use crate::error::{Error, Result};
use crate::serde::T;
use raad::le::W;
use serde::{Serialize, ser};
use std::io::Write;

pub fn to_bytes<T>(value: &T) -> Result<Vec<u8>>
where
    T: Serialize,
{
    let mut v = vec![];
    let mut serializer = Serializer { w: &mut v };
    value.serialize(&mut serializer)?;
    Ok(v)
}
pub struct Serializer<W: std::io::Write> {
    w: W,
}
impl<W: std::io::Write> Serializer<W> {
    fn wh(&mut self, h: T, w: impl raad::le::Writable) -> Result<()> {
        self.t(h)?;
        self.w.w(w)?;
        Ok(())
        // self.w.w(e);
    }
    fn t(&mut self, h: T) -> Result<()> {
        self.w.w(h as u8)?;
        Ok(())
    }
    fn leb128h(&mut self, h: T, w: impl Into<u128>) -> Result<()> {
        self.t(h)?;
        self.leb128(w)
    }
    fn leb128(&mut self, w: impl Into<u128>) -> Result<()> {
        let mut w = w.into();
        loop {
            let n = (w & 127) as u8;
            w >>= 7;
            if w == 0 {
                self.w.w(n)?;
                break;
            }
            self.w.w(n | 1 << 7)?;
        }
        Ok(())
    }
    fn sleb128(&mut self, mut w: i128) -> Result<()> {
        loop {
            let n = (w & 127) as i8;
            w >>= 7;
            let sign = (n & 64) != 0;
            if (w == 0 && !sign) || (w == -1 && sign) {
                self.w.w(n)?;
                break;
            }
            self.w.w(n | 1 << 7)?;
        }
        Ok(())
    }
}

impl<W: std::io::Write> ser::Serializer for &mut Serializer<W> {
    // The output type produced by this `Serializer` during successful
    // serialization. Most serializers that produce text or binary output should
    // set `Ok = ()` and serialize into an `io::Write` or buffer contained
    // within the `Serializer` instance, as happens here. Serializers that build
    // in-memory data structures may be simplified by using `Ok` to propagate
    // the data structure around.
    type Ok = ();

    // The error type when some error occurs during serialization.
    type Error = Error;

    // Associated types for keeping track of additional state while serializing
    // compound data structures like sequences and maps. In this case no
    // additional state is required beyond what is already stored in the
    // Serializer struct.
    type SerializeSeq = Self;
    type SerializeTuple = Self;
    type SerializeTupleStruct = Self;
    type SerializeTupleVariant = Self;
    type SerializeMap = Self;
    type SerializeStruct = Self;
    type SerializeStructVariant = Self;

    // Here we go with the simple methods. The following 12 methods receive one
    // of the primitive types of the data model and map it to JSON by appending
    // into the output string.
    fn serialize_bool(self, v: bool) -> Result<()> {
        // println!("serialize bool {v}");
        self.w.w(u8::from(v))?;
        Ok(())
    }

    // JSON does not distinguish between different sizes of integers, so all
    // signed integers will be serialized the same and all unsigned integers
    // will be serialized the same. Other formats, especially compact binary
    // formats, may need independent logic for the different sizes.
    fn serialize_i8(self, v: i8) -> Result<()> {
        self.serialize_i64(i64::from(v))
    }

    fn serialize_i16(self, v: i16) -> Result<()> {
        self.serialize_i64(i64::from(v))
    }

    fn serialize_i32(self, v: i32) -> Result<()> {
        self.serialize_i64(i64::from(v))
    }

    fn serialize_i64(self, v: i64) -> Result<()> {
        // println!("serialize i64 {v}");
        self.t(T::Int)?;
        self.sleb128(v.into())
    }

    fn serialize_u8(self, v: u8) -> Result<()> {
        self.serialize_u64(u64::from(v))
    }

    fn serialize_u16(self, v: u16) -> Result<()> {
        self.serialize_u64(u64::from(v))
    }

    fn serialize_u32(self, v: u32) -> Result<()> {
        self.serialize_u64(u64::from(v))
    }

    fn serialize_u64(self, v: u64) -> Result<()> {
        // println!("serialize u64 {v}");
        self.leb128h(T::Uint, v)
    }

    fn serialize_f32(self, v: f32) -> Result<()> {
        // println!("serialize f32 {v}");
        self.wh(T::Float, v)
    }

    fn serialize_f64(self, v: f64) -> Result<()> {
        // println!("serialize f64 {v}");
        self.wh(T::Double, v)
    }

    fn serialize_char(self, v: char) -> Result<()> {
        self.serialize_u32(u32::from(v))
    }

    fn serialize_str(self, v: &str) -> Result<()> {
        self.serialize_bytes(v.as_bytes())
    }

    fn serialize_bytes(self, v: &[u8]) -> Result<()> {
        // println!("serialize bytes {v:?}");
        self.leb128h(T::String, v.len() as u128)?;
        self.w.w(v)?;
        Ok(())
    }

    // An absent optional is represented as the JSON `null`.
    fn serialize_none(self) -> Result<()> {
        self.t(T::None)
    }

    fn serialize_some<U>(self, value: &U) -> Result<()>
    where
        U: ?Sized + Serialize,
    {
        self.t(T::Some)?;
        value.serialize(self)
    }

    fn serialize_unit(self) -> Result<()> {
        self.serialize_none()
    }

    fn serialize_unit_struct(self, _name: &'static str) -> Result<()> {
        self.serialize_none()
    }

    fn serialize_unit_variant(
        self,
        _name: &'static str,
        i: u32,
        _variant: &'static str,
    ) -> Result<()> {
        // println!("uv");
        self.w.w(T::UVariant as u8)?;
        self.serialize_u32(i)
    }

    // As is done here, serializers are encouraged to treat newtype structs as
    // insignificant wrappers around the data they contain.
    fn serialize_newtype_struct<T>(self, _name: &'static str, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(self)
    }

    // Note that newtype variant (and all of the other variant serialization
    // methods) refer exclusively to the "externally tagged" enum
    // representation.
    //
    // Serialize this to JSON in externally tagged form as `{ NAME: VALUE }`.
    fn serialize_newtype_variant<U>(
        self,
        _name: &'static str,
        ix: u32,
        _vname: &'static str,
        value: &U,
    ) -> Result<()>
    where
        U: ?Sized + Serialize,
    {
        // println!("serialize variant {_vname} of  {_name} ix {ix}");
        self.w.w(T::NVariant as u8)?;
        self.serialize_u32(ix)?;
        value.serialize(self)
    }

    // Now we get to the serialization of compound types.
    //
    // The start of the sequence, each value, and the end are three separate
    // method calls. This one is responsible only for serializing the start,
    // which in JSON is `[`.
    //
    // The length of the sequence may or may not be known ahead of time. This
    // doesn't make a difference in JSON because the length is not represented
    // explicitly in the serialized form. Some serializers may only be able to
    // support sequences for which the length is known up front.
    fn serialize_seq(self, l: Option<usize>) -> Result<Self::SerializeSeq> {
        // println!("serialize list of len {l:?}");
        self.leb128h(T::List, l.unwrap() as u128)?;
        Ok(self)
    }

    fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple> {
        self.serialize_seq(Some(len))
    }

    // Tuple structs look just like sequences in JSON.
    fn serialize_tuple_struct(
        self,
        _name: &'static str,
        len: usize,
    ) -> Result<Self::SerializeTupleStruct> {
        self.serialize_seq(Some(len))
    }

    // Tuple variants are represented in JSON as `{ NAME: [DATA...] }`. Again
    // this method is only responsible for the externally tagged representation.
    fn serialize_tuple_variant(
        self,
        _name: &'static str,
        idx: u32,
        _variant: &'static str,
        len: usize,
    ) -> Result<Self::SerializeTupleVariant> {
        // println!("serialize tuple variant {_variant} of {_name} {idx} {_variant}");
        self.w.w(T::TVariant as u8)?;
        self.serialize_u32(idx)?;
        self.leb128(len as u128)?;
        Ok(self)
    }

    // Maps are represented in JSON as `{ K: V, K: V, ... }`.
    fn serialize_map(self, len: Option<usize>) -> Result<Self::SerializeMap> {
        self.w.w(T::Map as u8)?;
        // println!("{_len:?}");
        self.leb128(len.ok_or(Error::LenLess)? as u128)?;
        Ok(self)

        // Ok(self)
    }

    // Structs look just like maps in JSON. In particular, JSON requires that we
    // serialize the field names of the struct. Other formats may be able to
    // omit the field names when serializing structs because the corresponding
    // Deserialize implementation is required to know what the keys are without
    // looking at the serialized data.
    fn serialize_struct(self, _name: &'static str, len: usize) -> Result<Self::SerializeStruct> {
        self.serialize_map(Some(len))
    }

    // Struct variants are represented in JSON as `{ NAME: { K: V, ... } }`.
    // This is the externally tagged representation.
    fn serialize_struct_variant(
        self,
        _name: &'static str,
        idx: u32,
        _variant: &'static str,
        len: usize,
    ) -> Result<Self::SerializeStructVariant> {
        // println!("ser struct v {_name} {_variant_index} {variant} {_len}");
        self.w.w(T::SVariant as u8)?;
        self.serialize_u32(idx)?;
        self.leb128(len as u128)?;
        Ok(self)
    }
}

// The following 7 impls deal with the serialization of compound types like
// sequences and maps. Serialization of such types is begun by a Serializer
// method and followed by zero or more calls to serialize individual elements of
// the compound type and one call to end the compound type.
//
// This impl is SerializeSeq so these methods are called after `serialize_seq`
// is called on the Serializer.
impl<W: Write> ser::SerializeSeq for &mut Serializer<W> {
    // Must match the `Ok` type of the serializer.
    type Ok = ();
    // Must match the `Error` type of the serializer.
    type Error = Error;

    // Serialize a single element of the sequence.
    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(&mut **self)
    }

    // Close the sequence.
    fn end(self) -> Result<()> {
        Ok(())
    }
}

// Same thing but for tuples.
impl<W: Write> ser::SerializeTuple for &mut Serializer<W> {
    type Ok = ();
    type Error = Error;

    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        Ok(())
    }
}

// Same thing but for tuple structs.
impl<W: Write> ser::SerializeTupleStruct for &mut Serializer<W> {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        Ok(())
    }
}
/// A Seq.
impl<W: Write> ser::SerializeTupleVariant for &mut Serializer<W> {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        Ok(())
    }
}

// Some `Serialize` types are not able to hold a key and value in memory at the
// same time so `SerializeMap` implementations are required to support
// `serialize_key` and `serialize_value` individually.
//
// There is a third optional method on the `SerializeMap` trait. The
// `serialize_entry` method allows serializers to optimize for the case where
// key and value are both available simultaneously. In JSON it doesn't make a
// difference so the default behavior for `serialize_entry` is fine.
impl<W: Write> ser::SerializeMap for &mut Serializer<W> {
    type Ok = ();
    type Error = Error;

    // The Serde data model allows map keys to be any serializable type. JSON
    // only allows string keys so the implementation below will produce invalid
    // JSON if the key serializes as something other than a string.
    //
    // A real JSON serializer would need to validate that map keys are strings.
    // This can be done by using a different Serializer to serialize the key
    // (instead of `&mut **self`) and having that other serializer only
    // implement `serialize_str` and return an error on any other data type.
    fn serialize_key<T>(&mut self, key: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        key.serialize(&mut **self)
    }

    // It doesn't make a difference whether the colon is printed at the end of
    // `serialize_key` or at the beginning of `serialize_value`. In this case
    // the code is a bit simpler having it here.
    fn serialize_value<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        Ok(())
    }
}

// Structs are like maps in which the keys are constrained to be compile-time
// constant strings.
impl<W: Write> ser::SerializeStruct for &mut Serializer<W> {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        // key.serialize(&mut **self)?;
        key.serialize(&mut **self)?;
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        Ok(())
    }

    fn skip_field(&mut self, key: &'static str) -> std::prelude::v1::Result<(), Self::Error> {
        let _ = key;
        Ok(())
    }
}

// Similar to `SerializeTupleVariant`, here the `end` method is responsible for
// closing both of the curly braces opened by `serialize_struct_variant`.
impl<W: Write> ser::SerializeStructVariant for &mut Serializer<W> {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        key.serialize(&mut **self)?;
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        Ok(())
    }
}
#[cfg(test)]
mod tests;