Stackoverflow while materializing

[He-Pin]

The Materializer is using JVM's stack too, maybe we can introduce a tailrec implementation too?
refs: CertainLach/jrsonnet#115

Maybe using : scala.util.control.TailCalls.TailRec ?

local reduce(func, array, default) =
//  assert std.isFunction(func) : error 'reduce(func=...) should be a `function`';
//  assert std.isArray(array) : error 'reduce(array=...) should be an `array`';
  //  assert std.length(array) > 0 : error 'reduce(array=...) should be a non-0 `array`';
  local aux(func, array, current, index) =
    if index < 0 then
      current
    else
      aux(func, array, func(array[index], current), index - 1) tailstrict;
  local length = std.length(array);
  if length == 0 then
    default
  else
    aux(func, array, array[length - 1], length - 2);

local visit(
  value,
  visitor,
  ctx,
  ctx_reducer,
) =
  local new_item = if std.isObject(value) then
    local merged = {
      [prop]: visit(value[prop], visitor, ctx, ctx_reducer)
      for prop in std.objectFields(value)
    };

    local new_item = {
      [prop]: merged[prop].item
      for prop in std.objectFields(merged)
    };
    local new_ctx = reduce(ctx_reducer, std.map(
      function(item) item.ctx,
      std.objectValues(merged)
    ), ctx);

    {
      item: new_item,
      ctx: new_ctx,
    }
  else if std.isArray(value) then
    local merged = std.map(
      function(item) visit(item, visitor, ctx, ctx_reducer),
      value,
    );

    // If we had a way to tee collections, that would be great... :(
    local new_item = std.map(function(item) item.item, merged);
    local all_ctx = std.map(function(item) item.ctx, merged);

    // Reduce all of the contexts
    local new_ctx = reduce(ctx_reducer, all_ctx, ctx);

    {
      item: new_item,
      ctx: new_ctx,
    }
  else
    {
      item: value,
      ctx: ctx,
    };
  local replacement = visitor(new_item.ctx, new_item.item);
  if replacement != null then
    local new_ctx = ctx_reducer(replacement.ctx, new_item.ctx);

    {
      item: replacement.item,
      ctx: new_ctx,
    }
  else
    new_item;


local routes = {
  "/inc/users/whoami": {
    "get": {
      "responses": {
        "200": {
          "content": {
            "application/json": {
              "schema": {
                "properties": {
                  "user": {
                    "properties": {
                      "#id": "the id this entity",
                      "id": {
                        "format": "uuid",
                        "type": "string",
                        "x-name": "users.User"
                      }
                    },
                    "type": "object",
                  }
                },
              }
            }
          },
        }
      }
    }
  }
};

visit(routes, function(ctx, item) { ctx: ctx, item: item }, {}, function(left, right) left + right)

result should be:

{
  "ctx": {},
  "item": {
    "/inc/users/whoami": {
      "get": {
        "responses": {
          "200": {
            "content": {
              "application/json": {
                "schema": {
                  "properties": {
                    "user": {
                      "properties": {
                        "#id": "the id this entity",
                        "id": {
                          "format": "uuid",
                          "type": "string",
                          "x-name": "users.User"
                        }
                      },
                      "type": "object"
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}