package main

import (
	"bytes"
	"errors"
	"fmt"
	"maps"
	"os"
	"path/filepath"
	"runtime"
	"slices"
	"strings"
	"testing"
)

// defaultExcludeWhy is what the scan says about a default exclude from
// the fixed list when its walk does not enter it.
const defaultExcludeWhy = "default exclude"

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

	// README "Rules for the walk": each system's list.
	cases := map[string][]string{
		goosLinux: {"/proc", "/sys", "/dev", "/run", "/tmp", "/var/tmp"},
		goosDarwin: {
			"/dev", "/private/tmp", "/private/var/tmp", "/private/var/vm",
			"/System/Volumes/VM", "/System/Volumes/Data",
		},
		"freebsd": nil,
	}

	for goos, want := range cases {
		if got := defaultExcludes(goos); !slices.Equal(got, want) {
			t.Errorf("defaultExcludes(%q) = %q, want %q", goos, got, want)
		}
	}
}

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

	// The second-to-last line has no optional fields. /mnt/over has an
	// ext4 filesystem mounted over its tmpfs, so it holds files.
	mountinfo := strings.Join([]string{
		"22 1 8:1 / / rw,relatime shared:1 - ext4 /dev/sda1 rw",
		"23 22 0:21 / /proc rw,nosuid shared:12 - proc none rw",
		"24 22 0:22 / /sys rw,nosuid shared:7 - sysfs none rw",
		`25 22 0:23 / /mnt/ram\040disk rw shared:2 - tmpfs none rw`,
		"26 22 0:24 / /mnt/over rw shared:3 - tmpfs none rw",
		"27 26 8:2 / /mnt/over rw - ext4 /dev/sda2 rw",
		"28 22 0:25 / /srv/auto rw shared:4 - autofs systemd-1 rw",
	}, "\n")

	got, err := kernelMounts(strings.NewReader(mountinfo))
	if err != nil {
		t.Fatal(err)
	}

	want := map[string]string{
		"/proc": "proc", "/sys": "sysfs", "/mnt/ram disk": "tmpfs",
		"/srv/auto": "autofs",
	}
	if !maps.Equal(got, want) {
		t.Errorf("kernelMounts = %q, want %q", got, want)
	}

	_, err = kernelMounts(strings.NewReader("22 1 8:1 / / rw,relatime\n"))
	if !errors.Is(err, errMountInfoLine) {
		t.Errorf("kernelMounts of a line without a type = %v, want %v",
			err, errMountInfoLine)
	}
}

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

	if runtime.GOOS != goosLinux {
		t.Skip("only Linux lists its mounts in " + mountInfoPath)
	}

	excludes, err := findDefaultExcludes(goosLinux)
	if err != nil {
		t.Fatal(err)
	}

	for _, dir := range defaultExcludes(goosLinux) {
		if _, ok := excludes[dir]; !ok {
			t.Errorf("%s is not a default exclude", dir)
		}
	}

	want := defaultExcludeWhy + ", proc filesystem"
	if got := excludes["/proc"]; got != want {
		t.Errorf("/proc is %q, want %q", got, want)
	}
}

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

	for _, goos := range []string{goosLinux, goosDarwin} {
		help := defaultExcludesHelp(goos)

		for _, dir := range defaultExcludes(goos) {
			if !strings.Contains(help, "\n  "+dir+"\n") {
				t.Errorf("help for %s does not list %s:\n%s", goos, dir, help)
			}
		}

		// Only Linux has filesystem types among its default excludes.
		for _, fsType := range kernelFilesystemTypes() {
			listed := strings.Contains(help, " "+fsType+",") ||
				strings.Contains(help, " "+fsType+"\n")
			if listed != (goos == goosLinux) {
				t.Errorf("help for %s lists %s: %v", goos, fsType, listed)
			}
		}
	}

	want := "This system has no default excludes."
	if got := defaultExcludesHelp("freebsd"); got != want {
		t.Errorf("help for freebsd = %q, want %q", got, want)
	}

	// scan's help shows those of the system it runs on.
	var stdout, stderr bytes.Buffer

	run([]string{cmdScan, "-h"}, &stdout, &stderr)

	help := strings.TrimSpace(defaultExcludesHelp(runtime.GOOS))
	if !strings.Contains(stderr.String(), help) {
		t.Errorf("scan --help = %q, want it to hold %q", stderr.String(), help)
	}
}

// TestScanDoesNotEnterDefaultExclude checks that the walk does not
// enter a default exclude below an operand. It says so on a line of its
// own and does not count it as skipped. The records below it count as
// outside the operands: the record of a file gone from it is kept, and
// its size joins the size census, while a file added to it is not
// recorded.
//
//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
func TestScanDoesNotEnterDefaultExclude(t *testing.T) {
	stderr := captureStderr(t)
	dir := t.TempDir()
	db := openTestDB(t)
	excluded := filepath.Join(dir, "tmp")

	// A scan with no default excludes records the file in excluded.
	gone := writeFile(t, excluded, "gone", pattern(1, 100))
	syncTree(t, db, dir)

	err := os.Remove(gone)
	if err != nil {
		t.Fatal(err)
	}

	unseen := writeFile(t, excluded, "new", pattern(2, 10))

	// The same size as gone, so it is hashed only if the census holds the
	// size of gone's record.
	added := writeFile(t, dir, "added", pattern(3, 100))

	st, err := syncScan(t.Context(), db, []string{dir}, 1, false,
		map[string]string{excluded: defaultExcludeWhy})
	if err != nil {
		t.Fatal(err)
	}

	if st.skipped != 0 {
		t.Errorf("skipped = %d, want 0", st.skipped)
	}

	recs := dbRecords(t, db)
	recordByPath(t, recs, gone)

	if recordByPath(t, recs, added).head == "" {
		t.Errorf("%s not hashed: the census lacks the size of %s",
			added, gone)
	}

	if slices.Contains(recordPaths(recs), unseen) {
		t.Errorf("%s recorded: the walk entered %s", unseen, excluded)
	}

	line := "\nscan: skipped " + excluded + " (" + defaultExcludeWhy + ")\n"
	if !strings.Contains(stderr(), line) {
		t.Errorf("stderr = %q, want %q", stderr(), line)
	}
}

// TestScanWalksOperandInDefaultExclude checks that an operand at or
// inside a default exclude is walked, also when it lies under another
// operand, whose walk does not enter the default exclude.
func TestScanWalksOperandInDefaultExclude(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	excluded := filepath.Join(dir, "tmp")
	f := writeFile(t, excluded, "sub/f", pattern(1, 10))
	sub := filepath.Dir(f)

	cases := map[string][]string{
		"at it":                      {excluded},
		"inside it":                  {sub},
		"inside it under an operand": {dir, sub},
	}

	for name, roots := range cases {
		t.Run(name, func(t *testing.T) {
			t.Parallel()

			db := openTestDB(t)

			st, err := syncScan(t.Context(), db, roots, 1, false,
				map[string]string{excluded: defaultExcludeWhy})
			if err != nil {
				t.Fatal(err)
			}

			if st.added != 1 {
				t.Errorf("added = %d, want %s recorded once", st.added, f)
			}

			recordByPath(t, dbRecords(t, db), f)
		})
	}
}

// TestRunScanTempDirOperand scans a tree in the tests' temporary
// directory, which on Linux lies inside the default exclude /tmp unless
// TMPDIR names another place, with the system's own default excludes and
// then with --no-default-excludes: each scan walks the whole tree and
// reports no default exclude.
func TestRunScanTempDirOperand(t *testing.T) {
	path := testDBPath(t)
	t.Setenv(databaseEnv, path)

	dir := t.TempDir()
	if !underAnyRoot(dir, defaultExcludes(runtime.GOOS)) {
		t.Skip(dir + " is not inside a default exclude")
	}

	for i, flags := range [][]string{nil, {"--no-default-excludes"}} {
		// A file added before each scan shows that the scan walked the
		// tree.
		f := writeFile(t, dir, fmt.Sprintf("sub/%d", i), pattern(1, 10))

		stderr := scanOK(t, append(flags, dir)...)
		if strings.Contains(stderr, defaultExcludeWhy) {
			t.Errorf("scan %q: stderr = %q, want no default exclude",
				flags, stderr)
		}

		db, err := openDB(path, reportParams)
		if err != nil {
			t.Fatal(err)
		}

		recordByPath(t, dbRecords(t, db), f)

		_ = db.Close()
	}
}