package simulation

import (
	"bytes"
	"fmt"

	tmkv "github.com/tendermint/tendermint/libs/kv"

	"github.com/cosmos/cosmos-sdk/x/evidence/types"
)

// NewDecodeStore returns a decoder function closure that unmarshals the KVPair's
// Value to the corresponding evidence type.
func NewDecodeStore(cdc types.Codec) func(kvA, kvB tmkv.Pair) string {
	return func(kvA, kvB tmkv.Pair) string {
		switch {
		case bytes.Equal(kvA.Key[:1], types.KeyPrefixEvidence):
			evidenceA, err := cdc.UnmarshalEvidence(kvA.Value)
			if err != nil {
				panic(fmt.Sprintf("cannot unmarshal evidence: %s", err.Error()))
			}
			evidenceB, err := cdc.UnmarshalEvidence(kvB.Value)
			if err != nil {
				panic(fmt.Sprintf("cannot unmarshal evidence: %s", err.Error()))
			}
			return fmt.Sprintf("%v\n%v", evidenceA, evidenceB)

		default:
			panic(fmt.Sprintf("invalid %s key prefix %X", types.ModuleName, kvA.Key[:1]))
		}
	}
}