Reads the JSON a model writes, which is often almost JSON.

Both readers accept what a model commonly gets wrong and a strict decoder rejects: a trailing comma before ] or }, and a raw line break or tab inside a string. When the text does not read as it is, they read it again with curly quotes straightened, so a curly quote inside a string that is otherwise valid JSON is kept.

iex> A2UIAgent.DirectJson.JsonReader.read(~s([{"a": 1,},]))
{:ok, [%{"a" => 1}]}

read_partial_items/3 reads a message list that is still arriving. It returns the messages read so far, each with whether its text was complete. An unfinished message is healed where that is safe: an open object or array is closed, and a string under one of the progressive_keys is cut where the text ends (unless it starts like a URL, which would name the wrong resource). Under one of the whole_item_keys, an array keeps only its finished items.

iex> A2UIAgent.DirectJson.JsonReader.read_partial_items(
...>   ~s([{"id": "a", "text": "Hel), ["text"])
[{%{"id" => "a", "text" => "Hel"}, false}]

A \u escape of an unpaired surrogate reads as U+FFFD, since an Elixir string cannot hold a lone surrogate.