using System.Net;
using System.Net.Sockets;
using System.Text.Json;
using System.Text.Json.Nodes;

namespace CommonwealthOnline.Server;

internal sealed class ServerOptions
{
    public string Host { get; set; } = "0.0.0.0";
    public int Port { get; set; } = 7777;
    public string ServerName { get; set; } = "Commonwealth Online Server";
    public string ServerDescription { get; set; } = string.Empty;
    public int MaxPlayers { get; set; } = 16;
    public string LogVerbosity { get; set; } = "info";
    public int AdminPort { get; set; } = 7779;
    public bool EnableGnsTransport { get; set; }
    public string? GnsBridgePath { get; set; }
    public string ConfigPath { get; set; } = Path.GetFullPath("commonwealth-server.json");

    public string BaseDirectory => Path.GetDirectoryName(ConfigPath)!;
    public string BansPath => Path.Combine(BaseDirectory, "bans.json");
    public string AdminTokenPath => Path.Combine(BaseDirectory, ".admin-token");

    public static ServerOptions Load(string path)
    {
        var fullPath = Path.GetFullPath(path);
        if (!File.Exists(fullPath)) throw new FileNotFoundException("Config file not found", fullPath);
        var root = JsonNode.Parse(File.ReadAllBytes(fullPath)) as JsonObject ?? throw new InvalidDataException("Config file must contain a JSON object at root level.");
        var options = new ServerOptions { ConfigPath = fullPath };
        options.Host = JsonHelpers.String(root["host"]) ?? options.Host;
        options.Port = ReadInt(root["port"], options.Port, "port");
        options.ServerName = JsonHelpers.String(root["server_name"] ?? root["serverName"]) ?? options.ServerName;
        options.ServerDescription = JsonHelpers.String(root["server_description"] ?? root["serverDescription"]) ?? options.ServerDescription;
        options.MaxPlayers = ReadInt(root["max_players"] ?? root["maxPlayers"], options.MaxPlayers, "max_players");
        options.LogVerbosity = (JsonHelpers.String(root["log_verbosity"] ?? root["logVerbosity"]) ?? options.LogVerbosity).Trim().ToLowerInvariant();
        options.AdminPort = ReadInt(root["admin_port"] ?? root["adminPort"], options.AdminPort, "admin_port");
        options.EnableGnsTransport = ReadBool(root["enable_gns_transport"] ?? root["enableGnsTransport"], false, "enable_gns_transport");
        var bridge = JsonHelpers.String(root["gns_bridge_path"] ?? root["gnsBridgePath"]);
        options.GnsBridgePath = string.IsNullOrWhiteSpace(bridge) ? null : bridge.Trim();
        return options;
    }

    public static ServerOptions CreateDefault(string path)
    {
        var options = new ServerOptions { ConfigPath = Path.GetFullPath(path) };
        options.Save();
        return options;
    }

    public void Save()
    {
        Directory.CreateDirectory(BaseDirectory);
        var root = new JsonObject
        {
            ["host"] = Host,
            ["port"] = Port,
            ["server_name"] = ServerName,
            ["server_description"] = ServerDescription,
            ["max_players"] = MaxPlayers,
            ["log_verbosity"] = LogVerbosity,
            ["admin_port"] = AdminPort,
            ["enable_gns_transport"] = EnableGnsTransport,
            ["gns_bridge_path"] = GnsBridgePath
        };
        using var stream = File.Create(ConfigPath);
        JsonSerializer.Serialize(stream, root, new JsonSerializerOptions { WriteIndented = true });
        stream.WriteByte((byte)'\n');
    }

    public IReadOnlyList<string> Validate()
    {
        var errors = new List<string>();
        if (string.IsNullOrWhiteSpace(Host))
            errors.Add("host cannot be empty");
        else if (!TryResolveIpv4(Host, out _))
            errors.Add($"host '{Host}' is not a valid IPv4 address or resolvable hostname");
        else if (EnableGnsTransport && (!IPAddress.TryParse(Host.Trim(), out var gnsAddress) || gnsAddress.AddressFamily != AddressFamily.InterNetwork))
            errors.Add("enable_gns_transport requires host to be an explicit IPv4 bind address such as 0.0.0.0 or 127.0.0.1");

        if (Port is < 1 or > 65535) errors.Add($"port must be 1-65535, got {Port}");
        if (AdminPort is < 1 or > 65535) errors.Add($"admin_port must be 1-65535, got {AdminPort}");
        else if (AdminPort == Port) errors.Add("admin_port must differ from the game port");
        if (string.IsNullOrEmpty(ServerName)) errors.Add("server_name cannot be empty");
        else if (ServerName.Length > 64) errors.Add($"server_name must be <= 64 characters, got {ServerName.Length}");
        if (ServerDescription.Length > 256) errors.Add($"server_description must be <= 256 characters, got {ServerDescription.Length}");
        if (MaxPlayers < 1) errors.Add($"max_players must be >= 1, got {MaxPlayers}");
        else if (MaxPlayers > 256) errors.Add($"max_players must be <= 256, got {MaxPlayers}");
        if (LogVerbosity is not ("debug" or "info" or "warning" or "error")) errors.Add($"log_verbosity must be debug/info/warning/error, got {LogVerbosity}");
        return errors;
    }

    public static bool TryResolveIpv4(string host, out IPAddress address)
    {
        if (IPAddress.TryParse(host.Trim(), out var parsed) && parsed.AddressFamily == AddressFamily.InterNetwork)
        {
            address = parsed;
            return true;
        }
        try
        {
            address = Dns.GetHostAddresses(host.Trim()).First(x => x.AddressFamily == AddressFamily.InterNetwork);
            return true;
        }
        catch
        {
            address = IPAddress.None;
            return false;
        }
    }

    private static int ReadInt(JsonNode? node, int defaultValue, string field)
    {
        if (node is null) return defaultValue;
        if (node is JsonValue value && value.TryGetValue<int>(out var number)) return number;
        if (node is JsonValue textValue && textValue.TryGetValue<string>(out var text) && int.TryParse(text, out number)) return number;
        throw new InvalidDataException($"Invalid numeric config field: {field}");
    }

    private static bool ReadBool(JsonNode? node, bool defaultValue, string field)
    {
        if (node is null) return defaultValue;
        if (node is JsonValue value && value.TryGetValue<bool>(out var boolean)) return boolean;
        if (node is JsonValue intValue && intValue.TryGetValue<int>(out var number) && number is 0 or 1) return number == 1;
        if (node is JsonValue textValue && textValue.TryGetValue<string>(out var text))
        {
            switch (text.Trim().ToLowerInvariant())
            {
                case "1": case "true": case "yes": case "on": return true;
                case "0": case "false": case "no": case "off": case "": return false;
            }
        }
        throw new InvalidDataException($"{field} must be a boolean or one of true/false, yes/no, on/off, 1/0");
    }
}