using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MinecraftClient.Protocol.Keys
{
    static class KeyUtils
    {
        private static string certificates = "https://api.minecraftservices.com/player/certificates";

        public static PlayerKeyPair? GetNewProfileKeys(string accessToken)
        {
            ProxiedWebRequest.Response? response = null;
            try
            {
                var request = new ProxiedWebRequest(certificates)
                {
                    Accept = "application/json"
                };
                request.Headers.Add("Authorization", string.Format("Bearer {0}", accessToken));

                response = request.Post("application/json", "");

                if (Settings.DebugMessages)
                {
                    ConsoleIO.WriteLine(response.Body.ToString());
                }

                string jsonString = response.Body;
                Json.JSONData json = Json.ParseJson(jsonString);

                PublicKey publicKey = new(pemKey: json.Properties["keyPair"].Properties["publicKey"].StringValue,
                    sig: json.Properties["publicKeySignature"].StringValue,
                    sigV2: json.Properties["publicKeySignatureV2"].StringValue);

                PrivateKey privateKey = new(pemKey: json.Properties["keyPair"].Properties["privateKey"].StringValue);

                return new PlayerKeyPair(publicKey, privateKey,
                    expiresAt: json.Properties["expiresAt"].StringValue,
                    refreshedAfter: json.Properties["refreshedAfter"].StringValue);
            }
            catch (Exception e)
            {
                int code = (response == null) ? 0 : response.StatusCode;
                ConsoleIO.WriteLineFormatted("§cFetch profile key failed: HttpCode = " + code + ", Error = " + e.Message);
                if (Settings.DebugMessages)
                {
                    ConsoleIO.WriteLineFormatted("§c" + e.StackTrace);
                }
                return null;
            }
        }

        public static byte[] DecodePemKey(String key, String prefix, String suffix)
        {
            int i = key.IndexOf(prefix);
            if (i != -1)
            {
                i += prefix.Length;
                int j = key.IndexOf(suffix, i);
                key = key[i..j];
            }
            key = key.Replace("\r", String.Empty);
            key = key.Replace("\n", String.Empty);
            return Convert.FromBase64String(key);
        }

        public static byte[] GetSignatureData(string message, string uuid, DateTimeOffset timestamp, ref byte[] salt)
        {
            List<byte> data = new();

            data.AddRange(salt);

            byte[] UUIDLeastSignificantBits = BitConverter.GetBytes(Convert.ToInt64(uuid[..16], 16));
            Array.Reverse(UUIDLeastSignificantBits);
            data.AddRange(UUIDLeastSignificantBits);

            byte[] UUIDMostSignificantBits = BitConverter.GetBytes(Convert.ToInt64(uuid.Substring(16, 16), 16));
            Array.Reverse(UUIDMostSignificantBits);
            data.AddRange(UUIDMostSignificantBits);

            byte[] timestampByte = BitConverter.GetBytes(timestamp.ToUnixTimeSeconds());
            Array.Reverse(timestampByte);
            data.AddRange(timestampByte);

            data.AddRange(Encoding.UTF8.GetBytes(message));

            return data.ToArray();
        }

        // https://github.com/mono/mono/blob/master/mcs/class/System.Json/System.Json/JsonValue.cs
        public static string EscapeString(string src)
        {
            StringBuilder sb = new();

            int start = 0;
            for (int i = 0; i < src.Length; i++)
            {
                char c = src[i];
                bool needEscape = c < 32 || c == '"' || c == '\\';
                // Broken lead surrogate
                needEscape = needEscape || (c >= '\uD800' && c <= '\uDBFF' &&
                    (i == src.Length - 1 || src[i + 1] < '\uDC00' || src[i + 1] > '\uDFFF'));
                // Broken tail surrogate
                needEscape = needEscape || (c >= '\uDC00' && c <= '\uDFFF' &&
                    (i == 0 || src[i - 1] < '\uD800' || src[i - 1] > '\uDBFF'));
                // To produce valid JavaScript
                needEscape = needEscape || c == '\u2028' || c == '\u2029';

                if (needEscape)
                {
                    sb.Append(src, start, i - start);
                    switch (src[i])
                    {
                        case '\b': sb.Append("\\b"); break;
                        case '\f': sb.Append("\\f"); break;
                        case '\n': sb.Append("\\n"); break;
                        case '\r': sb.Append("\\r"); break;
                        case '\t': sb.Append("\\t"); break;
                        case '\"': sb.Append("\\\""); break;
                        case '\\': sb.Append("\\\\"); break;
                        default:
                            sb.Append("\\u");
                            sb.Append(((int)src[i]).ToString("x04"));
                            break;
                    }
                    start = i + 1;
                }

            }
            sb.Append(src, start, src.Length - start);
            return sb.ToString();
        }
    }
}