finance-query 2.5.1

//! Higher-timeframe (HTF) condition wrapper.
//!
//! [`htf()`] wraps any [`Condition`] to evaluate it on a resampled
//! higher-timeframe candle series, enabling multi-timeframe confirmation
//! without look-ahead bias. Use [`htf_region()`] when the underlying instrument
//! trades on a non-UTC exchange (e.g. Tokyo, Hong Kong) to ensure weekly and
//! monthly bucket boundaries align with the local calendar.
//!
//! # How it works — fast path (engine pre-computation)
//!
//! When the strategy is built with [`StrategyBuilder`], the engine pre-computes
//! all HTF indicator arrays once before the main simulation loop:
//!
//! 1. Collects [`HtfIndicatorSpec`]s from `HtfCondition::htf_requirements()`.
//! 2. Resamples the full candle history to each unique HTF interval **once**.
//! 3. Computes the inner indicators on the resampled data.
//! 4. Stretches results back to base-timeframe length via `base_to_htf_index`.
//! 5. Stores stretched arrays in `StrategyContext::indicators` under `htf_key`.
//!
//! On each bar, `evaluate()` does only O(k) work (k = # inner indicators):
//! it reads the pre-computed values, builds a tiny 2-element indicator map, and
//! evaluates the inner condition. HTF crossovers work correctly because the map
//! stores `[prev, current]`.
//!
//! # Fallback (dynamic resampling)
//!
//! If the pre-computed arrays are not found in `ctx.indicators` (e.g. a raw
//! [`Strategy`] implementation that doesn't forward `htf_requirements()`), the
//! condition falls back to dynamic resampling — O(n) per bar, O(n²) total.
//! A `tracing::warn!` is emitted once per evaluation so the caller can diagnose
//! the performance issue.
//!
//! # Example
//!
//! ```ignore
//! use finance_query::backtesting::{StrategyBuilder, BacktestConfig, BacktestEngine};
//! use finance_query::backtesting::refs::*;
//! use finance_query::Interval;
//!
//! // Enter only when daily EMA10 crosses EMA30 AND weekly price > SMA20
//! let strategy = StrategyBuilder::new("MTF Confirmation")
//!     .entry(
//!         ema(10).crosses_above_ref(ema(30))
//!             .and(htf(Interval::OneWeek, price().above_ref(sma(20))))
//!     )
//!     .exit(ema(10).crosses_below_ref(ema(30)))
//!     .build();
//! ```
//!
//! For a Tokyo Stock Exchange strategy:
//!
//! ```ignore
//! use finance_query::backtesting::refs::*;
//! use finance_query::{Interval, Region};
//!
//! let weekly_trend = htf_region(Interval::OneWeek, Region::Japan, price().above_ref(sma(20)));
//! ```
//!
//! [`StrategyBuilder`]: crate::backtesting::strategy::StrategyBuilder
//! [`Strategy`]: crate::backtesting::strategy::Strategy

use std::collections::HashMap;

use crate::backtesting::condition::{Condition, HtfIndicatorSpec};
use crate::backtesting::engine::compute_for_candles;
use crate::backtesting::resample::resample;
use crate::backtesting::strategy::StrategyContext;
use crate::constants::{Interval, Region};
use crate::indicators::Indicator;

/// A condition that evaluates its inner condition on a resampled HTF candle series.
///
/// Created by [`htf()`] (UTC-aligned) or [`htf_region()`] (exchange-local calendar).
#[derive(Clone)]
pub struct HtfCondition<C: Condition> {
    interval: Interval,
    inner: C,
    /// UTC offset of the exchange. Shifts bucket boundaries so weekly/monthly
    /// periods align with the exchange's local calendar rather than UTC midnight.
    utc_offset_secs: i64,
}

impl<C: Condition> Condition for HtfCondition<C> {
    fn evaluate(&self, ctx: &StrategyContext) -> bool {
        let required = self.inner.required_indicators();

        // ── Fast path: use pre-computed stretched arrays from the engine ──────
        // The engine stores stretched HTF values in ctx.indicators under keys of
        // the form "htf_{interval}_{base_key}" (e.g. "htf_1wk_sma_20").
        //
        // We build a tiny 2-element indicators map [prev, curr] so that the inner
        // condition's crossover helpers (indicator_prev / crossed_above etc.) work
        // correctly, then evaluate with index=1.
        if !required.is_empty() {
            let interval_str = self.interval.as_str();
            let mut mini_indicators: HashMap<String, Vec<Option<f64>>> =
                HashMap::with_capacity(required.len());
            let mut all_found = true;

            for (base_key, _) in &required {
                let htf_key = format!("htf_{}_{}", interval_str, base_key);
                if let Some(stretched) = ctx.indicators.get(&htf_key) {
                    let curr = stretched.get(ctx.index).copied().flatten();
                    let prev = ctx
                        .index
                        .checked_sub(1)
                        .and_then(|pi| stretched.get(pi).copied().flatten());
                    // index=1 → curr; index=0 → prev (via indicator_prev)
                    mini_indicators.insert(base_key.clone(), vec![prev, curr]);
                } else {
                    all_found = false;
                    break;
                }
            }

            if all_found {
                // Use a 2-candle slice [prev_bar, current_bar] so that
                // current_candle() (index=1) returns the correct base bar.
                let start = ctx.index.saturating_sub(1);
                let htf_ctx = StrategyContext {
                    candles: &ctx.candles[start..=ctx.index],
                    index: ctx.index - start, // 1 unless at bar 0
                    position: ctx.position,
                    equity: ctx.equity,
                    indicators: &mini_indicators,
                };
                return self.inner.evaluate(&htf_ctx);
            }
        } else {
            // Pure price condition — no HTF indicators needed.
            // Evaluate directly so price() reads from the current base bar.
            return self.inner.evaluate(ctx);
        }

        // ── Fallback: dynamic resampling (O(n) per bar → O(n²) total) ────────
        // Reached only when the strategy does not implement htf_requirements()
        // (e.g. a raw Strategy impl). StrategyBuilder-based strategies never hit
        // this path because the engine pre-computes the stretched arrays.
        tracing::warn!(
            interval = %self.interval,
            "HtfCondition falling back to O(n²) dynamic resampling — \
             implement Strategy::htf_requirements() or use StrategyBuilder \
             to enable O(1) pre-computed HTF lookups"
        );
        self.evaluate_dynamic(ctx)
    }

    fn required_indicators(&self) -> Vec<(String, Indicator)> {
        // HtfCondition resolves its own indicators on resampled data.
        // The main engine must NOT pre-compute these on the base-TF candles.
        vec![]
    }

    fn htf_requirements(&self) -> Vec<HtfIndicatorSpec> {
        let interval_str = self.interval.as_str();
        self.inner
            .required_indicators()
            .into_iter()
            .map(|(base_key, indicator)| HtfIndicatorSpec {
                interval: self.interval,
                htf_key: format!("htf_{}_{}", interval_str, base_key),
                base_key,
                indicator,
                utc_offset_secs: self.utc_offset_secs,
            })
            .collect()
    }

    fn description(&self) -> String {
        format!("htf({}, {})", self.interval, self.inner.description())
    }
}

impl<C: Condition> HtfCondition<C> {
    /// Dynamic resampling fallback used when pre-computed data is unavailable.
    ///
    /// This is O(n) per bar (O(n²) overall). It finds the most recently
    /// *completed* HTF bar (timestamp < current bar) to avoid look-ahead bias.
    fn evaluate_dynamic(&self, ctx: &StrategyContext) -> bool {
        let htf_candles = resample(ctx.candles, self.interval, self.utc_offset_secs);

        // Find the most recently completed HTF bar — timestamp strictly less than
        // the current base bar's timestamp. In the dynamic path we use `<` (not
        // `<=`) to conservatively exclude the in-progress period: we only have
        // candles up to ctx.index, so the last HTF bar may be partial.
        let current_ts = ctx.current_candle().timestamp;
        let htf_idx = match htf_candles.iter().rposition(|c| c.timestamp < current_ts) {
            Some(i) => i,
            None => return false, // No completed HTF bar yet
        };

        let required = self.inner.required_indicators();
        let htf_indicators = if required.is_empty() {
            HashMap::new()
        } else {
            match compute_for_candles(&htf_candles, required) {
                Ok(map) => map,
                Err(e) => {
                    tracing::warn!("HTF indicator computation failed: {}", e);
                    return false;
                }
            }
        };

        let htf_ctx = StrategyContext {
            candles: &htf_candles,
            index: htf_idx,
            position: ctx.position,
            equity: ctx.equity,
            indicators: &htf_indicators,
        };

        self.inner.evaluate(&htf_ctx)
    }
}

/// Wrap a condition to be evaluated on a higher-timeframe candle series.
///
/// Bucket boundaries are UTC-aligned (offset = 0). For non-UTC exchanges use
/// [`htf_region()`] instead.
///
/// # Arguments
///
/// * `interval` – Target higher timeframe (e.g. `Interval::OneWeek`)
/// * `cond` – Any condition to evaluate on the HTF candles
///
/// # Example
///
/// ```ignore
/// use finance_query::backtesting::refs::*;
/// use finance_query::Interval;
///
/// // Entry only when weekly price is above its 20-bar SMA
/// let weekly_uptrend = htf(Interval::OneWeek, price().above_ref(sma(20)));
/// let entry = ema(10).crosses_above_ref(ema(30)).and(weekly_uptrend);
/// ```
pub fn htf<C: Condition>(interval: Interval, cond: C) -> HtfCondition<C> {
    HtfCondition {
        interval,
        inner: cond,
        utc_offset_secs: 0,
    }
}

/// Wrap a condition to be evaluated on a higher-timeframe candle series,
/// with bucket boundaries aligned to the exchange's local calendar.
///
/// Weekly and monthly boundaries are shifted by `region.utc_offset_secs()` so
/// that, for example, a Tokyo-listed stock's "Monday" starts at the correct
/// local midnight rather than UTC midnight.
///
/// # Arguments
///
/// * `interval` – Target higher timeframe (e.g. `Interval::OneWeek`)
/// * `region`   – Exchange region used to derive the UTC offset
/// * `cond`     – Any condition to evaluate on the HTF candles
///
/// # Example
///
/// ```ignore
/// use finance_query::backtesting::refs::*;
/// use finance_query::{Interval, Region};
///
/// let weekly_trend = htf_region(Interval::OneWeek, Region::Japan, price().above_ref(sma(20)));
/// ```
pub fn htf_region<C: Condition>(interval: Interval, region: Region, cond: C) -> HtfCondition<C> {
    HtfCondition {
        interval,
        inner: cond,
        utc_offset_secs: region.utc_offset_secs(),
    }
}