package util

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

func TestSHA256File(t *testing.T) {
	tests := []struct {
		name     string
		contents []byte
		expected string
	}{
		{
			"an empty file",
			[]byte{},
			"e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
		},
		{
			"a short file",
			[]byte("hello world\n"),
			"a948904f2f0f479b8f8197694b30184b0d2ed1c1cd2a1ec0fb85d299a192a447",
		},
		{
			"binary contents",
			[]byte{0x00, 0x01, 0x02, 0x03},
			"054edec1d0211f624fed0cbca9d4f9400b0e491c43742af2c5b0abebf0c990d8",
		},
		{
			"larger than one read buffer",
			bytes.Repeat([]byte("a"), 100000),
			"6d1cf22d7cc09b085dfc25ee1a1f3ae0265804c607bc2074ad253bcc82fd81ee",
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			path := filepath.Join(t.TempDir(), "file")
			if err := os.WriteFile(path, test.contents, 0644); err != nil {
				t.Fatalf("could not write the test file: %v", err)
			}

			got, err := SHA256File(path)
			if err != nil {
				t.Fatalf("did not expect an error, got %v", err)
			}
			if got != test.expected {
				t.Errorf("expected %q got %q", test.expected, got)
			}
			if got != strings.ToLower(got) {
				t.Errorf("expected lowercase hexadecimal, got %q", got)
			}
		})
	}
}

func TestSHA256FileReportsAMissingFile(t *testing.T) {
	path := filepath.Join(t.TempDir(), "not-there")

	got, err := SHA256File(path)
	if err == nil {
		t.Fatalf("expected an error for a file that does not exist, got %q", got)
	}
	if !os.IsNotExist(err) {
		t.Errorf("expected an error that os.IsNotExist recognises, got %v", err)
	}
}

func TestSHA256FileReportsADirectory(t *testing.T) {
	if _, err := SHA256File(t.TempDir()); err == nil {
		t.Errorf("expected an error for a directory")
	}
}