package main

import (
	"bytes"
	"context"
	"errors"
	"io"
	"io/fs"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"testing"
)

// usageMarker is the first line of cobra's usage text, which a usage
// error prints and a runtime failure must not.
const usageMarker = "Usage:"

// walSuffixes are the SQLite sidecar files a WAL-mode database keeps
// while it is open. A clean close checkpoints the WAL and removes
// both; finding either afterwards means the database was never closed.
//
//nolint:gochecknoglobals // a constant list, immutable by convention
var walSuffixes = []string{"-wal", "-shm"}

// assertNoSidecars fails when a WAL sidecar is still present beside the
// database at path.
func assertNoSidecars(t *testing.T, path string) {
	t.Helper()

	for _, suffix := range walSuffixes {
		_, err := os.Stat(path + suffix)
		if err == nil {
			t.Errorf("%s%s still present: the database was not closed",
				path, suffix)

			continue
		}

		if !errors.Is(err, fs.ErrNotExist) {
			t.Fatal(err)
		}
	}
}

// captureStdout redirects os.Stdout to a file for the rest of the test
// and returns a function reading back everything written to it. Only
// machine-readable data belongs on stdout (README design goal 4), so
// the tests assert on it directly.
func captureStdout(t *testing.T) func() string {
	t.Helper()

	f, err := os.Create(filepath.Join(t.TempDir(), "stdout"))
	if err != nil {
		t.Fatal(err)
	}

	saved := os.Stdout
	os.Stdout = f

	t.Cleanup(func() {
		os.Stdout = saved

		_ = f.Close()
	})

	return func() string {
		// Read what has been written without disturbing the write
		// offset, so the capture can be inspected more than once.
		size, err := f.Seek(0, io.SeekCurrent)
		if err != nil {
			t.Fatal(err)
		}

		if size == 0 {
			return ""
		}

		b := make([]byte, size)

		_, err = f.ReadAt(b, 0)
		if err != nil {
			t.Fatal(err)
		}

		return string(b)
	}
}

// brokenDatabase writes a database that opens cleanly and passes the
// schema-version check but has no files table, so the first query
// fails with the database already open: a fatal error on a path that
// owns an open database.
func brokenDatabase(t *testing.T) string {
	t.Helper()

	path := testDBPath(t)

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

	_, err = db.ExecContext(context.Background(),
		"PRAGMA user_version = "+strconv.Itoa(schemaVersion))
	if err != nil {
		t.Fatal(err)
	}

	err = db.Close()
	if err != nil {
		t.Fatal(err)
	}

	return path
}

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

	// The premise of the fatal-path tests below: an open database has
	// a -wal sidecar, so its absence afterwards is evidence that the
	// database was closed and its WAL checkpointed.
	path := testDBPath(t)

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

	_, err = os.Stat(path + "-wal")
	if err != nil {
		t.Fatalf("no -wal beside an open database: %v", err)
	}

	err = db.Close()
	if err != nil {
		t.Fatal(err)
	}

	assertNoSidecars(t, path)
}

func TestRunFatalAfterOpenClosesDatabase(t *testing.T) {
	// Every subcommand that owns an open database must close it when
	// it fails: no os.Exit between the open and the return.
	cases := map[string][]string{
		cmdScan:   {cmdScan},
		cmdReport: {cmdReport},
		cmdTrees:  {cmdTrees},
	}

	for name, args := range cases {
		t.Run(name, func(t *testing.T) {
			path := brokenDatabase(t)
			t.Setenv(databaseEnv, path)

			if name == cmdScan {
				args = append(args, t.TempDir())
			}

			var stderr bytes.Buffer

			stdout := captureStdout(t)

			code := run(args, &stderr)
			if code != exitFatal {
				t.Errorf("run(%v) = %d, want %d", args, code, exitFatal)
			}

			assertNoSidecars(t, path)
			assertFatalOutput(t, stderr.String(), stdout())

			// Proof that the failure happened after the open: only a
			// query against the opened database can report this.
			if !strings.Contains(stderr.String(), "no such table: files") {
				t.Errorf("stderr = %q, want the failure to come from a "+
					"query on the open database", stderr.String())
			}
		})
	}
}

func TestRunMissingOperandIsFatalNotUsage(t *testing.T) {
	// README §Error handling: a PATH operand that does not exist is a
	// fatal error (1), not a usage error (2) — and a runtime failure
	// must not dump the usage text.
	t.Setenv(databaseEnv, testDBPath(t))

	var stderr bytes.Buffer

	stdout := captureStdout(t)

	missing := filepath.Join(t.TempDir(), "nope")

	code := run([]string{cmdScan, missing}, &stderr)
	if code != exitFatal {
		t.Errorf("run(scan %s) = %d, want %d", missing, code, exitFatal)
	}

	assertFatalOutput(t, stderr.String(), stdout())
}

// assertFatalOutput checks that a fatal error was reported the way
// README §Error handling and design goal 4 require: the message on
// stderr, prefixed with the program name, no usage text, and nothing
// at all on stdout.
func assertFatalOutput(t *testing.T, stderr, stdout string) {
	t.Helper()

	if !strings.Contains(stderr, "sfdupes: ") {
		t.Errorf("stderr = %q, want a \"sfdupes: \" error report", stderr)
	}

	if strings.Contains(stderr, usageMarker) {
		t.Errorf("stderr = %q, want no usage text for a runtime failure",
			stderr)
	}

	if stdout != "" {
		t.Errorf("stdout = %q, want nothing (data only)", stdout)
	}
}

func TestRunUsageErrors(t *testing.T) {
	// Usage errors keep exiting 2 with cobra's own report on stderr.
	cases := map[string]struct {
		args []string
		want string
	}{
		"no subcommand":      {[]string{}, usageMarker},
		"scan without paths": {[]string{cmdScan}, usageMarker},
		"report with args":   {[]string{cmdReport, "x"}, usageMarker},
		"trees with args":    {[]string{cmdTrees, "x"}, usageMarker},
		"unknown flag":       {[]string{cmdScan, "--nope", "/"}, usageMarker},
		"unknown subcommand": {[]string{"nope"}, "unknown command"},
	}

	for name, tc := range cases {
		t.Run(name, func(t *testing.T) {
			// No usage error may reach the database, so point it at a
			// path that does not exist.
			t.Setenv(databaseEnv, testDBPath(t))

			var stderr bytes.Buffer

			stdout := captureStdout(t)

			code := run(tc.args, &stderr)
			if code != exitUsage {
				t.Errorf("run(%v) = %d, want %d", tc.args, code, exitUsage)
			}

			if !strings.Contains(stderr.String(), tc.want) {
				t.Errorf("stderr = %q, want %q", stderr.String(), tc.want)
			}

			if got := stdout(); got != "" {
				t.Errorf("stdout = %q, want nothing (data only)", got)
			}
		})
	}
}

// TestRunHelpAndVersionSucceed checks that the two informational flags
// exit 0 and keep their human-facing output on stderr.
//
//nolint:paralleltest // captureStdout replaces the process-wide os.Stdout
func TestRunHelpAndVersionSucceed(t *testing.T) {
	assertHumanOutput(t, "--help")
	assertHumanOutput(t, "--version")
}

// assertHumanOutput runs sfdupes with one informational flag and checks
// that it succeeds with its output on stderr and stdout untouched
// (README design goal 4).
func assertHumanOutput(t *testing.T, arg string) {
	t.Helper()

	var stderr bytes.Buffer

	stdout := captureStdout(t)

	code := run([]string{arg}, &stderr)
	if code != exitOK {
		t.Errorf("run(%s) = %d, want %d", arg, code, exitOK)
	}

	if stderr.Len() == 0 {
		t.Errorf("run(%s) wrote nothing to stderr", arg)
	}

	if got := stdout(); got != "" {
		t.Errorf("stdout = %q, want nothing (data only)", got)
	}
}

// scanFixture builds a small tree holding one duplicate pair and one
// unreadable file and scans it into the database the caller has
// pointed SFDUPES_DATABASE at. The unreadable file makes the scan warn
// and skip, which README §Error handling still calls a successful run.
// It returns the duplicate pair's paths.
func scanFixture(t *testing.T) []string {
	t.Helper()

	dir := t.TempDir()

	dupes := []string{
		writeFile(t, dir, "one/a.bin", pattern(1, 300)),
		writeFile(t, dir, "two/a.bin", pattern(1, 300)),
	}

	// Same size as the pair, so the scan queues it for hashing and the
	// read fails.
	unreadable := writeFile(t, dir, "unreadable.bin", pattern(2, 300))

	err := os.Chmod(unreadable, 0)
	if err != nil {
		t.Fatal(err)
	}

	var stderr bytes.Buffer

	stdout := captureStdout(t)

	code := run([]string{cmdScan, dir}, &stderr)
	if code != exitOK {
		t.Fatalf("run(scan) = %d, want %d; stderr: %s",
			code, exitOK, stderr.String())
	}

	if got := stdout(); got != "" {
		t.Errorf("scan stdout = %q, want nothing (data only)", got)
	}

	return dupes
}

func TestRunScanSucceedsDespiteWarnings(t *testing.T) {
	path := testDBPath(t)
	t.Setenv(databaseEnv, path)

	scanFixture(t)
	assertNoSidecars(t, path)
}

func TestRunReportSucceeds(t *testing.T) {
	path := testDBPath(t)
	t.Setenv(databaseEnv, path)

	dupes := scanFixture(t)

	var stderr bytes.Buffer

	stdout := captureStdout(t)

	code := run([]string{cmdReport}, &stderr)
	if code != exitOK {
		t.Fatalf("run(report) = %d, want %d; stderr: %s",
			code, exitOK, stderr.String())
	}

	want := "first\tdupe\tsize\n" + dupes[0] + "\t" + dupes[1] + "\t300\n"
	if got := stdout(); got != want {
		t.Errorf("stdout = %q, want %q", got, want)
	}

	assertNoSidecars(t, path)
}

func TestRunTreesSucceeds(t *testing.T) {
	path := testDBPath(t)
	t.Setenv(databaseEnv, path)

	dupes := scanFixture(t)

	var stderr bytes.Buffer

	stdout := captureStdout(t)

	code := run([]string{cmdTrees}, &stderr)
	if code != exitOK {
		t.Fatalf("run(trees) = %d, want %d; stderr: %s",
			code, exitOK, stderr.String())
	}

	// The two directories holding the duplicate pair are duplicate
	// trees of each other.
	want := "first\tdupe\tfiles\tsize\n" +
		filepath.Dir(dupes[0]) + "\t" + filepath.Dir(dupes[1]) + "\t1\t300\n"
	if got := stdout(); got != want {
		t.Errorf("stdout = %q, want %q", got, want)
	}

	assertNoSidecars(t, path)
}