package backtest

import (
	"math"
	"sig-pub/api/pb"
	"sig-pub/pkg/types"
	"sig-pub/pkg/types/decimals"
)

type Account struct {
	Cash           float64
	Positions      []*Position
	Trades         []Trade
	MaxPosPct      float64 // 最大仓位占比
	MaxExposurePct float64 // 最大总敞口占比
	MaxLots        float64 // 最大手数/数量 (optional)
	Simulator      *Simulator
}

func NewAccount(cash float64, sim *Simulator) *Account {
	return &Account{Cash: cash, Simulator: sim, MaxPosPct: 1.0, MaxExposurePct: 1.0}
}

func (a *Account) SetRiskLimits(maxPosPct, maxExposurePct float64) {
	if maxPosPct > 0 {
		a.MaxPosPct = maxPosPct
	}
	if maxExposurePct > 0 {
		a.MaxExposurePct = maxExposurePct
	}
}

// CurrentEquity 根据当前价格对仓位进行 mark-to-market，返回账户净值
func (a *Account) CurrentEquity(price float64) float64 {
	equity := a.Cash
	for _, p := range a.Positions {
		if p.Side == pb.Side_BUY {
			equity += (price - p.EntryPx) * p.Qty
		} else if p.Side == pb.Side_SELL {
			equity += (p.EntryPx - price) * p.Qty
		}
	}
	return equity
}

// CurrentExposure 返回当前仓位的名义总敞口（绝对值）
func (a *Account) CurrentExposure(price float64) float64 {
	var sum float64
	for _, p := range a.Positions {
		sum += math.Abs(p.Qty * price)
	}
	return sum
}

// CanOpen 判断在给定价格下是否可以开仓（基于 MaxPosPct 和 MaxExposurePct）
func (a *Account) CanOpen(side pb.Side, qty, price float64) bool {
	if qty <= 0 || price <= 0 {
		return false
	}
	equity := a.CurrentEquity(price)
	if equity <= 0 {
		return false
	}
	notional := math.Abs(qty * price)
	// 单仓位限制
	if a.MaxPosPct > 0 {
		if notional > a.MaxPosPct*equity {
			return false
		}
	}
	// 总敞口限制
	if a.MaxExposurePct > 0 {
		if a.CurrentExposure(price)+notional > a.MaxExposurePct*equity {
			return false
		}
	}
	return true
}

// ApplyMarketOrder 直接用市价下单（简化），qty为基础货币数量
func (a *Account) ApplyMarketOrder(side pb.Side, qty float64, klineTs int64, kline types.Kline) (t Trade, ok bool) {
	// risk check before executing
	price := decimals.MustToFloat64(kline.Close)
	if !a.CanOpen(side, qty, price) {
		return t, false
	}
	trade := a.Simulator.ExecuteMarket(side, qty, kline, klineTs)
	// apply cash/position
	if side == pb.Side_BUY {
		cost := trade.Price*qty + trade.Fee
		if cost > a.Cash {
			return trade, false
		}
		a.Cash -= cost
		// open/add position
		pos := &Position{Side: side, Qty: qty, EntryPx: trade.Price, EntryTs: klineTs, PeakPx: trade.Price}
		a.Positions = append(a.Positions, pos)
	} else if side == pb.Side_SELL {
		// simplify: allow short by increasing cash
		receive := trade.Price*qty - trade.Fee
		a.Cash += receive
		pos := &Position{Side: side, Qty: qty, EntryPx: trade.Price, EntryTs: klineTs, PeakPx: trade.Price}
		a.Positions = append(a.Positions, pos)
	}
	a.Trades = append(a.Trades, trade)
	return trade, true
}

// ClosePosition 根据索引平仓（全部平仓该仓位）
func (a *Account) ClosePosition(index int, kline types.Kline, ts int64, cause string) (t Trade, ok bool) {
	if index < 0 || index >= len(a.Positions) {
		return t, false
	}
	pos := a.Positions[index]
	if pos == nil {
		return t, false
	}
	// determine close side (opposite)
	var closeSide pb.Side
	if pos.Side == pb.Side_BUY {
		closeSide = pb.Side_SELL
	} else {
		closeSide = pb.Side_BUY
	}

	t = a.Simulator.ExecuteMarket(closeSide, pos.Qty, kline, ts)
	t.Cause = cause
	// apply cash change
	if closeSide == pb.Side_SELL {
		// selling a long position -> receive cash
		receive := t.Price*pos.Qty - t.Fee
		a.Cash += receive
	} else {
		// buying to close a short -> pay cash
		cost := t.Price*pos.Qty + t.Fee
		a.Cash -= cost
	}

	// remove position
	a.Positions = append(a.Positions[:index], a.Positions[index+1:]...)
	a.Trades = append(a.Trades, t)
	return t, true
}