## Nim-Libp2p
## Copyright (c) 2018 Status Research & Development GmbH
## Licensed under either of
##  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
##  * MIT license ([LICENSE-MIT](LICENSE-MIT))
## at your option.
## This file may not be copied, modified, or distributed except according to
## those terms.
import secp256k1 as s, stew/byteutils, nimcrypto/hash, nimcrypto/sha2
export sha2

const
  SkRawPrivateKeySize* = 256 div 8
    ## Size of private key in octets (bytes)
  SkRawSignatureSize* = SkRawPrivateKeySize * 2 + 1
    ## Size of signature in octets (bytes)
  SkRawPublicKeySize* = SkRawPrivateKeySize + 1
    ## Size of public key in octets (bytes)

type
  SkPublicKey* = distinct s.SkPublicKey
  SkPrivateKey* = distinct s.SkSecretKey
  SkKeyPair* = distinct s.SkKeyPair
  SkSignature* = distinct s.SkSignature

  Secp256k1Error* = object of CatchableError
    ## Exceptions generated by `libsecp256k1`

template toException(v: cstring): (ref Secp256k1Error) =
  (ref Secp256k1Error)(msg: $v)

template pubkey*(v: SkKeyPair): SkPublicKey = SkPublicKey(s.SkKeyPair(v).pubkey)
template seckey*(v: SkKeyPair): SkPrivateKey = SkPrivateKey(s.SkKeyPair(v).seckey)

proc init*(key: var SkPrivateKey, data: openarray[byte]): bool {.raises: [Defect].} =
  ## Initialize Secp256k1 `private key` ``key`` from raw binary
  ## representation ``data``.
  ##
  ## Procedure returns ``true`` on success.
  if (let v = SkSecretKey.fromRaw(data); v.isOk):
    key = SkPrivateKey(v[])
    return true

proc init*(key: var SkPrivateKey, data: string): bool {.raises: [Defect].} =
  ## Initialize Secp256k1 `private key` ``key`` from hexadecimal string
  ## representation ``data``.
  ##
  ## Procedure returns ``true`` on success.
  try:
    key = SkPrivateKey(SkSecretKey.fromHex(data).tryGet())
    return true
  except Secp256k1Error:
    discard

proc init*(key: var SkPublicKey, data: openarray[byte]): bool {.raises: [Defect].} =
  ## Initialize Secp256k1 `public key` ``key`` from raw binary
  ## representation ``data``.
  ##
  ## Procedure returns ``true`` on success.
  try:
    key = SkPublicKey(s.SkPublicKey.fromRaw(data).tryGet())
    return true
  except Secp256k1Error:
    discard

proc init*(key: var SkPublicKey, data: string): bool {.raises: [Defect].} =
  ## Initialize Secp256k1 `public key` ``key`` from hexadecimal string
  ## representation ``data``.
  ##
  ## Procedure returns ``true`` on success.
  try:
    key = SkPublicKey(s.SkPublicKey.fromHex(data).tryGet())
    return true
  except Secp256k1Error:
    discard

proc init*(sig: var SkSignature, data: openarray[byte]): bool {.raises: [Defect].} =
  ## Initialize Secp256k1 `signature` ``sig`` from raw binary
  ## representation ``data``.
  ##
  ## Procedure returns ``true`` on success.
  try:
    sig = SkSignature(s.SkSignature.fromDer(data).tryGet())
    return true
  except Secp256k1Error:
    discard

proc init*(sig: var SkSignature, data: string): bool {.raises: [Defect].} =
  ## Initialize Secp256k1 `signature` ``sig`` from hexadecimal string
  ## representation ``data``.
  ##
  ## Procedure returns ``true`` on success.
  # TODO DER vs raw here is fishy
  var buffer: seq[byte]
  try:
    buffer = hexToSeqByte(data)
  except ValueError:
    return false
  result = init(sig, buffer)

proc init*(t: typedesc[SkPrivateKey],
           data: openarray[byte]): SkPrivateKey {.raises: [Defect, Secp256k1Error].} =
  ## Initialize Secp256k1 `private key` from raw binary
  ## representation ``data``.
  ##
  ## Procedure returns `private key` on success.
  SkPrivateKey(s.SkSecretKey.fromRaw(data).tryGet())

proc init*(t: typedesc[SkPrivateKey],
           data: string): SkPrivateKey {.raises: [Defect, Secp256k1Error].} =
  ## Initialize Secp256k1 `private key` from hexadecimal string
  ## representation ``data``.
  ##
  ## Procedure returns `private key` on success.
  s.SkSecretKey.fromHex(data).tryGet()

proc init*(t: typedesc[SkPublicKey],
           data: openarray[byte]): SkPublicKey {.raises: [Defect, Secp256k1Error].} =
  ## Initialize Secp256k1 `public key` from raw binary
  ## representation ``data``.
  ##
  ## Procedure returns `public key` on success.
  if not init(result, data):
    raise newException(Secp256k1Error, "Incorrect binary form")

proc init*(t: typedesc[SkPublicKey],
           data: string): SkPublicKey {.raises: [Defect, Secp256k1Error].} =
  ## Initialize Secp256k1 `public key` from hexadecimal string
  ## representation ``data``.
  ##
  ## Procedure returns `public key` on success.
  if not init(result, data):
    raise newException(Secp256k1Error, "Incorrect binary form")

proc init*(t: typedesc[SkSignature],
           data: openarray[byte]): SkSignature {.raises: [Defect, Secp256k1Error].} =
  ## Initialize Secp256k1 `signature` from raw binary
  ## representation ``data``.
  ##
  ## Procedure returns `signature` on success.
  if not init(result, data):
    raise newException(Secp256k1Error, "Incorrect binary form")

proc init*(t: typedesc[SkSignature],
           data: string): SkSignature {.raises: [Defect, Secp256k1Error].} =
  ## Initialize Secp256k1 `signature` from hexadecimal string
  ## representation ``data``.
  ##
  ## Procedure returns `signature` on success.
  if not init(result, data):
    raise newException(Secp256k1Error, "Incorrect binary form")

proc getKey*(key: SkPrivateKey): SkPublicKey {.raises: [Defect, Secp256k1Error].} =
  ## Calculate and return Secp256k1 `public key` from `private key` ``key``.
  SkPublicKey(s.SkSecretKey(key).toPublicKey().tryGet())

proc random*(t: typedesc[SkPrivateKey]): SkPrivateKey =
  ## Generates new random private key.
  SkPrivateKey(s.SkSecretKey.random().tryGet())

proc random*(t: typedesc[SkKeyPair]): SkKeyPair {.inline.} =
  ## Generates new random key pair.
  SkKeyPair(s.SkKeyPair.random().tryGet())

proc toBytes*(key: SkPrivateKey, data: var openarray[byte]): int =
  ## Serialize Secp256k1 `private key` ``key`` to raw binary form and store it
  ## to ``data``.
  ##
  ## Procedure returns number of bytes (octets) needed to store
  ## Secp256k1 private key.
  result = SkRawPrivateKeySize
  if len(data) >= SkRawPrivateKeySize:
    data[0..<SkRawPrivateKeySize] = s.SkSecretKey(key).toRaw()

proc toBytes*(key: SkPublicKey, data: var openarray[byte]): int =
  ## Serialize Secp256k1 `public key` ``key`` to raw binary form and store it
  ## to ``data``.
  ##
  ## Procedure returns number of bytes (octets) needed to store
  ## Secp256k1 public key.
  result = SkRawPublicKeySize
  if len(data) >= SkRawPublicKeySize:
    data[0..<SkRawPublicKeySize] = s.SkPublicKey(key).toRawCompressed()

proc toBytes*(sig: SkSignature, data: var openarray[byte]): int =
  ## Serialize Secp256k1 `signature` ``sig`` to raw binary form and store it
  ## to ``data``.
  ##
  ## Procedure returns number of bytes (octets) needed to store
  ## Secp256k1 signature.
  s.SkSignature(sig).toDer(data)

proc getBytes*(key: SkPrivateKey): seq[byte] {.inline.} =
  ## Serialize Secp256k1 `private key` and return it.
  result = @(s.SkSecretKey(key).toRaw())

proc getBytes*(key: SkPublicKey): seq[byte] {.inline.} =
  ## Serialize Secp256k1 `public key` and return it.
  result = @(s.SkPublicKey(key).toRawCompressed())

proc getBytes*(sig: SkSignature): seq[byte] {.inline.} =
  ## Serialize Secp256k1 `signature` and return it.
  result = newSeq[byte](72)
  let length = toBytes(sig, result)
  result.setLen(length)

proc `==`*(ska, skb: SkPrivateKey): bool =
  ## Compare Secp256k1 `private key` objects for equality.
  result = (s.SkSecretKey(ska).toRaw == s.SkSecretKey(skb).toRaw)

proc `==`*(pka, pkb: SkPublicKey): bool =
  ## Compare Secp256k1 `public key` objects for equality.
  result = (s.SkPublicKey(pka).toRaw == s.SkPublicKey(pkb).toRaw)

proc `==`*(sia, sib: SkSignature): bool =
  ## Compare Secp256k1 `signature` objects for equality.
  result = (s.SkSignature(sia).toRaw == s.SkSignature(sib).toRaw)

proc `$`*(key: SkPrivateKey): string = s.SkSecretKey(key).toHex()
  ## Return string representation of Secp256k1 `private key`.

proc `$`*(key: SkPublicKey): string =
  ## Return string representation of Secp256k1 `private key`.s
  result = toHex(s.SkPublicKey(key).toRawCompressed())

proc `$`*(sig: SkSignature): string =
  ## Return string representation of Secp256k1 `signature`.s
  result = toHex(s.SkSignature(sig).toDer())

proc sign*[T: byte|char](key: SkPrivateKey, msg: openarray[T]): SkSignature =
  ## Sign message `msg` using private key `key` and return signature object.
  let h = sha256.digest(msg)
  SkSignature(sign(s.SkSecretKey(key), h).tryGet())

proc verify*[T: byte|char](sig: SkSignature, msg: openarray[T],
                           key: SkPublicKey): bool =
  let h = sha256.digest(msg)
  verify(s.SkSignature(sig), h, s.SkPublicKey(key))

proc clear*(key: var SkPrivateKey) {.borrow.}
  ## Wipe and clear memory of Secp256k1 `private key`.

proc clear*(key: var SkPublicKey) {.borrow.}
  ## Wipe and clear memory of Secp256k1 `public key`.

proc clear*(sig: var SkSignature) {.borrow.}
  ## Wipe and clear memory of Secp256k1 `signature`.
  # Internal memory representation size of signature object is 64 bytes.

proc clear*(pair: var SkKeyPair) {.borrow.}

proc verify*(seckey: SkPrivateKey): bool {.borrow.}