package chaincfg

import (
	sdk "github.com/cosmos/cosmos-sdk/types"
	minttypes "github.com/cosmos/cosmos-sdk/x/mint/types"
)

func NextInflationRate(ctx sdk.Context, minter minttypes.Minter, params minttypes.Params, bondedRatio sdk.Dec, circulatingRatio sdk.Dec) sdk.Dec {
	// The target annual inflation rate is recalculated for each previsions cycle. The
	// inflation is also subject to a rate change (positive or negative) depending on
	// the distance from the desired ratio (67%). The maximum rate change possible is
	// defined to be 13% per year, however the annual inflation is capped as between
	// 7% and 20%.

	// (1 - bondedRatio/GoalBonded) * InflationRateChange
	inflationRateChangePerYear := sdk.OneDec().
		Sub(bondedRatio.Quo(params.GoalBonded)).
		Mul(params.InflationRateChange)
	inflationRateChange := inflationRateChangePerYear.Quo(sdk.NewDec(int64(params.BlocksPerYear)))

	// adjust the new annual inflation for this next cycle
	inflation := minter.Inflation.Add(inflationRateChange) // note inflationRateChange may be negative
	if inflation.GT(params.InflationMax) {
		inflation = params.InflationMax
	}
	if inflation.LT(params.InflationMin) {
		inflation = params.InflationMin
	}

	ctx.Logger().Debug(
		"calculated new annual inflation",
		"bondedRatio", bondedRatio,
		"circulatingRatio", circulatingRatio,
		"inflation", inflation,
		"params", params,
		"minter", minter,
	)
	return inflation
}