using System.Text.Json;
using MAF1.Agents;

namespace MAF1.Route;

/// <summary>
/// 方案 C 的图：节点 = 主管能调的专家白名单；边 = 允许的交接。
/// 没有边时，名单上的节点可以按任意顺序调用。
/// </summary>
public sealed class RouteGraph
{
    public List<RouteNode> Nodes { get; set; } = [];
    public List<RouteEdge> Edges { get; set; } = [];

    public bool HasEdges => Edges.Count > 0;

    /// <summary>主管第一跳只能到这些节点：无边时整张白名单；有边时取没有入边的入口。</summary>
    public IReadOnlyList<RouteNode> EntryNodes()
    {
        if (!HasEdges)
        {
            return Nodes;
        }

        HashSet<string> targets = new(Edges.Select(e => e.To), StringComparer.OrdinalIgnoreCase);
        List<RouteNode> sources = Nodes.Where(n => !targets.Contains(n.Id)).ToList();
        return sources.Count > 0 ? sources : Nodes;
    }

    public bool HasOutgoing(string nodeId)
        => Edges.Any(e => e.From.Equals(nodeId, StringComparison.OrdinalIgnoreCase));

    public RouteNode? Find(string nodeId)
        => Nodes.FirstOrDefault(n => n.Id.Equals(nodeId, StringComparison.OrdinalIgnoreCase));

    public static JsonSerializerOptions JsonOptions { get; } = new()
    {
        PropertyNameCaseInsensitive = true,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        WriteIndented = true,
    };

    public static RouteGraph LoadFile(string path)
    {
        string json = File.ReadAllText(path);
        RouteGraph graph = JsonSerializer.Deserialize<RouteGraph>(json, JsonOptions)
            ?? throw new InvalidOperationException($"无法解析路由图：{path}");
        graph.Validate();
        return graph;
    }

    public void Validate()
    {
        if (Nodes.Count == 0)
        {
            throw new InvalidOperationException("图里没有任何节点。方案 C 至少要放一个专家到白名单。");
        }

        HashSet<string> ids = new(StringComparer.OrdinalIgnoreCase);
        foreach (RouteNode node in Nodes)
        {
            if (string.IsNullOrWhiteSpace(node.Id))
            {
                throw new InvalidOperationException("节点缺少 id。");
            }

            if (!ids.Add(node.Id))
            {
                throw new InvalidOperationException($"节点 id 重复：{node.Id}");
            }

            if (!SystemNodeTypes.IsKnown(node.Type))
            {
                throw new InvalidOperationException(
                    $"节点 `{node.Id}` 的类型 `{node.Type}` 不是系统专家。当前支持 {SystemNodeTypes.FileCity} / {SystemNodeTypes.Weather}。");
            }
        }

        foreach (RouteEdge edge in Edges)
        {
            if (Find(edge.From) is null)
            {
                throw new InvalidOperationException($"边的 from `{edge.From}` 不在图上。");
            }

            if (Find(edge.To) is null)
            {
                throw new InvalidOperationException($"边的 to `{edge.To}` 不在图上。");
            }
        }
    }
}

public sealed class RouteNode
{
    public string Id { get; set; } = "";
    public string Type { get; set; } = "";
    public string Title { get; set; } = "";
    public Dictionary<string, string> Config { get; set; } = new(StringComparer.OrdinalIgnoreCase);
}

public sealed class RouteEdge
{
    public string From { get; set; } = "";
    public string To { get; set; } = "";
    /// <summary>可选。hasValidCities / !hasValidCities / 空=只要拓扑允许就可以走。</summary>
    public string? When { get; set; }
}