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//! Hammer candlestick pattern.
use crate::ohlcv::Candle;
use crate::traits::Indicator;
/// Hammer — a single-bar bullish reversal candidate.
///
/// A Hammer has a small real body sitting near the top of the bar, a long
/// lower shadow at least twice the body, and a short or absent upper shadow.
/// It is traditionally read as a rejection of lower prices.
///
/// ```text
/// body = |close − open|
/// upper_shadow = high − max(open, close)
/// lower_shadow = min(open, close) − low
/// hammer = lower_shadow >= 2 * body
/// && upper_shadow <= body
/// && body > 0
/// ```
///
/// Output is `+1.0` when the shape matches, `0.0` otherwise. Pattern-shape
/// check only — no trend filter is applied; combine with a trend indicator
/// for actionable signals.
///
/// # Signed ±1 encoding
///
/// A Hammer is bullish by definition, so under the uniform candlestick sign
/// convention (`+1.0` bullish, `−1.0` bearish, `0.0` none) it emits `+1.0`
/// when the shape matches and `0.0` otherwise — it never emits `−1.0`. The
/// same geometry read at the top of an uptrend is the bearish `HangingMan`,
/// which carries the opposite sign.
///
/// # Example
///
/// ```
/// use wickra_core::{Candle, Hammer, Indicator};
///
/// let mut indicator = Hammer::new();
/// // Open 10, close 10.5, low 5, high 10.6: long lower shadow, tiny upper.
/// let candle = Candle::new(10.0, 10.6, 5.0, 10.5, 1.0, 0).unwrap();
/// assert_eq!(indicator.update(candle), Some(1.0));
/// ```
#[derive(Debug, Clone, Default)]
pub struct Hammer {
has_emitted: bool,
}
impl Hammer {
/// Construct a new Hammer detector.
pub const fn new() -> Self {
Self { has_emitted: false }
}
}
impl Indicator for Hammer {
type Input = Candle;
type Output = f64;
fn update(&mut self, candle: Candle) -> Option<f64> {
self.has_emitted = true;
let range = candle.high - candle.low;
if range <= 0.0 {
return Some(0.0);
}
let body = (candle.close - candle.open).abs();
if body <= 0.0 {
return Some(0.0);
}
let upper = candle.high - candle.open.max(candle.close);
let lower = candle.open.min(candle.close) - candle.low;
Some(if lower >= 2.0 * body && upper <= body {
1.0
} else {
0.0
})
}
fn reset(&mut self) {
self.has_emitted = false;
}
fn warmup_period(&self) -> usize {
1
}
fn is_ready(&self) -> bool {
self.has_emitted
}
fn name(&self) -> &'static str {
"Hammer"
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::traits::BatchExt;
fn c(open: f64, high: f64, low: f64, close: f64, ts: i64) -> Candle {
Candle::new(open, high, low, close, 1.0, ts).unwrap()
}
#[test]
fn accessors_and_metadata() {
let h = Hammer::new();
assert_eq!(h.name(), "Hammer");
assert_eq!(h.warmup_period(), 1);
assert!(!h.is_ready());
}
#[test]
fn clean_hammer_is_one() {
let mut h = Hammer::new();
// body 0.5 (10 -> 10.5), lower shadow 5.0, upper shadow 0.1.
assert_eq!(h.update(c(10.0, 10.6, 5.0, 10.5, 0)), Some(1.0));
}
#[test]
fn marubozu_is_not_hammer() {
let mut h = Hammer::new();
assert_eq!(h.update(c(10.0, 12.0, 10.0, 12.0, 0)), Some(0.0));
}
#[test]
fn shooting_star_shape_is_not_hammer() {
// Long upper, short lower -> not a hammer.
let mut h = Hammer::new();
assert_eq!(h.update(c(10.5, 15.0, 10.0, 10.0, 0)), Some(0.0));
}
#[test]
fn doji_is_not_hammer() {
let mut h = Hammer::new();
assert_eq!(h.update(c(10.0, 11.0, 9.0, 10.0, 0)), Some(0.0));
}
#[test]
fn zero_range_yields_zero() {
let mut h = Hammer::new();
assert_eq!(h.update(c(10.0, 10.0, 10.0, 10.0, 0)), Some(0.0));
}
#[test]
fn batch_equals_streaming() {
let candles: Vec<Candle> = (0..40)
.map(|i| {
let base = 100.0 + i as f64;
c(base, base + 2.0, base - 4.0, base + 0.5, i)
})
.collect();
let mut a = Hammer::new();
let mut b = Hammer::new();
assert_eq!(
a.batch(&candles),
candles.iter().map(|x| b.update(*x)).collect::<Vec<_>>()
);
}
#[test]
fn reset_clears_state() {
let mut h = Hammer::new();
h.update(c(10.0, 10.6, 5.0, 10.5, 0));
assert!(h.is_ready());
h.reset();
assert!(!h.is_ready());
}
}