package strategy

import (
	"github.com/markcheno/go-talib"
	"github.com/shopspring/decimal"
	"math"
	"testing"
)

func dv(v float64) decimal.Decimal { return decimal.NewFromFloat(v) }

func genPrices(n int) []float64 {
	out := make([]float64, n)
	base := 10.0
	for i := 0; i < n; i++ {
		out[i] = base + float64(i)*0.5 + math.Sin(float64(i)/3.0)*0.7
	}
	return out
}

func almostEqualDecFloat(dec decimal.Decimal, f float64, tol float64) bool {
	df, _ := dec.Float64()
	return math.Abs(df-f) <= tol
}

// 注意：使用 NewEMAForTalib(period)（First-Price seed）來比對 TA-Lib
func TestEMA_MatchesGoTalib(t *testing.T) {
	prices := genPrices(300)
	tol := 1e-7 // decimal<->float64 轉換微誤差

	periods := []uint{3, 5, 12, 26}
	for _, p := range periods {
		t.Run("EMA_p="+decimal.NewFromInt(int64(p)).String(), func(t *testing.T) {
			ema := NewEMA(p) // 重點：用 TA-Lib 兼容 seed

			our := make([]decimal.Decimal, len(prices))
			ready := make([]bool, len(prices))
			for i, px := range prices {
				out := ema.Update(dv(px))
				our[i] = out.Value
				ready[i] = out.Ready
			}
			ref := talib.Ema(prices, int(p))

			start := p // talib 第一個有效值在 index = period-1

			for i := start; i < uint(len(prices)); i++ {
				if !ready[i] {
					t.Fatalf("i=%d: our not ready but talib has value", i)
				}
				if !almostEqualDecFloat(our[i], ref[i], tol) {
					t.Fatalf("i=%d: EMA mismatch: our=%s ref=%f", i, our[i], ref[i])
				}
			}
		})
	}
}

func TestSMA_MatchesGoTalib(t *testing.T) {
	prices := genPrices(300)
	tol := 1e-9

	windows := []uint{3, 5, 20, 50}
	for _, w := range windows {
		t.Run("SMA_w="+decimal.NewFromInt(int64(w)).String(), func(t *testing.T) {
			sma := NewSMA(w)

			our := make([]decimal.Decimal, len(prices))
			ready := make([]bool, len(prices))
			for i, px := range prices {
				out := sma.Update(dv(px))
				our[i] = out.Value
				ready[i] = out.Ready
			}

			ref := talib.Sma(prices, int(w))
			start := w
			for i := start; i < uint(len(prices)); i++ {
				if !ready[i] {
					t.Fatalf("i=%d: our not ready but talib has value", i)
				}
				if !almostEqualDecFloat(our[i], ref[i], tol) {
					t.Fatalf("i=%d: SMA mismatch: our=%s ref=%f", i, our[i], ref[i])
				}
			}
		})
	}
}