package simulation

import (
	"math/rand"

	"github.com/cosmos/cosmos-sdk/baseapp"
	sdk "github.com/cosmos/cosmos-sdk/types"
	abci "github.com/tendermint/tendermint/abci/types"
	"github.com/tendermint/tendermint/crypto"
)

type (
	// Operation runs a state machine transition,
	// and ensures the transition happened as expected.
	// The operation could be running and testing a fuzzed transaction,
	// or doing the same for a message.
	//
	// For ease of debugging,
	// an operation returns a descriptive message "action",
	// which details what this fuzzed state machine transition actually did.
	//
	// Operations can optionally provide a list of "FutureOperations" to run later
	// These will be ran at the beginning of the corresponding block.
	Operation func(r *rand.Rand, app *baseapp.BaseApp, ctx sdk.Context,
		privKeys []crypto.PrivKey, event func(string),
	) (action string, futureOperations []FutureOperation, err error)

	// RandSetup performs the random setup the mock module needs.
	RandSetup func(r *rand.Rand, privKeys []crypto.PrivKey)

	// An Invariant is a function which tests a particular invariant.
	// If the invariant has been broken, it should return an error
	// containing a descriptive message about what happened.
	// The simulator will then halt and print the logs.
	Invariant func(app *baseapp.BaseApp) error

	mockValidator struct {
		val           abci.Validator
		livenessState int
	}

	// FutureOperation is an operation which will be ran at the
	// beginning of the provided BlockHeight.
	// In the (likely) event that multiple operations are queued at the same
	// block height, they will execute in a FIFO pattern.
	FutureOperation struct {
		BlockHeight int
		Op          Operation
	}

	// WeightedOperation is an operation with associated weight.
	// This is used to bias the selection operation within the simulator.
	WeightedOperation struct {
		Weight int
		Op     Operation
	}
)

// PeriodicInvariant returns an Invariant function closure that asserts
// a given invariant if the mock application's last block modulo the given
// period is congruent to the given offset.
func PeriodicInvariant(invariant Invariant, period int, offset int) Invariant {
	return func(app *baseapp.BaseApp) error {
		if int(app.LastBlockHeight())%period == offset {
			return invariant(app)
		}
		return nil
	}
}