// Copyright 2024 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 v2

import (
	"encoding/hex"
	"fmt"
	"github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/accounts/abi"
	"github.com/ethereum/go-ethereum/accounts/abi/bind"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/event"
	"regexp"
	"strings"
)

type ContractInstance struct {
	Address common.Address
	Backend bind.ContractBackend
}

// deployContract deploys a hex-encoded contract with the given constructor
// input.  It returns the deployment transaction, address on success.
func deployContract(backend bind.ContractBackend, auth *bind.TransactOpts, constructor []byte, contract string) (deploymentTx *types.Transaction, deploymentAddr common.Address, err error) {
	contractBinBytes, err := hex.DecodeString(contract[2:])
	if err != nil {
		return nil, common.Address{}, fmt.Errorf("contract bytecode is not a hex string: %s", contractBinBytes[2:])
	}
	addr, tx, _, err := bind.DeployContractRaw(auth, contractBinBytes, backend, constructor)
	if err != nil {
		return nil, common.Address{}, fmt.Errorf("failed to deploy contract: %v", err)
	}
	return tx, addr, nil
}

// deployLibs iterates the set contracts (map of pattern to hex-encoded
// contract deployer code). Each contract is deployed, and the
// resulting addresses/deployment-txs are returned on success.
func deployLibs(backend bind.ContractBackend, auth *bind.TransactOpts, contracts map[string]string) (deploymentTxs map[common.Address]*types.Transaction, deployAddrs map[string]common.Address, err error) {
	deploymentTxs = make(map[common.Address]*types.Transaction)
	deployAddrs = make(map[string]common.Address)

	for pattern, contractBin := range contracts {
		contractBinBytes, err := hex.DecodeString(contractBin[2:])
		if err != nil {
			return deploymentTxs, deployAddrs, fmt.Errorf("contract bytecode is not a hex string: %s", contractBin[2:])
		}
		// TODO: can pass nil for constructor?
		addr, tx, _, err := bind.DeployContractRaw(auth, contractBinBytes, backend, []byte{})
		if err != nil {
			return deploymentTxs, deployAddrs, fmt.Errorf("failed to deploy contract: %v", err)
		}
		deploymentTxs[addr] = tx
		deployAddrs[pattern] = addr
	}

	return deploymentTxs, deployAddrs, nil
}

// linkContract takes an unlinked contract deployer hex-encoded code, a map of
// already-deployed library dependencies, replaces references to deployed library
// dependencies in the contract code, and returns the contract deployment bytecode on
// success.
func linkContract(contract string, linkedLibs map[string]common.Address) (deployableContract string, err error) {
	reMatchSpecificPattern, err := regexp.Compile("__\\$([a-f0-9]+)\\$__")
	if err != nil {
		return "", err
	}
	// link in any library the contract depends on
	for _, match := range reMatchSpecificPattern.FindAllStringSubmatch(contract, -1) {
		matchingPattern := match[1]
		addr := linkedLibs[matchingPattern]
		contract = strings.ReplaceAll(contract, "__$"+matchingPattern+"$__", addr.String()[2:])
	}
	return contract, nil
}

// linkLibs iterates the set of dependencies that have yet to be
// linked/deployed (pending), replacing references to library dependencies
// (i.e. mutating pending) if those dependencies are fully linked/deployed
// (in 'linked').
//
// contracts that have become fully linked in the current invocation are
// returned.
func linkLibs(pending *map[string]string, linked map[string]common.Address) (deployableDeps map[string]string) {
	reMatchSpecificPattern, err := regexp.Compile("__\\$([a-f0-9]+)\\$__")
	if err != nil {
		panic(err)
	}
	reMatchAnyPattern, err := regexp.Compile("__\\$.*\\$__")
	if err != nil {
		panic(err)
	}
	deployableDeps = make(map[string]string)

	for pattern, dep := range *pending {
		// link references to dependent libraries that have been deployed
		for _, match := range reMatchSpecificPattern.FindAllStringSubmatch(dep, -1) {
			matchingPattern := match[1]
			addr, ok := linked[matchingPattern]
			if !ok {
				continue
			}
			(*pending)[pattern] = strings.ReplaceAll(dep, "__$"+matchingPattern+"$__", addr.String()[2:])
		}
		// if the library code became fully linked, move it from pending->linked.
		if !reMatchAnyPattern.MatchString((*pending)[pattern]) {
			deployableDeps[pattern] = (*pending)[pattern]
			delete(*pending, pattern)
		}
	}
	return deployableDeps
}

// ContractDeployParams represents state needed to deploy a contract:
// the metdata and constructor input (which can be nil if no input is specified).
type ContractDeployParams struct {
	Meta *bind.MetaData
	// Input is the ABI-encoded constructor input for the contract deployment.
	Input []byte
}

// DeploymentParams represents parameters needed to deploy a
// set of contracts, their dependency libraries.  It takes an optional override
// list to specify libraries that have already been deployed on-chain.
type DeploymentParams struct {
	// Contracts is the set of contract deployment parameters for contracts
	// that are about to be deployed.
	Contracts []ContractDeployParams
	// Libraries is a map of pattern to metadata for library contracts that
	// are to be deployed.
	Libraries []*bind.MetaData
	// Overrides is an optional map of pattern to deployment address.
	// Contracts/libraries that refer to dependencies in the override
	// set are linked to the provided address (an already-deployed contract).
	Overrides map[string]common.Address
}

// DeploymentResult contains the relevant information from the deployment of
// multiple contracts:  their deployment txs and addresses.
type DeploymentResult struct {
	// map of contract library pattern -> deploy transaction
	Txs map[string]*types.Transaction
	// map of contract library pattern -> deployed address
	Addrs map[string]common.Address
}

// LinkAndDeploy deploys a specified set of contracts and their dependent
// libraries.  If an error occurs, only contracts which were successfully
// deployed are returned in the result.
func LinkAndDeploy(auth *bind.TransactOpts, backend bind.ContractBackend, deployParams DeploymentParams) (res *DeploymentResult, err error) {
	libMetas := deployParams.Libraries
	overrides := deployParams.Overrides

	res = &DeploymentResult{
		Txs:   make(map[string]*types.Transaction),
		Addrs: make(map[string]common.Address),
	}

	// re-express libraries as a map of pattern -> pre-link binary
	pending := make(map[string]string)
	for _, meta := range libMetas {
		pending[meta.Pattern] = meta.Bin
	}

	// initialize the set of already-deployed contracts with given override addresses
	deployed := make(map[string]common.Address)
	for pattern, deployAddr := range overrides {
		deployed[pattern] = deployAddr
		if _, ok := pending[pattern]; ok {
			delete(pending, pattern)
		}
	}

	// link and deploy dynamic libraries
	for {
		deployableDeps := linkLibs(&pending, deployed)
		if len(deployableDeps) == 0 {
			break
		}
		deployTxs, deployAddrs, err := deployLibs(backend, auth, deployableDeps)
		for pattern, addr := range deployAddrs {
			deployed[pattern] = addr
			res.Addrs[pattern] = addr
			res.Txs[pattern] = deployTxs[addr]
		}
		if err != nil {
			return res, err
		}
	}

	// link and deploy contracts
	for _, contractParams := range deployParams.Contracts {
		linkedContract, err := linkContract(contractParams.Meta.Bin, deployed)
		if err != nil {
			return res, err
		}
		contractTx, contractAddr, err := deployContract(backend, auth, contractParams.Input, linkedContract)
		if err != nil {
			return res, err
		}
		res.Txs[contractParams.Meta.Pattern] = contractTx
		res.Addrs[contractParams.Meta.Pattern] = contractAddr
	}

	return res, nil
}

// TODO: adding docs soon (jwasinger)
func FilterLogs[T any](instance *ContractInstance, opts *bind.FilterOpts, eventID common.Hash, unpack func(*types.Log) (*T, error), topics ...[]any) (*EventIterator[T], error) {
	backend := instance.Backend
	c := bind.NewBoundContract(instance.Address, abi.ABI{}, backend, backend, backend)
	logs, sub, err := c.FilterLogs(opts, eventID.String(), topics...)
	if err != nil {
		return nil, err
	}
	return &EventIterator[T]{unpack: unpack, logs: logs, sub: sub}, nil
}

// TODO: adding docs soon (jwasinger)
func WatchLogs[T any](instance *ContractInstance, opts *bind.WatchOpts, eventID common.Hash, unpack func(*types.Log) (*T, error), sink chan<- *T, topics ...[]any) (event.Subscription, error) {
	backend := instance.Backend
	c := bind.NewBoundContract(instance.Address, abi.ABI{}, backend, backend, backend)
	logs, sub, err := c.WatchLogs(opts, eventID.String(), topics...)
	if err != nil {
		return nil, err
	}
	return event.NewSubscription(func(quit <-chan struct{}) error {
		defer sub.Unsubscribe()
		for {
			select {
			case log := <-logs:
				// New log arrived, parse the event and forward to the user
				ev, err := unpack(&log)
				if err != nil {
					return err
				}

				select {
				case sink <- ev:
				case err := <-sub.Err():
					return err
				case <-quit:
					return nil
				}
			case err := <-sub.Err():
				return err
			case <-quit:
				return nil
			}
		}
	}), nil
}

// EventIterator is returned from FilterLogs and is used to iterate over the raw logs and unpacked data for events.
type EventIterator[T any] struct {
	Event *T // Event containing the contract specifics and raw log

	unpack func(*types.Log) (*T, error) // Unpack function for the event

	logs chan types.Log        // Log channel receiving the found contract events
	sub  ethereum.Subscription // Subscription for errors, completion and termination
	done bool                  // Whether the subscription completed delivering logs
	fail error                 // Occurred error to stop iteration
}

// Next advances the iterator to the subsequent event, returning whether there
// are any more events found. In case of a retrieval or parsing error, false is
// returned and Error() can be queried for the exact failure.
func (it *EventIterator[T]) Next() bool {
	// If the iterator failed, stop iterating
	if it.fail != nil {
		return false
	}
	// If the iterator completed, deliver directly whatever's available
	if it.done {
		select {
		case log := <-it.logs:
			res, err := it.unpack(&log)
			if err != nil {
				it.fail = err
				return false
			}
			it.Event = res
			return true

		default:
			return false
		}
	}
	// Iterator still in progress, wait for either a data or an error event
	select {
	case log := <-it.logs:
		res, err := it.unpack(&log)
		if err != nil {
			it.fail = err
			return false
		}
		it.Event = res
		return true

	case err := <-it.sub.Err():
		it.done = true
		it.fail = err
		return it.Next()
	}
}

// Error returns any retrieval or parsing error occurred during filtering.
func (it *EventIterator[T]) Error() error {
	return it.fail
}

// Close terminates the iteration process, releasing any pending underlying
// resources.
func (it *EventIterator[T]) Close() error {
	it.sub.Unsubscribe()
	return nil
}

// Transact creates and submits a transaction to the bound contract instance
// using the provided abi-encoded input (or nil).
func Transact(instance bind.ContractInstance, opts *bind.TransactOpts, input []byte) (*types.Transaction, error) {
	var (
		addr    = instance.Address()
		backend = instance.Backend()
	)
	c := bind.NewBoundContract(addr, abi.ABI{}, backend, backend, backend)
	return c.RawTransact(opts, input)
}

// Call performs an eth_call on the given bound contract instance, using the
// provided abi-encoded input (or nil).
func Call(instance bind.ContractInstance, opts *bind.CallOpts, input []byte) ([]byte, error) {
	backend := instance.Backend()
	c := bind.NewBoundContract(instance.Address(), abi.ABI{}, backend, backend, backend)
	return c.CallRaw(opts, input)
}