package simulation

import (
	"fmt"
	"math/rand"

	"github.com/cosmos/cosmos-sdk/baseapp"
	"github.com/cosmos/cosmos-sdk/codec"
	"github.com/cosmos/cosmos-sdk/simapp/helpers"
	sdk "github.com/cosmos/cosmos-sdk/types"
	"github.com/cosmos/cosmos-sdk/x/simulation"

	appparams "github.com/kava-labs/kava/app/params"
	"github.com/kava-labs/kava/x/cdp/keeper"
	"github.com/kava-labs/kava/x/cdp/types"
)

// Simulation operation weights constants
const (
	OpWeightMsgCdp = "op_weight_msg_cdp"
)

// WeightedOperations returns all the operations from the module with their respective weights
func WeightedOperations(
	appParams simulation.AppParams, cdc *codec.Codec, ak types.AccountKeeper,
	k keeper.Keeper, pfk types.PricefeedKeeper,
) simulation.WeightedOperations {
	var weightMsgCdp int

	appParams.GetOrGenerate(cdc, OpWeightMsgCdp, &weightMsgCdp, nil,
		func(_ *rand.Rand) {
			weightMsgCdp = appparams.DefaultWeightMsgCdp
		},
	)

	return simulation.WeightedOperations{
		simulation.NewWeightedOperation(
			weightMsgCdp,
			SimulateMsgCdp(ak, k, pfk),
		),
	}
}

// SimulateMsgCdp generates a MsgCreateCdp or MsgDepositCdp with random values.
func SimulateMsgCdp(ak types.AccountKeeper, k keeper.Keeper, pfk types.PricefeedKeeper) simulation.Operation {
	return func(
		r *rand.Rand, app *baseapp.BaseApp, ctx sdk.Context, accs []simulation.Account, chainID string,
	) (simulation.OperationMsg, []simulation.FutureOperation, error) {

		simAccount, _ := simulation.RandomAcc(r, accs)
		acc := ak.GetAccount(ctx, simAccount.Address)
		if acc == nil {
			return simulation.NoOpMsg(types.ModuleName), nil, nil
		}

		coins := acc.GetCoins()
		collateralParams := k.GetParams(ctx).CollateralParams
		if len(collateralParams) == 0 {
			return simulation.NoOpMsg(types.ModuleName), nil, nil
		}

		randCollateralParam := collateralParams[r.Intn(len(collateralParams))]
		debtParam, _ := k.GetDebtParam(ctx, randCollateralParam.DebtLimit.Denom)
		if coins.AmountOf(randCollateralParam.Denom).IsZero() {
			return simulation.NoOpMsg(types.ModuleName), nil, nil
		}

		price, err := pfk.GetCurrentPrice(ctx, randCollateralParam.SpotMarketID)
		if err != nil {
			return simulation.NoOpMsg(types.ModuleName), nil, nil // pricefeed going down is an expected event
		}
		// convert the price to the same units as the debt param
		priceShifted := ShiftDec(price.Price, debtParam.ConversionFactor)

		spendableCoins := acc.SpendableCoins(ctx.BlockTime())
		fees, err := simulation.RandomFees(r, ctx, spendableCoins)
		if err != nil {
			return simulation.NoOpMsg(types.ModuleName), nil, err
		}
		spendableCoins = spendableCoins.Sub(fees)

		existingCDP, found := k.GetCdpByOwnerAndCollateralType(ctx, acc.GetAddress(), randCollateralParam.Type)
		if !found {
			// calculate the minimum amount of collateral that is needed to create a cdp with the debt floor amount of debt and the minimum liquidation ratio
			// (debtFloor * liquidationRatio)/priceShifted
			minCollateralDeposit := (sdk.NewDecFromInt(debtParam.DebtFloor).Mul(randCollateralParam.LiquidationRatio)).Quo(priceShifted)
			// convert to proper collateral units
			minCollateralDeposit = ShiftDec(minCollateralDeposit, randCollateralParam.ConversionFactor)
			// convert to integer and always round up
			minCollateralDepositRounded := minCollateralDeposit.TruncateInt().Add(sdk.OneInt())
			if spendableCoins.AmountOf(randCollateralParam.Denom).LT(minCollateralDepositRounded) {
				// account doesn't have enough funds to open a cdp for the min debt amount
				return simulation.NewOperationMsgBasic(types.ModuleName, "no-operation", "insufficient funds to open cdp", false, nil), nil, nil
			}
			// set the max collateral deposit to the amount of coins in the account
			maxCollateralDeposit := spendableCoins.AmountOf(randCollateralParam.Denom)

			// randomly select a collateral deposit amount
			collateralDeposit := sdk.NewInt(int64(simulation.RandIntBetween(r, int(minCollateralDepositRounded.Int64()), int(maxCollateralDeposit.Int64()))))
			// calculate how much the randomly selected deposit is worth
			collateralDepositValue := ShiftDec(sdk.NewDecFromInt(collateralDeposit), randCollateralParam.ConversionFactor.Neg()).Mul(priceShifted)
			// calculate the max amount of debt that could be drawn for the chosen deposit
			maxDebtDraw := collateralDepositValue.Quo(randCollateralParam.LiquidationRatio).TruncateInt()
			// check that the debt limit hasn't been reached
			availableAssetDebt := randCollateralParam.DebtLimit.Amount.Sub(k.GetTotalPrincipal(ctx, randCollateralParam.Type, debtParam.Denom))
			if availableAssetDebt.LTE(debtParam.DebtFloor) {
				// debt limit has been reached
				return simulation.NewOperationMsgBasic(types.ModuleName, "no-operation", "debt limit reached, cannot open cdp", false, nil), nil, nil
			}
			// ensure that the debt draw does not exceed the debt limit
			maxDebtDraw = sdk.MinInt(maxDebtDraw, availableAssetDebt)
			// randomly select a debt draw amount
			debtDraw := sdk.NewInt(int64(simulation.RandIntBetween(r, int(debtParam.DebtFloor.Int64()), int(maxDebtDraw.Int64()))))

			msg := types.NewMsgCreateCDP(acc.GetAddress(), sdk.NewCoin(randCollateralParam.Denom, collateralDeposit), sdk.NewCoin(debtParam.Denom, debtDraw), randCollateralParam.Type)

			tx := helpers.GenTx(
				[]sdk.Msg{msg},
				fees,
				helpers.DefaultGenTxGas,
				chainID,
				[]uint64{acc.GetAccountNumber()},
				[]uint64{acc.GetSequence()},
				simAccount.PrivKey,
			)

			_, _, err := app.Deliver(tx)
			if err != nil {
				// to aid debugging, add the stack trace to the comment field of the returned opMsg
				return simulation.NewOperationMsg(msg, false, fmt.Sprintf("%+v", err)), nil, err
			}

			return simulation.NewOperationMsg(msg, true, ""), nil, nil
		}

		// a cdp already exists, deposit to it, draw debt from it, or repay debt to it
		// close 25% of the time
		if canClose(spendableCoins, existingCDP, debtParam.Denom) && shouldClose(r) {
			repaymentAmount := spendableCoins.AmountOf(debtParam.Denom)
			msg := types.NewMsgRepayDebt(acc.GetAddress(), randCollateralParam.Type, sdk.NewCoin(debtParam.Denom, repaymentAmount))

			tx := helpers.GenTx(
				[]sdk.Msg{msg},
				fees,
				helpers.DefaultGenTxGas,
				chainID,
				[]uint64{acc.GetAccountNumber()},
				[]uint64{acc.GetSequence()},
				simAccount.PrivKey,
			)

			_, _, err := app.Deliver(tx)
			if err != nil {
				return simulation.NewOperationMsg(msg, false, fmt.Sprintf("%+v", err)), nil, err
			}

			return simulation.NewOperationMsg(msg, true, ""), nil, nil
		}

		// deposit 25% of the time
		if hasCoins(spendableCoins, randCollateralParam.Denom) && shouldDeposit(r) {
			randDepositAmount := sdk.NewInt(int64(simulation.RandIntBetween(r, 1, int(spendableCoins.AmountOf(randCollateralParam.Denom).Int64()))))
			msg := types.NewMsgDeposit(acc.GetAddress(), acc.GetAddress(), sdk.NewCoin(randCollateralParam.Denom, randDepositAmount), randCollateralParam.Type)

			tx := helpers.GenTx(
				[]sdk.Msg{msg},
				fees,
				helpers.DefaultGenTxGas,
				chainID,
				[]uint64{acc.GetAccountNumber()},
				[]uint64{acc.GetSequence()},
				simAccount.PrivKey,
			)

			_, _, err := app.Deliver(tx)
			if err != nil {
				return simulation.NewOperationMsg(msg, false, fmt.Sprintf("%+v", err)), nil, err
			}

			return simulation.NewOperationMsg(msg, true, ""), nil, nil
		}

		// draw debt 25% of the time
		if shouldDraw(r) {
			collateralShifted := ShiftDec(sdk.NewDecFromInt(existingCDP.Collateral.Amount), randCollateralParam.ConversionFactor.Neg())
			collateralValue := collateralShifted.Mul(priceShifted)
			newFeesAccumulated := k.CalculateNewInterest(ctx, existingCDP)
			totalFees := existingCDP.AccumulatedFees.Add(newFeesAccumulated)
			// given the current collateral value, calculate how much debt we could add while maintaining a valid liquidation ratio
			debt := existingCDP.Principal.Add(totalFees)
			maxTotalDebt := collateralValue.Quo(randCollateralParam.LiquidationRatio)
			maxDebt := (maxTotalDebt.Sub(sdk.NewDecFromInt(debt.Amount))).Mul(sdk.MustNewDecFromStr("0.95")).TruncateInt()
			if maxDebt.LTE(sdk.OneInt()) {
				// debt in cdp is maxed out
				return simulation.NewOperationMsgBasic(types.ModuleName, "no-operation", "cdp debt maxed out, cannot draw more debt", false, nil), nil, nil
			}
			// check if the debt limit has been reached
			availableAssetDebt := randCollateralParam.DebtLimit.Amount.Sub(k.GetTotalPrincipal(ctx, randCollateralParam.Type, debtParam.Denom))
			if availableAssetDebt.LTE(sdk.OneInt()) {
				// debt limit has been reached
				return simulation.NewOperationMsgBasic(types.ModuleName, "no-operation", "debt limit reached, cannot draw more debt", false, nil), nil, nil
			}
			maxDraw := sdk.MinInt(maxDebt, availableAssetDebt)

			randDrawAmount := sdk.NewInt(int64(simulation.RandIntBetween(r, 1, int(maxDraw.Int64()))))
			msg := types.NewMsgDrawDebt(acc.GetAddress(), randCollateralParam.Type, sdk.NewCoin(debtParam.Denom, randDrawAmount))

			tx := helpers.GenTx(
				[]sdk.Msg{msg},
				fees,
				helpers.DefaultGenTxGas,
				chainID,
				[]uint64{acc.GetAccountNumber()},
				[]uint64{acc.GetSequence()},
				simAccount.PrivKey,
			)

			_, _, err := app.Deliver(tx)
			if err != nil {
				return simulation.NewOperationMsg(msg, false, fmt.Sprintf("%+v", err)), nil, err
			}

			return simulation.NewOperationMsg(msg, true, ""), nil, nil
		}

		// repay debt 25% of the time
		if hasCoins(spendableCoins, debtParam.Denom) {
			debt := existingCDP.Principal.Amount
			payableDebt := debt.Sub(debtParam.DebtFloor)
			if payableDebt.IsZero() {
				return simulation.NewOperationMsgBasic(types.ModuleName, "no-operation", "cannot make partial repayment, cdp at debt floor", false, nil), nil, nil
			}
			maxRepay := sdk.MinInt(
				spendableCoins.AmountOf(debtParam.Denom),
				payableDebt,
			)
			var randRepayAmount sdk.Int
			if maxRepay.Equal(sdk.OneInt()) {
				randRepayAmount = sdk.OneInt()
			} else {
				randRepayAmount = sdk.NewInt(int64(simulation.RandIntBetween(r, 1, int(maxRepay.Int64()))))
			}

			msg := types.NewMsgRepayDebt(acc.GetAddress(), randCollateralParam.Type, sdk.NewCoin(debtParam.Denom, randRepayAmount))

			tx := helpers.GenTx(
				[]sdk.Msg{msg},
				fees,
				helpers.DefaultGenTxGas,
				chainID,
				[]uint64{acc.GetAccountNumber()},
				[]uint64{acc.GetSequence()},
				simAccount.PrivKey,
			)

			_, _, err := app.Deliver(tx)
			if err != nil {
				return simulation.NewOperationMsg(msg, false, fmt.Sprintf("%+v", err)), nil, err
			}

			return simulation.NewOperationMsg(msg, true, ""), nil, nil
		}

		return simulation.NoOpMsg(types.ModuleName), nil, nil
	}
}

func shouldDraw(r *rand.Rand) bool {
	threshold := 50
	value := simulation.RandIntBetween(r, 1, 100)
	return value > threshold
}

func shouldDeposit(r *rand.Rand) bool {
	threshold := 66
	value := simulation.RandIntBetween(r, 1, 100)
	return value > threshold
}

func hasCoins(spendableCoins sdk.Coins, denom string) bool {
	return spendableCoins.AmountOf(denom).IsPositive()
}

func shouldClose(r *rand.Rand) bool {
	threshold := 75
	value := simulation.RandIntBetween(r, 1, 100)
	return value > threshold
}

func canClose(spendableCoins sdk.Coins, c types.CDP, denom string) bool {
	repaymentAmount := c.Principal.Add(c.AccumulatedFees).Amount
	return spendableCoins.AmountOf(denom).GTE(repaymentAmount)
}
