using System.IO;

namespace JD.Guinness.WPF.Module.Extension
{
    public static class StringExtension
    {
        public static string ToRelativePath(this string filePath, string basePath)
        {
            if (string.IsNullOrEmpty(filePath))
            {
                return null;
            }

            string result = string.Empty;
            int offset;

            if (filePath.StartsWith(basePath))
            {
                return filePath.Substring(basePath.Length + 1);
            }

            string[] baseDirs = basePath.Split(new char[] { ':', '\\', '/' });
            string[] fileDirs = filePath.Split(new char[] { ':', '\\', '/' });

            if (baseDirs.Length == 0 || fileDirs.Length == 0 || baseDirs[0] != fileDirs[0])
            {
                return filePath;
            }

            for (offset = 1; offset < baseDirs.Length; offset++)
            {
                if (baseDirs[offset] != fileDirs[offset])
                    break;
            }

            for (int i = 0; i < (baseDirs.Length - offset); i++)
            {
                result += "..\\";
            }

            for (int i = offset; i < fileDirs.Length - 1; i++)
            {
                result += fileDirs[i] + "\\";
            }

            result += fileDirs[fileDirs.Length - 1];

            return result;
        }

        public static string FromDifferentDirectory(this string filePath, string directoryPath)
        {
            if (!string.IsNullOrEmpty(filePath))
            {
                string newFilePath = Path.Combine(directoryPath, Path.GetFileName(filePath));
                if (File.Exists(newFilePath))
                {
                    return newFilePath;
                }
            }

            return filePath;
        }
    }
}