package configkit

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

// Files disappearing between filesystem operations are not deterministic with
// real concurrent deletion. Exercise the private seam that controls optionality.
func TestRegularFileMissingFailurePhases(t *testing.T) {
	name := filepath.Join(t.TempDir(), "input.yml")
	if err := os.WriteFile(name, []byte("{}"), 0o600); err != nil {
		t.Fatal(err)
	}
	for _, test := range []struct {
		name    string
		stat    func(string) (fs.FileInfo, error)
		open    func(string) (*os.File, error)
		missing bool
	}{
		{"preflight", func(string) (fs.FileInfo, error) { return nil, fs.ErrNotExist }, os.Open, true},
		{"open", os.Stat, func(string) (*os.File, error) { return nil, fs.ErrNotExist }, true},
		{"post-open stat", os.Stat, func(name string) (*os.File, error) {
			file, err := os.Open(name)
			if err == nil {
				err = file.Close()
			}
			return file, err
		}, false},
	} {
		t.Run(test.name, func(t *testing.T) {
			data, failure := readRegularFile(name, test.stat, test.open, 16)
			if data != nil || failure == nil || failure.kind != sourceReadIO || failure.missingTarget != test.missing {
				t.Fatalf("data = %v, failure = %#v", data, failure)
			}
		})
	}
	_, failure := readBoundedSource(missingDuringRead{}, 16)
	if failure == nil || failure.kind != sourceReadIO || failure.missingTarget {
		t.Fatalf("late read failure = %#v", failure)
	}
}

type missingDuringRead struct{}

func (missingDuringRead) Read([]byte) (int, error) { return 0, fs.ErrNotExist }