using System.IO;

namespace SabreTools.Core.Tools
{
    /// <summary>
    /// Static utility functions used throughout the library
    /// </summary>
    public static class Utilities
    {
        /// <summary>
        /// Get a proper romba sub path
        /// </summary>
        /// <param name="hash">SHA-1 hash to get the path for</param>
        /// <param name="depth">Positive value representing the depth of the depot</param>
        /// <returns>Subfolder path for the given hash</returns>
        public static string? GetDepotPath(string? hash, int depth)
        {
            // If the hash is null or empty, then we return null
            if (string.IsNullOrEmpty(hash))
                return null;

            // If the hash isn't the right size, then we return null
            if (hash.Length != Constants.SHA1Length)
                return null;

            // Cap the depth between 0 and 20, for now
            if (depth < 0)
                depth = 0;
            else if (depth > Constants.SHA1ZeroBytes.Length)
                depth = Constants.SHA1ZeroBytes.Length;

            // Loop through and generate the subdirectory
            string path = string.Empty;
            for (int i = 0; i < depth; i++)
            {
                path += hash.Substring(i * 2, 2) + Path.DirectorySeparatorChar;
            }

            // Now append the filename
            path += $"{hash}.gz";
            return path;
        }

        /// <summary>
        /// Get if the given path has a valid DAT extension
        /// </summary>
        /// <param name="path">Path to check</param>
        /// <returns>True if the extension is valid, false otherwise</returns>
        public static bool HasValidDatExtension(string? path)
        {
            // If the path is null or empty, then we return false
            if (string.IsNullOrEmpty(path))
                return false;

            // Get the extension from the path, if possible
            string ext = Path.GetExtension(path).TrimStart('.').ToLowerInvariant();

            // Check against the list of known DAT extensions
            return ext switch
            {
                "csv" => true,
                "dat" => true,
                "json" => true,
                "md5" => true,
                "sfv" => true,
                "sha1" => true,
                "sha256" => true,
                "sha384" => true,
                "sha512" => true,
                "spamsum" => true,
                "ssv" => true,
                "tsv" => true,
                "txt" => true,
                "xml" => true,
                _ => false,
            };
        }

        //// <summary>
        /// Returns if the first byte array starts with the second array
        /// </summary>
        /// <param name="arr1">First byte array to compare</param>
        /// <param name="arr2">Second byte array to compare</param>
        /// <param name="exact">True if the input arrays should match exactly, false otherwise (default)</param>
        /// <returns>True if the first byte array starts with the second, false otherwise</returns>
        public static bool StartsWith(this byte[] arr1, byte[] arr2, bool exact = false)
        {
            // If we have any invalid inputs, we return false
            if (arr1 == null || arr2 == null
                || arr1.Length == 0 || arr2.Length == 0
                || arr2.Length > arr1.Length
                || (exact && arr1.Length != arr2.Length))
            {
                return false;
            }

            // Otherwise, loop through and see
            for (int i = 0; i < arr2.Length; i++)
            {
                if (arr1[i] != arr2[i])
                    return false;
            }

            return true;
        }
    }
}