package metadata

import (
	"crypto/ed25519"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/tendermint/tendermint/crypto"
	"github.com/tendermint/tendermint/crypto/merkle"
	"github.com/tendermint/tendermint/libs/bits"
	tmbytes "github.com/tendermint/tendermint/libs/bytes"
	tmmath "github.com/tendermint/tendermint/libs/math"
	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
)

var (
	// MaxSignatureSize is a maximum allowed signature size for the Proposal
	// and Vote.
	// XXX: secp256k1 does not have Size nor MaxSize defined.
	MaxSignatureSize = tmmath.MaxInt(ed25519.SignatureSize, 64)
)

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

const (
	// Max size of commit without any commitSigs -> 82 for BlockID, 8 for Height, 4 for Round.
	MaxCommitOverheadBytes int64 = 94
	// Commit sig size is made up of 64 bytes for the signature, 20 bytes for the address,
	// 1 byte for the flag and 14 bytes for the timestamp
	MaxCommitSigBytes int64 = 109
)

// CommitSig is a part of the Vote included in a Commit.
type CommitSig struct {
	BlockIDFlag      BlockIDFlag    `json:"block_id_flag"`
	ValidatorAddress crypto.Address `json:"validator_address"`
	Timestamp        time.Time      `json:"timestamp"`
	Signature        []byte         `json:"signature"`
}

// NewCommitSigForBlock returns new CommitSig with BlockIDFlagCommit.
func NewCommitSigForBlock(signature []byte, valAddr crypto.Address, ts time.Time) CommitSig {
	return CommitSig{
		BlockIDFlag:      BlockIDFlagCommit,
		ValidatorAddress: valAddr,
		Timestamp:        ts,
		Signature:        signature,
	}
}

func MaxCommitBytes(valCount int) int64 {
	// From the repeated commit sig field
	var protoEncodingOverhead int64 = 2
	return MaxCommitOverheadBytes + ((MaxCommitSigBytes + protoEncodingOverhead) * int64(valCount))
}

// NewCommitSigAbsent returns new CommitSig with BlockIDFlagAbsent. Other
// fields are all empty.
func NewCommitSigAbsent() CommitSig {
	return CommitSig{
		BlockIDFlag: BlockIDFlagAbsent,
	}
}

// ForBlock returns true if CommitSig is for the block.
func (cs CommitSig) ForBlock() bool {
	return cs.BlockIDFlag == BlockIDFlagCommit
}

// Absent returns true if CommitSig is absent.
func (cs CommitSig) Absent() bool {
	return cs.BlockIDFlag == BlockIDFlagAbsent
}

// CommitSig returns a string representation of CommitSig.
//
// 1. first 6 bytes of signature
// 2. first 6 bytes of validator address
// 3. block ID flag
// 4. timestamp
func (cs CommitSig) String() string {
	return fmt.Sprintf("CommitSig{%X by %X on %v @ %s}",
		tmbytes.Fingerprint(cs.Signature),
		tmbytes.Fingerprint(cs.ValidatorAddress),
		cs.BlockIDFlag,
		CanonicalTime(cs.Timestamp))
}

// BlockID returns the Commit's BlockID if CommitSig indicates signing,
// otherwise - empty BlockID.
func (cs CommitSig) BlockID(commitBlockID BlockID) BlockID {
	var blockID BlockID
	switch cs.BlockIDFlag {
	case BlockIDFlagAbsent:
		blockID = BlockID{}
	case BlockIDFlagCommit:
		blockID = commitBlockID
	case BlockIDFlagNil:
		blockID = BlockID{}
	default:
		panic(fmt.Sprintf("Unknown BlockIDFlag: %v", cs.BlockIDFlag))
	}
	return blockID
}

// ValidateBasic performs basic validation.
func (cs CommitSig) ValidateBasic() error {
	switch cs.BlockIDFlag {
	case BlockIDFlagAbsent:
	case BlockIDFlagCommit:
	case BlockIDFlagNil:
	default:
		return fmt.Errorf("unknown BlockIDFlag: %v", cs.BlockIDFlag)
	}

	switch cs.BlockIDFlag {
	case BlockIDFlagAbsent:
		if len(cs.ValidatorAddress) != 0 {
			return errors.New("validator address is present")
		}
		if !cs.Timestamp.IsZero() {
			return errors.New("time is present")
		}
		if len(cs.Signature) != 0 {
			return errors.New("signature is present")
		}
	default:
		if len(cs.ValidatorAddress) != crypto.AddressSize {
			return fmt.Errorf("expected ValidatorAddress size to be %d bytes, got %d bytes",
				crypto.AddressSize,
				len(cs.ValidatorAddress),
			)
		}
		// NOTE: Timestamp validation is subtle and handled elsewhere.
		if len(cs.Signature) == 0 {
			return errors.New("signature is missing")
		}
		if len(cs.Signature) > MaxSignatureSize {
			return fmt.Errorf("signature is too big (max: %d)", MaxSignatureSize)
		}
	}

	return nil
}

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

	return &tmproto.CommitSig{
		BlockIdFlag:      tmproto.BlockIDFlag(cs.BlockIDFlag),
		ValidatorAddress: cs.ValidatorAddress,
		Timestamp:        cs.Timestamp,
		Signature:        cs.Signature,
	}
}

// FromProto sets a protobuf CommitSig to the given pointer.
// It returns an error if the CommitSig is invalid.
func (cs *CommitSig) FromProto(csp tmproto.CommitSig) error {

	cs.BlockIDFlag = BlockIDFlag(csp.BlockIdFlag)
	cs.ValidatorAddress = csp.ValidatorAddress
	cs.Timestamp = csp.Timestamp
	cs.Signature = csp.Signature

	return cs.ValidateBasic()
}

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

// Commit contains the evidence that a block was committed by a set of validators.
// NOTE: Commit is empty for height 1, but never nil.
type Commit struct {
	// NOTE: The signatures are in order of address to preserve the bonded
	// ValidatorSet order.
	// Any peer with a block can gossip signatures by index with a peer without
	// recalculating the active ValidatorSet.
	Height     int64       `json:"height"`
	Round      int32       `json:"round"`
	BlockID    BlockID     `json:"block_id"`
	Signatures []CommitSig `json:"signatures"`

	// Memoized in first call to corresponding method.
	// NOTE: can't memoize in constructor because constructor isn't used for
	// unmarshaling.
	hash     tmbytes.HexBytes
	bitArray *bits.BitArray
}

// NewCommit returns a new Commit.
func NewCommit(height int64, round int32, blockID BlockID, commitSigs []CommitSig) *Commit {
	return &Commit{
		Height:     height,
		Round:      round,
		BlockID:    blockID,
		Signatures: commitSigs,
	}
}

// Type returns the vote type of the commit, which is always VoteTypePrecommit
// Implements VoteSetReader.
func (commit *Commit) Type() byte {
	return byte(tmproto.PrecommitType)
}

// GetHeight returns height of the commit.
// Implements VoteSetReader.
func (commit *Commit) GetHeight() int64 {
	return commit.Height
}

// GetRound returns height of the commit.
// Implements VoteSetReader.
func (commit *Commit) GetRound() int32 {
	return commit.Round
}

// Size returns the number of signatures in the commit.
// Implements VoteSetReader.
func (commit *Commit) Size() int {
	if commit == nil {
		return 0
	}
	return len(commit.Signatures)
}

// ClearCache removes the saved hash. This is predominantly used for testing.
func (commit *Commit) ClearCache() {
	commit.hash = nil
	commit.bitArray = nil
}

// BitArray returns a BitArray of which validators voted for BlockID or nil in this commit.
// Implements VoteSetReader.
func (commit *Commit) BitArray() *bits.BitArray {
	if commit.bitArray == nil {
		commit.bitArray = bits.NewBitArray(len(commit.Signatures))
		for i, commitSig := range commit.Signatures {
			// TODO: need to check the BlockID otherwise we could be counting conflicts,
			// not just the one with +2/3 !
			commit.bitArray.SetIndex(i, !commitSig.Absent())
		}
	}
	return commit.bitArray
}

// IsCommit returns true if there is at least one signature.
// Implements VoteSetReader.
func (commit *Commit) IsCommit() bool {
	return len(commit.Signatures) != 0
}

// ValidateBasic performs basic validation that doesn't involve state data.
// Does not actually check the cryptographic signatures.
func (commit *Commit) ValidateBasic() error {
	if commit.Height < 0 {
		return errors.New("negative Height")
	}
	if commit.Round < 0 {
		return errors.New("negative Round")
	}

	if commit.Height >= 1 {
		if commit.BlockID.IsZero() {
			return errors.New("commit cannot be for nil block")
		}

		if len(commit.Signatures) == 0 {
			return errors.New("no signatures in commit")
		}
		for i, commitSig := range commit.Signatures {
			if err := commitSig.ValidateBasic(); err != nil {
				return fmt.Errorf("wrong CommitSig #%d: %v", i, err)
			}
		}
	}
	return nil
}

// Hash returns the hash of the commit
func (commit *Commit) Hash() tmbytes.HexBytes {
	if commit == nil {
		return nil
	}
	if commit.hash == nil {
		bs := make([][]byte, len(commit.Signatures))
		for i, commitSig := range commit.Signatures {
			pbcs := commitSig.ToProto()
			bz, err := pbcs.Marshal()
			if err != nil {
				panic(err)
			}

			bs[i] = bz
		}
		commit.hash = merkle.HashFromByteSlices(bs)
	}
	return commit.hash
}

// StringIndented returns a string representation of the commit.
func (commit *Commit) StringIndented(indent string) string {
	if commit == nil {
		return "nil-Commit"
	}
	commitSigStrings := make([]string, len(commit.Signatures))
	for i, commitSig := range commit.Signatures {
		commitSigStrings[i] = commitSig.String()
	}
	return fmt.Sprintf(`Commit{
%s  Height:     %d
%s  Round:      %d
%s  BlockID:    %v
%s  Signatures:
%s    %v
%s}#%v`,
		indent, commit.Height,
		indent, commit.Round,
		indent, commit.BlockID,
		indent,
		indent, strings.Join(commitSigStrings, "\n"+indent+"    "),
		indent, commit.hash)
}

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

	c := new(tmproto.Commit)
	sigs := make([]tmproto.CommitSig, len(commit.Signatures))
	for i := range commit.Signatures {
		sigs[i] = *commit.Signatures[i].ToProto()
	}
	c.Signatures = sigs

	c.Height = commit.Height
	c.Round = commit.Round
	c.BlockID = commit.BlockID.ToProto()

	return c
}

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

	var (
		commit = new(Commit)
	)

	bi, err := BlockIDFromProto(&cp.BlockID)
	if err != nil {
		return nil, err
	}

	sigs := make([]CommitSig, len(cp.Signatures))
	for i := range cp.Signatures {
		if err := sigs[i].FromProto(cp.Signatures[i]); err != nil {
			return nil, err
		}
	}
	commit.Signatures = sigs

	commit.Height = cp.Height
	commit.Round = cp.Round
	commit.BlockID = *bi

	return commit, commit.ValidateBasic()
}