package extract

import (
	"errors"
	"os"
	"path/filepath"
	"strings"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

func rootWith(t *testing.T, name string, size int) *os.Root {
	t.Helper()
	dir := t.TempDir()
	require.NoError(t, os.WriteFile(filepath.Join(dir, name), []byte(strings.Repeat("x", size)), 0o644))
	r, err := os.OpenRoot(dir)
	require.NoError(t, err)
	t.Cleanup(func() { _ = r.Close() })
	return r
}

// hyperguild#198: the size check in the watcher is a pre-check on Lstat; a note
// that grows before it is read must still be capped at the read.
func TestTextInMax(t *testing.T) {
	tests := []struct {
		name    string
		size    int
		max     int64
		wantErr bool
	}{
		{"under the cap", 100, 1024, false},
		{"exactly at the cap", 1024, 1024, false},
		{"one byte over", 1025, 1024, true},
		{"far over", 1 << 20, 1024, true},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			r := rootWith(t, "n.md", tt.size)
			got, err := TextInMax(r, "n.md", tt.max)
			if tt.wantErr {
				require.Error(t, err)
				assert.True(t, errors.Is(err, ErrTooLarge))
				return
			}
			require.NoError(t, err)
			assert.Len(t, got, tt.size)
		})
	}
}

func TestTextInMax_TheBinaryTempCopyIsCappedToo(t *testing.T) {
	r := rootWith(t, "n.pdf", 4096)
	_, err := TextInMax(r, "n.pdf", 1024)
	require.Error(t, err)
	assert.True(t, errors.Is(err, ErrTooLarge), "the temp copy of a pdf must not exceed the cap either: %v", err)
}

func TestTextIn_HasADefaultCap(t *testing.T) {
	assert.Positive(t, DefaultMaxBytes)
}