wickra_core/indicators/
hammer.rs

1//! Hammer candlestick pattern.
2
3use crate::ohlcv::Candle;
4use crate::traits::Indicator;
5
6/// Hammer — a single-bar bullish reversal candidate.
7///
8/// A Hammer has a small real body sitting near the top of the bar, a long
9/// lower shadow at least twice the body, and a short or absent upper shadow.
10/// It is traditionally read as a rejection of lower prices.
11///
12/// ```text
13/// body         = |close − open|
14/// upper_shadow = high − max(open, close)
15/// lower_shadow = min(open, close) − low
16/// hammer       = lower_shadow >= 2 * body
17///               && upper_shadow <= body
18///               && body > 0
19/// ```
20///
21/// Output is `+1.0` when the shape matches, `0.0` otherwise. Pattern-shape
22/// check only — no trend filter is applied; combine with a trend indicator
23/// for actionable signals.
24///
25/// # Signed ±1 encoding
26///
27/// A Hammer is bullish by definition, so under the uniform candlestick sign
28/// convention (`+1.0` bullish, `−1.0` bearish, `0.0` none) it emits `+1.0`
29/// when the shape matches and `0.0` otherwise — it never emits `−1.0`. The
30/// same geometry read at the top of an uptrend is the bearish `HangingMan`,
31/// which carries the opposite sign.
32///
33/// # Example
34///
35/// ```
36/// use wickra_core::{Candle, Hammer, Indicator};
37///
38/// let mut indicator = Hammer::new();
39/// // Open 10, close 10.5, low 5, high 10.6: long lower shadow, tiny upper.
40/// let candle = Candle::new(10.0, 10.6, 5.0, 10.5, 1.0, 0).unwrap();
41/// assert_eq!(indicator.update(candle), Some(1.0));
42/// ```
43#[derive(Debug, Clone, Default)]
44pub struct Hammer {
45    has_emitted: bool,
46}
47
48impl Hammer {
49    /// Construct a new Hammer detector.
50    pub const fn new() -> Self {
51        Self { has_emitted: false }
52    }
53}
54
55impl Indicator for Hammer {
56    type Input = Candle;
57    type Output = f64;
58
59    #[inline]
60    fn update(&mut self, candle: Candle) -> Option<f64> {
61        self.has_emitted = true;
62        let range = candle.high - candle.low;
63        if range <= 0.0 {
64            return Some(0.0);
65        }
66        let body = (candle.close - candle.open).abs();
67        if body <= 0.0 {
68            return Some(0.0);
69        }
70        let upper = candle.high - candle.open.max(candle.close);
71        let lower = candle.open.min(candle.close) - candle.low;
72        Some(if lower >= 2.0 * body && upper <= body {
73            1.0
74        } else {
75            0.0
76        })
77    }
78
79    fn reset(&mut self) {
80        self.has_emitted = false;
81    }
82
83    #[inline]
84    fn warmup_period(&self) -> usize {
85        1
86    }
87
88    #[inline]
89    fn is_ready(&self) -> bool {
90        self.has_emitted
91    }
92
93    #[inline]
94    fn name(&self) -> &'static str {
95        "Hammer"
96    }
97}
98
99#[cfg(test)]
100mod tests {
101    use super::*;
102    use crate::traits::BatchExt;
103
104    fn c(open: f64, high: f64, low: f64, close: f64, ts: i64) -> Candle {
105        Candle::new(open, high, low, close, 1.0, ts).unwrap()
106    }
107
108    #[test]
109    fn accessors_and_metadata() {
110        let h = Hammer::new();
111        assert_eq!(h.name(), "Hammer");
112        assert_eq!(h.warmup_period(), 1);
113        assert!(!h.is_ready());
114    }
115
116    #[test]
117    fn clean_hammer_is_one() {
118        let mut h = Hammer::new();
119        // body 0.5 (10 -> 10.5), lower shadow 5.0, upper shadow 0.1.
120        assert_eq!(h.update(c(10.0, 10.6, 5.0, 10.5, 0)), Some(1.0));
121    }
122
123    #[test]
124    fn marubozu_is_not_hammer() {
125        let mut h = Hammer::new();
126        assert_eq!(h.update(c(10.0, 12.0, 10.0, 12.0, 0)), Some(0.0));
127    }
128
129    #[test]
130    fn shooting_star_shape_is_not_hammer() {
131        // Long upper, short lower -> not a hammer.
132        let mut h = Hammer::new();
133        assert_eq!(h.update(c(10.5, 15.0, 10.0, 10.0, 0)), Some(0.0));
134    }
135
136    #[test]
137    fn doji_is_not_hammer() {
138        let mut h = Hammer::new();
139        assert_eq!(h.update(c(10.0, 11.0, 9.0, 10.0, 0)), Some(0.0));
140    }
141
142    #[test]
143    fn zero_range_yields_zero() {
144        let mut h = Hammer::new();
145        assert_eq!(h.update(c(10.0, 10.0, 10.0, 10.0, 0)), Some(0.0));
146    }
147
148    #[test]
149    fn batch_equals_streaming() {
150        let candles: Vec<Candle> = (0..40)
151            .map(|i| {
152                let base = 100.0 + i as f64;
153                c(base, base + 2.0, base - 4.0, base + 0.5, i)
154            })
155            .collect();
156        let mut a = Hammer::new();
157        let mut b = Hammer::new();
158        assert_eq!(
159            a.batch(&candles),
160            candles.iter().map(|x| b.update(*x)).collect::<Vec<_>>()
161        );
162    }
163
164    #[test]
165    fn reset_clears_state() {
166        let mut h = Hammer::new();
167        h.update(c(10.0, 10.6, 5.0, 10.5, 0));
168        assert!(h.is_ready());
169        h.reset();
170        assert!(!h.is_ready());
171    }
172}
wickra_core/indicators/hammer.rs

wickra_core/indicators/
hammer.rs
