src: Move JSON parsing code to its own file

The `json_ui.cc` file contained both data-parsing and UI-related
code. This commit moves the JSON parsing code to its own `json.cc`
file, to separate concerns, make compilation faster when changes are
made to either UI or parsing code, and make the parsing code more
accessible to fuzzers.

The signature of the following function:

```
auto parse_json(StringView json);
```

was changed to:

```
JsonResult parse_json(StringView json);
```

to avoid `auto` deduction issues at compile-time.

1 files changed, 41 insertions, 0 deletions

diff --git a/src/json.hh b/src/json.hh
new file mode 100644
index 00000000..1f76739c
--- /dev/null
+++ b/src/json.hh
@@ -0,0 +1,41 @@
+#ifndef json_hh_INCLUDED
+#define json_hh_INCLUDED
+
+#include "hash_map.hh"
+#include "string.hh"
+#include "value.hh"
+
+namespace Kakoune
+{
+
+using JsonArray = Vector<Value>;
+using JsonObject = HashMap<String, Value>;
+
+template<typename T>
+String to_json(ArrayView<const T> array)
+{
+    return "[" + join(array | transform([](auto&& elem) { return to_json(elem); }), ", ") + "]";
+}
+
+template<typename T, MemoryDomain D>
+String to_json(const Vector<T, D>& vec) { return to_json(ArrayView<const T>{vec}); }
+
+template<typename K, typename V, MemoryDomain D>
+String to_json(const HashMap<K, V, D>& map)
+{
+    return "{" + join(map | transform([](auto&& i) { return format("{}: {}", to_json(i.key), to_json(i.value)); }),
+                      ',', false) + "}";
+}
+
+String to_json(int i);
+String to_json(bool b);
+String to_json(StringView str);
+
+struct JsonResult { Value value; const char* new_pos; };
+
+JsonResult parse_json(const char* pos, const char* end);
+JsonResult parse_json(StringView json);
+
+}
+
+#endif // json_hh_INCLUDED