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//! Three Line Strike candlestick pattern.
use crate::ohlcv::Candle;
use crate::traits::Indicator;
/// Three Line Strike — a 4-bar pattern: three candles marching in one direction
/// (a three-soldiers / three-crows advance) followed by a fourth candle of the
/// opposite colour that opens beyond the third candle and closes back past the
/// first candle's open, "striking" through the whole run.
///
/// **Bullish** (`+1.0`):
/// ```text
/// bar1..bar3 green, each opening inside the prior body and closing higher
/// bar4 red & opens above bar3's close & closes below bar1's open
/// ```
///
/// **Bearish** (`−1.0`): the mirror — three falling red candles struck by a
/// green bar4 that opens below bar3's close and closes above bar1's open.
///
/// Output is `0.0` otherwise. The first three bars always return `0.0` because
/// the four-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, `−1.0` bearish, `0.0` no pattern — so it
/// drops straight into a machine-learning feature matrix where the bullish and
/// bearish variants occupy a single dimension.
///
/// # Example
///
/// ```
/// use wickra_core::{Candle, Indicator, ThreeLineStrike};
///
/// let mut indicator = ThreeLineStrike::new();
/// indicator.update(Candle::new(10.0, 11.1, 9.9, 11.0, 1.0, 0).unwrap());
/// indicator.update(Candle::new(10.5, 12.1, 10.4, 12.0, 1.0, 1).unwrap());
/// indicator.update(Candle::new(11.5, 13.1, 11.4, 13.0, 1.0, 2).unwrap());
/// let out = indicator
/// .update(Candle::new(13.5, 13.6, 9.4, 9.5, 1.0, 3).unwrap());
/// assert_eq!(out, Some(1.0));
/// ```
#[derive(Debug, Clone, Default)]
pub struct ThreeLineStrike {
c1: Option<Candle>,
c2: Option<Candle>,
c3: Option<Candle>,
has_emitted: bool,
}
impl ThreeLineStrike {
/// Construct a new Three Line Strike detector.
pub const fn new() -> Self {
Self {
c1: None,
c2: None,
c3: None,
has_emitted: false,
}
}
}
impl Indicator for ThreeLineStrike {
type Input = Candle;
type Output = f64;
fn update(&mut self, candle: Candle) -> Option<f64> {
self.has_emitted = true;
let bar1 = self.c1;
let bar2 = self.c2;
let bar3 = self.c3;
self.c1 = self.c2;
self.c2 = self.c3;
self.c3 = Some(candle);
let (Some(bar1), Some(bar2), Some(bar3)) = (bar1, bar2, bar3) else {
return Some(0.0);
};
// Bullish: three rising green candles struck by a red bar4.
if bar1.close > bar1.open
&& bar2.close > bar2.open
&& bar3.close > bar3.open
&& bar2.open >= bar1.open
&& bar2.open <= bar1.close
&& bar2.close > bar1.close
&& bar3.open >= bar2.open
&& bar3.open <= bar2.close
&& bar3.close > bar2.close
&& candle.close < candle.open
&& candle.open > bar3.close
&& candle.close < bar1.open
{
return Some(1.0);
}
// Bearish: three falling red candles struck by a green bar4.
if bar1.close < bar1.open
&& bar2.close < bar2.open
&& bar3.close < bar3.open
&& bar2.open <= bar1.open
&& bar2.open >= bar1.close
&& bar2.close < bar1.close
&& bar3.open <= bar2.open
&& bar3.open >= bar2.close
&& bar3.close < bar2.close
&& candle.close > candle.open
&& candle.open < bar3.close
&& candle.close > bar1.open
{
return Some(-1.0);
}
Some(0.0)
}
fn reset(&mut self) {
self.c1 = None;
self.c2 = None;
self.c3 = None;
self.has_emitted = false;
}
fn warmup_period(&self) -> usize {
4
}
fn is_ready(&self) -> bool {
self.has_emitted
}
fn name(&self) -> &'static str {
"ThreeLineStrike"
}
}
#[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 = ThreeLineStrike::new();
assert_eq!(t.name(), "ThreeLineStrike");
assert_eq!(t.warmup_period(), 4);
assert!(!t.is_ready());
}
#[test]
fn bullish_three_line_strike_is_plus_one() {
let mut t = ThreeLineStrike::new();
assert_eq!(t.update(c(10.0, 11.1, 9.9, 11.0, 0)), Some(0.0));
assert_eq!(t.update(c(10.5, 12.1, 10.4, 12.0, 1)), Some(0.0));
assert_eq!(t.update(c(11.5, 13.1, 11.4, 13.0, 2)), Some(0.0));
assert_eq!(t.update(c(13.5, 13.6, 9.4, 9.5, 3)), Some(1.0));
}
#[test]
fn bearish_three_line_strike_is_minus_one() {
let mut t = ThreeLineStrike::new();
assert_eq!(t.update(c(13.0, 13.1, 11.9, 12.0, 0)), Some(0.0));
assert_eq!(t.update(c(12.5, 12.6, 10.9, 11.0, 1)), Some(0.0));
assert_eq!(t.update(c(11.5, 11.6, 9.9, 10.0, 2)), Some(0.0));
assert_eq!(t.update(c(9.5, 13.6, 9.4, 13.5, 3)), Some(-1.0));
}
#[test]
fn strike_not_clearing_first_open_yields_zero() {
let mut t = ThreeLineStrike::new();
t.update(c(10.0, 11.1, 9.9, 11.0, 0));
t.update(c(10.5, 12.1, 10.4, 12.0, 1));
t.update(c(11.5, 13.1, 11.4, 13.0, 2));
// bar4 closes 10.5, above bar1's open (10.0) -> does not strike through.
assert_eq!(t.update(c(13.5, 13.6, 10.4, 10.5, 3)), Some(0.0));
}
#[test]
fn first_three_bars_return_zero() {
let mut t = ThreeLineStrike::new();
assert_eq!(t.update(c(10.0, 11.1, 9.9, 11.0, 0)), Some(0.0));
assert_eq!(t.update(c(10.5, 12.1, 10.4, 12.0, 1)), Some(0.0));
assert_eq!(t.update(c(11.5, 13.1, 11.4, 13.0, 2)), 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 + 1.5, base - 0.2, base + 1.0, i)
})
.collect();
let mut a = ThreeLineStrike::new();
let mut b = ThreeLineStrike::new();
assert_eq!(
a.batch(&candles),
candles.iter().map(|x| b.update(*x)).collect::<Vec<_>>()
);
}
#[test]
fn reset_clears_state() {
let mut t = ThreeLineStrike::new();
t.update(c(10.0, 11.1, 9.9, 11.0, 0));
t.update(c(10.5, 12.1, 10.4, 12.0, 1));
t.update(c(11.5, 13.1, 11.4, 13.0, 2));
t.update(c(13.5, 13.6, 9.4, 9.5, 3));
assert!(t.is_ready());
t.reset();
assert!(!t.is_ready());
assert_eq!(t.update(c(10.0, 11.1, 9.9, 11.0, 0)), Some(0.0));
}
}