namespace PineScriptV6
{
    /// <summary>
    /// ta.sma / ta.highest / ta.lowest 의 증분(O(1)) 구현체를 관리합니다.
    /// 매 봉 최초 호출 시 전체 히스토리로 초기화되고,
    /// 이후 봉은 O(1) 증분 업데이트로 처리됩니다.
    /// Reset() 은 새 ExecuteOnCandles / WarmUp 시작 시 반드시 호출해야 합니다.
    /// </summary>
    public static class IndicatorEngine
    {
        // ValueTuple 키 — 문자열 포맷 할당($"{src}:{len}") 완전 제거
        private static readonly Dictionary<(string, int), IncrementalSma>     _smaMap  = new();
        private static readonly Dictionary<(string, int), IncrementalHighest> _highMap = new();
        private static readonly Dictionary<(string, int), IncrementalLowest>  _lowMap  = new();

        /// <summary>상태 전체 초기화 (재실행 또는 실시간 모드 전환 시 호출)</summary>
        public static void Reset()
        {
            _smaMap.Clear();
            _highMap.Clear();
            _lowMap.Clear();
        }

        // ── SMA ──────────────────────────────────────────────────────────

        /// <summary>
        /// ta.sma(src, length) 의 증분 값을 반환합니다.
        /// 히스토리 부족 시 null 반환 (초기 warmup 구간).
        /// </summary>
        public static double? QuerySma(string src, int length)
        {
            var key = (src, length);
            if (!_smaMap.TryGetValue(key, out var ind))
                _smaMap[key] = ind = new IncrementalSma(src, length);
            return ind.GetValue();
        }

        // ── HIGHEST ──────────────────────────────────────────────────────

        public static double? QueryHighest(string src, int length)
        {
            var key = (src, length);
            if (!_highMap.TryGetValue(key, out var ind))
                _highMap[key] = ind = new IncrementalHighest(src, length);
            return ind.GetValue();
        }

        // ── LOWEST ───────────────────────────────────────────────────────

        public static double? QueryLowest(string src, int length)
        {
            var key = (src, length);
            if (!_lowMap.TryGetValue(key, out var ind))
                _lowMap[key] = ind = new IncrementalLowest(src, length);
            return ind.GetValue();
        }
    }

    // ════════════════════════════════════════════════════════════════
    // 증분 SMA — 누적합 O(1)
    // ════════════════════════════════════════════════════════════════

    internal sealed class IncrementalSma
    {
        private readonly string _src;
        private readonly int    _len;
        private double _sum;
        private int    _lastBar = -1;
        private bool   _ready;

        public IncrementalSma(string src, int len) { _src = src; _len = len; }

        public double? GetValue()
        {
            int bar = PineContext.CurrentBarIndex;
            if (bar == _lastBar) return _ready ? _sum / _len : null;

            if (!_ready)
            {
                // 최초: 전체 윈도우 합산으로 초기화
                double[] hist = PineContext.GetLast(_src, _len, 0);
                if (hist.Length < _len) { _lastBar = bar; return null; }
                _sum   = 0;
                for (int i = 0; i < hist.Length; i++) _sum += hist[i];
                _ready = true;
            }
            else
            {
                // 증분: 새 값 추가, 만료값 차감 — CircularBuffer 직접 접근 (double[] 할당 0)
                var buf = PineContext.GetBuffer(_src);
                if (buf == null || buf.Count <= _len) { _lastBar = bar; return null; }
                double cur = buf.Get(0);       // 현재 봉
                double old = buf.Get(_len);    // len봉 전 (만료)
                if (double.IsNaN(cur) || double.IsNaN(old)) { _lastBar = bar; return null; }
                _sum += cur - old;
            }

            _lastBar = bar;
            return _sum / _len;
        }
    }

    // ════════════════════════════════════════════════════════════════
    // 증분 최고값 — 단조 덱(Monotonic Deque) O(1) amortized
    // ════════════════════════════════════════════════════════════════

    internal sealed class IncrementalHighest
    {
        private readonly string _src;
        private readonly int    _len;
        // 덱: 앞=최대값, 뒤=최소. 원소=(봉인덱스, 값)
        private readonly LinkedList<(int Bar, double Val)> _dq = new();
        private int     _lastBar = -1;
        private double? _value;

        public IncrementalHighest(string src, int len) { _src = src; _len = len; }

        public double? GetValue()
        {
            int bar = PineContext.CurrentBarIndex;
            if (bar == _lastBar) return _value;

            if (_lastBar < 0)
            {
                // 최초: 전체 윈도우로 덱 초기화 (고령→최신 순 처리)
                double[] hist = PineContext.GetLast(_src, _len, 0);
                if (hist.Length < _len) { _lastBar = bar; _value = null; return null; }

                _dq.Clear();
                for (int i = _len - 1; i >= 0; i--)   // hist[_len-1]=가장 오래된 봉
                {
                    int b = bar - i;
                    double v = hist[i];
                    while (_dq.Count > 0 && _dq.Last!.Value.Val <= v)
                        _dq.RemoveLast();
                    _dq.AddLast((b, v));
                }
            }
            else
            {
                // 증분: 현재 봉 1개 추가 — CircularBuffer 직접 접근 (double[] 할당 0)
                var buf = PineContext.GetBuffer(_src);
                if (buf == null || buf.Count == 0) { _lastBar = bar; _value = null; return null; }
                double newVal = buf.Get(0);
                if (double.IsNaN(newVal)) { _lastBar = bar; _value = null; return null; }

                // 만료 원소 앞에서 제거 (bar - len 이하)
                while (_dq.Count > 0 && _dq.First!.Value.Bar <= bar - _len)
                    _dq.RemoveFirst();
                // 새 값보다 작거나 같은 원소 뒤에서 제거
                while (_dq.Count > 0 && _dq.Last!.Value.Val <= newVal)
                    _dq.RemoveLast();
                _dq.AddLast((bar, newVal));
            }

            _value   = _dq.Count > 0 ? _dq.First!.Value.Val : null;
            _lastBar = bar;
            return _value;
        }
    }

    // ════════════════════════════════════════════════════════════════
    // 증분 최저값 — 단조 덱 O(1) amortized
    // ════════════════════════════════════════════════════════════════

    internal sealed class IncrementalLowest
    {
        private readonly string _src;
        private readonly int    _len;
        private readonly LinkedList<(int Bar, double Val)> _dq = new();
        private int     _lastBar = -1;
        private double? _value;

        public IncrementalLowest(string src, int len) { _src = src; _len = len; }

        public double? GetValue()
        {
            int bar = PineContext.CurrentBarIndex;
            if (bar == _lastBar) return _value;

            if (_lastBar < 0)
            {
                double[] hist = PineContext.GetLast(_src, _len, 0);
                if (hist.Length < _len) { _lastBar = bar; _value = null; return null; }

                _dq.Clear();
                for (int i = _len - 1; i >= 0; i--)
                {
                    int b = bar - i;
                    double v = hist[i];
                    while (_dq.Count > 0 && _dq.Last!.Value.Val >= v)
                        _dq.RemoveLast();
                    _dq.AddLast((b, v));
                }
            }
            else
            {
                // 증분: 현재 봉 1개 추가 — CircularBuffer 직접 접근 (double[] 할당 0)
                var buf = PineContext.GetBuffer(_src);
                if (buf == null || buf.Count == 0) { _lastBar = bar; _value = null; return null; }
                double newVal = buf.Get(0);
                if (double.IsNaN(newVal)) { _lastBar = bar; _value = null; return null; }

                while (_dq.Count > 0 && _dq.First!.Value.Bar <= bar - _len)
                    _dq.RemoveFirst();
                while (_dq.Count > 0 && _dq.Last!.Value.Val >= newVal)
                    _dq.RemoveLast();
                _dq.AddLast((bar, newVal));
            }

            _value   = _dq.Count > 0 ? _dq.First!.Value.Val : null;
            _lastBar = bar;
            return _value;
        }
    }
}