package metadata

import (
	"bytes"
	"errors"
	"fmt"
	"time"

	gogotypes "github.com/gogo/protobuf/types"

	"github.com/tendermint/tendermint/crypto"
	"github.com/tendermint/tendermint/crypto/merkle"
	tmbytes "github.com/tendermint/tendermint/libs/bytes"
	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
	"github.com/tendermint/tendermint/version"
)

const (
	// MaxHeaderBytes is a maximum header size.
	// NOTE: Because app hash can be of arbitrary size, the header is therefore not
	// capped in size and thus this number should be seen as a soft max
	MaxHeaderBytes int64 = 626

	// MaxOverheadForBlock - maximum overhead to encode a block (up to
	// MaxBlockSizeBytes in size) not including it's parts except Data.
	// This means it also excludes the overhead for individual transactions.
	//
	// Uvarint length of MaxBlockSizeBytes: 4 bytes
	// 2 fields (2 embedded):               2 bytes
	// Uvarint length of Data.Txs:          4 bytes
	// Data.Txs field:                      1 byte
	MaxOverheadForBlock int64 = 11

	// MaxChainIDLen is a maximum length of the chain ID.
	MaxChainIDLen = 50

	// MaxBlockSizeBytes is the maximum permitted size of the blocks.
	MaxBlockSizeBytes = 104857600 // 100MB
)

// Header defines the structure of a Tendermint block header.
// NOTE: changes to the Header should be duplicated in:
// - header.Hash()
// - abci.Header
// - https://github.com/tendermint/spec/blob/master/spec/blockchain/blockchain.md
type Header struct {
	// basic block info
	Version version.Consensus `json:"version"`
	ChainID string            `json:"chain_id"`
	Height  int64             `json:"height"`
	Time    time.Time         `json:"time"`

	// prev block info
	LastBlockID BlockID `json:"last_block_id"`

	// hashes of block data
	LastCommitHash tmbytes.HexBytes `json:"last_commit_hash"` // commit from validators from the last block
	DataHash       tmbytes.HexBytes `json:"data_hash"`        // transactions

	// hashes from the app output from the prev block
	ValidatorsHash     tmbytes.HexBytes `json:"validators_hash"`      // validators for the current block
	NextValidatorsHash tmbytes.HexBytes `json:"next_validators_hash"` // validators for the next block
	ConsensusHash      tmbytes.HexBytes `json:"consensus_hash"`       // consensus params for current block
	AppHash            tmbytes.HexBytes `json:"app_hash"`             // state after txs from the previous block
	// root hash of all results from the txs from the previous block
	// see `deterministicResponseDeliverTx` to understand which parts of a tx is hashed into here
	LastResultsHash tmbytes.HexBytes `json:"last_results_hash"`

	// consensus info
	EvidenceHash    tmbytes.HexBytes `json:"evidence_hash"`    // evidence included in the block
	ProposerAddress crypto.Address   `json:"proposer_address"` // original proposer of the block
}

// Populate the Header with state-derived data.
// Call this after MakeBlock to complete the Header.
func (h *Header) Populate(
	version version.Consensus, chainID string,
	timestamp time.Time, lastBlockID BlockID,
	valHash, nextValHash []byte,
	consensusHash, appHash, lastResultsHash []byte,
	proposerAddress crypto.Address,
) {
	h.Version = version
	h.ChainID = chainID
	h.Time = timestamp
	h.LastBlockID = lastBlockID
	h.ValidatorsHash = valHash
	h.NextValidatorsHash = nextValHash
	h.ConsensusHash = consensusHash
	h.AppHash = appHash
	h.LastResultsHash = lastResultsHash
	h.ProposerAddress = proposerAddress
}

// ValidateBasic performs stateless validation on a Header returning an error
// if any validation fails.
//
// NOTE: Timestamp validation is subtle and handled elsewhere.
func (h Header) ValidateBasic() error {
	if h.Version.Block != version.BlockProtocol {
		return fmt.Errorf("block protocol is incorrect: got: %d, want: %d ", h.Version.Block, version.BlockProtocol)
	}
	if len(h.ChainID) > MaxChainIDLen {
		return fmt.Errorf("chainID is too long; got: %d, max: %d", len(h.ChainID), MaxChainIDLen)
	}

	if h.Height < 0 {
		return errors.New("negative Height")
	} else if h.Height == 0 {
		return errors.New("zero Height")
	}

	if err := h.LastBlockID.ValidateBasic(); err != nil {
		return fmt.Errorf("wrong LastBlockID: %w", err)
	}

	if err := ValidateHash(h.LastCommitHash); err != nil {
		return fmt.Errorf("wrong LastCommitHash: %v", err)
	}

	if err := ValidateHash(h.DataHash); err != nil {
		return fmt.Errorf("wrong DataHash: %v", err)
	}

	if err := ValidateHash(h.EvidenceHash); err != nil {
		return fmt.Errorf("wrong EvidenceHash: %v", err)
	}

	if len(h.ProposerAddress) != crypto.AddressSize {
		return fmt.Errorf(
			"invalid ProposerAddress length; got: %d, expected: %d",
			len(h.ProposerAddress), crypto.AddressSize,
		)
	}

	// Basic validation of hashes related to application data.
	// Will validate fully against state in state#ValidateBlock.
	if err := ValidateHash(h.ValidatorsHash); err != nil {
		return fmt.Errorf("wrong ValidatorsHash: %v", err)
	}
	if err := ValidateHash(h.NextValidatorsHash); err != nil {
		return fmt.Errorf("wrong NextValidatorsHash: %v", err)
	}
	if err := ValidateHash(h.ConsensusHash); err != nil {
		return fmt.Errorf("wrong ConsensusHash: %v", err)
	}
	// NOTE: AppHash is arbitrary length
	if err := ValidateHash(h.LastResultsHash); err != nil {
		return fmt.Errorf("wrong LastResultsHash: %v", err)
	}

	return nil
}

// Hash returns the hash of the header.
// It computes a Merkle tree from the header fields
// ordered as they appear in the Header.
// Returns nil if ValidatorHash is missing,
// since a Header is not valid unless there is
// a ValidatorsHash (corresponding to the validator set).
func (h *Header) Hash() tmbytes.HexBytes {
	if h == nil || len(h.ValidatorsHash) == 0 {
		return nil
	}
	hpb := h.Version.ToProto()
	hbz, err := hpb.Marshal()
	if err != nil {
		return nil
	}

	pbt, err := gogotypes.StdTimeMarshal(h.Time)
	if err != nil {
		return nil
	}

	pbbi := h.LastBlockID.ToProto()
	bzbi, err := pbbi.Marshal()
	if err != nil {
		return nil
	}
	return merkle.HashFromByteSlices([][]byte{
		hbz,
		CdcEncode(h.ChainID),
		CdcEncode(h.Height),
		pbt,
		bzbi,
		CdcEncode(h.LastCommitHash),
		CdcEncode(h.DataHash),
		CdcEncode(h.ValidatorsHash),
		CdcEncode(h.NextValidatorsHash),
		CdcEncode(h.ConsensusHash),
		CdcEncode(h.AppHash),
		CdcEncode(h.LastResultsHash),
		CdcEncode(h.EvidenceHash),
		CdcEncode(h.ProposerAddress),
	})
}

// StringIndented returns an indented string representation of the header.
func (h *Header) StringIndented(indent string) string {
	if h == nil {
		return "nil-Header"
	}
	return fmt.Sprintf(`Header{
%s  Version:        %v
%s  ChainID:        %v
%s  Height:         %v
%s  Time:           %v
%s  LastBlockID:    %v
%s  LastCommit:     %v
%s  Data:           %v
%s  Validators:     %v
%s  NextValidators: %v
%s  App:            %v
%s  Consensus:      %v
%s  Results:        %v
%s  Evidence:       %v
%s  Proposer:       %v
%s}#%v`,
		indent, h.Version,
		indent, h.ChainID,
		indent, h.Height,
		indent, h.Time,
		indent, h.LastBlockID,
		indent, h.LastCommitHash,
		indent, h.DataHash,
		indent, h.ValidatorsHash,
		indent, h.NextValidatorsHash,
		indent, h.AppHash,
		indent, h.ConsensusHash,
		indent, h.LastResultsHash,
		indent, h.EvidenceHash,
		indent, h.ProposerAddress,
		indent, h.Hash())
}

// ToProto converts Header to protobuf
func (h *Header) ToProto() *tmproto.Header {
	if h == nil {
		return nil
	}

	return &tmproto.Header{
		Version:            h.Version.ToProto(),
		ChainID:            h.ChainID,
		Height:             h.Height,
		Time:               h.Time,
		LastBlockId:        h.LastBlockID.ToProto(),
		ValidatorsHash:     h.ValidatorsHash,
		NextValidatorsHash: h.NextValidatorsHash,
		ConsensusHash:      h.ConsensusHash,
		AppHash:            h.AppHash,
		DataHash:           h.DataHash,
		EvidenceHash:       h.EvidenceHash,
		LastResultsHash:    h.LastResultsHash,
		LastCommitHash:     h.LastCommitHash,
		ProposerAddress:    h.ProposerAddress,
	}
}

// FromProto sets a protobuf Header to the given pointer.
// It returns an error if the header is invalid.
func HeaderFromProto(ph *tmproto.Header) (Header, error) {
	if ph == nil {
		return Header{}, errors.New("nil Header")
	}

	h := new(Header)

	bi, err := BlockIDFromProto(&ph.LastBlockId)
	if err != nil {
		return Header{}, err
	}

	h.Version = version.Consensus{Block: ph.Version.Block, App: ph.Version.App}
	h.ChainID = ph.ChainID
	h.Height = ph.Height
	h.Time = ph.Time
	h.Height = ph.Height
	h.LastBlockID = *bi
	h.ValidatorsHash = ph.ValidatorsHash
	h.NextValidatorsHash = ph.NextValidatorsHash
	h.ConsensusHash = ph.ConsensusHash
	h.AppHash = ph.AppHash
	h.DataHash = ph.DataHash
	h.EvidenceHash = ph.EvidenceHash
	h.LastResultsHash = ph.LastResultsHash
	h.LastCommitHash = ph.LastCommitHash
	h.ProposerAddress = ph.ProposerAddress

	return *h, h.ValidateBasic()
}

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

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

// SignedHeader is a header along with the commits that prove it.
type SignedHeader struct {
	*Header `json:"header"`

	Commit *Commit `json:"commit"`
}

// ValidateBasic does basic consistency checks and makes sure the header
// and commit are consistent.
//
// NOTE: This does not actually check the cryptographic signatures.  Make sure
// to use a Verifier to validate the signatures actually provide a
// significantly strong proof for this header's validity.
func (sh SignedHeader) ValidateBasic(chainID string) error {
	if sh.Header == nil {
		return errors.New("missing header")
	}
	if sh.Commit == nil {
		return errors.New("missing commit")
	}

	if err := sh.Header.ValidateBasic(); err != nil {
		return fmt.Errorf("invalid header: %w", err)
	}
	if err := sh.Commit.ValidateBasic(); err != nil {
		return fmt.Errorf("invalid commit: %w", err)
	}

	if sh.ChainID != chainID {
		return fmt.Errorf("header belongs to another chain %q, not %q", sh.ChainID, chainID)
	}

	// Make sure the header is consistent with the commit.
	if sh.Commit.Height != sh.Height {
		return fmt.Errorf("header and commit height mismatch: %d vs %d", sh.Height, sh.Commit.Height)
	}
	if hhash, chash := sh.Header.Hash(), sh.Commit.BlockID.Hash; !bytes.Equal(hhash, chash) {
		return fmt.Errorf("commit signs block %X, header is block %X", chash, hhash)
	}

	return nil
}

// String returns a string representation of SignedHeader.
func (sh SignedHeader) String() string {
	return sh.StringIndented("")
}

// StringIndented returns an indented string representation of SignedHeader.
//
// Header
// Commit
func (sh SignedHeader) StringIndented(indent string) string {
	return fmt.Sprintf(`SignedHeader{
%s  %v
%s  %v
%s}`,
		indent, sh.Header.StringIndented(indent+"  "),
		indent, sh.Commit.StringIndented(indent+"  "),
		indent)
}

// ToProto converts SignedHeader to protobuf
func (sh *SignedHeader) ToProto() *tmproto.SignedHeader {
	if sh == nil {
		return nil
	}

	psh := new(tmproto.SignedHeader)
	if sh.Header != nil {
		psh.Header = sh.Header.ToProto()
	}
	if sh.Commit != nil {
		psh.Commit = sh.Commit.ToProto()
	}

	return psh
}

// FromProto sets a protobuf SignedHeader to the given pointer.
// It returns an error if the header or the commit is invalid.
func SignedHeaderFromProto(shp *tmproto.SignedHeader) (*SignedHeader, error) {
	if shp == nil {
		return nil, errors.New("nil SignedHeader")
	}

	sh := new(SignedHeader)

	if shp.Header != nil {
		h, err := HeaderFromProto(shp.Header)
		if err != nil {
			return nil, err
		}
		sh.Header = &h
	}

	if shp.Commit != nil {
		c, err := CommitFromProto(shp.Commit)
		if err != nil {
			return nil, err
		}
		sh.Commit = c
	}

	return sh, nil
}