using System.Text.Json;
using System.Text.Json.Serialization;
using Fleet.Rpc;
using Fleet.Server;
using MoShiro.Backend.Application;
using MoShiro.Protocol;

namespace MoShiro.Backend.Gateway;

/// <summary>
/// 期望状态：为每个 Agent 下发完整的 <see cref="TaskSet"/> 快照（有效任务集 + Probe 公钥）。
/// 节点应用之后回传 <c>applied_version</c> 和 <c>rejected[]</c>（<c>unsupported</c>、<c>budget_exceeded</c>、<c>policy_denied</c>），面板上可以看到。
/// </summary>
public sealed class TaskSetStateProvider : IStateProvider
{
    private readonly TaskPlanner _planner;
    private readonly IAgentStore _agents;

    public TaskSetStateProvider(TaskPlanner planner, IAgentStore agents)
    {
        _planner = planner;
        _agents = agents;
    }

    public string Type => TaskSet.StateType;

    public async ValueTask<StateDocument?> GetAsync(NodeRecord node, CancellationToken ct)
    {
        if (node.Id.Value.StartsWith(ProbeId.Prefix, StringComparison.Ordinal))
        {
            return null; // Probe 不运行任务集
        }

        DesiredTaskSet? desired = await _planner.GetDesiredAsync(node.Id, ct);
        return desired is null ? null : new StateDocument(desired.Version, JsonSerializer.SerializeToElement(desired.Document, MoShiroJsonContext.Default.TaskSet));
    }

    public async ValueTask OnAppliedAsync(NodeRecord node, long version, StateSyncResult result, CancellationToken ct)
    {
        string? rejected = result.Rejected.Count == 0 ? null : JsonSerializer.Serialize(result.Rejected, GatewayJson.Default.ListRejectedItem);
        await _agents.SetAppliedTaskStateAsync(node.Id, result.AppliedVersion, rejected, ct);
    }
}

[JsonSerializable(typeof(List<RejectedItem>))]
internal sealed partial class GatewayJson : JsonSerializerContext;