feat: init the repo

src/pattern/common.rs

@@ -0,0 +1,51 @@
+//! Shared helpers for candlestick pattern detection.
+
+use pyo3::prelude::PyResult;
+
+/// Validate that open, high, low, close arrays have the same length (for use in CDL* functions).
+pub fn validate_ohlc_length(
+    open_len: usize,
+    high_len: usize,
+    low_len: usize,
+    close_len: usize,
+) -> PyResult<()> {
+    crate::validation::validate_equal_length(&[
+        (open_len, "open"),
+        (high_len, "high"),
+        (low_len, "low"),
+        (close_len, "close"),
+    ])
+}
+
+/// Epsilon for doji-like candles (body ≈ 0) to avoid division by zero.
+pub const DOJI_BODY_EPSILON: f64 = 0.0001;
+
+#[inline]
+pub fn body_size(open: f64, close: f64) -> f64 {
+    (close - open).abs()
+}
+
+#[inline]
+pub fn upper_shadow(open: f64, high: f64, close: f64) -> f64 {
+    high - open.max(close)
+}
+
+#[inline]
+pub fn lower_shadow(open: f64, low: f64, close: f64) -> f64 {
+    open.min(close) - low
+}
+
+#[inline]
+pub fn candle_range(high: f64, low: f64) -> f64 {
+    high - low
+}
+
+#[inline]
+pub fn is_bullish(open: f64, close: f64) -> bool {
+    close >= open
+}
+
+#[inline]
+pub fn is_bearish(open: f64, close: f64) -> bool {
+    close < open
+}