package core

import (
	"encoding/base64"
	"fmt"
	"time"

	cfg "github.com/cometbft/cometbft/config"
	"github.com/cometbft/cometbft/crypto"
	cmtjson "github.com/cometbft/cometbft/libs/json"
	"github.com/cometbft/cometbft/libs/log"
	mempl "github.com/cometbft/cometbft/mempool"
	"github.com/cometbft/cometbft/p2p"
	"github.com/cometbft/cometbft/proxy"
	sm "github.com/cometbft/cometbft/state"
	"github.com/cometbft/cometbft/state/indexer"
	"github.com/cometbft/cometbft/state/txindex"
	"github.com/cometbft/cometbft/types"
)

const (
	// see README
	defaultPerPage = 30
	maxPerPage     = 100

	// SubscribeTimeout is the maximum time we wait to subscribe for an event.
	// must be less than the server's write timeout (see rpcserver.DefaultConfig)
	SubscribeTimeout = 5 * time.Second

	// genesisChunkSize is the maximum size, in bytes, of each
	// chunk in the genesis structure for the chunked API
	genesisChunkSize = 16 * 1024 * 1024 // 16
)

//----------------------------------------------
// These interfaces are used by RPC and must be thread safe

type Consensus interface {
	GetState() sm.State
	GetValidators() (int64, []*types.Validator)
	GetLastHeight() int64
	GetRoundStateJSON() ([]byte, error)
	GetRoundStateSimpleJSON() ([]byte, error)
}

type transport interface {
	Listeners() []string
	IsListening() bool
	NodeInfo() p2p.NodeInfo
}

type peers interface {
	AddPersistentPeers([]string) error
	AddUnconditionalPeerIDs([]string) error
	AddPrivatePeerIDs([]string) error
	DialPeersAsync([]string) error
	Peers() p2p.IPeerSet
}

type consensusReactor interface {
	WaitSync() bool
}

// ----------------------------------------------
// Environment contains objects and interfaces used by the RPC. It is expected
// to be setup once during startup.
type Environment struct {
	// external, thread safe interfaces
	ProxyAppQuery   proxy.AppConnQuery
	ProxyAppMempool proxy.AppConnMempool

	// interfaces defined in types and above
	StateStore       sm.Store
	BlockStore       sm.BlockStore
	EvidencePool     sm.EvidencePool
	ConsensusState   Consensus
	ConsensusReactor consensusReactor
	P2PPeers         peers
	P2PTransport     transport

	// objects
	PubKey       crypto.PubKey
	GenDoc       *types.GenesisDoc // cache the genesis structure
	TxIndexer    txindex.TxIndexer
	BlockIndexer indexer.BlockIndexer
	EventBus     *types.EventBus // thread safe
	Mempool      mempl.Mempool

	Logger log.Logger

	Config cfg.RPCConfig

	// cache of chunked genesis data.
	genChunks []string
}

//----------------------------------------------

func validatePage(pagePtr *int, perPage, totalCount int) (int, error) {
	if perPage < 1 {
		panic(fmt.Sprintf("zero or negative perPage: %d", perPage))
	}

	if pagePtr == nil { // no page parameter
		return 1, nil
	}

	pages := ((totalCount - 1) / perPage) + 1
	if pages == 0 {
		pages = 1 // one page (even if it's empty)
	}
	page := *pagePtr
	if page <= 0 || page > pages {
		return 1, fmt.Errorf("page should be within [1, %d] range, given %d", pages, page)
	}

	return page, nil
}

func (env *Environment) validatePerPage(perPagePtr *int) int {
	if perPagePtr == nil { // no per_page parameter
		return defaultPerPage
	}

	perPage := *perPagePtr
	if perPage < 1 {
		return defaultPerPage
	} else if perPage > maxPerPage {
		return maxPerPage
	}
	return perPage
}

func (env *Environment) validateUnconfirmedTxsPerPage(perPagePtr *int) int {
	if perPagePtr == nil { // no per_page parameter
		return defaultPerPage
	}

	perPage := *perPagePtr
	if perPage < -1 {
		return defaultPerPage
	}
	if perPage == 0 {
		return defaultPerPage
	}
	if perPage > maxPerPage {
		return maxPerPage
	}
	return perPage
}

// InitGenesisChunks configures the environment and should be called on service
// startup.
func (env *Environment) InitGenesisChunks() error {
	if env.genChunks != nil {
		return nil
	}

	if env.GenDoc == nil {
		return nil
	}

	data, err := cmtjson.Marshal(env.GenDoc)
	if err != nil {
		return err
	}

	for i := 0; i < len(data); i += genesisChunkSize {
		end := i + genesisChunkSize

		if end > len(data) {
			end = len(data)
		}

		env.genChunks = append(env.genChunks, base64.StdEncoding.EncodeToString(data[i:end]))
	}

	return nil
}

func validateSkipCount(page, perPage int) int {
	skipCount := (page - 1) * perPage
	if skipCount < 0 {
		return 0
	}

	return skipCount
}

// latestHeight can be either latest committed or uncommitted (+1) height.
func (env *Environment) getHeight(latestHeight int64, heightPtr *int64) (int64, error) {
	if heightPtr != nil {
		height := *heightPtr
		if height <= 0 {
			return 0, fmt.Errorf("height must be greater than 0, but got %d", height)
		}
		if height > latestHeight {
			return 0, fmt.Errorf("height %d must be less than or equal to the current blockchain height %d",
				height, latestHeight)
		}
		base := env.BlockStore.Base()
		if height < base {
			return 0, fmt.Errorf("height %d is not available, lowest height is %d",
				height, base)
		}
		return height, nil
	}
	return latestHeight, nil
}

func (env *Environment) latestUncommittedHeight() int64 {
	nodeIsSyncing := env.ConsensusReactor.WaitSync()
	if nodeIsSyncing {
		return env.BlockStore.Height()
	}
	return env.BlockStore.Height() + 1
}
