package keeper

import (
	"strings"

	sdk "github.com/cosmos/cosmos-sdk/types"
	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"

	"github.com/kava-labs/kava/x/harvest/types"
)

// Borrow funds
func (k Keeper) Borrow(ctx sdk.Context, borrower sdk.AccAddress, coins sdk.Coins) error {
	// Set any new denoms' global borrow index to 1.0
	for _, coin := range coins {
		_, foundBorrowIndex := k.GetBorrowIndex(ctx, coin.Denom)
		if !foundBorrowIndex {
			k.SetBorrowIndex(ctx, coin.Denom, sdk.OneDec())
		}
	}

	// Sync user's borrow balance (only for coins user is requesting to borrow)
	k.SyncBorrowInterest(ctx, borrower, coins)

	// Validate borrow amount within user and protocol limits
	err := k.ValidateBorrow(ctx, borrower, coins)
	if err != nil {
		return err
	}

	// Sends coins from Harvest module account to user
	err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleAccountName, borrower, coins)
	if err != nil {
		if strings.Contains(err.Error(), "insufficient account funds") {
			modAccCoins := k.supplyKeeper.GetModuleAccount(ctx, types.ModuleAccountName).GetCoins()
			for _, coin := range coins {
				_, isNegative := modAccCoins.SafeSub(sdk.NewCoins(coin))
				if isNegative {
					return sdkerrors.Wrapf(types.ErrBorrowExceedsAvailableBalance,
						"the requested borrow amount of %s exceeds the total amount of %s%s available to borrow",
						coin, modAccCoins.AmountOf(coin.Denom), coin.Denom,
					)
				}
			}
		}
	}

	borrow, found := k.GetBorrow(ctx, borrower)
	if !found {
		return types.ErrBorrowNotFound // This should never happen
	}
	// Add the newly borrowed coins to the user's borrow object
	borrow.Amount = borrow.Amount.Add(coins...)
	k.SetBorrow(ctx, borrow)

	// Update total borrowed amount by newly borrowed coins. Don't add user's pending interest as
	// it has already been included in the total borrowed coins by the BeginBlocker.
	k.IncrementBorrowedCoins(ctx, coins)

	ctx.EventManager().EmitEvent(
		sdk.NewEvent(
			types.EventTypeHarvestBorrow,
			sdk.NewAttribute(types.AttributeKeyBorrower, borrower.String()),
			sdk.NewAttribute(types.AttributeKeyBorrowCoins, coins.String()),
		),
	)

	return nil
}

// SyncBorrowInterest updates the user's owed interest on newly borrowed coins to the latest global state,
// returning an sdk.Coins object containing the amount of newly accumulated interest.
func (k Keeper) SyncBorrowInterest(ctx sdk.Context, borrower sdk.AccAddress, coins sdk.Coins) sdk.Coins {
	totalNewInterest := sdk.Coins{}

	// Update user's borrow index list for each asset in the 'coins' array.
	// We use a list of BorrowIndexItem here because Amino doesn't support marshaling maps.
	borrow, found := k.GetBorrow(ctx, borrower)
	if !found { // User's first borrow
		// Build borrow index list containing (denoms, borrow index value at borrow time)
		var borrowIndexes types.BorrowIndexes
		for _, coin := range coins {
			borrowIndexValue, _ := k.GetBorrowIndex(ctx, coin.Denom)
			borrowIndex := types.NewBorrowIndexItem(coin.Denom, borrowIndexValue)
			borrowIndexes = append(borrowIndexes, borrowIndex)
		}
		borrow = types.NewBorrow(borrower, sdk.Coins{}, borrowIndexes)
	} else { // User has existing borrow
		for _, coin := range coins {
			// Locate the borrow index item by coin denom in the user's list of borrow indexes
			foundAtIndex := -1
			for i := range borrow.Index {
				if borrow.Index[i].Denom == coin.Denom {
					foundAtIndex = i
					break
				}
			}

			borrowIndexValue, _ := k.GetBorrowIndex(ctx, coin.Denom)
			if foundAtIndex == -1 { // First time user has borrowed this denom
				borrow.Index = append(borrow.Index, types.NewBorrowIndexItem(coin.Denom, borrowIndexValue))
			} else { // User has an existing borrow index for this denom
				// Calculate interest owed by user since asset's last borrow index update
				storedAmount := sdk.NewDecFromInt(borrow.Amount.AmountOf(coin.Denom))
				userLastBorrowIndex := borrow.Index[foundAtIndex].Value
				interest := (storedAmount.Quo(userLastBorrowIndex).Mul(borrowIndexValue)).Sub(storedAmount)
				totalNewInterest = totalNewInterest.Add(sdk.NewCoin(coin.Denom, interest.TruncateInt()))
				// We're synced up, so update user's borrow index value to match the current global borrow index value
				borrow.Index[foundAtIndex].Value = borrowIndexValue
			}
		}
		// Add all pending interest to user's borrow
		borrow.Amount = borrow.Amount.Add(totalNewInterest...)
	}

	// Update user's borrow in the store
	k.SetBorrow(ctx, borrow)

	return totalNewInterest
}

// ValidateBorrow validates a borrow request against borrower and protocol requirements
func (k Keeper) ValidateBorrow(ctx sdk.Context, borrower sdk.AccAddress, amount sdk.Coins) error {
	if amount.IsZero() {
		return types.ErrBorrowEmptyCoins
	}

	// Get the proposed borrow USD value
	moneyMarketCache := map[string]types.MoneyMarket{}
	proprosedBorrowUSDValue := sdk.ZeroDec()
	for _, coin := range amount {
		moneyMarket, ok := moneyMarketCache[coin.Denom]
		// Fetch money market and store in local cache
		if !ok {
			newMoneyMarket, found := k.GetMoneyMarketParam(ctx, coin.Denom)
			if !found {
				return sdkerrors.Wrapf(types.ErrMarketNotFound, "no market found for denom %s", coin.Denom)
			}
			moneyMarketCache[coin.Denom] = newMoneyMarket
			moneyMarket = newMoneyMarket
		}

		// Calculate this coin's USD value and add it borrow's total USD value
		assetPriceInfo, err := k.pricefeedKeeper.GetCurrentPrice(ctx, moneyMarket.SpotMarketID)
		if err != nil {
			return sdkerrors.Wrapf(types.ErrPriceNotFound, "no price found for market %s", moneyMarket.SpotMarketID)
		}
		coinUSDValue := sdk.NewDecFromInt(coin.Amount).Quo(sdk.NewDecFromInt(moneyMarket.ConversionFactor)).Mul(assetPriceInfo.Price)

		// Validate the requested borrow value for the asset against the money market's global borrow limit
		if moneyMarket.BorrowLimit.HasMaxLimit {
			var assetTotalBorrowedAmount sdk.Int
			totalBorrowedCoins, found := k.GetBorrowedCoins(ctx)
			if !found {
				assetTotalBorrowedAmount = sdk.ZeroInt()
			} else {
				assetTotalBorrowedAmount = totalBorrowedCoins.AmountOf(coin.Denom)
			}
			newProposedAssetTotalBorrowedAmount := sdk.NewDecFromInt(assetTotalBorrowedAmount.Add(coin.Amount))
			if newProposedAssetTotalBorrowedAmount.GT(moneyMarket.BorrowLimit.MaximumLimit) {
				return sdkerrors.Wrapf(types.ErrGreaterThanAssetBorrowLimit,
					"proposed borrow would result in %s borrowed, but the maximum global asset borrow limit is %s",
					newProposedAssetTotalBorrowedAmount, moneyMarket.BorrowLimit.MaximumLimit)
			}
		}
		proprosedBorrowUSDValue = proprosedBorrowUSDValue.Add(coinUSDValue)
	}

	// Get the total borrowable USD amount at user's existing deposits
	deposits := k.GetDepositsByUser(ctx, borrower)
	if len(deposits) == 0 {
		return sdkerrors.Wrapf(types.ErrDepositsNotFound, "no deposits found for %s", borrower)
	}
	totalBorrowableAmount := sdk.ZeroDec()
	for _, deposit := range deposits {
		moneyMarket, ok := moneyMarketCache[deposit.Amount.Denom]
		// Fetch money market and store in local cache
		if !ok {
			newMoneyMarket, found := k.GetMoneyMarketParam(ctx, deposit.Amount.Denom)
			if !found {
				return sdkerrors.Wrapf(types.ErrMarketNotFound, "no market found for denom %s", deposit.Amount.Denom)
			}
			moneyMarketCache[deposit.Amount.Denom] = newMoneyMarket
			moneyMarket = newMoneyMarket
		}

		// Calculate the borrowable amount and add it to the user's total borrowable amount
		assetPriceInfo, err := k.pricefeedKeeper.GetCurrentPrice(ctx, moneyMarket.SpotMarketID)
		if err != nil {
			sdkerrors.Wrapf(types.ErrPriceNotFound, "no price found for market %s", moneyMarket.SpotMarketID)
		}
		depositUSDValue := sdk.NewDecFromInt(deposit.Amount.Amount).Quo(sdk.NewDecFromInt(moneyMarket.ConversionFactor)).Mul(assetPriceInfo.Price)
		borrowableAmountForDeposit := depositUSDValue.Mul(moneyMarket.BorrowLimit.LoanToValue)
		totalBorrowableAmount = totalBorrowableAmount.Add(borrowableAmountForDeposit)
	}

	// Get the total USD value of user's existing borrows
	existingBorrowUSDValue := sdk.ZeroDec()
	existingBorrow, found := k.GetBorrow(ctx, borrower)
	if found {
		for _, borrowedCoin := range existingBorrow.Amount {
			moneyMarket, ok := moneyMarketCache[borrowedCoin.Denom]
			// Fetch money market and store in local cache
			if !ok {
				newMoneyMarket, found := k.GetMoneyMarketParam(ctx, borrowedCoin.Denom)
				if !found {
					return sdkerrors.Wrapf(types.ErrMarketNotFound, "no market found for denom %s", borrowedCoin.Denom)
				}
				moneyMarketCache[borrowedCoin.Denom] = newMoneyMarket
				moneyMarket = newMoneyMarket
			}

			// Calculate this borrow coin's USD value and add it to the total previous borrowed USD value
			assetPriceInfo, err := k.pricefeedKeeper.GetCurrentPrice(ctx, moneyMarket.SpotMarketID)
			if err != nil {
				return sdkerrors.Wrapf(types.ErrPriceNotFound, "no price found for market %s", moneyMarket.SpotMarketID)
			}
			coinUSDValue := sdk.NewDecFromInt(borrowedCoin.Amount).Quo(sdk.NewDecFromInt(moneyMarket.ConversionFactor)).Mul(assetPriceInfo.Price)
			existingBorrowUSDValue = existingBorrowUSDValue.Add(coinUSDValue)
		}
	}

	// Validate that the proposed borrow's USD value is within user's borrowable limit
	if proprosedBorrowUSDValue.GT(totalBorrowableAmount.Sub(existingBorrowUSDValue)) {
		return sdkerrors.Wrapf(types.ErrInsufficientLoanToValue, "requested borrow %s is greater than maximum valid borrow", amount)
	}
	return nil
}

// IncrementBorrowedCoins increments the amount of borrowed coins by the newCoins parameter
func (k Keeper) IncrementBorrowedCoins(ctx sdk.Context, newCoins sdk.Coins) {
	borrowedCoins, found := k.GetBorrowedCoins(ctx)
	if !found {
		k.SetBorrowedCoins(ctx, newCoins)
	} else {
		k.SetBorrowedCoins(ctx, borrowedCoins.Add(newCoins...))
	}
}

// DecrementBorrowedCoins decrements the amount of borrowed coins by the coins parameter
func (k Keeper) DecrementBorrowedCoins(ctx sdk.Context, coins sdk.Coins) error {
	borrowedCoins, found := k.GetBorrowedCoins(ctx)
	if !found {
		return sdkerrors.Wrapf(types.ErrBorrowedCoinsNotFound, "cannot repay coins if no coins are currently borrowed")
	}

	updatedBorrowedCoins, isAnyNegative := borrowedCoins.SafeSub(coins)
	if isAnyNegative {
		return types.ErrNegativeBorrowedCoins
	}

	k.SetBorrowedCoins(ctx, updatedBorrowedCoins)
	return nil
}