
func TestFreshenLeavesLeftoverTempFileOutOfListing(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	manifestPath := filepath.Join(root, "index.mf")

	fs := afero.NewOsFs()
	writeTestFile(t, fs, filepath.Join(root, testFileTxt), "hello")

	opts := testOpts([]string{testApp, cmdGenerate, "-q", "-o", manifestPath, root}, fs)
	require.Equal(t, 0, runCLI(opts), "stderr: %s", testStderr(t, opts))

	writeTestFile(t, fs, manifestTempPath(manifestPath), "part of a manifest")
	// A new file gives freshen something to write.
	writeTestFile(t, fs, filepath.Join(root, "added.txt"), "added")

	opts = testOpts([]string{
		testApp, "freshen", "-q", testFlagBase, root, manifestPath,
	}, fs)
	require.Equal(t, 0, runCLI(opts), "stderr: %s", testStderr(t, opts))

	assert.ElementsMatch(t, []string{testFileTxt, "added.txt"},
		manifestPaths(t, fs, manifestPath))
}

// 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"

	// The scanned file's mtime is the Unix epoch. If recordEntry ever misreads
	// an absent manifest mtime as the epoch, the "absent" case below would
	// compare equal to this and be classified unchanged, so the test fails.
	mtime := time.Unix(0, 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()

	hash, err := multihash.Encode(make([]byte, sha256.Size), multihash.SHA2_256)
	require.NoError(t, err)

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

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

// TestFreshenAddExistingRejectsShortHash pins that an existing manifest
// entry whose hash the builder refuses is reported as a problem with the
// manifest, with the command that fixes it.
func TestFreshenAddExistingRejectsShortHash(t *testing.T) {
	t.Parallel()

	sha1Hash, err := multihash.Encode(make([]byte, 20), multihash.SHA1)
	require.NoError(t, err)

	b := mfer.NewBuilder()
	entry := &mfer.MFFilePath{
		Path:  "old.txt",
		Size:  8,
		Mtime: &mfer.Timestamp{Seconds: 1_700_000_000},
		Hashes: []*mfer.MFFileChecksum{
			{MultiHash: sha1Hash},
		},
	}

	err = addExistingToBuilder(b, entry)
	require.Error(t, err)
	assert.Contains(t, err.Error(), "manifest entry old.txt")
	assert.Contains(t, err.Error(), "mfer generate")
	assert.Zero(t, b.FileCount())
}

// 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)
}