package common

import (
	"bytes"
	"database/sql/driver"
	"encoding/hex"
	"fmt"
	"math/big"
	"reflect"

	"github.com/ledgerwatch/erigon-lib/common/hexutility"
	"github.com/ledgerwatch/erigon-lib/common/length"
	"github.com/ledgerwatch/erigon-lib/crypto/cryptopool"
)

var (
	addressT = reflect.TypeOf(Address{})
)

// Address represents the 20 byte address of an Ethereum account.
type Address [length.Addr]byte

// BytesToAddress returns Address with value b.
// If b is larger than len(h), b will be cropped from the left.
func BytesToAddress(b []byte) Address {
	var a Address
	a.SetBytes(b)
	return a
}

// BytesToAddressNoCopy - see https://tip.golang.org/ref/spec#Conversions_from_slice_to_array_pointer
func BytesToAddressNoCopy(b []byte) Address { return *(*Address)(b) }

// BigToAddress returns Address with byte values of b.
// If b is larger than len(h), b will be cropped from the left.
func BigToAddress(b *big.Int) Address { return BytesToAddress(b.Bytes()) }

// HexToAddress returns Address with byte values of s.
// If s is larger than len(h), s will be cropped from the left.
func HexToAddress(s string) Address { return BytesToAddress(hexutility.FromHex(s)) }

// IsHexAddress verifies whether a string can represent a valid hex-encoded
// Ethereum address or not.
func IsHexAddress(s string) bool {
	if hexutility.Has0xPrefix(s) {
		s = s[2:]
	}
	return len(s) == 2*length.Addr && hexutility.IsHex(s)
}

// Bytes gets the string representation of the underlying address.
func (a Address) Bytes() []byte { return a[:] }

// Hash converts an address to a hash by left-padding it with zeros.
func (a Address) Hash() Hash { return BytesToHash(a[:]) }

// Hex returns an EIP55-compliant hex string representation of the address.
func (a Address) Hex() string {
	return string(a.checksumHex())
}

// String implements fmt.Stringer.
func (a Address) String() string {
	return a.Hex()
}

func (a *Address) checksumHex() []byte {
	buf := a.hex()

	// compute checksum
	sha := cryptopool.GetLegacyKeccak256()
	//nolint:errcheck
	sha.Write(buf[2:])
	hash := sha.Sum(nil)
	cryptopool.ReturnLegacyKeccak256(sha)

	for i := 2; i < len(buf); i++ {
		hashByte := hash[(i-2)/2]
		if i%2 == 0 {
			hashByte = hashByte >> 4
		} else {
			hashByte &= 0xf
		}
		if buf[i] > '9' && hashByte > 7 {
			buf[i] -= 32
		}
	}
	return buf
}

func (a Address) hex() []byte {
	var buf [len(a)*2 + 2]byte
	copy(buf[:2], "0x")
	hex.Encode(buf[2:], a[:])
	return buf[:]
}

// Format implements fmt.Formatter.
// Address supports the %v, %s, %v, %x, %X and %d format verbs.
func (a Address) Format(s fmt.State, c rune) {
	switch c {
	case 'v', 's':
		s.Write(a.checksumHex())
	case 'q':
		q := []byte{'"'}
		s.Write(q)
		s.Write(a.checksumHex())
		s.Write(q)
	case 'x', 'X':
		// %x disables the checksum.
		hex := a.hex()
		if !s.Flag('#') {
			hex = hex[2:]
		}
		if c == 'X' {
			hex = bytes.ToUpper(hex)
		}
		s.Write(hex)
	case 'd':
		fmt.Fprint(s, ([len(a)]byte)(a))
	default:
		fmt.Fprintf(s, "%%!%c(address=%x)", c, a)
	}
}

// SetBytes sets the address to the value of b.
// If b is larger than len(a), b will be cropped from the left.
func (a *Address) SetBytes(b []byte) {
	if len(b) > len(a) {
		b = b[len(b)-length.Addr:]
	}
	copy(a[length.Addr-len(b):], b)
}

// MarshalText returns the hex representation of a.
func (a Address) MarshalText() ([]byte, error) {
	b := a[:]
	result := make([]byte, len(b)*2+2)
	copy(result, hexPrefix)
	hex.Encode(result[2:], b)
	return result, nil
}

// UnmarshalText parses a hash in hex syntax.
func (a *Address) UnmarshalText(input []byte) error {
	return hexutility.UnmarshalFixedText("Address", input, a[:])
}

// UnmarshalJSON parses a hash in hex syntax.
func (a *Address) UnmarshalJSON(input []byte) error {
	return hexutility.UnmarshalFixedJSON(addressT, input, a[:])
}

// Scan implements Scanner for database/sql.
func (a *Address) Scan(src interface{}) error {
	srcB, ok := src.([]byte)
	if !ok {
		return fmt.Errorf("can't scan %T into Address", src)
	}
	if len(srcB) != length.Addr {
		return fmt.Errorf("can't scan []byte of len %d into Address, want %d", len(srcB), length.Addr)
	}
	copy(a[:], srcB)
	return nil
}

// Value implements valuer for database/sql.
func (a Address) Value() (driver.Value, error) {
	return a[:], nil
}