Finlytic/FinlyticTechnicals/Patterns/Candlesticks/CandlestickPatternDetectors.cs

using System;
using System.Collections.Generic;
using System.Linq;
using FinlyticCore.Dtos.TechnicalAnalysis;

namespace FinlyticTechnicals.Patterns.Candlesticks;

/// <summary>
/// Detects Bullish Hammer (long lower wick at support) and Bearish Shooting Star (long upper wick at resistance).
/// </summary>
public class HammerShootingStarDetector : IPatternDetector
{
    public PatternType HandledType => PatternType.Hammer;
    public PatternCategory Category => PatternCategory.Candlestick;

    public PatternResultDto? Evaluate(TechnicalContext context)
    {
        var candles = context.PrimaryCandles;
        if (candles.Count < 5) return null;

        var current = candles.Last();
        var prev = candles[^2];

        decimal body = Math.Abs(current.Close - current.Open);
        decimal upperShadow = current.High - Math.Max(current.Open, current.Close);
        decimal lowerShadow = Math.Min(current.Open, current.Close) - current.Low;
        decimal totalRange = current.High - current.Low;

        if (totalRange <= 0) return null;

        // Hammer: Lower shadow >= 2x body, upper shadow <= 0.2x body, downtrend context
        if (lowerShadow >= 2.0m * Math.Max(body, 0.01m) && upperShadow <= 0.3m * totalRange && current.Close < prev.Close * 1.02m)
        {
            decimal score = Math.Min(95m, 60m + (lowerShadow / totalRange * 40m));
            return new PatternResultDto(
                Id: Guid.NewGuid(),
                Type: PatternType.Hammer,
                Category: PatternCategory.Candlestick,
                Bias: PatternBias.Bullish,
                Name: "Bullish Hammer",
                Timeframe: context.Timeframe,
                DetectedAt: current.Timestamp,
                KeyPriceLevel: current.Low,
                UpperBoundary: current.High,
                LowerBoundary: current.Low,
                InvalidationLevel: current.Low * 0.995m,
                QualityScore: score,
                Description: $"Bullish hammer with {lowerShadow / totalRange:P0} rejection lower wick at {current.Low:F2}."
            );
        }

        // Shooting Star: Upper shadow >= 2x body, lower shadow <= 0.2x body, uptrend context
        if (upperShadow >= 2.0m * Math.Max(body, 0.01m) && lowerShadow <= 0.3m * totalRange && current.Close > prev.Close * 0.98m)
        {
            decimal score = Math.Min(95m, 60m + (upperShadow / totalRange * 40m));
            return new PatternResultDto(
                Id: Guid.NewGuid(),
                Type: PatternType.ShootingStar,
                Category: PatternCategory.Candlestick,
                Bias: PatternBias.Bearish,
                Name: "Bearish Shooting Star",
                Timeframe: context.Timeframe,
                DetectedAt: current.Timestamp,
                KeyPriceLevel: current.High,
                UpperBoundary: current.High,
                LowerBoundary: current.Low,
                InvalidationLevel: current.High * 1.005m,
                QualityScore: score,
                Description: $"Bearish shooting star with {upperShadow / totalRange:P0} rejection upper wick at {current.High:F2}."
            );
        }

        return null;
    }
}

/// <summary>
/// Detects Bullish and Bearish Engulfing candles.
/// </summary>
public class EngulfingPatternDetector : IPatternDetector
{
    public PatternType HandledType => PatternType.BullishEngulfing;
    public PatternCategory Category => PatternCategory.Candlestick;

    public PatternResultDto? Evaluate(TechnicalContext context)
    {
        var candles = context.PrimaryCandles;
        if (candles.Count < 3) return null;

        var curr = candles.Last();
        var prev = candles[^2];

        bool prevBearish = prev.Close < prev.Open;
        bool currBullish = curr.Close > curr.Open;

        // Bullish Engulfing: previous red, current green completely engulfing previous body
        if (prevBearish && currBullish && curr.Open <= prev.Close && curr.Close >= prev.Open)
        {
            decimal score = Math.Min(90m, 70m + (curr.Volume > prev.Volume ? 15m : 0m));
            return new PatternResultDto(
                Id: Guid.NewGuid(),
                Type: PatternType.BullishEngulfing,
                Category: PatternCategory.Candlestick,
                Bias: PatternBias.Bullish,
                Name: "Bullish Engulfing",
                Timeframe: context.Timeframe,
                DetectedAt: curr.Timestamp,
                KeyPriceLevel: curr.Open,
                UpperBoundary: curr.High,
                LowerBoundary: curr.Low,
                InvalidationLevel: curr.Low * 0.995m,
                QualityScore: score,
                Description: $"Bullish engulfing candle covering previous range [{prev.Close:F2} - {prev.Open:F2}]."
            );
        }

        bool prevBullish = prev.Close > prev.Open;
        bool currBearish = curr.Close < curr.Open;

        // Bearish Engulfing: previous green, current red completely engulfing previous body
        if (prevBullish && currBearish && curr.Open >= prev.Close && curr.Close <= prev.Open)
        {
            decimal score = Math.Min(90m, 70m + (curr.Volume > prev.Volume ? 15m : 0m));
            return new PatternResultDto(
                Id: Guid.NewGuid(),
                Type: PatternType.BearishEngulfing,
                Category: PatternCategory.Candlestick,
                Bias: PatternBias.Bearish,
                Name: "Bearish Engulfing",
                Timeframe: context.Timeframe,
                DetectedAt: curr.Timestamp,
                KeyPriceLevel: curr.Open,
                UpperBoundary: curr.High,
                LowerBoundary: curr.Low,
                InvalidationLevel: curr.High * 1.005m,
                QualityScore: score,
                Description: $"Bearish engulfing candle covering previous range [{prev.Open:F2} - {prev.Close:F2}]."
            );
        }

        return null;
    }
}

/// <summary>
/// Detects Morning Star and Evening Star 3-bar reversal patterns.
/// </summary>
public class MorningEveningStarDetector : IPatternDetector
{
    public PatternType HandledType => PatternType.MorningStar;
    public PatternCategory Category => PatternCategory.Candlestick;

    public PatternResultDto? Evaluate(TechnicalContext context)
    {
        var candles = context.PrimaryCandles;
        if (candles.Count < 4) return null;

        var c1 = candles[^3];
        var c2 = candles[^2]; // Star
        var c3 = candles.Last();

        decimal body1 = Math.Abs(c1.Close - c1.Open);
        decimal body2 = Math.Abs(c2.Close - c2.Open);
        decimal body3 = Math.Abs(c3.Close - c3.Open);

        // Morning Star: Large Bearish + Small Star + Strong Bullish closing > 50% into candle 1
        if (c1.Close < c1.Open && body2 < body1 * 0.4m && c3.Close > c3.Open && c3.Close >= (c1.Open + c1.Close) / 2m)
        {
            return new PatternResultDto(
                Id: Guid.NewGuid(),
                Type: PatternType.MorningStar,
                Category: PatternCategory.Candlestick,
                Bias: PatternBias.Bullish,
                Name: "Morning Star",
                Timeframe: context.Timeframe,
                DetectedAt: c3.Timestamp,
                KeyPriceLevel: c2.Low,
                UpperBoundary: c3.High,
                LowerBoundary: c2.Low,
                InvalidationLevel: c2.Low * 0.995m,
                QualityScore: 85m,
                Description: $"Morning star reversal with low at {c2.Low:F2}."
            );
        }

        // Evening Star: Large Bullish + Small Star + Strong Bearish closing < 50% into candle 1
        if (c1.Close > c1.Open && body2 < body1 * 0.4m && c3.Close < c3.Open && c3.Close <= (c1.Open + c1.Close) / 2m)
        {
            return new PatternResultDto(
                Id: Guid.NewGuid(),
                Type: PatternType.EveningStar,
                Category: PatternCategory.Candlestick,
                Bias: PatternBias.Bearish,
                Name: "Evening Star",
                Timeframe: context.Timeframe,
                DetectedAt: c3.Timestamp,
                KeyPriceLevel: c2.High,
                UpperBoundary: c2.High,
                LowerBoundary: c3.Low,
                InvalidationLevel: c2.High * 1.005m,
                QualityScore: 85m,
                Description: $"Evening star reversal with peak at {c2.High:F2}."
            );
        }

        return null;
    }
}

/// <summary>
/// Detects Doji indecision candles at key swing points.
/// </summary>
public class DojiPatternDetector : IPatternDetector
{
    public PatternType HandledType => PatternType.Doji;
    public PatternCategory Category => PatternCategory.Candlestick;

    public PatternResultDto? Evaluate(TechnicalContext context)
    {
        var candles = context.PrimaryCandles;
        if (candles.Count < 3) return null;

        var curr = candles.Last();
        decimal body = Math.Abs(curr.Close - curr.Open);
        decimal totalRange = curr.High - curr.Low;

        if (totalRange <= 0) return null;

        if (body <= totalRange * 0.10m)
        {
            return new PatternResultDto(
                Id: Guid.NewGuid(),
                Type: PatternType.Doji,
                Category: PatternCategory.Candlestick,
                Bias: PatternBias.Neutral,
                Name: "Doji",
                Timeframe: context.Timeframe,
                DetectedAt: curr.Timestamp,
                KeyPriceLevel: curr.Close,
                UpperBoundary: curr.High,
                LowerBoundary: curr.Low,
                InvalidationLevel: curr.Low,
                QualityScore: 65m,
                Description: $"Doji indecision bar with tight body ({body:F2}) and range [{curr.Low:F2} - {curr.High:F2}]."
            );
        }

        return null;
    }
}