json_handler.ml

open Common
open Yojson
open Metadata
open Parameters

exception JSON_parsing_failure

(* find the value associated with a key, return default if not found *)
let find_int meta assoc_list = 
  let rec check_value = function 
    | [] -> (match meta.default with
      | None -> raise JSON_parsing_failure
      | Some i -> i)
    | (k,`Int v)::_ when k=meta.name -> v
    | _::rest -> check_value rest in
  check_value assoc_list

let find_int_option meta assoc_list = 
  let rec check_value = function 
    | [] -> meta.default
    | (k,`Int v)::_ when k=meta.name -> Some v
    | _::rest -> check_value rest in
  check_value assoc_list

(* given a json file, return record of parameters *)
let json_from_file filename = 
  try Safe.from_file filename with
   _ -> raise JSON_parsing_failure

 let parameters_from_json = function
   | `Assoc config -> {
      term = find_int term config;
      seed = find_int_option seed config;
      network = json_assoc "network" config |> Network.parse; 
      workload = Numbergen.to_distribution 
        (find_int_option workload_min config, 
        find_int_option workload_max config);
      }
   | _ -> raise JSON_parsing_failure

let get_protocol filename = try (
  Safe.from_file filename
  |> function `Assoc config -> config
  |> json_assoc "consensus"
  |> function `Assoc proto -> proto
  |> json_assoc "protocol" 
  |> function `String str -> str
  |> function "raft" -> `Raft | "vrr" -> `VRR | "dummy" -> `Dummy
  ) with _ -> raise JSON_parsing_failure

let proto_json_from_json = function 
  | `Assoc config -> json_assoc "consensus" config
  | _ -> raise JSON_parsing_failure