import React, { useMemo, useCallback, useEffect, useRef, useState } from 'react';
import {
  ReactFlow,
  Background,
  MiniMap,
  useEdgesState,
  useNodesState,
  addEdge,
  MarkerType,
  Handle,
  Position,
} from '@xyflow/react';
import '@xyflow/react/dist/style.css';
import { IconZoomIn, IconZoomOut, IconMaximize, IconMinimize } from '@tabler/icons-react';

function GraphView({ servers, connections, onCreateConnection }) {
  const flowRef = useRef(null);
  const instanceRef = useRef(null);
  const containerRef = useRef(null);
  const [isFullscreen, setIsFullscreen] = useState(false);

  const getTunnelStyle = useCallback((tunnelType) => {
    const map = {
      GRE: { color: '#206bc4', dash: '0', width: 2.5 },
      IPSec: { color: '#f59f00', dash: '6,4', width: 2.5 },
      WireGuard: { color: '#2fb344', dash: '0', width: 3.2 },
      OpenVPN: { color: '#be4bdb', dash: '3,3', width: 2.5 },
    };
    return map[tunnelType] || { color: '#667382', dash: '5,5', width: 2 };
  }, []);

  const getCountryColor = useCallback((country) => {
    const colors = {
      RU: '#dc2626',
      US: '#2563eb',
      DE: '#059669',
      SE: '#7c3aed',
      NL: '#ea580c',
      SG: '#0891b2',
    };
    return colors[country] || '#6b7280';
  }, []);

  const computeGridPosition = useCallback((index, total) => {
    const cols = Math.ceil(Math.sqrt(total));
    const row = Math.floor(index / cols);
    const col = index % cols;
    const spacingX = 280;
    const spacingY = 180;
    return { x: 80 + col * spacingX, y: 80 + row * spacingY };
  }, []);

  const initialNodesData = useMemo(() => {
    return (servers || []).map((s, i) => ({
      id: String(s.ip),
      type: 'server',
      position: computeGridPosition(i, servers.length),
      data: { server: s },
    }));
  }, [servers, computeGridPosition]);

  const [nodes, setNodes, onNodesChange] = useNodesState(initialNodesData);

  useEffect(() => {
    setNodes(initialNodesData);
  }, [initialNodesData, setNodes]);

  const initialEdgesData = useMemo(() => {
    return (connections || []).map((c, idx) => {
      const style = getTunnelStyle(c.tunnelType);
      return {
        id: `${c.from}-${c.to}-${idx}`,
        source: String(c.from),
        target: String(c.to),
        label: c.ipA && c.ipB ? `${c.tunnelType}  ${c.ipA} ⇄ ${c.ipB}` : c.tunnelType,
        style: { stroke: style.color, strokeWidth: style.width, strokeDasharray: style.dash },
        markerEnd: { type: MarkerType.ArrowClosed, color: style.color, width: 20, height: 20 },
        animated: false,
      };
    });
  }, [connections, getTunnelStyle]);

  const [edges, setEdges, onEdgesChange] = useEdgesState(initialEdgesData);

  useEffect(() => {
    setEdges(initialEdgesData);
  }, [initialEdgesData, setEdges]);

  const onConnect = useCallback(
    (params) => {
      // Делегируем создание связи в родителя, чтобы сохранить единую логику хранения
      if (!params?.source || !params?.target || params.source === params.target) return;
      if (onCreateConnection) {
        onCreateConnection({ from: params.source, to: params.target });
      }
    },
    [onCreateConnection]
  );

  const nodeTypes = useMemo(
    () => ({
      server: ({ data }) => {
        const s = data.server || {};
        const countryColor = getCountryColor(s.country);
        const getFlagEmoji = (code) => {
          if (!code) return '';
          const map = { SWE: 'SE', UK: 'GB' };
          const ccRaw = String(code).trim().toUpperCase();
          const cc = (map[ccRaw] || ccRaw).slice(0, 2);
          if (cc.length !== 2) return ccRaw;
          return cc.replace(/./g, (ch) => String.fromCodePoint(127397 + ch.charCodeAt()));
        };
        const flag = getFlagEmoji(s.country);
        return (
          <div
            className="card shadow-sm"
            style={{
              width: 200,
              borderRadius: 12,
              border: `2px solid ${countryColor}`,
              overflow: 'hidden',
              background: '#fff',
            }}
          >
            {/* Точка входа соединений */}
            <Handle type="target" position={Position.Left} style={{ background: countryColor }} />
            <div className="px-2 py-1 d-flex align-items-center" style={{ background: '#f8fafc', borderBottom: '1px solid #eef2f7' }}>
              <div className="d-flex align-items-center" style={{ gap: 6 }}>
                <span style={{ fontSize: 16, lineHeight: '1' }}>{flag}</span>
                <span
                  className="badge"
                  style={{
                    background: '#fff',
                    color: '#475569',
                    border: `1px solid ${countryColor}`,
                    borderRadius: 8,
                    fontSize: 11,
                  }}
                >
                  {String(s.country || '').toUpperCase().slice(0, 3)}
                </span>
              </div>
              <div className="ms-2 text-truncate" style={{ fontWeight: 700, color: '#1f2937', fontSize: 13 }}>{s.dns}</div>
            </div>
            <div className="px-2 py-2" style={{ lineHeight: 1.2 }}>
              <div style={{ fontSize: 12, color: '#334155' }}>{s.ip}</div>
              <div style={{ fontSize: 10, color: '#6b7280' }}>{s.provider}</div>
            </div>
            {/* Точка исхода соединений */}
            <Handle type="source" position={Position.Right} style={{ background: countryColor }} />
          </div>
        );
      },
    }),
    [getCountryColor]
  );

  const onInit = useCallback((inst) => {
    instanceRef.current = inst;
    // Автоподгон при инициализации
    requestAnimationFrame(() => {
      try {
        inst.fitView({ padding: 0.2, includeHiddenNodes: true, minZoom: 0.2, maxZoom: 2 });
      } catch {}
    });
  }, []);

  useEffect(() => {
    if (!instanceRef.current) return;
    // Подгон при изменении данных
    const i = instanceRef.current;
    const t = setTimeout(() => {
      try {
        i.fitView({ padding: 0.2, includeHiddenNodes: true, minZoom: 0.2, maxZoom: 2 });
      } catch {}
    }, 50);
    return () => clearTimeout(t);
  }, [servers, connections]);

  // Трек полноэкранного режима и авто-fit после входа/выхода
  useEffect(() => {
    const handler = () => {
      const fs = Boolean(document.fullscreenElement);
      setIsFullscreen(fs);
      if (instanceRef.current) {
        setTimeout(() => {
          try {
            instanceRef.current.fitView({ padding: 0.2 });
          } catch {}
        }, 60);
      }
    };
    document.addEventListener('fullscreenchange', handler);
    return () => document.removeEventListener('fullscreenchange', handler);
  }, []);

  if (!servers || servers.length === 0) {
    return (
      <div className="text-center py-5">
        <div className="text-muted">
          <h4>Нет серверов для отображения</h4>
          <p>Добавьте серверы, чтобы увидеть граф связей</p>
        </div>
      </div>
    );
  }

  return (
    <div
      ref={containerRef}
      style={{
        width: '100%',
        height: isFullscreen ? '100vh' : 500,
        border: '1px solid #e5e7eb',
        borderRadius: 8,
        overflow: 'hidden',
        position: 'relative',
        background: '#f8fafc',
      }}
    >
      <ReactFlow
        ref={flowRef}
        nodes={nodes}
        edges={edges}
        onNodesChange={onNodesChange}
        onEdgesChange={onEdgesChange}
        onConnect={onConnect}
        nodeTypes={nodeTypes}
        fitView
        defaultEdgeOptions={{
          type: 'default',
          markerEnd: { type: MarkerType.ArrowClosed },
        }}
        onInit={onInit}
        style={{ width: '100%', height: '100%', background: '#f8fafc' }}
      >
        <Background variant="dots" gap={20} size={1} color="#e5e7eb" />
        <MiniMap
          nodeColor={(n) => getCountryColor(n.data?.server?.country)}
          nodeStrokeWidth={2}
          maskColor="rgba(0,0,0,0.05)"
        />
      </ReactFlow>
      {/* Своя панель управления: -, +, Fit, Fullscreen */}
      <div className="position-absolute" style={{ right: 10, top: 10, zIndex: 10, pointerEvents: 'auto' }}>
        <div className="btn-group btn-group-sm">
          <button
            type="button"
            className="btn btn-outline-secondary"
            onClick={() => instanceRef.current?.zoomOut?.()}
            title="Уменьшить"
          >
            <IconZoomOut size={16} />
          </button>
          <button
            type="button"
            className="btn btn-outline-secondary"
            onClick={() => instanceRef.current?.zoomIn?.()}
            title="Увеличить"
          >
            <IconZoomIn size={16} />
          </button>
          <button
            type="button"
            className="btn btn-outline-secondary"
            onClick={() => instanceRef.current?.fitView?.({ padding: 0.2 })}
            title="Подогнать к окну"
          >
            Fit
          </button>
          <button
            type="button"
            className="btn btn-outline-secondary"
            onClick={() => {
              const el = containerRef.current;
              if (!el) return;
              if (!document.fullscreenElement) {
                el.requestFullscreen?.();
              } else {
                document.exitFullscreen?.();
              }
            }}
            title="Во весь экран"
          >
            {isFullscreen ? <IconMinimize size={16} /> : <IconMaximize size={16} />}
          </button>
        </div>
      </div>
    </div>
  );
}

export default GraphView;