using System.Text.Json;

namespace WxAgent.Core;

public static class ReportingAuthorization
{
    public static ReportingDecision Check(
        ReportingConfig? config,
        string accountId,
        string chatId,
        ReportingChatType chatType,
        ReportingDataType dataType)
    {
        if (config is null)
            return Denied("ReportingConfigInvalid");
        try
        {
            config.NormalizeAndValidate();
        }
        catch (WxAgentException)
        {
            return Denied("ReportingConfigInvalid");
        }

        if (!config.Enabled)
            return Denied("ReportingDisabled");
        if (string.IsNullOrWhiteSpace(accountId) || string.IsNullOrWhiteSpace(chatId))
            return Denied("ChatIdentityUnconfirmed");

        var account = config.FindAccount(accountId);
        if (account is null || !account.Enabled)
            return Denied("AccountNotAuthorized");

        var chat = account.AllowedChats.FirstOrDefault(candidate =>
            candidate.Type == chatType && (candidate.ChatId == "*" || string.Equals(candidate.ChatId, chatId, StringComparison.Ordinal)));
        if (chat is null)
            return Denied("ChatNotAuthorized");
        if (!chat.Enabled)
            return Denied("ChatNotAuthorized");
        if (!chat.IdentityVerified)
            return Denied("ChatIdentityUnconfirmed");
        if (!IsDataTypeAllowed(dataType))
            return Denied("DataTypeNotAuthorized");

        return new ReportingDecision(true, "Authorized", config.ConfigVersion);
    }

    public static bool IsAllowed(
        ReportingConfig? config,
        string accountId,
        string chatId,
        ReportingChatType chatType,
        ReportingDataType dataType) => Check(config, accountId, chatId, chatType, dataType).Allowed;

    public static RemoteMessageEvent? FilterEvent(
        ReportingConfig? config,
        RemoteMessageEvent messageEvent,
        out ReportingDecision decision)
    {
        decision = Check(config, messageEvent.AccountId, messageEvent.ChatId, messageEvent.ChatType, ReportingDataType.Message);
        if (!decision.Allowed)
            return null;

        RemoteAgentOptions.ValidateIdentifier(messageEvent.NodeId, "nodeId", 200);
        RemoteAgentOptions.ValidateIdentifier(messageEvent.EventType, "eventType", 80);
        RemoteAgentOptions.ValidateIdentifier(messageEvent.CorrelationId, "correlationId", 128);
        if (messageEvent.EventSeq <= 0)
            throw new WxAgentException(WxAgentErrorCode.InvalidArgument, "eventSeq must be positive.");
        if (messageEvent.Content is { Length: > RemoteProtocol.MaxEventContentLength })
            throw new WxAgentException(WxAgentErrorCode.InvalidArgument, "Event content is too large.");
        if (messageEvent.Content is null)
            return messageEvent with { AuthorizationVersion = decision.AuthorizationVersion, Authorized = true };
        return messageEvent with { AuthorizationVersion = decision.AuthorizationVersion, Authorized = true };
    }

    public static RemoteTaskResult FilterTaskResult(
        ReportingConfig? config,
        RemoteTaskResult result,
        string? chatId,
        ReportingChatType? chatType,
        out ReportingDecision decision)
    {
        if (result.Content is null || string.IsNullOrWhiteSpace(chatId) || chatType is null)
        {
            decision = new ReportingDecision(true, "ControlMetadataOnly", config?.ConfigVersion ?? 0);
            return result with { Content = null, Message = result.Message is null ? null : "Control metadata only." };
        }

        decision = Check(config, result.AccountId, chatId, chatType.Value, ReportingDataType.TaskResult);
        return decision.Allowed
            ? result
            : result with { Content = null, Message = "Control metadata only." };
    }

    public static RemoteTaskResult FilterTaskResultForChats(
        ReportingConfig? config,
        RemoteTaskResult result,
        IReadOnlyList<RemoteReportingScope> chatScopes,
        out ReportingDecision decision)
    {
        if (result.Content is null)
        {
            decision = new ReportingDecision(true, "ControlMetadataOnly", config?.ConfigVersion ?? 0);
            return result;
        }
        if (chatScopes.Count == 0)
        {
            decision = Denied("ChatNotAuthorized");
            return result with { Content = null, Message = "Control metadata only." };
        }

        var decisions = chatScopes.Select(scope => Check(config, result.AccountId, scope.ChatId, scope.ChatType, ReportingDataType.TaskResult)).ToArray();
        decision = decisions.FirstOrDefault(item => !item.Allowed) ?? new ReportingDecision(true, "Authorized", config?.ConfigVersion ?? 0);
        return decision.Allowed
            ? result
            : result with { Content = null, Message = "Control metadata only." };
    }

    private static bool IsDataTypeAllowed(ReportingDataType dataType) => dataType is ReportingDataType.Message or ReportingDataType.TaskResult;

    private static ReportingDecision Denied(string reason) => new(false, reason, 0);
}

public static class ReportingConfigStore
{
    private static readonly SemaphoreSlim Gate = new(1, 1);

    public static async Task<ReportingConfig> LoadAsync(string path, CancellationToken cancellationToken = default)
    {
        try
        {
            await using var stream = File.OpenRead(path);
            var config = await JsonSerializer.DeserializeAsync<ReportingConfig>(stream, RemoteJson.Options, cancellationToken);
            return (config ?? new ReportingConfig()).NormalizeAndValidate();
        }
        catch (FileNotFoundException)
        {
            return new ReportingConfig();
        }
        catch (DirectoryNotFoundException)
        {
            return new ReportingConfig();
        }
        catch (JsonException)
        {
            return new ReportingConfig();
        }
        catch (WxAgentException)
        {
            return new ReportingConfig();
        }
    }

    public static async Task SaveAsync(string path, ReportingConfig config, CancellationToken cancellationToken = default)
    {
        var normalized = config.NormalizeAndValidate();
        var fullPath = Path.GetFullPath(path);
        var directory = Path.GetDirectoryName(fullPath) ?? AppContext.BaseDirectory;
        Directory.CreateDirectory(directory);
        await Gate.WaitAsync(cancellationToken);
        try
        {
            var temporary = fullPath + ".tmp-" + Guid.NewGuid().ToString("N");
            try
            {
                await using (var stream = new FileStream(temporary, FileMode.CreateNew, FileAccess.Write, FileShare.None, 4096, FileOptions.WriteThrough))
                {
                    await JsonSerializer.SerializeAsync(stream, normalized, RemoteJson.Options, cancellationToken);
                    await stream.FlushAsync(cancellationToken);
                }
                ReplaceFile(temporary, fullPath);
            }
            finally
            {
                if (File.Exists(temporary)) File.Delete(temporary);
            }
        }
        finally
        {
            Gate.Release();
        }
    }

    public static ReportingConfig Update(ReportingConfig current, Func<ReportingConfig, ReportingConfig> change)
    {
        ArgumentNullException.ThrowIfNull(current);
        ArgumentNullException.ThrowIfNull(change);
        var changed = change(current) with { ConfigVersion = checked(current.ConfigVersion + 1) };
        return changed.NormalizeAndValidate();
    }

    private static void ReplaceFile(string temporary, string destination)
    {
        if (OperatingSystem.IsWindows() && File.Exists(destination))
        {
            File.Replace(temporary, destination, null);
            return;
        }
        File.Move(temporary, destination, true);
        if (!OperatingSystem.IsWindows())
        {
            try { File.SetUnixFileMode(destination, UnixFileMode.UserRead | UnixFileMode.UserWrite); }
            catch (PlatformNotSupportedException) { }
        }
    }
}