#
# Nim Ethereum Keys (nim-eth-keys)
# Copyright (c) 2018 Status Research & Development GmbH
# Licensed under either of
# - Apache License, version 2.0, (LICENSE-APACHEv2)
# - MIT license (LICENSE-MIT)
#

import nimcrypto/hash, nimcrypto/keccak

type
  EthKeysStatus* = enum
    Success,  ## Operation was successful
    Error     ## Operation failed

  EthKeysException* = object of Exception
    ## Exception generated by this module

when not defined(native):
  include eth/keys/libsecp256k1

  proc ekErrorMsg*(): string {.inline.} =
    ## Return current error message.
    result = libsecp256k1ErrorMsg()

proc isZeroKey*(seckey: PrivateKey): bool =
  ## Check if private key `seckey` contains only 0 bytes.
  result = true
  for i in seckey.data:
    if i != byte(0):
      result = false

proc isZeroKey*(pubkey: PublicKey): bool =
  ## Check if public key `pubkey` contains only 0 bytes.
  result = true
  for i in pubkey.data:
    if i != byte(0):
      result = false

proc signMessage*(seckey: PrivateKey,
                  data: openarray[byte]): Signature {.inline.} =
  ## Sign message of arbitrary length `data` using private key `seckey`.
  let hash = keccak256.digest(data)
  if signRawMessage(hash.data, seckey, result) != EthKeysStatus.Success:
    raise newException(EthKeysException, ekErrorMsg())

proc signMessage*(seckey: PrivateKey, data: string): Signature {.inline.} =
  ## Sign message of arbitrary length `data` using private key `seckey`.
  signMessage(seckey, cast[seq[byte]](data))

proc signMessage*(seckey: PrivateKey,
                  hash: MDigest[256]): Signature {.inline.} =
  ## Sign 256bit `hash` using private key `seckey`.
  result = signMessage(seckey, hash.data)

proc verifyMessage*(data: openarray[byte], message: openarray[byte]): bool =
  ## Verify binary data blob `data` has properly signed message `message`.
  var pubkey: PublicKey
  if recoverSignatureKey(data, message, pubkey) == EthKeysStatus.Success:
    result = true
  else:
    result = false

proc verifyMessage*(data: openarray[byte],
                    hash: MDigest[256]): bool {.inline.} =
  ## Verify binary data blob `data` has properly signed hash `hash`.
  result = verifyMessage(data, hash.data)

proc recoverKeyFromMessage*(data: openarray[byte],
                            hash: MDigest[256]): PublicKey {.inline.} =
  ## Recover public key from signed binary blob `data` using 256bit hash `hash`.
  if recoverSignatureKey(data, hash.data, result) != EthKeysStatus.Success:
    raise newException(EthKeysException, ekErrorMsg())

proc recoverKeyFromMessage*(data: openarray[byte],
                            message: string): PublicKey {.inline.} =
  ## Recover public key from signed binary blob `data` using `message`.
  var hash = keccak256.digest(message)
  if recoverSignatureKey(data, hash.data, result) != EthKeysStatus.Success:
    raise newException(EthKeysException, ekErrorMsg())

proc recoverKeyFromSignature*(signature: Signature,
                              message: string): PublicKey {.inline.} =
  ## Recover public key from signature `signature` using `message`.
  var hash = keccak256.digest(message)
  if recoverSignatureKey(signature, hash.data, result) != EthKeysStatus.Success:
    raise newException(EthKeysException, ekErrorMsg())

proc recoverKeyFromSignature*(signature: Signature,
                              hash: MDigest[256]): PublicKey {.inline.} =
  ## Recover public key from signature `signature` using `message`.
  if recoverSignatureKey(signature, hash.data, result) != EthKeysStatus.Success:
    raise newException(EthKeysException, ekErrorMsg())

proc toAddress*(pubkey: PublicKey, with0x = true): string =
  ## Convert public key to hexadecimal string address.
  var hash = keccak256.digest(pubkey.getRaw())
  result = if with0x: "0x" else: ""
  result.add(toHex(toOpenArray(hash.data, 12, len(hash.data) - 1), true))

proc toChecksumAddress*(pubkey: PublicKey, with0x = true): string =
  ## Convert public key to checksumable mixed-case address (EIP-55).
  result = if with0x: "0x" else: ""
  var hash1 = keccak256.digest(pubkey.getRaw())
  var hhash1 = toHex(toOpenArray(hash1.data, 12, len(hash1.data) - 1), true)
  var hash2 = keccak256.digest(hhash1)
  var hhash2 = toHex(hash2.data, true)
  for i in 0..<len(hhash1):
    if hhash2[i] >= '0' and hhash2[i] <= '7':
      result.add(hhash1[i])
    else:
      if hhash1[i] >= '0' and hhash1[i] <= '9':
        result.add(hhash1[i])
      else:
        let ch = chr(ord(hhash1[i]) - ord('a') + ord('A'))
        result.add(ch)

proc validateChecksumAddress*(a: string): bool =
  ## Validate checksumable mixed-case address (EIP-55).
  var address = ""
  var check = "0x"
  if len(a) != 42:
    return false
  if a[0] != '0' and a[1] != 'x':
    return false
  for i in 2..41:
    let ch = a[i]
    if ch in {'0'..'9'} or ch in {'a'..'f'}:
      address &= ch
    elif ch in {'A'..'F'}:
      address &= chr(ord(ch) - ord('A') + ord('a'))
    else:
      return false
  var hash = keccak256.digest(address)
  var hexhash = toHex(hash.data, true)
  for i in 0..<len(address):
    if hexhash[i] >= '0' and hexhash[i] <= '7':
      check.add(address[i])
    else:
      if address[i] >= '0' and address[i] <= '9':
        check.add(address[i])
      else:
        let ch = chr(ord(address[i]) - ord('a') + ord('A'))
        check.add(ch)
  result = (check == a)

proc toCanonicalAddress*(pubkey: PublicKey): array[20, byte] =
  ## Convert public key to canonical address.
  var hash = keccak256.digest(pubkey.getRaw())
  copyMem(addr result[0], addr hash.data[12], 20)

proc `$`*(pubkey: PublicKey): string =
  ## Convert public key to hexadecimal string representation.
  result = toHex(pubkey.getRaw(), true)

proc `$`*(sig: Signature): string =
  ## Convert signature to hexadecimal string representation.
  result = toHex(sig.getRaw(), true)

proc `$`*(seckey: PrivateKey): string =
  ## Convert private key to hexadecimal string representation
  result = toHex(seckey.data, true)