package main

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

// TestIsCharDeviceRejectsNonConsoles pins down the half of the check that can
// be tested without a terminal: a pipe, a regular file and a closed handle
// must all read as "not a console", because each of them means something other
// than a person waiting at a keyboard.
//
// Getting this wrong in this direction is the dangerous one: it would drop a
// script or a build pipeline into an interactive prompt and hang it forever.
func TestIsCharDeviceRejectsNonConsoles(t *testing.T) {
	r, w, err := os.Pipe()
	if err != nil {
		t.Fatalf("pipe: %v", err)
	}
	defer r.Close()
	defer w.Close()

	tmp, err := os.CreateTemp(t.TempDir(), "out")
	if err != nil {
		t.Fatalf("temp file: %v", err)
	}
	defer tmp.Close()

	devNull, err := os.Open(os.DevNull)
	if err != nil {
		t.Fatalf("open %s: %v", os.DevNull, err)
	}
	defer devNull.Close()

	for _, tc := range []struct {
		name string
		file *os.File
		want bool
	}{
		{"read end of a pipe", r, false},
		{"write end of a pipe", w, false},
		{"regular file", tmp, false},
		// os.DevNull IS a character device on Unix, so this case documents a
		// real limitation rather than asserting a value that differs by
		// platform: `prog < /dev/null` on Unix looks interactive on stdin.
		// It is harmless, because stdout must ALSO be a console, and a script
		// redirecting stdin almost always redirects stdout too.
	} {
		if got := isCharDevice(tc.file); got != tc.want {
			t.Errorf("isCharDevice(%s) = %v, want %v", tc.name, got, tc.want)
		}
	}
	_ = devNull
}

// TestIsCharDeviceHandlesAClosedFile makes sure a handle we cannot stat is
// treated as "not a console" rather than panicking or defaulting to true.
func TestIsCharDeviceHandlesAClosedFile(t *testing.T) {
	f, err := os.CreateTemp(t.TempDir(), "closed")
	if err != nil {
		t.Fatalf("temp file: %v", err)
	}
	f.Close()
	if isCharDevice(f) {
		t.Error("isCharDevice(closed file) = true, want false")
	}
}

// TestInteractiveConsoleNeedsBothEnds asserts the AND: one console end is not
// enough. Under `go test` stdout is not a terminal, so this must be false.
func TestInteractiveConsoleNeedsBothEnds(t *testing.T) {
	if interactiveConsole() {
		t.Error("interactiveConsole() = true under `go test`, where output is captured; " +
			"the guided prompt would hang any non-interactive run")
	}
}

// TestSuggestedImageIsScannableOrEmpty guards the one-keypress default.
// SectorPilot asks for a file to read rather than a folder, so the equivalent
// promise is that whatever it offers is a file this program can actually open
// and scan — or nothing at all. Anything else greets the reader with an error
// on their very first interaction.
func TestSuggestedImageIsScannableOrEmpty(t *testing.T) {
	got := suggestedImage()
	if got == "" {
		return // nothing to offer; the prompt just asks for a location
	}
	tgt, err := openTarget(got)
	if err != nil {
		t.Fatalf("suggestedImage() = %q, which sectorpilot cannot scan: %v", got, err)
	}
	tgt.Close()
}

// TestFirstImageInSkipsUnscannableFiles keeps the default honest: an empty
// file and a directory both carry an image-looking name easily enough, and
// either one would fail the moment the reader pressed Enter.
func TestFirstImageInSkipsUnscannableFiles(t *testing.T) {
	dir := t.TempDir()
	if err := os.WriteFile(filepath.Join(dir, "a-empty.img"), nil, 0o644); err != nil {
		t.Fatalf("write: %v", err)
	}
	if err := os.Mkdir(filepath.Join(dir, "b-folder.iso"), 0o755); err != nil {
		t.Fatalf("mkdir: %v", err)
	}
	if err := os.WriteFile(filepath.Join(dir, "c-notes.txt"), []byte("hello"), 0o644); err != nil {
		t.Fatalf("write: %v", err)
	}
	if got := firstImageIn(dir); got != "" {
		t.Fatalf("firstImageIn(dir with nothing scannable) = %q, want \"\"", got)
	}

	good := filepath.Join(dir, "d-real.img")
	if err := os.WriteFile(good, make([]byte, 4096), 0o644); err != nil {
		t.Fatalf("write: %v", err)
	}
	if got := firstImageIn(dir); got != good {
		t.Errorf("firstImageIn(dir) = %q, want %q", got, good)
	}
}