using System.Net;
using SnmpSharpNet;

namespace ETTerms.PduCore;

/// <summary>
/// PDU controller for iPoMan II/III models via SNMP。
/// GUI 與 ETTerms.PduMcp 共用的唯一實作（v0.4.0 起取代兩份複製的版本）。
/// 診斷輸出走建構子注入的 log 委派：GUI 給 AppLogger、MCP server 給 stderr
/// （stdio MCP 的 stdout 專供 JSON-RPC，不可污染）。
/// SNMP 走 UDP、非獨佔，多個行程可同時對同一台 PDU 操作。
/// </summary>
public sealed class PduController : IDisposable
{
    private readonly string _ip;
    private readonly Action<string>? _logInfo;
    private readonly Action<string>? _logWarn;

    private const string Community = "private";
    private const int SnmpPort = 161;
    private const int Timeout = 3000;

    public string Ip => _ip;

    public PduController(string ip, Action<string>? logInfo = null, Action<string>? logWarn = null)
    {
        _ip = ip;
        _logInfo = logInfo;
        _logWarn = logWarn;
    }

    /// <summary>讀 PDU 型號/名稱 OID；非空且含 "PDU" 代表連得上。</summary>
    public string? GetModelName() => SnmpGet(".1.3.6.1.4.1.2468.1.4.2.1.1.4");

    public bool CheckConnection()
    {
        var name = GetModelName();
        _logInfo?.Invoke($"[PDU] CheckConnection {_ip}: name='{name ?? "<null>"}'");
        return !string.IsNullOrEmpty(name) && name.Contains("PDU");
    }

    public bool SetPortOn(int port) => SnmpSet(PortControlOid(port), new Integer32(3));
    public bool SetPortOff(int port) => SnmpSet(PortControlOid(port), new Integer32(4));

    /// <summary>true = on, false = off, null = unknown/unreachable.</summary>
    public bool? GetPortState(int port) => ParseState(SnmpGet(PortStateOid(port)));

    public int? GetPortCurrent(int port) => int.TryParse(SnmpGet(PortCurrentOid(port)), out int v) ? v : null;
    public double? GetPortPowerWatts(int port) => int.TryParse(SnmpGet(PortPowerOid(port)), out int v) ? v / 10.0 : null;

    /// <summary>
    /// 一次讀回所有插座的狀態 / 電流(mA) / 功率(W)。
    /// 以 3 個批次 SNMP GET（每個 PDU 含 <paramref name="portCount"/> 個 varbind）取代
    /// 逐 port 逐 OID 的 3×N 個請求 —— 12 port 從 36 個 UDP 來回縮成 3 個，
    /// 逾時時的最壞情況也從 36×Timeout 縮到 3×Timeout。
    /// </summary>
    public (bool? State, int? CurrentMilliAmps, double? PowerWatts)[] GetAllPortsStatus(int portCount)
    {
        var ports = Enumerable.Range(1, portCount).ToArray();
        var states = SnmpGetMany(ports.Select(PortStateOid).ToArray());
        var currents = SnmpGetMany(ports.Select(PortCurrentOid).ToArray());
        var powers = SnmpGetMany(ports.Select(PortPowerOid).ToArray());

        var result = new (bool?, int?, double?)[portCount];
        for (int i = 0; i < portCount; i++)
        {
            result[i] = (
                ParseState(states[i]),
                int.TryParse(currents[i], out int c) ? c : null,
                int.TryParse(powers[i], out int p) ? p / 10.0 : null);
        }
        return result;
    }

    private static bool? ParseState(string? r) => r == "3" ? true : (r == "2" || r == "4") ? false : null;

    private static string PortControlOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.4.1.2.{port}";
    private static string PortStateOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.2.{port}";
    private static string PortCurrentOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.3.{port}";
    private static string PortPowerOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.5.{port}";

    private bool SnmpSet(string oid, AsnType value)
    {
        try
        {
            var param = new AgentParameters(new OctetString(Community)) { Version = SnmpVersion.Ver1 };
            using var target = new UdpTarget((IPAddress)new IpAddress(_ip), SnmpPort, Timeout, 1);
            var pdu = new SnmpSharpNet.Pdu(PduType.Set);
            pdu.VbList.Add(new Oid(oid), value);
            var result = (SnmpV1Packet)target.Request(pdu, param);
            return result?.Pdu.ErrorStatus == 0;
        }
        catch (Exception ex) { _logWarn?.Invoke($"[PDU] SNMP SET {oid} exception: {ex.Message}"); return false; }
    }

    private string? SnmpGet(string oid)
    {
        var r = SnmpGetMany(new[] { oid });
        return r[0];
    }

    /// <summary>一個 SNMP GET 帶多個 OID（varbind），回傳同序的值；失敗整批回 null。</summary>
    private string?[] SnmpGetMany(string[] oids)
    {
        var result = new string?[oids.Length];
        try
        {
            var param = new AgentParameters(new OctetString(Community)) { Version = SnmpVersion.Ver1 };
            using var target = new UdpTarget((IPAddress)new IpAddress(_ip), SnmpPort, Timeout, 1);
            var pdu = new SnmpSharpNet.Pdu(PduType.Get);
            foreach (var oid in oids) pdu.VbList.Add(new Oid(oid));
            var resp = (SnmpV1Packet)target.Request(pdu, param);
            if (resp == null) { _logWarn?.Invoke($"[PDU] SNMP GET ({oids.Length} oids): no response (timeout)"); return result; }
            if (resp.Pdu.ErrorStatus != 0) { _logWarn?.Invoke($"[PDU] SNMP GET ({oids.Length} oids): ErrorStatus={resp.Pdu.ErrorStatus}"); return result; }
            // SNMP GET 回應的 varbind 順序與請求一致，直接依 index 對回去。
            int n = Math.Min(oids.Length, resp.Pdu.VbList.Count);
            for (int i = 0; i < n; i++) result[i] = resp.Pdu.VbList[i].Value.ToString();
        }
        catch (Exception ex) { _logWarn?.Invoke($"[PDU] SNMP GET ({oids.Length} oids) exception: {ex.Message}"); }
        return result;
    }

    public void Dispose() { }
}