// Copyright (C) 2019-2025, Lux Industries, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
//
// This file is a derived work, based on the go-ethereum library whose original
// notices appear below.
//
// It is distributed under a license compatible with the licensing terms of the
// original code from which it is derived.
//
// Much love to the original authors for their work.
// **********
// Copyright 2023 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 eth

import (
	"compress/gzip"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"strings"

	"github.com/luxfi/geth/core/rawdb"
	"github.com/luxfi/geth/core/types"
	"github.com/luxfi/geth/rlp"
	log "github.com/luxfi/log"
)

// AdminAPI is the collection of Ethereum full node related APIs for node
// administration.
type AdminAPI struct {
	eth *Ethereum
}

// NewAdminAPI creates a new instance of AdminAPI.
func NewAdminAPI(eth *Ethereum) *AdminAPI {
	return &AdminAPI{eth: eth}
}

// ExportChain exports the current blockchain into a local file,
// or a range of blocks if first and last are non-nil.
func (api *AdminAPI) ExportChain(file string, first *uint64, last *uint64) (bool, error) {
	if first == nil && last != nil {
		return false, errors.New("last cannot be specified without first")
	}
	if first != nil && last == nil {
		head := api.eth.BlockChain().CurrentHeader().Number.Uint64()
		last = &head
	}
	if _, err := os.Stat(file); err == nil {
		// File already exists. Allowing overwrite could be a DoS vector,
		// since the 'file' may point to arbitrary paths on the drive.
		return false, errors.New("location would overwrite an existing file")
	}
	// Make sure we can create the file to export into
	out, err := os.OpenFile(file, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
	if err != nil {
		return false, err
	}
	defer out.Close()

	var writer io.Writer = out
	if strings.HasSuffix(file, ".gz") {
		writer = gzip.NewWriter(writer)
		defer writer.(*gzip.Writer).Close()
	}

	// Export the blockchain
	if first != nil {
		if err := api.eth.BlockChain().ExportN(writer, *first, *last); err != nil {
			return false, err
		}
	} else if err := api.eth.BlockChain().Export(writer); err != nil {
		return false, err
	}
	return true, nil
}

// ImportChain imports a blockchain from a local file.
// State is committed periodically during import for restart-safety.
func (api *AdminAPI) ImportChain(file string) (bool, error) {
	in, err := os.Open(file)
	if err != nil {
		return false, err
	}
	defer in.Close()

	var reader io.Reader = in
	if strings.HasSuffix(file, ".gz") {
		if reader, err = gzip.NewReader(reader); err != nil {
			return false, err
		}
	}

	chain := api.eth.BlockChain()
	if err := chain.EnsureGenesisState(); err != nil {
		return false, fmt.Errorf("failed to ensure genesis state: %w", err)
	}

	stream := rlp.NewStream(reader, 0)
	blocks, index := make([]*types.Block, 0, 2500), 0
	var lastInsertedBlock *types.Block
	commitInterval := chain.CommitInterval()
	var lastCommitHeight uint64

	log.Info("ImportChain: starting", "file", file, "currentBlock", chain.CurrentBlock().Number, "commitInterval", commitInterval)

	for batch := 0; ; batch++ {
		for len(blocks) < cap(blocks) {
			block := new(types.Block)
			if err := stream.Decode(block); err == io.EOF {
				break
			} else if err != nil {
				return false, fmt.Errorf("block %d: failed to parse: %v", index, err)
			}
			if block.NumberU64() == 0 {
				continue
			}
			blocks = append(blocks, block)
			index++
		}
		if len(blocks) == 0 {
			break
		}

		log.Info("ImportChain: inserting batch", "batch", batch, "blocks", len(blocks), "firstNum", blocks[0].NumberU64())
		n, err := chain.InsertChain(blocks)
		if err != nil {
			return false, fmt.Errorf("batch %d: failed to insert after %d blocks: %v", batch, n, err)
		}
		if n > 0 {
			lastInsertedBlock = blocks[n-1]
			currentHeight := lastInsertedBlock.NumberU64()

			if err := chain.SetLastAcceptedBlockDirect(lastInsertedBlock); err != nil {
				return false, fmt.Errorf("failed to set last accepted block: %v", err)
			}

			// Periodically commit state trie to disk for restart-safety
			if currentHeight-lastCommitHeight >= commitInterval {
				log.Info("ImportChain: committing state", "block", currentHeight)
				if err := chain.ForceCommitState(lastInsertedBlock); err != nil {
					return false, fmt.Errorf("failed to commit state at block %d: %v", currentHeight, err)
				}
				lastCommitHeight = currentHeight
			}
		}
		blocks = blocks[:0]
	}

	if lastInsertedBlock != nil {
		// Final state commit
		finalHeight := lastInsertedBlock.NumberU64()
		if finalHeight > lastCommitHeight {
			log.Info("ImportChain: final state commit", "block", finalHeight)
			if err := chain.ForceCommitState(lastInsertedBlock); err != nil {
				return false, fmt.Errorf("failed to commit final state: %v", err)
			}
		}

		// Update VM layer via callback
		if err := api.eth.CallPostImportCallback(lastInsertedBlock.Hash(), finalHeight); err != nil {
			log.Warn("ImportChain: post-import callback failed", "error", err)
		}

		log.Info("ImportChain: completed", "blocks", index, "height", finalHeight)
	}

	return true, nil
}

// WriteGenesisStateSpec writes the genesis state spec to the database.
// This is required for RLP import to work when the genesis state trie is not accessible.
// The genesis allocs are stored in the database, enabling block_validator.go's special
// handling for block 1 (which allows import even without the genesis state trie).
func (api *AdminAPI) WriteGenesisStateSpec(genesisFile string) (bool, error) {
	// Read genesis file
	data, err := os.ReadFile(genesisFile)
	if err != nil {
		return false, fmt.Errorf("failed to read genesis file: %w", err)
	}

	// Parse genesis to get alloc
	var genesis struct {
		Alloc types.GenesisAlloc `json:"alloc"`
	}
	if err := json.Unmarshal(data, &genesis); err != nil {
		return false, fmt.Errorf("failed to parse genesis: %w", err)
	}

	// Marshal alloc to JSON
	allocJSON, err := json.Marshal(genesis.Alloc)
	if err != nil {
		return false, fmt.Errorf("failed to marshal alloc: %w", err)
	}

	// Get the genesis block hash
	chain := api.eth.BlockChain()
	genesisBlock := chain.GetBlockByNumber(0)
	if genesisBlock == nil {
		return false, errors.New("genesis block not found")
	}

	// Write to database using proper rawdb method
	db := api.eth.ChainDb()
	rawdb.WriteGenesisStateSpec(db, genesisBlock.Hash(), allocJSON)

	log.Info("WriteGenesisStateSpec: written",
		"genesisHash", genesisBlock.Hash().Hex(),
		"allocSize", len(allocJSON))

	return true, nil
}