// Copyright 2018 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library 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.
//
// The go-ethereum library 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 the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package core

import (
	"context"
	"fmt"
	"time"

	"github.com/ledgerwatch/turbo-geth/common"
	"github.com/ledgerwatch/turbo-geth/common/mclock"
	"github.com/ledgerwatch/turbo-geth/consensus"
	"github.com/ledgerwatch/turbo-geth/core/rawdb"
	"github.com/ledgerwatch/turbo-geth/core/types"
	"github.com/ledgerwatch/turbo-geth/ethdb"
	"github.com/ledgerwatch/turbo-geth/log"
)

// InsertStats tracks and reports on block insertion.
type InsertStats struct {
	queued, lastIndex, ignored int
	UsedGas                    uint64
	Processed                  int
	StartTime                  mclock.AbsTime
}

// statsReportLimit is the time limit during import and export after which we
// always print out progress. This avoids the user wondering what's going on.
//const statsReportLimit = 8 * time.Second

// report prints statistics if some number of blocks have been processed
// or more than a few seconds have passed since the last message.
/*
func (st *InsertStats) report(chain []*types.Block, index int, cache common.StorageSize) {
	// Fetch the timings for the batch
	var (
		now     = mclock.Now()
		elapsed = now.Sub(st.startTime)
	)
	// If we're at the last block of the batch or report period reached, log
	if index == len(chain)-1 || elapsed >= statsReportLimit {
		// Count the number of transactions in this segment
		var txs int
		for _, block := range chain[st.lastIndex : index+1] {
			txs += len(block.Transactions())
		}
		end := chain[index]

		// Assemble the log context and send it to the logger
		context := []interface{}{
			"blocks", st.processed, "txs", txs, "mgas", float64(st.usedGas) / 1000000,
			"elapsed", common.PrettyDuration(elapsed), "mgasps", float64(st.usedGas) * 1000 / float64(elapsed),
			"number", end.Number(), "hash", end.Hash(),
		}
		if timestamp := time.Unix(int64(end.Time()), 0); time.Since(timestamp) > time.Minute {
			context = append(context, []interface{}{"age", common.PrettyAge(timestamp)}...)
		}
		context = append(context, []interface{}{"dirty", dirty}...)

		if st.queued > 0 {
			context = append(context, []interface{}{"queued", st.queued}...)
		}
		if st.ignored > 0 {
			context = append(context, []interface{}{"ignored", st.ignored}...)
		}
		log.Info("Imported new chain segment", context...)

		// Bump the stats reported to the next section
		*st = InsertStats{startTime: now, lastIndex: index + 1}
	}
}
*/

// insertIterator is a helper to assist during chain import.
type insertIterator struct {
	chain types.Blocks // Chain of blocks being iterated over

	results <-chan error // Verification result sink from the consensus engine
	errors  []error      // Header verification errors for the blocks

	index     int       // Current offset of the iterator
	validator Validator // Validator to run if verification succeeds
}

// newInsertIterator creates a new iterator based on the given blocks, which are
// assumed to be a contiguous chain.
func newInsertIterator(chain types.Blocks, results <-chan error, validator Validator) *insertIterator {
	return &insertIterator{
		chain:     chain,
		results:   results,
		errors:    make([]error, 0, len(chain)),
		index:     -1,
		validator: validator,
	}
}

// next returns the next block in the iterator, along with any potential validation
// error for that block. When the end is reached, it will return (nil, nil).
func (it *insertIterator) next(ctx context.Context) (*types.Block, error) {
	if it.index+1 >= len(it.chain) {
		it.index = len(it.chain)
		return nil, nil
	}
	// Advance the iterator and wait for verification result if not yet done
	it.index++
	if len(it.errors) <= it.index {
		it.errors = append(it.errors, <-it.results)
	}
	if it.errors[it.index] != nil {
		return it.chain[it.index], it.errors[it.index]
	}
	return it.chain[it.index], it.validator.ValidateBody(ctx, it.chain[it.index])
}

// peek returns the next block in the iterator, along with any potential validation
// error for that block, but does **not** advance the iterator.
//
// Both header and body validation errors (nil too) is cached into the iterator
// to avoid duplicating work on the following next() call.
func (it *insertIterator) peek() (*types.Block, error) {
	// If we reached the end of the chain, abort
	if it.index+1 >= len(it.chain) {
		return nil, nil
	}
	// Wait for verification result if not yet done
	if len(it.errors) <= it.index+1 {
		it.errors = append(it.errors, <-it.results)
	}
	if it.errors[it.index+1] != nil {
		return it.chain[it.index+1], it.errors[it.index+1]
	}
	// Block header valid, ignore body validation since we don't have a parent anyway
	return it.chain[it.index+1], nil
}

// previous returns the previous header that was being processed, or nil.
func (it *insertIterator) previous() *types.Header {
	if it.index < 1 {
		return nil
	}
	return it.chain[it.index-1].Header()
}

// first returns the first block in the it.
func (it *insertIterator) first() *types.Block {
	return it.chain[0]
}

// remaining returns the number of remaining blocks.
func (it *insertIterator) remaining() int {
	return len(it.chain) - it.index
}

// processed returns the number of processed blocks.
func (it *insertIterator) processed() int {
	return it.index + 1
}

// InsertBodyChain attempts to insert the given batch of block into the
// canonical chain, without executing those blocks
func InsertBodyChain(logPrefix string, ctx context.Context, db ethdb.Database, chain types.Blocks, newCanonical bool) (bool, error) {
	// Sanity check that we have something meaningful to import
	if len(chain) == 0 {
		return true, nil
	}
	// Remove already known canon-blocks
	var (
		block, prev *types.Block
	)
	// Do a sanity check that the provided chain is actually ordered and linked
	for i := 1; i < len(chain); i++ {
		block = chain[i]
		prev = chain[i-1]
		if block.NumberU64() != prev.NumberU64()+1 || block.ParentHash() != prev.Hash() {
			// Chain broke ancestry, log a message (programming error) and skip insertion
			log.Error("Non contiguous block insert", "number", block.Number(), "hash", block.Hash(),
				"parent", block.ParentHash(), "prevnumber", prev.Number(), "prevhash", prev.Hash())

			return true, fmt.Errorf("non contiguous insert: item %d is #%d [%x…], item %d is #%d [%x…] (parent [%x…])", i-1, prev.NumberU64(),
				prev.Hash().Bytes()[:4], i, block.NumberU64(), block.Hash().Bytes()[:4], block.ParentHash().Bytes()[:4])
		}
	}

	return InsertBodies(
		logPrefix,
		ctx,
		chain,
		db,
		newCanonical,
	)
}

// InsertBodies is insertChain with execute=false and ommission of blockchain object
func InsertBodies(
	logPrefix string,
	ctx context.Context,
	chain types.Blocks,
	db ethdb.Database,
	newCanonical bool,
) (bool, error) {
	tx, err := db.Begin(ctx, ethdb.RW)
	if err != nil {
		return false, err
	}
	defer tx.Rollback()
	batch := tx.NewBatch()
	defer batch.Rollback()
	stats := InsertStats{StartTime: mclock.Now()}

	var parentNumber = chain[0].NumberU64() - 1
	parentHash := chain[0].ParentHash()

	if parent := rawdb.ReadStorageBodyRLP(batch, parentHash, parentNumber); parent == nil {
		log.Error("chain segment could not be inserted, missing parent", "hash", parentHash)
		return true, fmt.Errorf("chain segment could not be inserted, missing parent %x", parentHash)
	}

	// Iterate over the blocks and insert when the verifier permits
	for _, block := range chain {
		start := time.Now()

		// Calculate the total difficulty of the block
		ptd, err := rawdb.ReadTd(batch, block.ParentHash(), block.NumberU64()-1)
		if err != nil {
			return true, err
		}

		if ptd == nil {
			return true, consensus.ErrUnknownAncestor
		}

		// Irrelevant of the canonical status, write the block itself to the database
		if common.IsCanceled(ctx) {
			return true, ctx.Err()
		}

		err = rawdb.WriteBody(batch, block.Hash(), block.NumberU64(), block.Body())
		if err != nil {
			return true, err
		}

		log.Debug("Inserted new block", "number", block.Number(), "hash", block.Hash(),
			"uncles", len(block.Uncles()), "txs", len(block.Transactions()), "gas", block.GasUsed(),
			"elapsed", common.PrettyDuration(time.Since(start)),
			"root", block.Root())
	}
	stats.Processed = len(chain)
	stats.Report(logPrefix, chain, len(chain)-1, true)
	if newCanonical {
		rawdb.WriteHeadBlockHash(batch, chain[len(chain)-1].Hash())
	}
	if _, err := batch.Commit(); err != nil {
		return true, fmt.Errorf("commit inserting bodies: %w", err)
	}
	if _, err := tx.Commit(); err != nil {
		return true, fmt.Errorf("commit inserting bodies: %w", err)
	}
	return false, nil
}