'use client';

import { useEffect, useState } from 'react';
import Link from 'next/link';

interface Instrument {
    symbol: string;
    enabled: boolean;
}

interface ResolvedContract {
    name: string;
    alternative?: string;
    frontVolume?: number;
    rolledVolume?: number;
}

interface AppSettings {
    max_concurrent_accounts: string | null;
}

export default function SettingsPage() {
    const [instruments, setInstruments] = useState<Instrument[]>([]);
    const [contracts, setContracts] = useState<Record<string, ResolvedContract | null>>({});
    const [maxConcurrent, setMaxConcurrent] = useState<string>('5');
    const [saving, setSaving] = useState(false);
    const [saved, setSaved] = useState(false);

    useEffect(() => {
        fetch('/api/instruments')
            .then((r) => r.json())
            .then(setInstruments);

        fetch('/api/settings')
            .then((r) => r.json())
            .then((s: AppSettings) => {
                if (s.max_concurrent_accounts != null) {
                    setMaxConcurrent(s.max_concurrent_accounts);
                }
            });

        // Load cached contracts; if cache is empty, auto-resolve
        fetch('/api/instruments/contracts')
            .then((r) => r.json())
            .then((data: Record<string, ResolvedContract | null>) => {
                if (data.error) return;
                const hasData = Object.values(data).some((v) => v !== null);
                if (hasData) {
                    setContracts(data);
                } else {
                    // Cache empty — trigger a fresh resolve automatically
                    fetch('/api/instruments/contracts', { method: 'POST' })
                        .then((r) => r.json())
                        .then((fresh) => { if (!fresh.error) setContracts(fresh); })
                        .catch(() => {});
                }
            })
            .catch(() => {});
    }, []);

    async function toggle(symbol: string, enabled: boolean) {
        setInstruments((prev) =>
            prev.map((i) => (i.symbol === symbol ? { ...i, enabled } : i))
        );
        await fetch(`/api/instruments/${symbol}`, {
            method: 'PATCH',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ enabled }),
        });
    }

    async function saveSettings() {
        setSaving(true);
        setSaved(false);
        await fetch('/api/settings', {
            method: 'PATCH',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ max_concurrent_accounts: maxConcurrent }),
        });
        setSaving(false);
        setSaved(true);
        setTimeout(() => setSaved(false), 2000);
    }

    return (
        <div className="min-h-screen bg-slate-50 p-8">
            <div className="max-w-7xl mx-auto">

                <div className="flex items-center gap-3 mb-6">
                    <Link
                        href="/"
                        className="text-slate-400 hover:text-slate-600 text-sm transition-colors"
                    >
                        ← Back
                    </Link>
                    <h1 className="text-2xl font-bold text-slate-900">Settings</h1>
                </div>

                {/* ── Trading ── */}
                <h2 className="text-sm font-semibold uppercase tracking-wider text-slate-500 mb-3">
                    Trading
                </h2>
                <div className="bg-white border border-slate-200 rounded-xl shadow-sm mb-8">
                    <div className="flex items-center justify-between px-4 py-3">
                        <div>
                            <p className="text-sm font-medium text-slate-800">Max concurrent accounts</p>
                            <p className="text-xs text-slate-400 mt-0.5">
                                How many accounts trade in parallel per /api/trade call
                            </p>
                        </div>
                        <div className="flex items-center gap-3">
                            <input
                                type="number"
                                min={1}
                                max={500}
                                value={maxConcurrent}
                                onChange={(e) => setMaxConcurrent(e.target.value)}
                                className="w-20 rounded-lg border border-slate-200 bg-slate-50 px-3 py-1.5 text-sm text-right font-mono text-slate-800 focus:outline-none focus:ring-2 focus:ring-blue-500"
                            />
                            <button
                                onClick={saveSettings}
                                disabled={saving}
                                className={`text-sm px-3 py-1.5 rounded-lg font-medium transition-colors ${
                                    saved
                                        ? 'bg-green-500 text-white'
                                        : 'bg-blue-500 hover:bg-blue-600 text-white disabled:opacity-50'
                                }`}
                            >
                                {saved ? 'Saved ✓' : saving ? 'Saving…' : 'Save'}
                            </button>
                        </div>
                    </div>
                </div>

                {/* ── Instruments ── */}
                <h2 className="text-sm font-semibold uppercase tracking-wider text-slate-500 mb-3">
                    Instruments
                </h2>

                <div className="bg-white border border-slate-200 rounded-xl overflow-hidden shadow-sm">
                    {instruments.length === 0 ? (
                        <div className="px-4 py-8 text-center text-sm text-slate-400 italic">
                            Loading…
                        </div>
                    ) : (
                        <table className="w-full text-sm border-collapse">
                            <thead>
                                <tr className="border-b border-slate-200 bg-slate-50">
                                    <th className="px-4 py-3 text-left text-xs font-semibold uppercase tracking-wider text-slate-400">Symbol</th>
                                    <th className="px-4 py-3 text-left text-xs font-semibold uppercase tracking-wider text-slate-400">Active Contract</th>
                                    <th className="px-4 py-3 text-right text-xs font-semibold uppercase tracking-wider text-slate-400">Enabled</th>
                                </tr>
                            </thead>
                            <tbody>
                                {instruments.map((instr) => {
                                    const c = contracts[instr.symbol];
                                    const wasRolled = c?.alternative && c.rolledVolume != null && c.frontVolume != null && c.rolledVolume > c.frontVolume;
                                    return (
                                        <tr key={instr.symbol} className="border-b border-slate-100 last:border-0">
                                            <td className="px-4 py-2.5 font-mono font-semibold text-slate-800">
                                                {instr.symbol}
                                            </td>
                                            <td className="px-4 py-2.5">
                                                {c ? (
                                                    <div className="flex items-center gap-2">
                                                        <span className={`font-mono text-sm ${wasRolled ? 'text-amber-600 font-semibold' : 'text-slate-600'}`}>
                                                            {c.name}
                                                        </span>
                                                        {c.frontVolume != null && c.rolledVolume != null && (
                                                            <span className="text-xs text-slate-400">
                                                                vol {Math.max(c.frontVolume, c.rolledVolume).toLocaleString()}
                                                            </span>
                                                        )}
                                                        {wasRolled && (
                                                            <span className="text-xs bg-amber-100 text-amber-700 px-1.5 py-0.5 rounded font-medium">
                                                                rolled
                                                            </span>
                                                        )}
                                                    </div>
                                                ) : (
                                                    <span className="text-xs text-slate-300 italic">—</span>
                                                )}
                                            </td>
                                            <td className="px-4 py-2.5 text-right">
                                                <button
                                                    onClick={() => toggle(instr.symbol, !instr.enabled)}
                                                    className={`relative inline-flex h-5 w-9 items-center rounded-full transition-colors focus:outline-none ${
                                                        instr.enabled ? 'bg-blue-500' : 'bg-slate-200'
                                                    }`}
                                                >
                                                    <span
                                                        className={`inline-block h-3.5 w-3.5 transform rounded-full bg-white shadow transition-transform ${
                                                            instr.enabled ? 'translate-x-4' : 'translate-x-1'
                                                        }`}
                                                    />
                                                </button>
                                            </td>
                                        </tr>
                                    );
                                })}
                            </tbody>
                        </table>
                    )}
                </div>
            </div>
        </div>
    );
}