package strategy

import (
	"alpaca-bot/internal/model"

	talib "github.com/markcheno/go-talib"
)

type EMACross struct {
	FastPeriod int
	SlowPeriod int
	prices     []float64
	lastFast   float64
	lastSlow   float64
	init       bool
}

func NewEMACross(fast, slow int) *EMACross {
	return &EMACross{
		FastPeriod: fast,
		SlowPeriod: slow,
	}
}

func (s *EMACross) OnBar(bar model.Bar) model.Signal {
	s.prices = append(s.prices, bar.Close)

	if len(s.prices) < s.SlowPeriod {
		return model.Hold
	}

	fast := talib.Ema(s.prices, s.FastPeriod)
	slow := talib.Ema(s.prices, s.SlowPeriod)

	curFast := fast[len(fast)-1]
	curSlow := slow[len(slow)-1]

	if !s.init {
		s.lastFast = curFast
		s.lastSlow = curSlow
		s.init = true
		return model.Hold
	}

	if s.lastFast <= s.lastSlow && curFast > curSlow {
		s.lastFast = curFast
		s.lastSlow = curSlow
		return model.Buy
	}

	if s.lastFast >= s.lastSlow && curFast < curSlow {
		s.lastFast = curFast
		s.lastSlow = curSlow
		return model.Sell
	}

	s.lastFast = curFast
	s.lastSlow = curSlow
	return model.Hold
}