package config

import (
	"io"
	"io/fs"
	"os"
	"syscall"
)

func readRegular(path string, limit int, tooLarge string, check func(fs.FileMode) string) ([]byte, string) {
	f, err := os.OpenFile(path, os.O_RDONLY|syscall.O_NONBLOCK, 0)
	if err != nil {
		return nil, reasonUnreadable
	}
	defer f.Close()
	info, err := f.Stat()
	if err != nil || !info.Mode().IsRegular() {
		return nil, reasonUnreadable
	}
	if check != nil {
		if reason := check(info.Mode()); reason != "" {
			return nil, reason
		}
	}
	if info.Size() > int64(limit) {
		return nil, tooLarge
	}
	data, err := io.ReadAll(io.LimitReader(f, int64(limit)+1))
	if err != nil {
		return nil, reasonUnreadable
	}
	if len(data) > limit {
		return nil, tooLarge
	}
	return data, ""
}