package backtest

import (
	"sig-pub/pkg/indicator"
	"sig-pub/pkg/types"
	"sig-pub/pkg/types/series"
)

// SigStrategyContext 是一个轻量的策略上下文，用于回测时把历史k线提供给策略
type SigStrategyContext struct {
	klines []types.Kline // 时间升序: oldest ... newest
	offset int16         // offset applied when indicators request
	indReg *indicator.IndicatorRegistry
}

func NewSigStrategyContext(klines []types.Kline, indReg *indicator.IndicatorRegistry) *SigStrategyContext {
	return &SigStrategyContext{klines: klines, indReg: indReg}
}

func (c *SigStrategyContext) Get(offset int16) (k types.Kline) {
	// offset relative to current (0 = latest)
	idx := len(c.klines) - 1 - int(offset+c.offset)
	if idx < 0 {
		// return zero kline if out of range
		return types.Kline{}
	}
	return c.klines[idx]
}

func (c *SigStrategyContext) Series(offset, count int16) (klines series.Klines) {
	// return slice in descending time order as expected by series.Klines
	var ret series.Klines
	for i := int16(0); i < count; i++ {
		k := c.Get(offset + i)
		ret = append(ret, k)
	}
	return ret
}

// WindowIndicatorSeriesLocal 实现 indicator.IIndicatorSeries
type WindowIndicatorSeriesLocal struct {
	window int16
	ind    indicator.IWindowIndicator
	ctx    *SigStrategyContext
}

func NewWindowIndicatorSeriesLocal(window int16, ind indicator.IWindowIndicator, ctx *SigStrategyContext) *WindowIndicatorSeriesLocal {
	return &WindowIndicatorSeriesLocal{window: window, ind: ind, ctx: ctx}
}

func (w *WindowIndicatorSeriesLocal) Get(offset int16) (vector float64) {
	// tell indicator to use offset by shifting internal offset then restore
	prev := w.ctx.offset
	w.ctx.offset += offset
	vector = w.ind.Calculate(w.ctx, w.window)
	w.ctx.offset = prev
	return
}

func (w *WindowIndicatorSeriesLocal) Series(offset, count int16) (matrix series.Floats) {
	prev := w.ctx.offset
	w.ctx.offset += offset
	for i := int16(0); i < count; i++ {
		v := w.ind.Calculate(w.ctx, w.window)
		matrix.Push(v)
		w.ctx.offset++
	}
	w.ctx.offset = prev
	return
}

func (c *SigStrategyContext) IndicatorW(name string, window int16) indicator.IIndicatorSeries {
	ind, ok := c.indReg.IndicatorW(name)
	if !ok {
		panic("indicator not found: " + name)
	}
	return NewWindowIndicatorSeriesLocal(window, ind, c)
}