F3: add MOM, CMO, TSI and PMO momentum indicators

Completes the F3 family (Momentum) end to end:

- Rust core: mom.rs (raw price-difference momentum), cmo.rs (Chande
  Momentum Oscillator — unsmoothed gain/loss sum, bounded [-100,100]),
  tsi.rs (True Strength Index — double-EMA-smoothed momentum ratio),
  pmo.rs (DecisionPoint Price Momentum Oscillator — doubly-smoothed ROC
  with the 2/period custom smoothing). Each with a full Indicator impl,
  runnable doctest and reference-value / saturation / warmup / reset /
  batch==streaming / non-finite tests.
- Python: PyMom / PyCmo / PyTsi / PyPmo PyO3 classes + module
  registration + .pyi stubs (defaults MOM=10, CMO=14, TSI=(25,13),
  PMO=(35,20)).
- Node: MomNode / CmoNode via the scalar macro, explicit TsiNode and
  PmoNode; index.d.ts and index.js updated.
- WASM: WasmMom / WasmCmo / WasmTsi / WasmPmo via the scalar macro.
- Wiki: Indicator-Mom/Cmo/Tsi/Pmo.md plus rows in Indicators-Overview.md
  and entries in Home.md.

cargo fmt + clippy (core/wickra/data/wasm/node) clean; 262 core tests,
25 data tests and 37 doctests green.

crates/wickra-core/src/indicators/cmo.rs

@@ -0,0 +1,218 @@
+//! Chande Momentum Oscillator.
+
+use std::collections::VecDeque;
+
+use crate::error::{Error, Result};
+use crate::traits::Indicator;
+
+/// Chande Momentum Oscillator — Tushar Chande's bounded momentum gauge.
+///
+/// Over the last `period` price *changes* it sums the gains and the losses
+/// separately and reports:
+///
+/// ```text
+/// CMO = 100 · (Σ gains − Σ losses) / (Σ gains + Σ losses)
+/// ```
+///
+/// The result is bounded in `[−100, 100]`: `+100` is a window of pure gains,
+/// `−100` a window of pure losses, `0` a perfect balance. Unlike RSI the sums
+/// are *unsmoothed* — every change in the window carries equal weight — so CMO
+/// reacts faster and swings wider.
+///
+/// # Example
+///
+/// ```
+/// use wickra_core::{Indicator, Cmo};
+///
+/// let mut indicator = Cmo::new(14).unwrap();
+/// let mut last = None;
+/// for i in 0..80 {
+///     last = indicator.update(100.0 + f64::from(i));
+/// }
+/// assert_eq!(last, Some(100.0)); // pure uptrend saturates at +100
+/// ```
+#[derive(Debug, Clone)]
+pub struct Cmo {
+    period: usize,
+    prev_price: Option<f64>,
+    /// Rolling window of `(gain, loss)` pairs, oldest at the front.
+    window: VecDeque<(f64, f64)>,
+    sum_gain: f64,
+    sum_loss: f64,
+    current: Option<f64>,
+}
+
+impl Cmo {
+    /// Construct a new CMO with the given period.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`Error::PeriodZero`] if `period == 0`.
+    pub fn new(period: usize) -> Result<Self> {
+        if period == 0 {
+            return Err(Error::PeriodZero);
+        }
+        Ok(Self {
+            period,
+            prev_price: None,
+            window: VecDeque::with_capacity(period),
+            sum_gain: 0.0,
+            sum_loss: 0.0,
+            current: None,
+        })
+    }
+
+    /// Configured period.
+    pub const fn period(&self) -> usize {
+        self.period
+    }
+
+    /// Current value if available.
+    pub const fn value(&self) -> Option<f64> {
+        self.current
+    }
+}
+
+impl Indicator for Cmo {
+    type Input = f64;
+    type Output = f64;
+
+    fn update(&mut self, input: f64) -> Option<f64> {
+        if !input.is_finite() {
+            // Non-finite input is ignored; state is left untouched.
+            return self.current;
+        }
+        let Some(prev) = self.prev_price else {
+            self.prev_price = Some(input);
+            return None;
+        };
+        self.prev_price = Some(input);
+
+        let change = input - prev;
+        let gain = change.max(0.0);
+        let loss = (-change).max(0.0);
+
+        if self.window.len() == self.period {
+            let (old_gain, old_loss) = self.window.pop_front().expect("window is non-empty");
+            self.sum_gain -= old_gain;
+            self.sum_loss -= old_loss;
+        }
+        self.window.push_back((gain, loss));
+        self.sum_gain += gain;
+        self.sum_loss += loss;
+
+        if self.window.len() < self.period {
+            return None;
+        }
+        let denom = self.sum_gain + self.sum_loss;
+        let cmo = if denom == 0.0 {
+            // A flat window (no gains and no losses): momentum is exactly zero.
+            0.0
+        } else {
+            100.0 * (self.sum_gain - self.sum_loss) / denom
+        };
+        self.current = Some(cmo);
+        Some(cmo)
+    }
+
+    fn reset(&mut self) {
+        self.prev_price = None;
+        self.window.clear();
+        self.sum_gain = 0.0;
+        self.sum_loss = 0.0;
+        self.current = None;
+    }
+
+    fn warmup_period(&self) -> usize {
+        self.period + 1
+    }
+
+    fn is_ready(&self) -> bool {
+        self.current.is_some()
+    }
+
+    fn name(&self) -> &'static str {
+        "CMO"
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::traits::BatchExt;
+    use approx::assert_relative_eq;
+
+    #[test]
+    fn new_rejects_zero_period() {
+        assert!(matches!(Cmo::new(0), Err(Error::PeriodZero)));
+    }
+
+    #[test]
+    fn reference_value() {
+        // CMO(3) over [10, 11, 10, 12]: changes +1, −1, +2.
+        // Σgain = 3, Σloss = 1 -> 100·(3−1)/(3+1) = 50.
+        let mut cmo = Cmo::new(3).unwrap();
+        let out = cmo.batch(&[10.0, 11.0, 10.0, 12.0]);
+        assert_eq!(cmo.warmup_period(), 4);
+        assert_eq!(out[0], None);
+        assert_eq!(out[2], None);
+        assert_relative_eq!(out[3].unwrap(), 50.0, epsilon = 1e-12);
+    }
+
+    #[test]
+    fn pure_uptrend_saturates_at_plus_100() {
+        let mut cmo = Cmo::new(5).unwrap();
+        let out = cmo.batch(&(1..=20).map(f64::from).collect::<Vec<_>>());
+        for v in out.iter().skip(6).flatten() {
+            assert_relative_eq!(*v, 100.0, epsilon = 1e-12);
+        }
+    }
+
+    #[test]
+    fn pure_downtrend_saturates_at_minus_100() {
+        let mut cmo = Cmo::new(5).unwrap();
+        let out = cmo.batch(&(1..=20).rev().map(f64::from).collect::<Vec<_>>());
+        for v in out.iter().skip(6).flatten() {
+            assert_relative_eq!(*v, -100.0, epsilon = 1e-12);
+        }
+    }
+
+    #[test]
+    fn constant_series_yields_zero() {
+        let mut cmo = Cmo::new(5).unwrap();
+        let out = cmo.batch(&[42.0; 20]);
+        for v in out.iter().skip(6).flatten() {
+            assert_relative_eq!(*v, 0.0, epsilon = 1e-12);
+        }
+    }
+
+    #[test]
+    fn ignores_non_finite_input() {
+        let mut cmo = Cmo::new(3).unwrap();
+        let out = cmo.batch(&[10.0, 11.0, 10.0, 12.0]);
+        let ready = out[3].expect("CMO(3) ready after four inputs");
+        assert_eq!(cmo.update(f64::NAN), Some(ready));
+        assert_eq!(cmo.update(f64::INFINITY), Some(ready));
+    }
+
+    #[test]
+    fn reset_clears_state() {
+        let mut cmo = Cmo::new(3).unwrap();
+        cmo.batch(&[10.0, 11.0, 12.0, 13.0, 14.0]);
+        assert!(cmo.is_ready());
+        cmo.reset();
+        assert!(!cmo.is_ready());
+        assert_eq!(cmo.update(10.0), None);
+    }
+
+    #[test]
+    fn batch_equals_streaming() {
+        let prices: Vec<f64> = (1..=60)
+            .map(|i| 100.0 + (f64::from(i) * 0.4).sin() * 6.0)
+            .collect();
+        let batch = Cmo::new(9).unwrap().batch(&prices);
+        let mut b = Cmo::new(9).unwrap();
+        let streamed: Vec<_> = prices.iter().map(|p| b.update(*p)).collect();
+        assert_eq!(batch, streamed);
+    }
+}

crates/wickra-core/src/indicators/mod.rs

@@ -10,6 +10,7 @@ mod atr;
 mod awesome_oscillator;
 mod bollinger;
 mod cci;
+mod cmo;
 mod dema;
 mod donchian;
 mod ema;
@@ -18,7 +19,9 @@ mod kama;
 mod keltner;
 mod macd;
 mod mfi;
+mod mom;
 mod obv;
+mod pmo;
 mod psar;
 mod roc;
 mod rsi;
@@ -29,6 +32,7 @@ mod t3;
 mod tema;
 mod trima;
 mod trix;
+mod tsi;
 mod vwap;
 mod vwma;
 mod williams_r;
@@ -41,6 +45,7 @@ pub use atr::Atr;
 pub use awesome_oscillator::AwesomeOscillator;
 pub use bollinger::{BollingerBands, BollingerOutput};
 pub use cci::Cci;
+pub use cmo::Cmo;
 pub use dema::Dema;
 pub use donchian::{Donchian, DonchianOutput};
 pub use ema::Ema;
@@ -49,7 +54,9 @@ pub use kama::Kama;
 pub use keltner::{Keltner, KeltnerOutput};
 pub use macd::{MacdIndicator, MacdOutput};
 pub use mfi::Mfi;
+pub use mom::Mom;
 pub use obv::Obv;
+pub use pmo::Pmo;
 pub use psar::Psar;
 pub use roc::Roc;
 pub use rsi::Rsi;
@@ -60,6 +67,7 @@ pub use t3::T3;
 pub use tema::Tema;
 pub use trima::Trima;
 pub use trix::Trix;
+pub use tsi::Tsi;
 pub use vwap::{RollingVwap, Vwap};
 pub use vwma::Vwma;
 pub use williams_r::WilliamsR;

crates/wickra-core/src/indicators/mom.rs

@@ -0,0 +1,167 @@
+//! Momentum (absolute price change over a fixed lookback).
+
+use std::collections::VecDeque;
+
+use crate::error::{Error, Result};
+use crate::traits::Indicator;
+
+/// Momentum: the raw price change over `period` bars, `price_t − price_{t−period}`.
+///
+/// Unlike [`Roc`](crate::Roc), which divides by the old price to give a
+/// percentage, `Mom` reports the change in absolute price units. It is the
+/// simplest momentum primitive: positive values mean price is higher than it
+/// was `period` bars ago, negative values mean lower.
+///
+/// Non-finite inputs are ignored and leave the window untouched; the last
+/// computed value is returned instead.
+///
+/// # Example
+///
+/// ```
+/// use wickra_core::{Indicator, Mom};
+///
+/// let mut indicator = Mom::new(3).unwrap();
+/// let mut last = None;
+/// for i in 0..80 {
+///     last = indicator.update(100.0 + f64::from(i));
+/// }
+/// assert!(last.is_some());
+/// ```
+#[derive(Debug, Clone)]
+pub struct Mom {
+    period: usize,
+    /// Rolling buffer of the last `period + 1` inputs, oldest at the front.
+    window: VecDeque<f64>,
+    last: Option<f64>,
+}
+
+impl Mom {
+    /// Construct a new momentum indicator with the given lookback period.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`Error::PeriodZero`] if `period == 0`.
+    pub fn new(period: usize) -> Result<Self> {
+        if period == 0 {
+            return Err(Error::PeriodZero);
+        }
+        Ok(Self {
+            period,
+            window: VecDeque::with_capacity(period + 1),
+            last: None,
+        })
+    }
+
+    /// Configured lookback period.
+    pub const fn period(&self) -> usize {
+        self.period
+    }
+
+    /// Current value if available.
+    pub const fn value(&self) -> Option<f64> {
+        self.last
+    }
+}
+
+impl Indicator for Mom {
+    type Input = f64;
+    type Output = f64;
+
+    fn update(&mut self, input: f64) -> Option<f64> {
+        if !input.is_finite() {
+            // Non-finite input is ignored; the window is left untouched.
+            return self.last;
+        }
+        if self.window.len() == self.period + 1 {
+            self.window.pop_front();
+        }
+        self.window.push_back(input);
+        if self.window.len() < self.period + 1 {
+            return None;
+        }
+        let prev = *self.window.front().expect("window is non-empty");
+        let mom = input - prev;
+        self.last = Some(mom);
+        Some(mom)
+    }
+
+    fn reset(&mut self) {
+        self.window.clear();
+        self.last = None;
+    }
+
+    fn warmup_period(&self) -> usize {
+        self.period + 1
+    }
+
+    fn is_ready(&self) -> bool {
+        self.window.len() == self.period + 1
+    }
+
+    fn name(&self) -> &'static str {
+        "MOM"
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::traits::BatchExt;
+    use approx::assert_relative_eq;
+
+    #[test]
+    fn new_rejects_zero_period() {
+        assert!(matches!(Mom::new(0), Err(Error::PeriodZero)));
+    }
+
+    #[test]
+    fn reference_values() {
+        // MOM(3): price_t − price_{t-3}.
+        let mut mom = Mom::new(3).unwrap();
+        let out = mom.batch(&[1.0, 2.0, 3.0, 4.0, 7.0]);
+        assert_eq!(mom.warmup_period(), 4);
+        assert_eq!(out[0], None);
+        assert_eq!(out[2], None);
+        assert_relative_eq!(out[3].unwrap(), 4.0 - 1.0, epsilon = 1e-12);
+        assert_relative_eq!(out[4].unwrap(), 7.0 - 2.0, epsilon = 1e-12);
+    }
+
+    #[test]
+    fn constant_series_yields_zero() {
+        let mut mom = Mom::new(5).unwrap();
+        let out = mom.batch(&[10.0; 20]);
+        for v in out.iter().skip(5).flatten() {
+            assert_relative_eq!(*v, 0.0, epsilon = 1e-12);
+        }
+    }
+
+    #[test]
+    fn ignores_non_finite_input() {
+        let mut mom = Mom::new(3).unwrap();
+        let out = mom.batch(&[1.0, 2.0, 3.0, 4.0]);
+        let ready = out[3].expect("MOM(3) ready after four inputs");
+        assert_eq!(mom.update(f64::NAN), Some(ready));
+        assert_eq!(mom.update(f64::INFINITY), Some(ready));
+        // Window untouched: the next finite input still references price 2.
+        assert_relative_eq!(mom.update(10.0).unwrap(), 10.0 - 2.0, epsilon = 1e-12);
+    }
+
+    #[test]
+    fn reset_clears_state() {
+        let mut mom = Mom::new(3).unwrap();
+        mom.batch(&[1.0, 2.0, 3.0, 4.0, 5.0]);
+        assert!(mom.is_ready());
+        mom.reset();
+        assert!(!mom.is_ready());
+        assert_eq!(mom.update(1.0), None);
+    }
+
+    #[test]
+    fn batch_equals_streaming() {
+        let prices: Vec<f64> = (1..=40).map(|i| f64::from(i) * 1.5).collect();
+        let batch = Mom::new(7).unwrap().batch(&prices);
+        let mut b = Mom::new(7).unwrap();
+        let streamed: Vec<_> = prices.iter().map(|p| b.update(*p)).collect();
+        assert_eq!(batch, streamed);
+    }
+}

crates/wickra-core/src/indicators/pmo.rs

@@ -0,0 +1,213 @@
+//! Price Momentum Oscillator (`DecisionPoint`).
+
+use crate::error::{Error, Result};
+use crate::traits::Indicator;
+
+use super::Ema;
+
+/// Price Momentum Oscillator — Carl Swenlin's `DecisionPoint` PMO line.
+///
+/// PMO is a doubly-smoothed rate of change. The 1-bar percentage change is
+/// smoothed once, scaled by `10`, then smoothed again:
+///
+/// ```text
+/// roc_t       = (price_t / price_{t−1} − 1) · 100
+/// smoothed_t  = customEMA(roc, smoothing1)_t
+/// PMO_t       = customEMA(10 · smoothed, smoothing2)_t
+/// ```
+///
+/// `customEMA` is the `DecisionPoint` smoothing: an exponential average whose
+/// smoothing constant is `2 / period` (not the textbook `2 / (period + 1)`),
+/// seeded from the very first value. The conventional periods are `35` and
+/// `20`. The classic PMO **signal line** is simply a 10-period EMA of this
+/// PMO line — compose it with [`Chain`](crate::Chain) and an [`Ema`] if you
+/// need it.
+///
+/// # Example
+///
+/// ```
+/// use wickra_core::{Indicator, Pmo};
+///
+/// let mut indicator = Pmo::new(35, 20).unwrap();
+/// let mut last = None;
+/// for i in 0..120 {
+///     last = indicator.update(100.0 + f64::from(i));
+/// }
+/// assert!(last.is_some());
+/// ```
+#[derive(Debug, Clone)]
+pub struct Pmo {
+    smoothing1: usize,
+    smoothing2: usize,
+    prev_price: Option<f64>,
+    ema1: Ema,
+    ema2: Ema,
+    current: Option<f64>,
+}
+
+impl Pmo {
+    /// Construct a new PMO with the two smoothing periods.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`Error::PeriodZero`] if either period is `0`, or
+    /// [`Error::InvalidPeriod`] if either is `1` (the smoothing constant
+    /// `2 / period` must not exceed `1`).
+    pub fn new(smoothing1: usize, smoothing2: usize) -> Result<Self> {
+        if smoothing1 == 0 || smoothing2 == 0 {
+            return Err(Error::PeriodZero);
+        }
+        if smoothing1 < 2 || smoothing2 < 2 {
+            return Err(Error::InvalidPeriod {
+                message: "PMO smoothing periods must be >= 2",
+            });
+        }
+        Ok(Self {
+            smoothing1,
+            smoothing2,
+            prev_price: None,
+            ema1: Ema::with_alpha(2.0 / smoothing1 as f64)?,
+            ema2: Ema::with_alpha(2.0 / smoothing2 as f64)?,
+            current: None,
+        })
+    }
+
+    /// The `(smoothing1, smoothing2)` periods.
+    pub const fn periods(&self) -> (usize, usize) {
+        (self.smoothing1, self.smoothing2)
+    }
+
+    /// Current value if available.
+    pub const fn value(&self) -> Option<f64> {
+        self.current
+    }
+}
+
+impl Indicator for Pmo {
+    type Input = f64;
+    type Output = f64;
+
+    fn update(&mut self, input: f64) -> Option<f64> {
+        if !input.is_finite() {
+            // Non-finite input is ignored; state is left untouched.
+            return self.current;
+        }
+        let Some(prev) = self.prev_price else {
+            self.prev_price = Some(input);
+            return None;
+        };
+        self.prev_price = Some(input);
+
+        let roc = if prev == 0.0 {
+            // Undefined ratio against a zero price: treat momentum as flat.
+            0.0
+        } else {
+            (input / prev - 1.0) * 100.0
+        };
+        let smoothed = self.ema1.update(roc)?;
+        let pmo = self.ema2.update(10.0 * smoothed)?;
+        self.current = Some(pmo);
+        Some(pmo)
+    }
+
+    fn reset(&mut self) {
+        self.prev_price = None;
+        self.ema1.reset();
+        self.ema2.reset();
+        self.current = None;
+    }
+
+    fn warmup_period(&self) -> usize {
+        // The first ROC needs a previous price; both customEMAs seed from
+        // their first input, so the first PMO lands on the second update.
+        2
+    }
+
+    fn is_ready(&self) -> bool {
+        self.current.is_some()
+    }
+
+    fn name(&self) -> &'static str {
+        "PMO"
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::traits::BatchExt;
+    use approx::assert_relative_eq;
+
+    #[test]
+    fn new_rejects_zero_period() {
+        assert!(matches!(Pmo::new(0, 20), Err(Error::PeriodZero)));
+        assert!(matches!(Pmo::new(35, 0), Err(Error::PeriodZero)));
+    }
+
+    #[test]
+    fn new_rejects_period_one() {
+        assert!(matches!(Pmo::new(1, 20), Err(Error::InvalidPeriod { .. })));
+        assert!(matches!(Pmo::new(35, 1), Err(Error::InvalidPeriod { .. })));
+    }
+
+    #[test]
+    fn first_emission_at_second_update() {
+        let mut pmo = Pmo::new(35, 20).unwrap();
+        assert_eq!(pmo.warmup_period(), 2);
+        assert_eq!(pmo.update(100.0), None);
+        assert!(pmo.update(101.0).is_some());
+    }
+
+    #[test]
+    fn constant_series_yields_zero() {
+        // Flat prices -> ROC is always 0 -> both smoothings stay at 0.
+        let mut pmo = Pmo::new(35, 20).unwrap();
+        let out = pmo.batch(&[100.0; 60]);
+        for v in out.iter().skip(2).flatten() {
+            assert_relative_eq!(*v, 0.0, epsilon = 1e-12);
+        }
+    }
+
+    #[test]
+    fn steady_uptrend_is_positive() {
+        let mut pmo = Pmo::new(35, 20).unwrap();
+        let prices: Vec<f64> = (1..=120).map(|i| 100.0 * 1.01_f64.powi(i)).collect();
+        let out = pmo.batch(&prices);
+        let last = out.iter().rev().flatten().next().unwrap();
+        assert!(
+            *last > 0.0,
+            "steady uptrend PMO should be positive, got {last}"
+        );
+    }
+
+    #[test]
+    fn ignores_non_finite_input() {
+        let mut pmo = Pmo::new(35, 20).unwrap();
+        let out = pmo.batch(&(1..=60).map(f64::from).collect::<Vec<_>>());
+        let last = *out.last().unwrap();
+        assert!(last.is_some());
+        assert_eq!(pmo.update(f64::NAN), last);
+        assert_eq!(pmo.update(f64::INFINITY), last);
+    }
+
+    #[test]
+    fn reset_clears_state() {
+        let mut pmo = Pmo::new(35, 20).unwrap();
+        pmo.batch(&(1..=60).map(f64::from).collect::<Vec<_>>());
+        assert!(pmo.is_ready());
+        pmo.reset();
+        assert!(!pmo.is_ready());
+        assert_eq!(pmo.update(1.0), None);
+    }
+
+    #[test]
+    fn batch_equals_streaming() {
+        let prices: Vec<f64> = (1..=120)
+            .map(|i| 100.0 + (f64::from(i) * 0.25).sin() * 8.0)
+            .collect();
+        let batch = Pmo::new(35, 20).unwrap().batch(&prices);
+        let mut b = Pmo::new(35, 20).unwrap();
+        let streamed: Vec<_> = prices.iter().map(|p| b.update(*p)).collect();
+        assert_eq!(batch, streamed);
+    }
+}

crates/wickra-core/src/indicators/tsi.rs

@@ -0,0 +1,223 @@
+//! True Strength Index.
+
+use crate::error::{Error, Result};
+use crate::traits::Indicator;
+
+use super::Ema;
+
+/// True Strength Index — William Blau's double-smoothed momentum oscillator.
+///
+/// The 1-bar momentum `price_t − price_{t−1}` and its absolute value are each
+/// smoothed twice — first with an EMA of length `long`, then with an EMA of
+/// length `short` — and the indicator reports their ratio scaled to a
+/// percentage:
+///
+/// ```text
+/// TSI = 100 · EMA_short(EMA_long(momentum)) / EMA_short(EMA_long(|momentum|))
+/// ```
+///
+/// The double smoothing strips most of the noise while the ratio normalises
+/// the result into a roughly `[−100, 100]` oscillator centred on zero:
+/// positive means net upward pressure, negative net downward.
+///
+/// # Example
+///
+/// ```
+/// use wickra_core::{Indicator, Tsi};
+///
+/// let mut indicator = Tsi::new(25, 13).unwrap();
+/// let mut last = None;
+/// for i in 0..80 {
+///     last = indicator.update(100.0 + f64::from(i));
+/// }
+/// assert_eq!(last, Some(100.0)); // pure uptrend saturates at +100
+/// ```
+#[derive(Debug, Clone)]
+pub struct Tsi {
+    long: usize,
+    short: usize,
+    prev_price: Option<f64>,
+    ema_long_mom: Ema,
+    ema_short_mom: Ema,
+    ema_long_abs: Ema,
+    ema_short_abs: Ema,
+    current: Option<f64>,
+}
+
+impl Tsi {
+    /// Construct a new TSI with the `long` and `short` smoothing periods.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`Error::PeriodZero`] if either period is `0`.
+    pub fn new(long: usize, short: usize) -> Result<Self> {
+        if long == 0 || short == 0 {
+            return Err(Error::PeriodZero);
+        }
+        Ok(Self {
+            long,
+            short,
+            prev_price: None,
+            ema_long_mom: Ema::new(long)?,
+            ema_short_mom: Ema::new(short)?,
+            ema_long_abs: Ema::new(long)?,
+            ema_short_abs: Ema::new(short)?,
+            current: None,
+        })
+    }
+
+    /// The `(long, short)` smoothing periods.
+    pub const fn periods(&self) -> (usize, usize) {
+        (self.long, self.short)
+    }
+
+    /// Current value if available.
+    pub const fn value(&self) -> Option<f64> {
+        self.current
+    }
+}
+
+impl Indicator for Tsi {
+    type Input = f64;
+    type Output = f64;
+
+    fn update(&mut self, input: f64) -> Option<f64> {
+        if !input.is_finite() {
+            // Non-finite input is ignored; state is left untouched.
+            return self.current;
+        }
+        let Some(prev) = self.prev_price else {
+            self.prev_price = Some(input);
+            return None;
+        };
+        self.prev_price = Some(input);
+
+        let momentum = input - prev;
+        let ds_mom = self
+            .ema_long_mom
+            .update(momentum)
+            .and_then(|v| self.ema_short_mom.update(v));
+        let ds_abs = self
+            .ema_long_abs
+            .update(momentum.abs())
+            .and_then(|v| self.ema_short_abs.update(v));
+
+        match (ds_mom, ds_abs) {
+            (Some(m), Some(a)) => {
+                let tsi = if a == 0.0 {
+                    // Flat double-smoothed range: there is no momentum at all.
+                    0.0
+                } else {
+                    100.0 * m / a
+                };
+                self.current = Some(tsi);
+                Some(tsi)
+            }
+            _ => None,
+        }
+    }
+
+    fn reset(&mut self) {
+        self.prev_price = None;
+        self.ema_long_mom.reset();
+        self.ema_short_mom.reset();
+        self.ema_long_abs.reset();
+        self.ema_short_abs.reset();
+        self.current = None;
+    }
+
+    fn warmup_period(&self) -> usize {
+        self.long + self.short
+    }
+
+    fn is_ready(&self) -> bool {
+        self.current.is_some()
+    }
+
+    fn name(&self) -> &'static str {
+        "TSI"
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::traits::BatchExt;
+    use approx::assert_relative_eq;
+
+    #[test]
+    fn new_rejects_zero_period() {
+        assert!(matches!(Tsi::new(0, 13), Err(Error::PeriodZero)));
+        assert!(matches!(Tsi::new(25, 0), Err(Error::PeriodZero)));
+    }
+
+    #[test]
+    fn first_emission_at_warmup_period() {
+        let mut tsi = Tsi::new(5, 3).unwrap();
+        assert_eq!(tsi.warmup_period(), 8);
+        let out = tsi.batch(&(1..=40).map(f64::from).collect::<Vec<_>>());
+        for v in out.iter().take(7) {
+            assert!(v.is_none());
+        }
+        assert!(out[7].is_some());
+    }
+
+    #[test]
+    fn pure_uptrend_saturates_at_plus_100() {
+        // Every momentum is +1, so |momentum| == momentum and the ratio is 1.
+        let mut tsi = Tsi::new(5, 3).unwrap();
+        let out = tsi.batch(&(1..=40).map(f64::from).collect::<Vec<_>>());
+        for v in out.iter().skip(8).flatten() {
+            assert_relative_eq!(*v, 100.0, epsilon = 1e-9);
+        }
+    }
+
+    #[test]
+    fn pure_downtrend_saturates_at_minus_100() {
+        let mut tsi = Tsi::new(5, 3).unwrap();
+        let out = tsi.batch(&(1..=40).rev().map(f64::from).collect::<Vec<_>>());
+        for v in out.iter().skip(8).flatten() {
+            assert_relative_eq!(*v, -100.0, epsilon = 1e-9);
+        }
+    }
+
+    #[test]
+    fn constant_series_yields_zero() {
+        let mut tsi = Tsi::new(5, 3).unwrap();
+        let out = tsi.batch(&[50.0; 40]);
+        for v in out.iter().skip(8).flatten() {
+            assert_relative_eq!(*v, 0.0, epsilon = 1e-12);
+        }
+    }
+
+    #[test]
+    fn ignores_non_finite_input() {
+        let mut tsi = Tsi::new(5, 3).unwrap();
+        let out = tsi.batch(&(1..=40).map(f64::from).collect::<Vec<_>>());
+        let last = *out.last().unwrap();
+        assert!(last.is_some());
+        assert_eq!(tsi.update(f64::NAN), last);
+        assert_eq!(tsi.update(f64::INFINITY), last);
+    }
+
+    #[test]
+    fn reset_clears_state() {
+        let mut tsi = Tsi::new(5, 3).unwrap();
+        tsi.batch(&(1..=40).map(f64::from).collect::<Vec<_>>());
+        assert!(tsi.is_ready());
+        tsi.reset();
+        assert!(!tsi.is_ready());
+        assert_eq!(tsi.update(1.0), None);
+    }
+
+    #[test]
+    fn batch_equals_streaming() {
+        let prices: Vec<f64> = (1..=80)
+            .map(|i| 100.0 + (f64::from(i) * 0.3).sin() * 9.0)
+            .collect();
+        let batch = Tsi::new(13, 7).unwrap().batch(&prices);
+        let mut b = Tsi::new(13, 7).unwrap();
+        let streamed: Vec<_> = prices.iter().map(|p| b.update(*p)).collect();
+        assert_eq!(batch, streamed);
+    }
+}