using System.Text.Json;
using System.Text.Json.Serialization;

namespace VoiceCat.Core;

public enum ServerAuthentication { Guest, Account }

public sealed record ServerProfile(Guid Id, string Host, ushort Port, ServerAuthentication Authentication, string? Username, string? Nickname,
    [property: JsonIgnore] string? LegacyKeychainTag = null)
{
    public static ServerProfile Create(string host, ushort port, ServerAuthentication authentication, string? username = null, string? nickname = null, Guid? id = null)
    {
        host = host.Trim(); username = Normalize(username); nickname = Normalize(nickname);
        if (host.Length == 0) throw new ArgumentException("Server host is required.", nameof(host));
        if (port == 0) throw new ArgumentOutOfRangeException(nameof(port));
        if (authentication == ServerAuthentication.Account && username is null) throw new ArgumentException("Username is required for account authentication.", nameof(username));
        return new(id.GetValueOrDefault(Guid.NewGuid()), host, port, authentication,
            authentication == ServerAuthentication.Account ? username : null,
            authentication == ServerAuthentication.Guest ? nickname : null);
    }

    [JsonIgnore]
    public string DisplayName => Authentication == ServerAuthentication.Account
        ? $"{Username}@{Host}:{Port}"
        : $"{Host}:{Port} (Guest{(Nickname is null ? "" : $": {Nickname}")})";

    internal bool IsValid => Id != Guid.Empty && !string.IsNullOrWhiteSpace(Host) && Port != 0 &&
        (Authentication == ServerAuthentication.Guest || !string.IsNullOrWhiteSpace(Username));

    private static string? Normalize(string? value) => string.IsNullOrWhiteSpace(value) ? null : value.Trim();
}

public sealed class ServerProfileStore(string path)
{
    public IReadOnlyList<ServerProfile> Load()
    {
        try
        {
            if (!File.Exists(path)) return [];
            byte[] contents = File.ReadAllBytes(path);
            using JsonDocument document = JsonDocument.Parse(contents);
            if (document.RootElement.ValueKind == JsonValueKind.Array && document.RootElement.EnumerateArray().Any(LooksLegacy))
                return LoadLegacy(document.RootElement);
            return (JsonSerializer.Deserialize(contents, ServerProfileJsonContext.Default.ServerProfileArray) ?? [])
                .Where(profile => profile.IsValid).ToArray();
        }
        catch (Exception exception) when (exception is IOException or UnauthorizedAccessException or JsonException) { return []; }
    }

    public void Save(IEnumerable<ServerProfile> profiles)
    {
        ArgumentNullException.ThrowIfNull(profiles);
        ServerProfile[] valid = profiles.Where(profile => profile is not null && profile.IsValid).ToArray();
        string fullPath = Path.GetFullPath(path);
        Directory.CreateDirectory(Path.GetDirectoryName(fullPath)!);
        PreserveLegacyBackup(fullPath);
        string temporary = fullPath + "." + Guid.NewGuid().ToString("N") + ".tmp";
        try
        {
            File.WriteAllBytes(temporary, JsonSerializer.SerializeToUtf8Bytes(valid, ServerProfileJsonContext.Default.ServerProfileArray));
            File.Move(temporary, fullPath, true);
        }
        finally { if (File.Exists(temporary)) File.Delete(temporary); }
    }

    private static bool LooksLegacy(JsonElement item) => item.ValueKind == JsonValueKind.Object && item.TryGetProperty("authMode", out _);

    private static IReadOnlyList<ServerProfile> LoadLegacy(JsonElement root)
    {
        var profiles = new List<ServerProfile>();
        foreach (JsonElement item in root.EnumerateArray())
        {
            if (!item.TryGetProperty("id", out JsonElement idValue) || !Guid.TryParse(idValue.GetString(), out Guid id) ||
                !item.TryGetProperty("host", out JsonElement hostValue) || !item.TryGetProperty("port", out JsonElement portValue) ||
                !portValue.TryGetUInt16(out ushort port)) continue;
            string? mode = item.TryGetProperty("authMode", out JsonElement modeValue) ? modeValue.GetString() : null;
            string? username = item.TryGetProperty("savedUsername", out JsonElement usernameValue) ? usernameValue.GetString() : null;
            string? nickname = item.TryGetProperty("nickname", out JsonElement nicknameValue) ? nicknameValue.GetString() : null;
            string? keychainTag = item.TryGetProperty("keychainTag", out JsonElement tagValue) ? tagValue.GetString() : null;
            ServerAuthentication authentication = mode == "password" ? ServerAuthentication.Account : ServerAuthentication.Guest;
            try { profiles.Add(ServerProfile.Create(hostValue.GetString() ?? "", port, authentication, username, nickname, id) with { LegacyKeychainTag = keychainTag }); }
            catch (ArgumentException) { }
        }
        return profiles;
    }

    private static void PreserveLegacyBackup(string fullPath)
    {
        if (!File.Exists(fullPath)) return;
        try
        {
            using JsonDocument document = JsonDocument.Parse(File.ReadAllBytes(fullPath));
            if (document.RootElement.ValueKind != JsonValueKind.Array || !document.RootElement.EnumerateArray().Any(LooksLegacy)) return;
            string backup = fullPath + ".swift-backup.json";
            if (!File.Exists(backup)) File.Copy(fullPath, backup);
        }
        catch (JsonException) { }
    }
}

[JsonSourceGenerationOptions(PropertyNamingPolicy = JsonKnownNamingPolicy.CamelCase, WriteIndented = true, UseStringEnumConverter = true)]
[JsonSerializable(typeof(ServerProfile[]))]
internal sealed partial class ServerProfileJsonContext : JsonSerializerContext;