//! Support for Serde serialization of Rust data types into Preserves *values* (not syntax).

use crate::value::{repr::Record, IOValue, Map, Value};
use serde::Serialize;

/// Empty/placeholder type for representing serialization errors: serialization to values
/// cannot fail.
#[derive(Debug)]
pub enum Error {}
impl serde::ser::Error for Error {
    fn custom<T>(_: T) -> Self
    where
        T: std::fmt::Display,
    {
        unreachable!()
    }
}
impl std::error::Error for Error {}
impl std::fmt::Display for Error {
    fn fmt(&self, _fmt: &mut std::fmt::Formatter) -> std::result::Result<(), std::fmt::Error> {
        unreachable!()
    }
}

type Result<T> = std::result::Result<T, Error>;

/// Serde serializer for converting Rust data to in-memory Preserves values, which can then be
/// serialized using text or binary syntax, analyzed further, etc.
pub struct Serializer;

#[doc(hidden)]
pub struct SerializeDictionary {
    next_key: Option<IOValue>,
    items: Map<IOValue, IOValue>,
}

#[doc(hidden)]
pub struct SerializeRecord {
    r: Record<IOValue>,
}

#[doc(hidden)]
pub struct SerializeSequence {
    vec: Vec<IOValue>,
}

impl serde::Serializer for Serializer {
    type Ok = IOValue;
    type Error = Error;
    type SerializeSeq = SerializeSequence;
    type SerializeTuple = SerializeRecord;
    type SerializeTupleStruct = SerializeRecord;
    type SerializeTupleVariant = SerializeRecord;
    type SerializeMap = SerializeDictionary;
    type SerializeStruct = SerializeRecord;
    type SerializeStructVariant = SerializeRecord;

    fn serialize_bool(self, v: bool) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_i8(self, v: i8) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_i16(self, v: i16) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_i32(self, v: i32) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_i64(self, v: i64) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_u8(self, v: u8) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_u16(self, v: u16) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_u32(self, v: u32) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_u64(self, v: u64) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_f32(self, v: f32) -> Result<Self::Ok> {
        Ok(Value::from(v as f64).wrap())
    }

    fn serialize_f64(self, v: f64) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_char(self, v: char) -> Result<Self::Ok> {
        Ok(Value::simple_record1("UnicodeScalar", Value::from(v as u32).wrap()).wrap())
    }

    fn serialize_str(self, v: &str) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_bytes(self, v: &[u8]) -> Result<Self::Ok> {
        Ok(Value::from(v).wrap())
    }

    fn serialize_none(self) -> Result<Self::Ok> {
        Ok(Value::simple_record0("None").wrap())
    }

    fn serialize_some<T: ?Sized>(self, v: &T) -> Result<Self::Ok>
    where
        T: Serialize,
    {
        Ok(Value::simple_record1("Some", to_value(v)).wrap())
    }

    fn serialize_unit(self) -> Result<Self::Ok> {
        Ok(Value::simple_record0("tuple").wrap())
    }

    fn serialize_unit_struct(self, name: &'static str) -> Result<Self::Ok> {
        Ok(Value::simple_record0(name).wrap())
    }

    fn serialize_unit_variant(
        self,
        _name: &'static str,
        _variant: u32,
        variant_name: &'static str,
    ) -> Result<Self::Ok> {
        Ok(Value::simple_record0(variant_name).wrap())
    }

    fn serialize_newtype_struct<T: ?Sized>(self, name: &'static str, value: &T) -> Result<Self::Ok>
    where
        T: Serialize,
    {
        match super::magic::receive_output_value(name, value) {
            Some(v) => Ok(v),
            None => {
                // TODO: This is apparently discouraged, and we should apparently just serialize `value`?
                Ok(Value::simple_record1(name, to_value(value)).wrap())
            }
        }
    }

    fn serialize_newtype_variant<T: ?Sized>(
        self,
        _name: &'static str,
        _variant: u32,
        variant_name: &'static str,
        value: &T,
    ) -> Result<Self::Ok>
    where
        T: Serialize,
    {
        Ok(Value::simple_record1(variant_name, to_value(value)).wrap())
    }

    fn serialize_seq(self, count: Option<usize>) -> Result<Self::SerializeSeq> {
        let vec = match count {
            Some(n) => Vec::with_capacity(n),
            None => Vec::new(),
        };
        Ok(SerializeSequence { vec })
    }

    fn serialize_tuple(self, count: usize) -> Result<Self::SerializeTuple> {
        Ok(SerializeRecord {
            r: Value::simple_record("tuple", count),
        })
    }

    fn serialize_tuple_struct(
        self,
        name: &'static str,
        count: usize,
    ) -> Result<Self::SerializeTupleStruct> {
        Ok(SerializeRecord {
            r: Value::simple_record(name, count),
        })
    }

    fn serialize_tuple_variant(
        self,
        _name: &'static str,
        _variant: u32,
        variant_name: &'static str,
        count: usize,
    ) -> Result<Self::SerializeTupleVariant> {
        Ok(SerializeRecord {
            r: Value::simple_record(variant_name, count),
        })
    }

    fn serialize_map(self, _count: Option<usize>) -> Result<Self::SerializeMap> {
        Ok(SerializeDictionary {
            next_key: None,
            items: Map::new(),
        })
    }

    fn serialize_struct(self, name: &'static str, count: usize) -> Result<Self::SerializeStruct> {
        Ok(SerializeRecord {
            r: Value::simple_record(name, count),
        })
    }

    fn serialize_struct_variant(
        self,
        _name: &'static str,
        _variant: u32,
        variant_name: &'static str,
        count: usize,
    ) -> Result<Self::SerializeStructVariant> {
        Ok(SerializeRecord {
            r: Value::simple_record(variant_name, count),
        })
    }
}

impl serde::ser::SerializeMap for SerializeDictionary {
    type Ok = IOValue;
    type Error = Error;

    fn serialize_key<T: ?Sized>(&mut self, key: &T) -> Result<()>
    where
        T: Serialize,
    {
        self.next_key = Some(to_value(key));
        Ok(())
    }

    fn serialize_value<T: ?Sized>(&mut self, value: &T) -> Result<()>
    where
        T: Serialize,
    {
        let key = self.next_key.take().unwrap();
        self.items.insert(key, to_value(value));
        Ok(())
    }

    fn end(self) -> Result<Self::Ok> {
        Ok(Value::from(self.items).wrap())
    }
}

impl SerializeRecord {
    fn push<T: ?Sized>(&mut self, value: &T)
    where
        T: Serialize,
    {
        self.r.fields_vec_mut().push(to_value(value))
    }

    fn finish(self) -> IOValue {
        self.r.finish().wrap()
    }
}

impl serde::ser::SerializeStruct for SerializeRecord {
    type Ok = IOValue;
    type Error = Error;

    fn serialize_field<T: ?Sized>(&mut self, _name: &'static str, value: &T) -> Result<()>
    where
        T: Serialize,
    {
        self.push(value);
        Ok(())
    }

    fn end(self) -> Result<Self::Ok> {
        Ok(self.finish())
    }
}

impl serde::ser::SerializeStructVariant for SerializeRecord {
    type Ok = IOValue;
    type Error = Error;

    fn serialize_field<T: ?Sized>(&mut self, _name: &'static str, value: &T) -> Result<()>
    where
        T: Serialize,
    {
        self.push(value);
        Ok(())
    }

    fn end(self) -> Result<Self::Ok> {
        Ok(self.finish())
    }
}

impl serde::ser::SerializeTuple for SerializeRecord {
    type Ok = IOValue;
    type Error = Error;

    fn serialize_element<T: ?Sized>(&mut self, value: &T) -> Result<()>
    where
        T: Serialize,
    {
        self.push(value);
        Ok(())
    }

    fn end(self) -> Result<Self::Ok> {
        Ok(self.finish())
    }
}

impl serde::ser::SerializeTupleStruct for SerializeRecord {
    type Ok = IOValue;
    type Error = Error;

    fn serialize_field<T: ?Sized>(&mut self, value: &T) -> Result<()>
    where
        T: Serialize,
    {
        self.push(value);
        Ok(())
    }

    fn end(self) -> Result<Self::Ok> {
        Ok(self.finish())
    }
}

impl serde::ser::SerializeTupleVariant for SerializeRecord {
    type Ok = IOValue;
    type Error = Error;

    fn serialize_field<T: ?Sized>(&mut self, value: &T) -> Result<()>
    where
        T: Serialize,
    {
        self.push(value);
        Ok(())
    }

    fn end(self) -> Result<Self::Ok> {
        Ok(self.finish())
    }
}

impl serde::ser::SerializeSeq for SerializeSequence {
    type Ok = IOValue;
    type Error = Error;

    fn serialize_element<T: ?Sized>(&mut self, value: &T) -> Result<()>
    where
        T: Serialize,
    {
        self.vec.push(to_value(value));
        Ok(())
    }

    fn end(self) -> Result<Self::Ok> {
        Ok(Value::from(self.vec).wrap())
    }
}

/// Convenience function for directly converting a Serde-serializable `T` to an [IOValue].
pub fn to_value<T>(value: T) -> IOValue
where
    T: Serialize,
{
    value.serialize(Serializer).unwrap()
}