(**************************************************************************)
(*                                BELENIOS                                *)
(*                                                                        *)
(*  Copyright © 2012-2023 Inria                                           *)
(*                                                                        *)
(*  This program is free software: you can redistribute it and/or modify  *)
(*  it under the terms of the GNU Affero General Public License as        *)
(*  published by the Free Software Foundation, either version 3 of the    *)
(*  License, or (at your option) any later version, with the additional   *)
(*  exemption that compiling, linking, and/or using OpenSSL is allowed.   *)
(*                                                                        *)
(*  This program is distributed in the hope that it will be useful, but   *)
(*  WITHOUT ANY WARRANTY; without even the implied warranty of            *)
(*  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU     *)
(*  Affero General Public License for more details.                       *)
(*                                                                        *)
(*  You should have received a copy of the GNU Affero General Public      *)
(*  License along with this program.  If not, see                         *)
(*  <http://www.gnu.org/licenses/>.                                       *)
(**************************************************************************)

open Lwt.Syntax
open Js_of_ocaml
open Belenios
open Belenios_js.Common
open Belenios_js.Session

let () = relative_root := "../"

let install_handler (id, handler) =
  let f _ =
    let@ () = finally Js._false in
    let@ () = Lwt.async in
    try handler ()
    with e ->
      let msg = "Unexpected error: " ^ Printexc.to_string e in
      alert msg;
      Lwt.return_unit
  in
  let$ e = document##getElementById (Js.string id) in
  e##.onclick := Dom_html.handler f

module Tests = struct
  open Crypto_primitives

  let unit_tests () =
    let a = "13133254971699857128" and b = "31748915560162976106" in
    let c = Z.of_string a and d = Z.of_string b in
    let ntests = ref 0 in
    let check name f =
      if not (f ()) then Printf.ksprintf failwith "test %s failed" name;
      incr ntests
    in
    check "ZERO" (fun () -> Z.to_string Z.zero = "0");
    check "ONE" (fun () -> Z.to_string Z.one = "1");
    let string_roundtrip a c () = a = Z.to_string c in
    check "string_roundtrip_a" (string_roundtrip a c);
    check "string_roundtrip_b" (string_roundtrip b d);
    let operator op expected () = expected = Z.to_string (op c d) in
    check "add" (operator Z.( + ) "44882170531862833234");
    check "mul" (operator Z.( * ) "416966603126589360375328894595477783568");
    check "sub" (operator Z.( - ) "-18615660588463118978");
    let a = 132180439 and b = 41907500 in
    let c = Z.of_int a and d = Z.of_int b in
    let int_roundtrip a c () = a = Z.to_int c in
    check "int_roundtrip_a" (int_roundtrip a c);
    check "int_roundtrip_b" (int_roundtrip b d);
    let m = Z.of_int 181944121 in
    check "mod" (fun () -> Z.to_int Z.(c * d mod m) = 30881634);
    check "erem" (fun () -> Z.to_int Z.(erem (zero - (c * d)) m) = 151062487);
    check "powm" (fun () -> Z.to_int (Z.powm c d m) = 81171525);
    check "invert" (fun () -> Z.to_int (Z.invert c m) = 54455411);
    check "eq" (fun () -> Z.(c =% c));
    check "neq" (fun () -> Z.(not (c =% d)));
    check "geq" (fun () -> Z.compare c d >= 0);
    check "lt" (fun () -> Z.compare d c < 0);
    let i = Z.of_string "272660753928370030481696309961224617984" in
    check "bit_length" (fun () -> Z.bit_length i = 128);
    let j = Z.of_bits "\x81\xab\xd3\xed\x0b\x19\x2e\x40\x7a\xca" in
    let k = Z.of_string "956173156978067279948673" in
    check "of_bits" (fun () -> Z.(j =% k));
    let* () =
      let module E = (val get_endecrypt "AES-GCM") in
      let key = "00000000000000000000000000000000" in
      let iv = "000000000000000000000000" in
      let plaintext = Hex.to_string (`Hex "00000000000000000000000000000000") in
      let ciphertext =
        "0388dace60b6a392f328c2b971b2fe78ab6e47d42cec13bdf53a67b21257bddf"
      in
      let* t_ciphertext = E.encrypt ~key ~iv ~plaintext in
      check "AES-GCM-encrypt" (fun () -> t_ciphertext = ciphertext);
      let* t_plaintext = E.decrypt ~key ~iv ~ciphertext in
      check "AES-GCM-decrypt" (fun () -> t_plaintext = Some plaintext);
      Lwt.return_unit
    in
    Printf.ksprintf alert "%d tests were successful!" !ntests;
    Lwt.return_unit

  let bench_powm () =
    let n = 100 in
    let a =
      Z.of_string
        "30853945840174597120626721846450126314606685045265314267738848011863412997744965327336348477924933167005834532279700438305205349395799555380298036421360430773460934119892692300142378546873667179079814466491492611759008787000622911850181117319179885358518118087002567200494558111372663472816700979626698342136091679008920714916697606979211099532626875131128698361120616072546047452123223884113018200823661347210982961457277048742341447670150939858292248553304276963050079119868152424939371279866285547894450497179332713959439322280562800964537259975022546560313279576398606921294360105203419399168177202864123326706057"
    in
    let b =
      Z.of_string
        "14819939028953781742828614102646561767503175195767893300754792157264784353156516390124979555585996023489169949126621747230243670356270820011579970610574477122782323554808537054373243587469800532780586920093499586498630387766110427230278269993001982734422697704386244907459536870293258944887480320668921711004376689265489289358917367072320310010159231121859887203513856330972371464518400704528743841045232559484451944478789199135455911802951204157526268950262470405753241413631071106235874367101847758053982230081762103923406326223085485533921832052842253002365731936871982755922663988441352675836760402401740328212260"
    in
    let p =
      Z.of_string
        "32317006071311007300338913926423828248817941241140239112842009751400741706634354222619689417363569347117901737909704191754605873209195028853758986185622153212175412514901774520270235796078236248884246189477587641105928646099411723245426622522193230540919037680524235519125679715870117001058055877651038861847280257976054903569732561526167081339361799541336476559160368317896729073178384589680639671900977202194168647225871031411336429319536193471636533209717077448227988588565369208645296636077250268955505928362751121174096972998068410554359584866583291642136218231078990999448652468262416972035911852507045361090559"
    in
    let start = new%js Js.date_now in
    for _ = 1 to n do
      ignore (Z.powm a b p)
    done;
    let stop = new%js Js.date_now in
    let delta =
      int_of_float
        (ceil (Js.to_float stop##valueOf -. Js.to_float start##valueOf))
    in
    Printf.ksprintf alert "%d modular exponentiations in %d ms!" n delta;
    Lwt.return_unit

  let bytes_to_sample q =
    (* we take 128 additional bits of random before the mod q, so that
       the statistical distance with a uniform distribution in [0,q[ is
       negligible *)
    (Z.bit_length q / 8) + 17

  let gen n i =
    let j = n * i in
    let xs = Array.init n (fun i -> sha256_hex (string_of_int (j + i))) in
    xs |> Array.to_list |> String.concat ""

  let bench_group () =
    let group =
      get_select "bench_group_group" |> Belenios.Group.of_string ~version:1
    in
    let module G = (val group) in
    let n = get_input "bench_group_nb" |> int_of_string in
    let byte_length = bytes_to_sample G.Zq.q in
    let xs = Array.init n (fun i -> gen byte_length i |> G.Zq.reduce_hex) in
    let start = new%js Js.date_now in
    let ys = Array.map (fun x -> G.(g **~ x)) xs in
    let stop = new%js Js.date_now in
    let delta_exp =
      int_of_float
        (ceil (Js.to_float stop##valueOf -. Js.to_float start##valueOf))
    in
    let start = new%js Js.date_now in
    ignore (Array.fold_left G.( *~ ) G.one ys);
    let stop = new%js Js.date_now in
    let delta_mul =
      int_of_float
        (ceil (Js.to_float stop##valueOf -. Js.to_float start##valueOf))
    in
    Printf.ksprintf alert "Bench result (size %d): %d ms (exp), %d ms (mul)!\n"
      n delta_exp delta_mul;
    Lwt.return_unit

  let cmds =
    [
      ("do_unit_tests", unit_tests);
      ("bench_powm", bench_powm);
      ("bench_group", bench_group);
    ]
end

module Credgen = struct
  let derive () =
    let version = get_textarea "version" |> int_of_string in
    let uuid = get_textarea "election_uuid" |> Uuid.wrap in
    let group = get_textarea "election_group" in
    let module G = (val Belenios.Group.of_string ~version group : GROUP) in
    let module Cred =
      Credential.Make
        (G)
        (struct
          type 'a t = 'a

          let return = Fun.id
          let bind x f = f x
          let pause () = ()
          let uuid = uuid
        end) in
    let cred = get_textarea "credgen_derive_input" in
    let () =
      match Cred.derive cred with
      | Ok x -> set_textarea "credgen_derive_output" G.(g **~ x |> to_string)
      | Error _ -> alert "invalid credential"
    in
    Lwt.return_unit

  let generate ids =
    let version = get_textarea "version" |> int_of_string in
    let uuid = get_textarea "election_uuid" |> Uuid.wrap in
    let group = get_textarea "election_group" in
    let module G = (val Belenios.Group.of_string ~version group : GROUP) in
    let module Cred =
      Credential.Make
        (G)
        (struct
          type 'a t = 'a

          let return = Fun.id
          let bind x f = f x
          let pause () = ()
          let uuid = uuid
        end) in
    let c = Cred.generate ids in
    set_textarea "credgen_generated_creds"
      (string_of_private_credentials c.private_creds);
    set_textarea "credgen_generated_pks"
      (c.public_with_ids |> String.concat "\n");
    Lwt.return_unit

  let generate_n () =
    get_textarea "credgen_number" |> int_of_string |> Voter.generate |> generate

  let generate_ids () =
    get_textarea "credgen_ids" |> Voter.list_of_string |> generate

  let cmds =
    [
      ("do_credgen_derive", derive);
      ("do_credgen_generate", generate_n);
      ("do_credgen_ids", generate_ids);
    ]
end

let new_uuid () =
  let uuid = generate_token () in
  set_textarea "election_uuid" uuid;
  Lwt.return_unit

module Schulze = struct
  let compute () =
    let ballots =
      get_textarea "schulze_raw_plaintext_ballots"
      |> condorcet_ballots_of_string
    in
    let nchoices = get_input "schulze_nchoices" |> int_of_string in
    let blank_allowed = get_checked "schulze_blank" in
    let output = Methods.Schulze.compute ~nchoices ~blank_allowed ballots in
    set_textarea "schulze_output" (string_of_schulze_result output);
    Lwt.return_unit

  let cmds = [ ("do_schulze", compute) ]
end

module BuggyPartialDecryption = struct
  open Belenios_web_api

  let compute () =
    let hash = get_input "buggy_pd_hash" in
    let seed = get_input "buggy_pd_seed" in
    let@ uuid, token =
     fun cont ->
      match String.split_on_char '-' hash with
      | [ uuid; token ] -> cont (Uuid.wrap uuid, token)
      | _ ->
          Printf.ksprintf alert "%s is not a valid access code" hash;
          Lwt.return_unit
    in
    let@ raw_election cont =
      let* x = Api.(get (election uuid) `Nobody) in
      match x with
      | Error _ ->
          Printf.ksprintf alert "Election %s could not be found!"
            (Uuid.unwrap uuid);
          Lwt.return_unit
      | Ok (x, _) -> cont x
    in
    let@ encrypted_tally cont =
      let* x = Api.(get (election_encrypted_tally uuid) `Nobody) in
      match x with
      | Error _ ->
          Printf.ksprintf alert "Could not get encrypted tally of election %s!"
            (Uuid.unwrap uuid);
          Lwt.return_unit
      | Ok (x, _) -> cont x
    in
    let@ epk cont =
      let* x = Api.(get (trustee_election uuid) (`Trustee token)) in
      match x with
      | Ok ({ tally_trustee_private_key = Some x }, _) -> cont x
      | _ ->
          alert "Could not get encrypted private key!";
          Lwt.return_unit
    in
    let module P = (val Election.of_string raw_election) in
    let encrypted_tally =
      encrypted_tally |> encrypted_tally_of_string (sread P.G.of_string)
    in
    let* private_key =
      let module Trustees = (val Belenios.Trustees.get_by_version P.version) in
      let module PKI = Pki.Make (P.G) in
      let module C = Pki.MakeChannels (PKI) in
      let sk = PKI.derive_sk seed and dk = PKI.derive_dk seed in
      let vk = P.G.(g **~ sk) in
      let* epk =
        let* x =
          epk |> encrypted_msg_of_string P.(sread G.of_string) |> C.recv dk vk
        in
        Lwt.return @@ partial_decryption_key_of_string (sread Z.of_string) x
      in
      let buggy = epk.pdk_decryption_key in
      Lwt.return @@ P.G.Zq.reduce buggy
    in
    let factor = P.E.compute_factor encrypted_tally private_key in
    set_textarea "buggy_pd_output"
      (string_of_partial_decryption (swrite P.G.to_string)
         (swrite P.G.Zq.to_string) factor);
    Lwt.return_unit

  let cmds = [ ("do_buggy_pd", compute) ]
end

let cmds =
  [ ("new_uuid", new_uuid) ]
  @ Tests.cmds @ Credgen.cmds @ Schulze.cmds @ BuggyPartialDecryption.cmds

let () =
  Lwt.async (fun () ->
      let* _ = Js_of_ocaml_lwt.Lwt_js_events.onload () in
      List.iter install_handler cmds;
      Lwt.return_unit)
