using Grpc.Core;
using Grpc.AspNetCore.Server;
using Microsoft.Extensions.Options;
using ScrapperAPI.AgentGrpc;
using ScrapperAPI.Interfaces;
using ScrapperAPI.Options;

namespace ScrapperAPI.AgentGrpc;

public sealed class AgentServiceImpl : AgentService.AgentServiceBase
{
    private readonly IAgentRepository _agents;
    private readonly IQueueRepository _queue;
    private readonly IContentRepository _content;
    private readonly WorkerOptions _opts;

    public AgentServiceImpl(
        IAgentRepository agents,
        IQueueRepository queue,
        IContentRepository content,
        IOptions<WorkerOptions> options)
    {
        _agents = agents;
        _queue = queue;
        _content = content;
        _opts = options.Value;
    }

    public override async Task<RegisterAgentResponse> RegisterAgent(RegisterAgentRequest request, ServerCallContext context)
    {
        EnsureAgentsEnabled();

        var (agentId, displayName) = (request.AgentId?.Trim(), request.DisplayName?.Trim());
        if (string.IsNullOrWhiteSpace(agentId))
            throw new RpcException(new Status(StatusCode.InvalidArgument, "agent_id is required"));

        var thumbprint = GetClientCertThumbprint(context);
        await _agents.UpsertAsync(agentId, string.IsNullOrWhiteSpace(displayName) ? null : displayName, thumbprint, context.CancellationToken);

        return new RegisterAgentResponse { Ok = true };
    }

    public override async Task<HeartbeatResponse> Heartbeat(HeartbeatRequest request, ServerCallContext context)
    {
        EnsureAgentsEnabled();
        var agentId = request.AgentId?.Trim();
        if (string.IsNullOrWhiteSpace(agentId))
            throw new RpcException(new Status(StatusCode.InvalidArgument, "agent_id is required"));

        await ValidateAgentAsync(agentId, context);
        await _agents.TouchAsync(agentId, context.CancellationToken);

        return new HeartbeatResponse { Ok = true };
    }

    public override async Task<LeaseWorkResponse> LeaseWork(LeaseWorkRequest request, ServerCallContext context)
    {
        EnsureAgentsEnabled();

        if (_opts.Mode == DistributedMode.LocalOnly)
        {
            return new LeaseWorkResponse
            {
                ServerTimeUtcMs = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()
            };
        }

        var agentId = request.AgentId?.Trim();
        if (string.IsNullOrWhiteSpace(agentId))
            throw new RpcException(new Status(StatusCode.InvalidArgument, "agent_id is required"));

        await ValidateAgentAsync(agentId, context);
        await _agents.TouchAsync(agentId, context.CancellationToken);

        var capacity = Math.Clamp(request.Capacity, 0, 1000);
        if (capacity == 0)
        {
            return new LeaseWorkResponse
            {
                ServerTimeUtcMs = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()
            };
        }

        var workerId = $"agent:{agentId}";
        var leaseFor = TimeSpan.FromSeconds(Math.Max(5, _opts.LeaseSeconds));

        var batch = await _queue.LeaseBatchAsync(request.SessionId, workerId, capacity, leaseFor, context.CancellationToken);

        var resp = new LeaseWorkResponse
        {
            ServerTimeUtcMs = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()
        };

        foreach (var it in batch)
        {
            resp.Items.Add(new WorkItem
            {
                QueueId = it.Id,
                SessionId = it.SessionId,
                Url = it.Url,
                LeaseExpiresUtcMs = DateTimeOffset.UtcNow.Add(leaseFor).ToUnixTimeMilliseconds()
            });
        }

        return resp;
    }

    public override async Task<SubmitResultResponse> SubmitResult(SubmitResultRequest request, ServerCallContext context)
    {
        EnsureAgentsEnabled();

        var agentId = request.AgentId?.Trim();
        if (string.IsNullOrWhiteSpace(agentId))
            throw new RpcException(new Status(StatusCode.InvalidArgument, "agent_id is required"));

        await ValidateAgentAsync(agentId, context);
        await _agents.TouchAsync(agentId, context.CancellationToken);

        if (request.QueueId <= 0)
            throw new RpcException(new Status(StatusCode.InvalidArgument, "queue_id must be > 0"));

        var workerId = $"agent:{agentId}";

        try
        {
            if (request.Success)
            {
                if (request.ContentBytes is { Length: > 0 })
                {
                    var encoding = string.IsNullOrWhiteSpace(request.ContentEncoding) ? "gzip" : request.ContentEncoding;
                    var origLen = request.OriginalLength > 0 ? request.OriginalLength : 0;
                    var compLen = request.CompressedLength > 0 ? request.CompressedLength : request.ContentBytes.Length;

                    await _content.SaveCompressedAsync(
                        request.QueueId,
                        encoding,
                        request.ContentBytes.ToByteArray(),
                        origLen,
                        compLen,
                        context.CancellationToken);
                }
                else
                {
                    await _content.SaveAsync(request.QueueId, request.ContentText ?? string.Empty, context.CancellationToken);
                }

                var ok = await _queue.MarkDoneAsync(request.QueueId, workerId, context.CancellationToken);
                if (!ok)
                    return new SubmitResultResponse { Ok = false, Message = "Lease is not valid for this agent" };

                return new SubmitResultResponse { Ok = true, Message = "Stored" };
            }

            var error = string.IsNullOrWhiteSpace(request.Error) ? "unknown error" : request.Error;
            var failed = await _queue.MarkFailedAsync(request.QueueId, workerId, error, context.CancellationToken);
            if (!failed)
                return new SubmitResultResponse { Ok = false, Message = "Lease is not valid for this agent" };

            return new SubmitResultResponse { Ok = true, Message = "Marked failed" };
        }
        catch (Exception ex)
        {
            throw new RpcException(new Status(StatusCode.Internal, ex.Message));
        }
    }

    private void EnsureAgentsEnabled()
    {
        if (!_opts.Agents.Enabled)
            throw new RpcException(new Status(StatusCode.Unavailable, "Agents are disabled"));
    }

    private async Task ValidateAgentAsync(string agentId, ServerCallContext context)
    {
        var row = await _agents.GetAsync(agentId, context.CancellationToken);
        if (row is null)
            throw new RpcException(new Status(StatusCode.PermissionDenied, "Agent not registered"));

        if (!row.IsEnabled)
            throw new RpcException(new Status(StatusCode.PermissionDenied, "Agent disabled"));

        var thumbprint = GetClientCertThumbprint(context);
        if (!string.Equals(row.CertThumbprint, thumbprint, StringComparison.OrdinalIgnoreCase))
            throw new RpcException(new Status(StatusCode.PermissionDenied, "Client certificate does not match agent"));
    }

    private string GetClientCertThumbprint(ServerCallContext context)
    {
        if (!_opts.Agents.RequireMutualTls)
            return "";

        var http = context.GetHttpContext();
        var cert = http.Connection.ClientCertificate;
        if (cert is null)
            throw new RpcException(new Status(StatusCode.Unauthenticated, "Client certificate is required"));

        return (cert.Thumbprint ?? string.Empty).Replace(" ", string.Empty);
    }
}