package main

import (
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"
)

// spinnerIdle comfortably outlasts the 100ms interval at which the
// progressbar library redraws a spinner from its own goroutine.
const spinnerIdle = 500 * time.Millisecond

// captureStderr points os.Stderr at a file for the rest of the test and
// returns a function reading back everything written to it.
func captureStderr(t *testing.T) func() string {
	t.Helper()

	path := filepath.Join(t.TempDir(), "stderr")

	f, err := os.Create(path) //nolint:gosec // test-controlled path
	if err != nil {
		t.Fatal(err)
	}

	saved := os.Stderr
	os.Stderr = f

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

		_ = f.Close()
	})

	return func() string {
		b, err := os.ReadFile(path) //nolint:gosec // test-controlled path
		if err != nil {
			t.Fatal(err)
		}

		return string(b)
	}
}

//nolint:paralleltest // replaces the process-wide os.Stderr
func TestStderrIsTTYFalseForNonTerminals(t *testing.T) {
	r, pipe, err := os.Pipe()
	if err != nil {
		t.Fatal(err)
	}

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

	devNull, err := os.OpenFile(os.DevNull, os.O_WRONLY, 0)
	if err != nil {
		t.Fatal(err)
	}

	saved := os.Stderr

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

		for _, f := range []*os.File{r, pipe, regular, devNull} {
			_ = f.Close()
		}
	})

	cases := map[string]*os.File{
		"a pipe":         pipe,
		"a regular file": regular,
		os.DevNull:       devNull,
	}

	for name, f := range cases {
		os.Stderr = f

		if stderrIsTTY() {
			t.Errorf("stderrIsTTY() = true with stderr on %s", name)
		}
	}
}

// TestNewProgressPrintsBeforeFirstItem checks that each pass shows its
// zero state the moment it starts when stderr is not a terminal, and
// that the next line still waits for plainInterval.
//
//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
func TestNewProgressPrintsBeforeFirstItem(t *testing.T) {
	stderr := captureStderr(t)

	newProgress("walk", -1).increment()
	newProgress("hash", 10).increment()

	want := "walk: 0 files, elapsed 0s\n" +
		"hash: [0/10] 0% 0 files/s elapsed 0s eta ?\n"
	if got := stderr(); got != want {
		t.Errorf("stderr = %q, want %q", got, want)
	}
}

// newWalkSpinner returns the walk pass's terminal display, writing to
// os.Stderr whether or not it is a terminal, and stops the library's
// redraws when the test ends.
func newWalkSpinner(t *testing.T) *progress {
	t.Helper()

	p := &progress{
		label: "walk", total: -1, start: time.Now(),
		bar: newBar("walk", -1),
	}
	t.Cleanup(p.finish)

	return p
}

// TestProgressWarningsOnOwnLines drives the terminal display of the walk
// pass through a run of warnings with no items between them, as when the
// walk meets many unreadable paths, for several of the spinner's
// redraws: every warning must land on a line of its own, never inside a
// redraw.
//
//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
func TestProgressWarningsOnOwnLines(t *testing.T) {
	stderr := captureStderr(t)
	p := newWalkSpinner(t)

	// No pause between warnings: one written straight to stderr is
	// garbled only if a redraw lands while it is being written.
	issued := 0
	for start := time.Now(); time.Since(start) < spinnerIdle; issued++ {
		p.warnf("warning")
	}

	// The spinner prints the warnings at its next redraw.
	time.Sleep(spinnerIdle)

	// A terminal shows each line as the text after its last carriage
	// return.
	shown := 0

	for line := range strings.SplitSeq(stderr(), "\n") {
		if !strings.Contains(line, "warning") {
			continue
		}

		shown++

		if text := line[strings.LastIndex(line, "\r")+1:]; text != "warning" {
			t.Errorf("terminal shows %q, want %q", text, "warning")
		}
	}

	if shown != issued {
		t.Errorf("%d warning lines, want %d", shown, issued)
	}
}

// TestSpinnerShowsCountAfterBurst checks that once a burst of items
// faster than the redraw limit is over, the walk display shows every
// item completed while it waits for the next one.
//
//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
func TestSpinnerShowsCountAfterBurst(t *testing.T) {
	stderr := captureStderr(t)
	p := newWalkSpinner(t)

	for range 50 {
		p.increment()
	}

	time.Sleep(spinnerIdle)

	// A terminal shows the last frame drawn. The library starts each
	// frame with a carriage return and erases the previous one with
	// spaces first.
	var shown string

	for frame := range strings.SplitSeq(stderr(), "\r") {
		if strings.TrimSpace(frame) != "" {
			shown = frame
		}
	}

	if !strings.Contains(shown, "(50/-,") {
		t.Errorf("terminal shows %q, want a count of 50", shown)
	}
}