serde_v8vs 0.1.0

use alloc::collections::BTreeMap;
#[cfg(any(test, feature = "std"))]
use std::collections::HashMap;

use serde_core::ser::{Impossible, Serialize, Serializer};

use crate::{
	Error, SerializationTag,
	ser::{V8Serializer, Write}
};

pub(crate) const OBJECT_MAGIC: &str = "{f51cd328-f113-4921-8238-f18108f5e37a}";

/// Serialize a map-like type as a JS object. The default behavior would serialize them as a
/// [`Map`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map).
///
/// Supported map-like types are:
/// - [`HashMap<K, V>`]
/// - [`BTreeMap<K, V>`]
///
/// **Note that `K` must be a string type**, or else the serialized value will be invalid and most implementations will
/// fail to deserialize it.
pub fn as_object<T: AsObject, S>(set: &T, serializer: S) -> Result<S::Ok, S::Error>
where
	S: Serializer
{
	set.serialize_as_object(serializer)
}

#[diagnostic::on_unimplemented(message = "{Self} is not a map-like type", note = "valid map-like types are HashMap<K, V> or BTreeMap<K, V>")]
pub trait AsObject {
	fn serialize_as_object<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
	where
		S: Serializer;
}

#[cfg(any(test, feature = "std"))]
impl<K: Serialize, V: Serialize, St> AsObject for HashMap<K, V, St> {
	fn serialize_as_object<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
	where
		S: Serializer
	{
		serializer.serialize_newtype_struct(OBJECT_MAGIC, self)
	}
}

impl<K: Serialize, V: Serialize> AsObject for BTreeMap<K, V> {
	fn serialize_as_object<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
	where
		S: Serializer
	{
		serializer.serialize_newtype_struct(OBJECT_MAGIC, self)
	}
}

pub(crate) struct ObjectSerializer<'a, W: Write>
where
	Error: From<W::Error>
{
	pub(crate) ser: &'a mut V8Serializer<W>
}

impl<'a, W: Write> Serializer for ObjectSerializer<'a, W>
where
	Error: From<W::Error>
{
	type Ok = ();
	type Error = Error;

	type SerializeMap = SerializeObject<'a, W>;
	type SerializeSeq = Impossible<Self::Ok, Self::Error>;
	type SerializeStruct = Impossible<Self::Ok, Self::Error>;
	type SerializeStructVariant = Impossible<Self::Ok, Self::Error>;
	type SerializeTuple = Impossible<Self::Ok, Self::Error>;
	type SerializeTupleStruct = Impossible<Self::Ok, Self::Error>;
	type SerializeTupleVariant = Impossible<Self::Ok, Self::Error>;

	fn serialize_map(self, _: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
		self.ser.writer.push(SerializationTag::BeginJSObject as u8)?;
		Ok(SerializeObject { ser: self.ser, entries: 0 })
	}

	fn serialize_bool(self, _: bool) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_bytes(self, _: &[u8]) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_char(self, _: char) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_f32(self, _: f32) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_f64(self, _: f64) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_i16(self, _: i16) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_i128(self, _: i128) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_i32(self, _: i32) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_i64(self, _: i64) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_i8(self, _: i8) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_newtype_struct<T>(self, _: &'static str, _: &T) -> Result<Self::Ok, Self::Error>
	where
		T: ?Sized + Serialize
	{
		unreachable!()
	}
	fn serialize_newtype_variant<T>(self, _: &'static str, _: u32, _: &'static str, _: &T) -> Result<Self::Ok, Self::Error>
	where
		T: ?Sized + Serialize
	{
		unreachable!()
	}
	fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_seq(self, _: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
		unreachable!()
	}
	fn serialize_some<T>(self, _: &T) -> Result<Self::Ok, Self::Error>
	where
		T: ?Sized + Serialize
	{
		unreachable!()
	}
	fn serialize_str(self, _: &str) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_struct(self, _: &'static str, _: usize) -> Result<Self::SerializeStruct, Self::Error> {
		unreachable!()
	}
	fn serialize_struct_variant(self, _: &'static str, _: u32, _: &'static str, _: usize) -> Result<Self::SerializeStructVariant, Self::Error> {
		unreachable!()
	}
	fn serialize_tuple(self, _: usize) -> Result<Self::SerializeTuple, Self::Error> {
		unreachable!()
	}
	fn serialize_tuple_struct(self, _: &'static str, _: usize) -> Result<Self::SerializeTupleStruct, Self::Error> {
		unreachable!()
	}
	fn serialize_tuple_variant(self, _: &'static str, _: u32, _: &'static str, _: usize) -> Result<Self::SerializeTupleVariant, Self::Error> {
		unreachable!()
	}
	fn serialize_u128(self, _: u128) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_u16(self, _: u16) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_u32(self, _: u32) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_u64(self, _: u64) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_u8(self, _: u8) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_unit_struct(self, _: &'static str) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
	fn serialize_unit_variant(self, _: &'static str, _: u32, _: &'static str) -> Result<Self::Ok, Self::Error> {
		unreachable!()
	}
}

pub struct SerializeObject<'a, W: Write>
where
	Error: From<W::Error>
{
	ser: &'a mut V8Serializer<W>,
	entries: usize
}

impl<'a, W: Write> serde_core::ser::SerializeMap for SerializeObject<'a, W>
where
	Error: From<W::Error>
{
	type Ok = ();
	type Error = Error;

	fn serialize_key<T>(&mut self, key: &T) -> Result<(), Self::Error>
	where
		T: ?Sized + serde_core::Serialize
	{
		key.serialize(&mut *self.ser)
	}

	fn serialize_value<T>(&mut self, value: &T) -> Result<(), Self::Error>
	where
		T: ?Sized + serde_core::Serialize
	{
		let res = value.serialize(&mut *self.ser);
		self.entries += 1;
		res
	}

	fn end(self) -> Result<Self::Ok, Self::Error> {
		self.ser.writer.push(SerializationTag::EndJSObject as _)?;
		self.ser.write_var_int(self.entries as u32)?;
		Ok(())
	}
}