// 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 mru

import (
	"encoding/binary"
	"hash"

	"github.com/ethereum/go-ethereum/swarm/storage"
)

// LookupParams is used to specify constraints when performing an update lookup
// Limit defines whether or not the lookup should be limited
// If Limit is set to true then Max defines the amount of hops that can be performed
type LookupParams struct {
	UpdateLookup
	Limit uint32
}

// RootAddr returns the metadata chunk address
func (r *LookupParams) RootAddr() storage.Address {
	return r.rootAddr
}

func NewLookupParams(rootAddr storage.Address, period, version uint32, limit uint32) *LookupParams {
	return &LookupParams{
		UpdateLookup: UpdateLookup{
			period:   period,
			version:  version,
			rootAddr: rootAddr,
		},
		Limit: limit,
	}
}

// LookupLatest generates lookup parameters that look for the latest version of a resource
func LookupLatest(rootAddr storage.Address) *LookupParams {
	return NewLookupParams(rootAddr, 0, 0, 0)
}

// LookupLatestVersionInPeriod generates lookup parameters that look for the latest version of a resource in a given period
func LookupLatestVersionInPeriod(rootAddr storage.Address, period uint32) *LookupParams {
	return NewLookupParams(rootAddr, period, 0, 0)
}

// LookupVersion generates lookup parameters that look for a specific version of a resource
func LookupVersion(rootAddr storage.Address, period, version uint32) *LookupParams {
	return NewLookupParams(rootAddr, period, version, 0)
}

// UpdateLookup represents the components of a resource update search key
type UpdateLookup struct {
	period   uint32
	version  uint32
	rootAddr storage.Address
}

// 4 bytes period
// 4 bytes version
// storage.Keylength for rootAddr
const updateLookupLength = 4 + 4 + storage.KeyLength

// UpdateAddr calculates the resource update chunk address corresponding to this lookup key
func (u *UpdateLookup) UpdateAddr() (updateAddr storage.Address) {
	serializedData := make([]byte, updateLookupLength)
	u.binaryPut(serializedData)
	hasher := hashPool.Get().(hash.Hash)
	defer hashPool.Put(hasher)
	hasher.Reset()
	hasher.Write(serializedData)
	return hasher.Sum(nil)
}

// binaryPut serializes this UpdateLookup instance into the provided slice
func (u *UpdateLookup) binaryPut(serializedData []byte) error {
	if len(serializedData) != updateLookupLength {
		return NewErrorf(ErrInvalidValue, "Incorrect slice size to serialize UpdateLookup. Expected %d, got %d", updateLookupLength, len(serializedData))
	}
	if len(u.rootAddr) != storage.KeyLength {
		return NewError(ErrInvalidValue, "UpdateLookup.binaryPut called without rootAddr set")
	}
	binary.LittleEndian.PutUint32(serializedData[:4], u.period)
	binary.LittleEndian.PutUint32(serializedData[4:8], u.version)
	copy(serializedData[8:], u.rootAddr[:])
	return nil
}

// binaryLength returns the expected size of this structure when serialized
func (u *UpdateLookup) binaryLength() int {
	return updateLookupLength
}

// binaryGet restores the current instance from the information contained in the passed slice
func (u *UpdateLookup) binaryGet(serializedData []byte) error {
	if len(serializedData) != updateLookupLength {
		return NewErrorf(ErrInvalidValue, "Incorrect slice size to read UpdateLookup. Expected %d, got %d", updateLookupLength, len(serializedData))
	}
	u.period = binary.LittleEndian.Uint32(serializedData[:4])
	u.version = binary.LittleEndian.Uint32(serializedData[4:8])
	u.rootAddr = storage.Address(make([]byte, storage.KeyLength))
	copy(u.rootAddr[:], serializedData[8:])
	return nil
}