urbit/lib/ethereum.hoon

::
/-  ethereum
=,  ^ethereum
=,  keccak:crypto
=,  mimes:html
::
|%
::
::  making calls to nodes
::
::  see also the json rpc api spec
::  https://ethereum.gitbooks.io/frontier-guide/content/rpc.html
::
++  json-request
  =,  eyre
  |=  [url=purl jon=json]
  ^-  hiss
  :^  url  %post
    (malt ~[content-type+['application/x-www-form-urlencoded']~])
  (some (as-octt (en-json:html jon)))
::
++  read-request
  |=  [adr=@ux fun=@t das=(list data)]
  %-  request-to-json
  :+  %eth-call
    [~ `@`adr ~ ~ ~ `tape`(encode-call fun das)]
  [%label %latest]
::
++  request-to-json
  =,  enjs:format
  |=  req=request
  ^-  json
  %-  pairs
  =;  cal=[m=@t p=(list json)]
    :~  jsonrpc+s+'2.0'
        id+s+'use wire to id response in hoon'
        method+s+m.cal
        params+a+p.cal
    ==
  ?+  -.req  ~|([%unsupported-request -.req] !!)
      %eth-block-number
    ['eth_blockNumber' ~]
  ::
      %eth-call
    :-  'eth_call'
    :~  (eth-call-to-json cal.req)
        (default-block-to-json deb.req)
    ==
  ==
::
++  eth-call-to-json
  |=  cal=call
  ^-  json
  :-  %o  %-  ~(gas by *(map @t json))
  =-  (murn - same)
  ^-  (list (unit (pair @t json)))
  :~  ?~  from.cal  ~
      `['from' s+(crip (render-hex-bytes 20 `@`u.from.cal))]
    ::
      `['to' s+(crip (render-hex-bytes 20 `@`to.cal))]
    ::
      ?~  gas.cal  ~
      `['gas' n+(crip ((d-co:co 0) u.gas.cal))]
    ::
      ?~  gas-price.cal  ~
      `['gasPrice' n+(crip ((d-co:co 0) u.gas-price.cal))]
    ::
      ?~  value.cal  ~
      `['value' n+(crip ((d-co:co 0) u.value.cal))]
    ::
      ?~  data.cal  ~
      `['data' s+(crip data.cal)]
  ==
::
++  default-block-to-json
  |=  dob=default-block
  ^-  json
  ?-  -.dob
    %quantity   n+(crip ((d-co:co 0) n.dob))
    %label      s+l.dob
  ==
::
::  encoding
::
::  ABI spec used for reference:
::  https://ethereum.gitbooks.io/frontier-guide/content/abi.html
::
++  encode-call
  |=  [fun=@t das=(list data)]
  ^-  tape
  ::TODO  should this check to see if the data matches the function signature?
  =-  (weld - (encode-args das))
  %+  scag  8
  (render-hex-bytes 32 (keccak-256 (as-octs fun)))
::
++  encode-args
  :>  encode list of arguments.
  ::
  |=  das=(list data)
  ^-  tape
  (encode-data [%array-n das])
::
++  encode-data
  :>  encode typed data into ABI bytestring.
  ::
  |=  dat=data
  ^-  tape
  ?+  -.dat
    ~|  [%unsupported-type -.dat]
    !!
  ::
      %array-n
    ::  enc(X) = head(X[0]) ... head(X[k-1]) tail(X[0]) ... tail(X[k-1])
    ::  where head and tail are defined for X[i] being of a static type as
    ::  head(X[i]) = enc(X[i]) and tail(X[i]) = "" (the empty string), or as
    ::  head(X[i]) = enc(len(head(X[0])..head(X[k-1]) tail(X[0])..tail(X[i-1])))
    ::  and tail(X[i]) = enc(X[i]) otherwise.
    ::
    ::  so: if it's a static type, data goes in the head. if it's a dynamic
    ::  type, a reference goes into the head and data goes into the tail.
    ::
    ::  in the head, we first put a placeholder where references need to go.
    =+  hol=(reap 64 'x')
    =/  hes=(list tape)
      %+  turn  p.dat
      |=  d=data
      ?.  (is-dynamic-type d)  ^$(dat d)
      hol
    =/  tas=(list tape)
      %+  turn  p.dat
      |=  d=data
      ?.  (is-dynamic-type d)  ""
      ^$(dat d)
    ::  once we know the head and tail, we can fill in the references in head.
    =-  (weld nes `tape`(zing tas))
    ^-  [@ud nes=tape]
    =+  led=(lent (zing hes))
    %+  roll  hes
    |=  [t=tape i=@ud nes=tape]
    :-  +(i)
    ::  if no reference needed, just put the data.
    ?.  =(t hol)  (weld nes t)
    ::  calculate byte offset of data we need to reference.
    =/  ofs/@ud
      =-  (div - 2)       ::  two hex digits per byte.
      %+  add  led        ::  count head, and
      %-  lent  %-  zing  ::  count all tail data
      (scag i tas)        ::  preceding ours.
    =+  ref=^$(dat [%uint ofs])
    ::  shouldn't hit this unless we're sending over 2gb of data?
    ~|  [%weird-ref-lent (lent ref)]
    ?>  =((lent ref) (lent hol))
    (weld nes ref)
  ::
      %array  ::  where X has k elements (k is assumed to be of type uint256):
    ::  enc(X) = enc(k) enc([X[1], ..., X[k]])
    ::  i.e. it is encoded as if it were an array of static size k, prefixed
    ::  with the number of elements.
    %+  weld  $(dat [%uint (lent p.dat)])
    $(dat [%array-n p.dat])
  ::
      %bytes-n
    ::  enc(X) is the sequence of bytes in X padded with zero-bytes to a length
    ::  of 32.
    ::  Note that for any X, len(enc(X)) is a multiple of 32.
    (pad-to-multiple (render-hex-bytes p.dat) 64 %right)
  ::
      %bytes  ::  of length k (which is assumed to be of type uint256)
    ::  enc(X) = enc(k) pad_right(X), i.e. the number of bytes is encoded as a
    ::  uint256 followed by the actual value of X as a byte sequence, followed
    ::  by the minimum number of zero-bytes such that len(enc(X)) is a multiple
    ::  of 32.
    %+  weld  $(dat [%uint p.p.dat])
    $(dat [%bytes-n p.dat])
  ::
      %string
    ::  enc(X) = enc(enc_utf8(X)), i.e. X is utf-8 encoded and this value is
    ::  interpreted as of bytes type and encoded further. Note that the length
    ::  used in this subsequent encoding is the number of bytes of the utf-8
    ::  encoded string, not its number of characters.
    $(dat [%bytes (lent p.dat) (swp 3 (crip p.dat))])
  ::
      %uint
    ::  enc(X) is the big-endian encoding of X, padded on the higher-order
    ::  (left) side with zero-bytes such that the length is a multiple of 32
    ::  bytes.
    (pad-to-multiple (render-hex-bytes (as-octs p.dat)) 64 %left)
  ::
      %bool
    ::  as in the uint8 case, where 1 is used for true and 0 for false
    $(dat [%uint ?:(p.dat 1 0)])
  ::
      %address
    ::  as in the uint160 case
    $(dat [%uint `@ud`p.dat])
  ==
::
++  is-dynamic-type
  |=  a=data
  ?.  ?=(%array-n -.a)
    ?=(?(%string %bytes %array) -.a)
  &(!=((lent p.a) 0) (lien p.a is-dynamic-type))
::
::
++  render-hex-bytes
  :>  atom to string of hex bytes without 0x prefix and dots.
  |=  a=octs
  ^-  tape
  ((x-co:co (mul 2 p.a)) q.a)
::
++  pad-to-multiple
  |=  [wat=tape mof=@ud wer=?(%left %right)]
  =+  len=(lent wat)
  =+  tad=(reap (sub mof (mod len mof)) '0')
  %-  weld
  ?:(?=(%left wer) [tad wat] [wat tad])
--