// Copyright 2017 The go-ethereum Authors
// (original work)
// Copyright 2024 The Erigon Authors
// (modifications)
// This file is part of Erigon.
//
// Erigon is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Erigon is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with Erigon. If not, see <http://www.gnu.org/licenses/>.

package testutil

import (
	"fmt"

	"github.com/holiman/uint256"

	"github.com/erigontech/erigon/common"
	"github.com/erigontech/erigon/common/empty"
	"github.com/erigontech/erigon/common/math"
	"github.com/erigontech/erigon/execution/chain"
	"github.com/erigontech/erigon/execution/protocol/rules/ethash"
	"github.com/erigontech/erigon/execution/types"
)

//go:generate gencodec -type DifficultyTest -field-override difficultyTestMarshaling -out gen_difficultytest.go

type DifficultyTest struct {
	ParentTimestamp    uint64      `json:"parentTimestamp"`
	ParentDifficulty   uint256.Int `json:"parentDifficulty"`
	ParentUncles       uint64      `json:"parentUncles"`
	CurrentTimestamp   uint64      `json:"currentTimestamp"`
	CurrentBlockNumber uint64      `json:"currentBlockNumber"`
	CurrentDifficulty  uint256.Int `json:"currentDifficulty"`
}

type difficultyTestMarshaling struct {
	ParentTimestamp    math.HexOrDecimal64
	ParentDifficulty   math.HexOrDecimal256
	CurrentTimestamp   math.HexOrDecimal64
	CurrentDifficulty  math.HexOrDecimal256
	ParentUncles       math.HexOrDecimal64
	CurrentBlockNumber math.HexOrDecimal64
}

func (test *DifficultyTest) Run(config *chain.Config) error {
	parent := &types.Header{
		Difficulty: test.ParentDifficulty,
		Time:       test.ParentTimestamp,
	}
	parent.Number.SetUint64(test.CurrentBlockNumber - 1)

	if test.ParentUncles == 0 {
		parent.UncleHash = empty.UncleHash
	} else {
		parent.UncleHash = common.HexToHash("ab") // some dummy != EmptyUncleHash
	}

	actual := ethash.CalcDifficulty(config, test.CurrentTimestamp, parent.Time, parent.Difficulty, parent.Number.Uint64(), parent.UncleHash)
	exp := test.CurrentDifficulty

	if actual.Cmp(&exp) != 0 {
		return fmt.Errorf("parent[time %v diff %v unclehash:%x] child[time %v number %v] diff %v != expected %v",
			test.ParentTimestamp, test.ParentDifficulty, test.ParentUncles,
			test.CurrentTimestamp, test.CurrentBlockNumber, &actual, &exp)
	}
	return nil
}
