import React, { useState, useEffect, useCallback } from 'react';
import { RotateCcw } from 'lucide-react';
import NetworkDiagram from './NetworkDiagram';
import SensorInputForm from './SensorInputForm';
import CommandBuilder from './CommandBuilder';
import ResultsPanel from './ResultsPanel';
import StatsTable from './StatsTable';
import HistoryTimeline from './HistoryTimeline';
import {
  getNetwork, getCommands, getStats, getHistory,
  submitSensorInput, runSimulation, createCommand, deleteCommand, resetSimulation,
} from '../../utils/api';
import '../../styles/decidron.css';

const DEFAULT_VALUE = '97';

export default function DecidronSimulator({ settings }) {
  const [network, setNetwork] = useState(null);
  const [commands, setCommands] = useState([]);
  const [stats, setStats] = useState(null);
  const [history, setHistory] = useState([]);
  const [results, setResults] = useState([]);
  const [pending, setPending] = useState([]);
  const [selected, setSelected] = useState(null); // null = live network
  const [running, setRunning] = useState(false);
  const [error, setError] = useState(null);
  // Live sensor-input form values, pre-populated so the user can press
  // "Run Simulation" immediately and see the network react.
  const [channel, setChannel] = useState('');
  const [value, setValue] = useState(DEFAULT_VALUE);

  const refreshAll = useCallback(async () => {
    try {
      const [net, cmds, st, hist] = await Promise.all([
        getNetwork(), getCommands(), getStats(), getHistory(),
      ]);
      setNetwork(net);
      setCommands(cmds);
      setStats(st);
      setHistory(hist.snapshots);
    } catch (err) {
      setError(err.message);
    }
  }, []);

  useEffect(() => { refreshAll(); }, [refreshAll]);

  // Default the channel to the first sensor once the network loads.
  useEffect(() => {
    if (network && !channel) {
      const firstSensor = network.nodes.find((n) => n.type === 'sensor');
      if (firstSensor) setChannel(firstSensor.id);
    }
  }, [network, channel]);

  const handleQueue = async () => {
    if (!channel || value === '') return;
    setError(null);
    try {
      await submitSensorInput(channel, value);
      setPending((prev) => [...prev, { channel, value }]);
    } catch (err) {
      setError(err.message);
    }
  };

  const handleRun = async () => {
    // Run queued inputs if any; otherwise run the current form value
    // inline so a single click works on first load.
    const inputs = pending.length > 0 ? null : [{ channel, value }];
    if (pending.length === 0 && (!channel || value === '')) return;
    setRunning(true);
    setError(null);
    try {
      const resp = await runSimulation(inputs);
      setResults(resp.results);
      setNetwork(resp.network);
      setSelected(null);
      setPending([]);
      const [st, hist] = await Promise.all([getStats(), getHistory()]);
      setStats(st);
      setHistory(hist.snapshots);
    } catch (err) {
      setError(err.message);
    } finally {
      setRunning(false);
    }
  };

  const handleCreate = async (cmd, replaceName = null) => {
    await createCommand(cmd);
    if (replaceName && replaceName !== cmd.name) {
      await deleteCommand(replaceName);
    }
    setCommands(await getCommands());
  };

  const handleDelete = async (name) => {
    setError(null);
    try {
      await deleteCommand(name);
      setCommands(await getCommands());
    } catch (err) {
      setError(err.message);
    }
  };

  const handleReset = async () => {
    setError(null);
    try {
      await resetSimulation();
      setResults([]);
      setPending([]);
      setSelected(null);
      await refreshAll();
    } catch (err) {
      setError(err.message);
    }
  };

  if (!network) {
    return (
      <div className="decidron-app">
        {error ? <div className="decidron-error">{error}</div> : <p>Loading…</p>}
      </div>
    );
  }

  const sensors = network.nodes.filter((n) => n.type === 'sensor');
  const shownDiagram = selected ? selected.diagram : network.diagram;
  const shownVersion = selected ? selected.version : network.version;
  const { panels, layoutMode } = settings;

  return (
    <div className="decidron-app">
      {error && <div className="decidron-error">{error}</div>}
      <div className="decidron-grid">
        <div>
          <div className="decidron-panel">
            <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center' }}>
              <h2>Decidron Network (v{shownVersion}{selected ? ' — historical' : ' — live'})</h2>
              <button type="button" className="decidron-btn secondary" onClick={handleReset}>
                <RotateCcw size={13} style={{ marginRight: 4, verticalAlign: 'middle' }} />
                Reset
              </button>
            </div>
            <p className="panel-hint">
              Sensors (blue) feed coupled Decidrons (purple) that drive
              actuators (green). Commands can modify this topology.
            </p>
            <NetworkDiagram data={shownDiagram} layoutMode={layoutMode} />
          </div>
          <HistoryTimeline
            snapshots={history}
            selectedVersion={selected ? selected.version : null}
            onSelect={(s) => setSelected(
              s.version === network.version ? null : s
            )}
          />
        </div>

        <div>
          {panels.sensorInput && (
            <SensorInputForm
              sensors={sensors}
              channel={channel}
              value={value}
              onChannelChange={setChannel}
              onValueChange={setValue}
              pending={pending}
              onQueue={handleQueue}
              onRun={handleRun}
              running={running}
            />
          )}
          {panels.commands && (
            <CommandBuilder
              commands={commands}
              sensors={sensors}
              nodes={network.nodes}
              onCreate={handleCreate}
              onDelete={handleDelete}
            />
          )}
          {panels.results && <ResultsPanel results={results} />}
          {panels.stats && <StatsTable stats={stats} />}
        </div>
      </div>
    </div>
  );
}