package socket

import (
	"fmt"

	altv1 "git.toki-labs.com/toki/alt/packages/contracts/gen/go/alt/v1"
	"git.toki-labs.com/toki/alt/packages/domain/backtest"
	"git.toki-labs.com/toki/alt/packages/domain/market"
	"git.toki-labs.com/toki/alt/services/worker/internal/papertrading"
)

// paper_mapping.go owns paper-trading-specific conversions between the ALT
// contract and the worker-owned paper runtime. As with backtest mapping, keeping
// proto<->domain conversion in the worker honours the rail design where the
// worker owns runtime shapes and the API stays a thin pass-through.

// startPaperRequestFromProto validates an inbound StartPaperTradingRequest and
// converts it into the paper service start request. Validation lives next to the
// conversion so a malformed request never reaches the runtime.
func startPaperRequestFromProto(req *altv1.StartPaperTradingRequest) (papertrading.StartRequest, error) {
	if req.GetAccountId() == "" {
		return papertrading.StartRequest{}, fmt.Errorf("account_id is required")
	}
	spec, err := runSpecFromProto(req.GetSpec())
	if err != nil {
		return papertrading.StartRequest{}, err
	}
	cash, err := priceFromProto(req.GetStartingCash())
	if err != nil {
		return papertrading.StartRequest{}, fmt.Errorf("starting_cash: %w", err)
	}
	return papertrading.StartRequest{
		AccountID:    backtest.PaperAccountID(req.GetAccountId()),
		Spec:         spec,
		StartingCash: cash,
	}, nil
}

// priceFromProto converts a contract Price into the domain Price, requiring a
// concrete currency and amount so paper cash math never runs on an empty value.
func priceFromProto(price *altv1.Price) (market.Price, error) {
	if price == nil {
		return market.Price{}, fmt.Errorf("price is required")
	}
	currency, err := currencyFromProto(price.GetCurrency())
	if err != nil {
		return market.Price{}, err
	}
	if price.GetAmount().GetValue() == "" {
		return market.Price{}, fmt.Errorf("amount is required")
	}
	return market.Price{
		Currency: currency,
		Amount:   market.Decimal{Value: price.GetAmount().GetValue()},
	}, nil
}

func currencyFromProto(c altv1.Currency) (market.Currency, error) {
	switch c {
	case altv1.Currency_CURRENCY_KRW:
		return market.CurrencyKRW, nil
	case altv1.Currency_CURRENCY_USD:
		return market.CurrencyUSD, nil
	default:
		return "", fmt.Errorf("unsupported currency %q", c.String())
	}
}

// paperStateToProto converts a paper service State into the contract state,
// reusing the shared backtest run/position/trade/equity payload shapes.
func paperStateToProto(accountID backtest.PaperAccountID, state papertrading.State) *altv1.PaperTradingState {
	return &altv1.PaperTradingState{
		AccountId:      string(accountID),
		Run:            runToProto(state.Run),
		Cash:           priceToProto(state.Cash),
		Positions:      paperPositionsToProto(state.Positions),
		Fills:          fillsToProto(state.Fills),
		EquityCurve:    equityCurveToProto(state.EquityCurve),
		RiskRejections: paperRiskRejectionsToProto(state.Rejected),
	}
}

// paperRiskRejectionsToProto converts the engine's rejected orders into the
// contract risk rejection summary. It uses the rejection's resolved Instrument
// (always populated, even for the empty-order-id strategy bug case) so the
// operator surface can distinguish a clear run from a blocked one.
func paperRiskRejectionsToProto(rejected []papertrading.RejectedOrder) []*altv1.PaperRiskRejection {
	if len(rejected) == 0 {
		return nil
	}
	out := make([]*altv1.PaperRiskRejection, len(rejected))
	for i, r := range rejected {
		out[i] = &altv1.PaperRiskRejection{
			InstrumentId:    string(r.Instrument),
			Side:            string(r.Order.Side),
			Quantity:        quantityToProto(r.Order.Quantity),
			Reason:          r.Reason,
			TimestampUnixMs: timeToUnixMs(r.BarTime),
		}
	}
	return out
}

func paperPositionsToProto(positions []backtest.Position) []*altv1.BacktestPosition {
	if len(positions) == 0 {
		return nil
	}
	out := make([]*altv1.BacktestPosition, len(positions))
	for i, p := range positions {
		out[i] = &altv1.BacktestPosition{
			InstrumentId: string(p.InstrumentID),
			Quantity:     quantityToProto(p.Quantity),
			LastPrice:    priceToProto(p.LastPrice),
		}
	}
	return out
}

func fillsToProto(fills []backtest.Fill) []*altv1.BacktestTrade {
	if len(fills) == 0 {
		return nil
	}
	out := make([]*altv1.BacktestTrade, len(fills))
	for i, f := range fills {
		out[i] = fillToProto(f)
	}
	return out
}

// fillToProto renders a single domain Fill as the shared BacktestTrade payload,
// reused for paper fills and for a filled order's fill summary.
func fillToProto(f backtest.Fill) *altv1.BacktestTrade {
	return &altv1.BacktestTrade{
		InstrumentId:    string(f.InstrumentID),
		Side:            string(f.Side),
		Quantity:        quantityToProto(f.Quantity),
		Price:           priceToProto(f.Price),
		TimestampUnixMs: timeToUnixMs(f.Timestamp),
	}
}

// submitPaperOrderRequestFromProto validates an inbound SubmitPaperOrderRequest
// and converts it into the paper service submit request. Validation lives next
// to the conversion so a malformed order never reaches the runtime.
func submitPaperOrderRequestFromProto(req *altv1.SubmitPaperOrderRequest) (papertrading.SubmitOrderRequest, error) {
	if req.GetAccountId() == "" {
		return papertrading.SubmitOrderRequest{}, fmt.Errorf("account_id is required")
	}
	intent, err := orderIntentFromProto(req.GetInstrumentId(), req.GetSide(), req.GetQuantity(), req.GetType(), req.GetLimitPrice())
	if err != nil {
		return papertrading.SubmitOrderRequest{}, err
	}
	return papertrading.SubmitOrderRequest{
		AccountID: backtest.PaperAccountID(req.GetAccountId()),
		Intent:    intent,
	}, nil
}

// orderIntentFromProto converts the wire order fields into a domain OrderIntent.
// A limit order requires a limit price; a market order ignores it.
func orderIntentFromProto(instrumentID, side string, quantity *altv1.Quantity, orderType string, limitPrice *altv1.Price) (backtest.OrderIntent, error) {
	if instrumentID == "" {
		return backtest.OrderIntent{}, fmt.Errorf("instrument_id is required")
	}
	domainSide, err := orderSideFromProto(side)
	if err != nil {
		return backtest.OrderIntent{}, err
	}
	domainQuantity, err := quantityFromProto(quantity)
	if err != nil {
		return backtest.OrderIntent{}, err
	}
	domainType, err := orderTypeFromProto(orderType)
	if err != nil {
		return backtest.OrderIntent{}, err
	}
	intent := backtest.OrderIntent{
		InstrumentID: market.InstrumentID(instrumentID),
		Side:         domainSide,
		Quantity:     domainQuantity,
		Type:         domainType,
	}
	if domainType == backtest.OrderTypeLimit {
		price, err := priceFromProto(limitPrice)
		if err != nil {
			return backtest.OrderIntent{}, fmt.Errorf("limit_price: %w", err)
		}
		if err := papertrading.ValidateOrderDecimal("limit_price", price.Amount.Value, false); err != nil {
			return backtest.OrderIntent{}, err
		}
		intent.LimitPrice = price
	}
	return intent, nil
}

func orderSideFromProto(side string) (backtest.OrderSide, error) {
	switch side {
	case string(backtest.OrderSideBuy):
		return backtest.OrderSideBuy, nil
	case string(backtest.OrderSideSell):
		return backtest.OrderSideSell, nil
	default:
		return "", fmt.Errorf("unsupported order side %q (want \"buy\" or \"sell\")", side)
	}
}

// orderTypeFromProto maps the wire type onto the domain order type. An empty
// type defaults to market, mirroring OrderIntent.OrderType.
func orderTypeFromProto(orderType string) (backtest.OrderType, error) {
	switch orderType {
	case "", string(backtest.OrderTypeMarket):
		return backtest.OrderTypeMarket, nil
	case string(backtest.OrderTypeLimit):
		return backtest.OrderTypeLimit, nil
	default:
		return "", fmt.Errorf("unsupported order type %q (want \"market\" or \"limit\")", orderType)
	}
}

func quantityFromProto(quantity *altv1.Quantity) (market.Quantity, error) {
	if quantity == nil || quantity.GetAmount().GetValue() == "" {
		return market.Quantity{}, fmt.Errorf("quantity is required")
	}
	value := quantity.GetAmount().GetValue()
	if err := papertrading.ValidateOrderDecimal("quantity", value, true); err != nil {
		return market.Quantity{}, err
	}
	return market.Quantity{Amount: market.Decimal{Value: value}}, nil
}

// paperOrderToProto renders a lifecycle order onto the contract message. The
// limit price is only set for limit orders and the fill summary only for filled
// orders, keeping a pending/canceled order's payload minimal.
func paperOrderToProto(order papertrading.PaperOrder) *altv1.PaperOrder {
	out := &altv1.PaperOrder{
		OrderId:         order.OrderID,
		AccountId:       string(order.AccountID),
		InstrumentId:    string(order.Intent.InstrumentID),
		Side:            string(order.Intent.Side),
		Quantity:        quantityToProto(order.Intent.Quantity),
		Type:            string(order.Intent.OrderType()),
		Status:          string(order.Status),
		Reason:          order.Reason,
		CreatedAtUnixMs: timeToUnixMs(order.CreatedAt),
		UpdatedAtUnixMs: timeToUnixMs(order.UpdatedAt),
	}
	if order.Intent.OrderType() == backtest.OrderTypeLimit {
		out.LimitPrice = priceToProto(order.Intent.LimitPrice)
	}
	if order.Fill != nil {
		out.Fill = fillToProto(*order.Fill)
	}
	return out
}