to-edn/to-edn.nix

{ lib }:

with lib;
let
  isSymbol = str: !(isNull (builtins.match "^'.+" str));
  stripQuote = str:
    if (isSymbol str) then head (builtins.match "^'(.+)" str) else str;
  parseStr = str: if (isSymbol str) then (stripQuote str) else ''"${str}"'';
  parseKeyword = str: if (isSymbol str) then (stripQuote str) else ":${str}";
  join-str = concatStringsSep " ";

  toEDN = ds:
    if isString ds then
      parseStr ds
    else
      (if isInt ds then
        ds
      else
        (if isList ds then
          "[ ${join-str (map toEDN ds)} ]"
        else
          (if isAttrs ds then
            "{ ${
              join-str
              (mapAttrsToList (k: v: "${parseKeyword k} ${toEDN v}") ds)
            } }"
          else
            throw "unsupported type: ${builtins.typeOf ds}: ${ds}")));

in ds: toEDN ds