package keeper

import (
	"fmt"
	"time"

	sdk "github.com/cosmos/cosmos-sdk/types"
	"github.com/cosmos/cosmos-sdk/x/supply"
	"github.com/kava-labs/kava/x/auction/types"
)

// StartSurplusAuction starts a new surplus (forward) auction.
func (k Keeper) StartSurplusAuction(ctx sdk.Context, seller string, lot sdk.Coin, bidDenom string) (uint64, sdk.Error) {
	// create auction
	auction := types.NewSurplusAuction(seller, lot, bidDenom, ctx.BlockTime().Add(types.DefaultMaxAuctionDuration))

	// take coins from module account
	err := k.supplyKeeper.SendCoinsFromModuleToModule(ctx, seller, types.ModuleName, sdk.NewCoins(lot))
	if err != nil {
		return 0, err
	}
	// store the auction
	auctionID, err := k.StoreNewAuction(ctx, auction)
	if err != nil {
		return 0, err
	}
	return auctionID, nil
}

// StartDebtAuction starts a new debt (reverse) auction.
func (k Keeper) StartDebtAuction(ctx sdk.Context, buyer string, bid sdk.Coin, initialLot sdk.Coin) (uint64, sdk.Error) {
	// create auction
	auction := types.NewDebtAuction(buyer, bid, initialLot, ctx.BlockTime().Add(types.DefaultMaxAuctionDuration))

	// This auction type mints coins at close. Need to check module account has minting privileges to avoid potential err in endblocker.
	macc := k.supplyKeeper.GetModuleAccount(ctx, buyer)
	if !macc.HasPermission(supply.Minter) {
		return 0, sdk.ErrInternal("module does not have minting permissions")
	}
	// store the auction
	auctionID, err := k.StoreNewAuction(ctx, auction)
	if err != nil {
		return 0, err
	}
	return auctionID, nil
}

// StartCollateralAuction starts a new collateral (2-phase) auction where bidders bid up to a maxBid, then switch to bidding down on the Lot.
func (k Keeper) StartCollateralAuction(ctx sdk.Context, seller string, lot sdk.Coin, maxBid sdk.Coin, lotReturnAddrs []sdk.AccAddress, lotReturnWeights []sdk.Int) (uint64, sdk.Error) {
	// create auction
	weightedAddresses, err := types.NewWeightedAddresses(lotReturnAddrs, lotReturnWeights)
	if err != nil {
		return 0, err
	}
	auction := types.NewCollateralAuction(seller, lot, ctx.BlockTime().Add(types.DefaultMaxAuctionDuration), maxBid, weightedAddresses)

	// take coins from module account
	err = k.supplyKeeper.SendCoinsFromModuleToModule(ctx, seller, types.ModuleName, sdk.NewCoins(lot))
	if err != nil {
		return 0, err
	}
	// store the auction
	auctionID, err := k.StoreNewAuction(ctx, auction)
	if err != nil {
		return 0, err
	}
	return auctionID, nil
}

// PlaceBid places a bid on any auction.
func (k Keeper) PlaceBid(ctx sdk.Context, auctionID uint64, bidder sdk.AccAddress, newAmount sdk.Coin) sdk.Error {

	// get auction from store
	auction, found := k.GetAuction(ctx, auctionID)
	if !found {
		return sdk.ErrInternal("auction doesn't exist")
	}

	// validate
	if ctx.BlockTime().After(auction.GetEndTime()) {
		return sdk.ErrInternal("auction has closed")
	}

	// place bid
	var err sdk.Error
	var updatedAuction types.Auction
	switch a := auction.(type) {
	case types.SurplusAuction:
		if updatedAuction, err = k.PlaceBidSurplus(ctx, a, bidder, newAmount); err != nil {
			return err
		}
	case types.DebtAuction:
		if updatedAuction, err = k.PlaceBidDebt(ctx, a, bidder, newAmount); err != nil {
			return err
		}
	case types.CollateralAuction:
		if !a.IsReversePhase() {
			updatedAuction, err = k.PlaceForwardBidCollateral(ctx, a, bidder, newAmount)
		} else {
			updatedAuction, err = k.PlaceReverseBidCollateral(ctx, a, bidder, newAmount)
		}
		if err != nil {
			return err
		}
	default:
		panic(fmt.Sprintf("unrecognized auction type: %T", auction))
	}

	// store updated auction
	k.SetAuction(ctx, updatedAuction)
	return nil
}

// PlaceBidSurplus places a forward bid on a surplus auction, moving coins and returning the updated auction.
func (k Keeper) PlaceBidSurplus(ctx sdk.Context, a types.SurplusAuction, bidder sdk.AccAddress, bid sdk.Coin) (types.SurplusAuction, sdk.Error) {
	// Validate New Bid
	if bid.Denom != a.Bid.Denom {
		return a, sdk.ErrInternal("bid denom doesn't match auction")
	}
	if !a.Bid.IsLT(bid) { // TODO add minimum bid size
		return a, sdk.ErrInternal("bid not greater than last bid")
	}

	// Move Coins
	if !bidder.Equals(a.Bidder) && !a.Bid.IsZero() { // catch edge case of someone updating their bid with a low balance, also don't send if amt is zero
		// pay back previous bidder
		err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, types.ModuleName, sdk.NewCoins(a.Bid))
		if err != nil {
			return a, err
		}
		err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Bid))
		if err != nil {
			return a, err
		}
	}
	// burn increase in bid
	err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, a.Initiator, sdk.NewCoins(bid.Sub(a.Bid)))
	if err != nil {
		return a, err
	}
	err = k.supplyKeeper.BurnCoins(ctx, a.Initiator, sdk.NewCoins(bid.Sub(a.Bid)))
	if err != nil {
		return a, err
	}

	// Update Auction
	a.Bidder = bidder
	a.Bid = bid
	// increment timeout
	a.EndTime = earliestTime(ctx.BlockTime().Add(types.DefaultBidDuration), a.MaxEndTime)

	return a, nil
}

// PlaceForwardBidCollateral places a forward bid on a collateral auction, moving coins and returning the updated auction.
func (k Keeper) PlaceForwardBidCollateral(ctx sdk.Context, a types.CollateralAuction, bidder sdk.AccAddress, bid sdk.Coin) (types.CollateralAuction, sdk.Error) {
	// Validate new bid
	if bid.Denom != a.Bid.Denom {
		return a, sdk.ErrInternal("bid denom doesn't match auction")
	}
	if a.IsReversePhase() {
		return a, sdk.ErrInternal("auction is not in forward phase")
	}
	if !a.Bid.IsLT(bid) {
		return a, sdk.ErrInternal("auction in forward phase, new bid not higher than last bid")
	}
	if a.MaxBid.IsLT(bid) {
		return a, sdk.ErrInternal("bid higher than max bid")
	}
	// Move Coins
	// pay back previous bidder
	if !bidder.Equals(a.Bidder) && !a.Bid.IsZero() { // catch edge case of someone updating their bid with a low balance, also don't send if amt is zero
		err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, types.ModuleName, sdk.NewCoins(a.Bid))
		if err != nil {
			return a, err
		}
		err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Bid))
		if err != nil {
			return a, err
		}
	}
	// pay increase in bid to auction initiator
	err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, a.Initiator, sdk.NewCoins(bid.Sub(a.Bid)))
	if err != nil {
		return a, err
	}

	// Update Auction
	a.Bidder = bidder
	a.Bid = bid
	// increment timeout
	a.EndTime = earliestTime(ctx.BlockTime().Add(types.DefaultBidDuration), a.MaxEndTime)

	return a, nil
}

// PlaceReverseBidCollateral places a reverse bid on a collateral auction, moving coins and returning the updated auction.
func (k Keeper) PlaceReverseBidCollateral(ctx sdk.Context, a types.CollateralAuction, bidder sdk.AccAddress, lot sdk.Coin) (types.CollateralAuction, sdk.Error) {
	// Validate bid
	if lot.Denom != a.Lot.Denom {
		return a, sdk.ErrInternal("lot denom doesn't match auction")
	}
	if !a.IsReversePhase() {
		return a, sdk.ErrInternal("auction not in reverse phase")
	}
	if lot.IsNegative() {
		return a, sdk.ErrInternal("can't bid negative amount")
	}
	if !lot.IsLT(a.Lot) {
		return a, sdk.ErrInternal("auction in reverse phase, new bid not less than previous amount")
	}

	// Move Coins
	if !bidder.Equals(a.Bidder) { // catch edge case of someone updating their bid with a low balance
		err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, types.ModuleName, sdk.NewCoins(a.Bid))
		if err != nil {
			return a, err
		}
		err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Bid))
		if err != nil {
			return a, err
		}
	}
	// FIXME paying out rateably to cdp depositors is vulnerable to errors compounding over multiple bids
	lotPayouts, err := splitCoinIntoWeightedBuckets(a.Lot.Sub(lot), a.LotReturns.Weights)
	if err != nil {
		return a, err
	}
	for i, payout := range lotPayouts {
		err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.LotReturns.Addresses[i], sdk.NewCoins(payout))
		if err != nil {
			return a, err
		}
	}

	// Update Auction
	a.Bidder = bidder
	a.Lot = lot
	// increment timeout
	a.EndTime = earliestTime(ctx.BlockTime().Add(types.DefaultBidDuration), a.MaxEndTime)

	return a, nil
}

// PlaceBidDebt places a reverse bid on a debt auction, moving coins and returning the updated auction.
func (k Keeper) PlaceBidDebt(ctx sdk.Context, a types.DebtAuction, bidder sdk.AccAddress, lot sdk.Coin) (types.DebtAuction, sdk.Error) {
	// Validate New Bid
	if lot.Denom != a.Lot.Denom {
		return a, sdk.ErrInternal("lot denom doesn't match auction")
	}
	if lot.IsNegative() {
		return a, sdk.ErrInternal("lot less than 0")
	}
	if !lot.IsLT(a.Lot) { // TODO add min bid decrements
		return a, sdk.ErrInternal("lot not smaller than last lot")
	}

	// Move Coins
	if !bidder.Equals(a.Bidder) { // catch edge case of someone updating their bid with a low balance
		err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, types.ModuleName, sdk.NewCoins(a.Bid))
		if err != nil {
			return a, err
		}
		err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Bid))
		if err != nil {
			return a, err
		}
	}

	// Update Auction
	a.Bidder = bidder
	a.Lot = lot
	// increment timeout
	a.EndTime = earliestTime(ctx.BlockTime().Add(types.DefaultBidDuration), a.MaxEndTime)

	return a, nil
}

// CloseAuction closes an auction and distributes funds to the highest bidder.
func (k Keeper) CloseAuction(ctx sdk.Context, auctionID uint64) sdk.Error {

	// get the auction from the store
	auction, found := k.GetAuction(ctx, auctionID)
	if !found {
		return sdk.ErrInternal("auction doesn't exist")
	}
	// error if auction has not reached the end time
	if ctx.BlockTime().Before(auction.GetEndTime()) {
		return sdk.ErrInternal(fmt.Sprintf("auction can't be closed as curent block time (%v) is under auction end time (%v)", ctx.BlockTime(), auction.GetEndTime()))
	}

	// payout to the last bidder
	switch auc := auction.(type) {
	case types.SurplusAuction:
		if err := k.PayoutSurplusAuction(ctx, auc); err != nil {
			return err
		}
	case types.DebtAuction:
		if err := k.PayoutDebtAuction(ctx, auc); err != nil {
			return err
		}
	case types.CollateralAuction:
		if err := k.PayoutCollateralAuction(ctx, auc); err != nil {
			return err
		}
	default:
		panic("unrecognized auction type")
	}

	k.DeleteAuction(ctx, auctionID)
	return nil
}

// PayoutDebtAuction pays out the proceeds for a debt auction, first minting the coins.
func (k Keeper) PayoutDebtAuction(ctx sdk.Context, a types.DebtAuction) sdk.Error {
	err := k.supplyKeeper.MintCoins(ctx, a.Initiator, sdk.NewCoins(a.Lot))
	if err != nil {
		return err
	}
	err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, a.Initiator, a.Bidder, sdk.NewCoins(a.Lot))
	if err != nil {
		return err
	}
	return nil
}

// PayoutSurplusAuction pays out the proceeds for a surplus auction.
func (k Keeper) PayoutSurplusAuction(ctx sdk.Context, a types.SurplusAuction) sdk.Error {
	err := k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Lot))
	if err != nil {
		return err
	}
	return nil
}

// PayoutCollateralAuction pays out the proceeds for a collateral auction.
func (k Keeper) PayoutCollateralAuction(ctx sdk.Context, a types.CollateralAuction) sdk.Error {
	err := k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Lot))
	if err != nil {
		return err
	}
	return nil
}

// earliestTime returns the earliest of two times.
func earliestTime(t1, t2 time.Time) time.Time {
	if t1.Before(t2) {
		return t1
	} else {
		return t2 // also returned if times are equal
	}
}

// splitCoinIntoWeightedBuckets divides up some amount of coins according to some weights.
func splitCoinIntoWeightedBuckets(coin sdk.Coin, buckets []sdk.Int) ([]sdk.Coin, sdk.Error) {
	for _, bucket := range buckets {
		if bucket.IsNegative() {
			return nil, sdk.ErrInternal("cannot split coin into bucket with negative weight")
		}
	}
	amounts := splitIntIntoWeightedBuckets(coin.Amount, buckets)
	result := make([]sdk.Coin, len(amounts))
	for i, a := range amounts {
		result[i] = sdk.NewCoin(coin.Denom, a)
	}
	return result, nil
}