import "drand_lib.aqua"
-- import "@fluencelabs/aqua-lib/math.aqua"


-- get randomness from one peer/service  and verifiication and randomeness from another peer/service
-- returns verification bool and the randomness from the initial reuqest peer and the verification peer, which should be the same
func verified_randomness(addrs: []ServiceAddress, url:string) -> bool, string, string:
  on addrs[0].peer_id:
    Drand addrs[0].service_id
    c_res <- Drand.chains(url)
    i_res <- Drand.info(url, c_res.chains[0])
    r_res <- Drand.latest(url, c_res.chains[0])

  on addrs[1].peer_id:
    Drand addrs[1].service_id
    v_res <- Drand.verify_bls(i_res.info.public_key, r_res.randomness.round, r_res.randomness.previous_signature, r_res.randomness.signature)
  
  <- v_res.verified, v_res.randomness, r_res.randomness.randomness

-- possible end use function that gets randomness from peer/service, gets the prior 
-- round for signature matching from another peer/servive and verifies the latest randomness
data Result:
  success: bool
  randomness: string
  error: string

service MyMath("math"):
  -- careful with this
  sub(x: u64, y: u64) -> u64

func verified_randomness_plus(addrs: []ServiceAddress, url:string) -> Result:
  result: *Result

  on addrs[0].peer_id:
    Drand addrs[0].service_id
    c_res <- Drand.chains(url)
    i_res <- Drand.info(url, c_res.chains[0])
    r_res <- Drand.latest(url, c_res.chains[0])

  on addrs[1].peer_id:
    Drand addrs[1].service_id
    prev_r_res <- Drand.round(url, c_res.chains[0],  MyMath.sub(r_res.randomness.round, 1))
    v_res <- Drand.verify_bls(i_res.info.public_key, r_res.randomness.round, r_res.randomness.previous_signature, r_res.randomness.signature)

  if r_res.randomness.previous_signature != prev_r_res.randomness.signature:
    result <<- Result(success = false, randomness = "", error = "signatures don't match between latest and previous round")
  else:
    if v_res.randomness != r_res.randomness.randomness:
      result <<- Result(success = false, randomness = "", error = "randomness doesn't match between latest request and verification")
    else:
      if v_res.verified:
        result <<- Result(success = v_res.verified, randomness = v_res.randomness, error = "")
      else:
        result <<- Result(success = v_res.verified, randomness =  "", error = "verification failed for round ? and hash ?")
  <- result[0]