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//! Homing Pigeon candlestick pattern.
use crate::ohlcv::Candle;
use crate::traits::Indicator;
/// Homing Pigeon — a 2-bar bullish reversal. Two black candles in a decline, the
/// second a small body sitting entirely inside the first body (a same-colour
/// harami). The shrinking range signals selling pressure is fading.
///
/// ```text
/// bar1 black (close < open)
/// bar2 black & its body sits inside bar1's body
/// (open2 <= open1 && close2 >= close1)
/// bar2 body is smaller than bar1's
/// ```
///
/// Output is `+1.0` when the pattern completes and `0.0` otherwise. Homing Pigeon
/// is a single-direction (bullish-only) reversal, so it never emits `−1.0`. The
/// first bar always returns `0.0` because the two-bar window is not yet filled.
/// Pattern-shape check only — no trend filter is applied; combine with a trend
/// indicator for actionable signals.
///
/// # Signed ±1 encoding
///
/// This detector emits the uniform candlestick sign convention shared across the
/// pattern family — `+1.0` bullish, `0.0` no pattern — so it drops straight into
/// a machine-learning feature matrix as a single dimension.
///
/// # Example
///
/// ```
/// use wickra_core::{Candle, HomingPigeon, Indicator};
///
/// let mut indicator = HomingPigeon::new();
/// indicator.update(Candle::new(15.0, 15.1, 9.9, 10.0, 1.0, 0).unwrap());
/// let out = indicator
/// .update(Candle::new(14.0, 14.1, 10.9, 11.0, 1.0, 1).unwrap());
/// assert_eq!(out, Some(1.0));
/// ```
#[derive(Debug, Clone, Default)]
pub struct HomingPigeon {
prev: Option<Candle>,
has_emitted: bool,
}
impl HomingPigeon {
/// Construct a new Homing Pigeon detector.
pub const fn new() -> Self {
Self {
prev: None,
has_emitted: false,
}
}
}
impl Indicator for HomingPigeon {
type Input = Candle;
type Output = f64;
fn update(&mut self, candle: Candle) -> Option<f64> {
self.has_emitted = true;
let prev = self.prev;
self.prev = Some(candle);
let Some(bar1) = prev else {
return Some(0.0);
};
// Both bars black, bar2's body inside bar1's body and smaller.
if bar1.close < bar1.open
&& candle.close < candle.open
&& candle.open <= bar1.open
&& candle.close >= bar1.close
&& (candle.open - candle.close) < (bar1.open - bar1.close)
{
return Some(1.0);
}
Some(0.0)
}
fn reset(&mut self) {
self.prev = None;
self.has_emitted = false;
}
fn warmup_period(&self) -> usize {
2
}
fn is_ready(&self) -> bool {
self.has_emitted
}
fn name(&self) -> &'static str {
"HomingPigeon"
}
}
#[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 t = HomingPigeon::new();
assert_eq!(t.name(), "HomingPigeon");
assert_eq!(t.warmup_period(), 2);
assert!(!t.is_ready());
}
#[test]
fn homing_pigeon_is_plus_one() {
let mut t = HomingPigeon::new();
assert_eq!(t.update(c(15.0, 15.1, 9.9, 10.0, 0)), Some(0.0));
assert_eq!(t.update(c(14.0, 14.1, 10.9, 11.0, 1)), Some(1.0));
}
#[test]
fn second_bar_white_yields_zero() {
let mut t = HomingPigeon::new();
t.update(c(15.0, 15.1, 9.9, 10.0, 0));
// bar2 white -> not a homing pigeon.
assert_eq!(t.update(c(11.0, 14.1, 10.9, 14.0, 1)), Some(0.0));
}
#[test]
fn second_body_not_inside_yields_zero() {
let mut t = HomingPigeon::new();
t.update(c(15.0, 15.1, 9.9, 10.0, 0));
// bar2 opens above bar1's open -> body not contained.
assert_eq!(t.update(c(16.0, 16.1, 10.9, 11.0, 1)), Some(0.0));
}
#[test]
fn first_bar_returns_zero() {
let mut t = HomingPigeon::new();
assert_eq!(t.update(c(15.0, 15.1, 9.9, 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 + 5.0, base + 5.1, base - 0.1, base, i)
})
.collect();
let mut a = HomingPigeon::new();
let mut b = HomingPigeon::new();
assert_eq!(
a.batch(&candles),
candles.iter().map(|x| b.update(*x)).collect::<Vec<_>>()
);
}
#[test]
fn reset_clears_state() {
let mut t = HomingPigeon::new();
t.update(c(15.0, 15.1, 9.9, 10.0, 0));
t.update(c(14.0, 14.1, 10.9, 11.0, 1));
assert!(t.is_ready());
t.reset();
assert!(!t.is_ready());
assert_eq!(t.update(c(15.0, 15.1, 9.9, 10.0, 0)), Some(0.0));
}
}