//! Change MessagePack behavior with configuration wrappers.
use rmp::encode;
use serde::{Serialize, Serializer};

use crate::encode::{Error, UnderlyingWrite};

/// Represents configuration that dicatates what the serializer does.
///
/// Implemented as an empty trait depending on a hidden trait in order to allow changing the
/// methods of this trait without breaking backwards compatibility.
pub trait SerializerConfig: sealed::SerializerConfig {}

impl<T: sealed::SerializerConfig> SerializerConfig for T {}

mod sealed {
    use serde::{Serialize, Serializer};

    use crate::encode::{Error, UnderlyingWrite};

    /// This is the inner trait - the real SerializerConfig.
    ///
    /// This hack disallows external implementations and usage of SerializerConfig and thus
    /// allows us to change SerializerConfig methods freely without breaking backwards compatibility.
    pub trait SerializerConfig {
        fn write_struct_len<S>(ser: &mut S, len: usize) -> Result<(), Error>
        where
            S: UnderlyingWrite,
            for<'a> &'a mut S: Serializer<Ok = (), Error = Error>;

        fn write_struct_field<S, T>(ser: &mut S, key: &'static str, value: &T) -> Result<(), Error>
        where
            S: UnderlyingWrite,
            for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
            T: ?Sized + Serialize;

        /// Encodes an enum variant ident (id or name) according to underlying writer.
        ///
        /// Used in `Serializer::serialize_*_variant` methods.
        fn write_variant_ident<S>(
            ser: &mut S,
            variant_index: u32,
            variant: &'static str,
        ) -> Result<(), Error>
        where
            S: UnderlyingWrite,
            for<'a> &'a mut S: Serializer<Ok = (), Error = Error>;
    }
}

/// The default serializer configuration.
///
/// This writes structs as a tuple, without field names, and enum variants as integers.
/// This is the most compact representation.
#[derive(Copy, Clone, Debug)]
pub struct DefaultConfig;

impl sealed::SerializerConfig for DefaultConfig {
    fn write_struct_len<S>(ser: &mut S, len: usize) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
    {
        encode::write_array_len(ser.get_mut(), len as u32)?;

        Ok(())
    }

    fn write_struct_field<S, T>(ser: &mut S, _key: &'static str, value: &T) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
        T: ?Sized + Serialize,
    {
        value.serialize(ser)
    }

    fn write_variant_ident<S>(
        ser: &mut S,
        variant_index: u32,
        _variant: &'static str,
    ) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
    {
        ser.serialize_u32(variant_index)
    }
}

/// Config wrapper, that overrides struct serialization by packing as a map with field names.
///
/// MessagePack specification does not tell how to serialize structs. This trait allows you to
/// extend serialization to match your app's requirements.
///
/// Default `Serializer` implementation writes structs as a tuple, i.e. only its length is encoded,
/// because it is the most compact representation.
#[derive(Copy, Clone, Debug)]
pub struct StructMapConfig<C>(C);

impl<C> StructMapConfig<C> {
    /// Creates a `StructMapConfig` inheriting unchanged configuration options from the given configuration.
    pub fn new(inner: C) -> Self {
        StructMapConfig(inner)
    }
}

impl<C> sealed::SerializerConfig for StructMapConfig<C>
where
    C: sealed::SerializerConfig,
{
    fn write_struct_len<S>(ser: &mut S, len: usize) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
    {
        encode::write_map_len(ser.get_mut(), len as u32)?;

        Ok(())
    }

    fn write_struct_field<S, T>(ser: &mut S, key: &'static str, value: &T) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
        T: ?Sized + Serialize,
    {
        encode::write_str(ser.get_mut(), key)?;
        value.serialize(ser)
    }

    fn write_variant_ident<S>(
        ser: &mut S,
        variant_index: u32,
        variant: &'static str,
    ) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
    {
        C::write_variant_ident(ser, variant_index, variant)
    }
}

/// Config wrapper that overrides struct serlization by packing as a tuple without field
/// names.
#[derive(Copy, Clone, Debug)]
pub struct StructTupleConfig<C>(C);

impl<C> StructTupleConfig<C> {
    /// Creates a `StructTupleConfig` inheriting unchanged configuration options from the given configuration.
    pub fn new(inner: C) -> Self {
        StructTupleConfig(inner)
    }
}

impl<C> sealed::SerializerConfig for StructTupleConfig<C>
where
    C: sealed::SerializerConfig,
{
    fn write_struct_len<S>(ser: &mut S, len: usize) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
    {
        encode::write_array_len(ser.get_mut(), len as u32)?;

        Ok(())
    }

    fn write_struct_field<S, T>(ser: &mut S, _key: &'static str, value: &T) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
        T: ?Sized + Serialize,
    {
        value.serialize(ser)
    }

    fn write_variant_ident<S>(
        ser: &mut S,
        variant_index: u32,
        variant: &'static str,
    ) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
    {
        C::write_variant_ident(ser, variant_index, variant)
    }
}

/// Config wrapper, that overrides enum serialization by serializing enum variant names as strings.
///
/// Default `Serializer` implementation writes enum names as integers, i.e. only indices are encoded,
/// because it is the most compact representation.
#[derive(Copy, Clone, Debug)]
pub struct VariantStringConfig<C>(C);

impl<C> VariantStringConfig<C> {
    /// Creates a `VariantStringConfig` inheriting unchanged configuration options from the given configuration.
    pub fn new(inner: C) -> Self {
        VariantStringConfig(inner)
    }
}

impl<C> sealed::SerializerConfig for VariantStringConfig<C>
where
    C: sealed::SerializerConfig,
{
    fn write_struct_len<S>(ser: &mut S, len: usize) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
    {
        C::write_struct_len(ser, len)
    }

    fn write_struct_field<S, T>(ser: &mut S, key: &'static str, value: &T) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
        T: ?Sized + Serialize,
    {
        C::write_struct_field(ser, key, value)
    }

    fn write_variant_ident<S>(
        ser: &mut S,
        _variant_index: u32,
        variant: &'static str,
    ) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
    {
        ser.serialize_str(variant)
    }
}

/// Config wrapper that overrides enum variant serialization by packing enum names as their integer indices.
#[derive(Copy, Clone, Debug)]
pub struct VariantIntegerConfig<C>(C);

impl<C> VariantIntegerConfig<C> {
    /// Creates a `VariantIntegerConfig` inheriting unchanged configuration options from the given configuration.
    pub fn new(inner: C) -> Self {
        VariantIntegerConfig(inner)
    }
}

impl<C> sealed::SerializerConfig for VariantIntegerConfig<C>
where
    C: sealed::SerializerConfig,
{
    fn write_struct_len<S>(ser: &mut S, len: usize) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
    {
        C::write_struct_len(ser, len)
    }

    fn write_struct_field<S, T>(ser: &mut S, key: &'static str, value: &T) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
        T: ?Sized + Serialize,
    {
        C::write_struct_field(ser, key, value)
    }

    fn write_variant_ident<S>(
        ser: &mut S,
        variant_index: u32,
        _variant: &'static str,
    ) -> Result<(), Error>
    where
        S: UnderlyingWrite,
        for<'a> &'a mut S: Serializer<Ok = (), Error = Error>,
    {
        ser.serialize_u32(variant_index)
    }
}