use serde::{ser, Serialize};

use crate::bipack_sink::{BipackSink, IntoU64};
use crate::bipack_source::BipackError;
use crate::buffer_sink::BufferSink;
use crate::error::{Result};

pub struct Serializer<S: BipackSink> {
    // This string starts empty and JSON is appended as values are serialized.
    output: S,
}

pub fn to_bytes<T>(value: &T) -> Result<Vec<u8>>
    where T: Serialize + ?Sized,
{
    let mut serializer = Serializer { output: Vec::new() };
    value.serialize(&mut serializer)?;
    Ok(serializer.output)
}

pub fn to_buffer<'a, T: Serialize>(value: &T, buffer: & 'a mut [u8]) -> Result<& 'a [u8]> {
    let mut serializer = Serializer { output: BufferSink { buffer, pos: 0}};
    value.serialize(&mut serializer)?;
    Ok(serializer.output.result_slice())
}

impl<'a, S: BipackSink> ser::Serializer for &'a mut Serializer<S> {
    type Ok = ();
    type Error = BipackError;
    type SerializeSeq = Self;
    type SerializeTuple = Self;
    type SerializeTupleStruct = Self;
    type SerializeTupleVariant = Self;
    type SerializeMap = Self;
    type SerializeStruct = Self;
    type SerializeStructVariant = Self;

    fn serialize_bool(self, v: bool) -> Result<()> {
        self.output.put_u8(if v { 1 } else { 0 })?;
        Ok(())
    }

    fn serialize_i8(self, v: i8) -> Result<()> {
        self.output.put_i8(v)?;
        Ok(())
    }

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

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

    fn serialize_i64(self, v: i64) -> Result<()> {
        self.output.put_signed(v)?;
        Ok(())
    }

    fn serialize_u8(self, v: u8) -> Result<()> {
        self.output.put_u8(v)?;
        Ok(())
    }
    fn serialize_u16(self, v: u16) -> Result<()> {
        self.serialize_u64(v.into_u64())?;
        Ok(())
    }
    fn serialize_u32(self, v: u32) -> Result<()> {
        self.serialize_u64(v.into())?;
        Ok(())
    }
    fn serialize_u64(self, v: u64) -> Result<()> {
        self.output.put_unsigned(v)?;
        Ok(())
    }

    fn serialize_f32(self, v: f32) -> Result<()> {
        Err(ser::Error::custom("not implemented"))
    }

    fn serialize_f64(self, v: f64) -> Result<()> {
        Err(ser::Error::custom("not implemented"))
    }

    /// Serialize a char as a single-character string, because this is a UTF8-encoded
    /// char, e.g. variable length:
    fn serialize_char(self, v: char) -> Result<()> {
        self.serialize_str(&v.to_string())
    }

    fn serialize_str(self, v: &str) -> Result<()> {
        self.output.put_str(v)?;
        Ok(())
    }

    fn serialize_bytes(self, v: &[u8]) -> Result<()> {
        self.output.put_var_bytes(v)?;
        Ok(())
    }

    fn serialize_none(self) -> Result<()> {
        self.serialize_u8(0)?;
        Ok(())
    }

    fn serialize_some<T>(self, value: &T) -> Result<()>
        where
            T: ?Sized + Serialize,
    {
        self.serialize_u8(1)?;
        value.serialize(self)
    }

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

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

    fn serialize_unit_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
    ) -> Result<()> {
        self.serialize_u32(_variant_index)
    }

    fn serialize_newtype_struct<T>(
        self,
        _name: &'static str,
        value: &T,
    ) -> Result<()>
        where
            T: ?Sized + Serialize,
    {

        value.serialize(self)
    }

    fn serialize_newtype_variant<T>(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
        value: &T,
    ) -> Result<()>
        where
            T: ?Sized + Serialize,
    {
        self.serialize_u32(_variant_index)?;
        value.serialize(self)
    }

    /// We expect it to use with vairable-length arrays...
    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq> {
        self.output.put_unsigned(_len.unwrap_or(0))?;
        Ok(self)
    }

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

    fn serialize_tuple_struct(
        self,
        _name: &'static str,
        len: usize,
    ) -> Result<Self::SerializeTupleStruct> {
        Ok(self)
    }

    fn serialize_tuple_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleVariant> {
        _variant_index.serialize(&mut *self)?;
        Ok(self)
    }

    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap> {
        self.output.put_unsigned(_len.unwrap_or(0))?;
        Ok(self)
    }

    fn serialize_struct(
        self,
        _name: &'static str,
        len: usize,
    ) -> Result<Self::SerializeStruct> {
        // self.serialize_map(Some(len))
        Ok(self)
    }
    fn serialize_struct_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeStructVariant> {
        self.output.put_unsigned(_variant_index)?;
        Ok(self)
    }
}

impl<'a, S: BipackSink> ser::SerializeSeq for &'a mut Serializer<S> {
    // Must match the `Ok` type of the serializer.
    type Ok = ();
    // Must match the `Error` type of the serializer.
    type Error = BipackError;

    // 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(())
    }
}

impl<'a, S: BipackSink> ser::SerializeTuple for &'a mut Serializer<S> {
    type Ok = ();
    type Error = BipackError;

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

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

impl<'a, S: BipackSink> ser::SerializeTupleStruct for &'a mut Serializer<S> {
    type Ok = ();
    type Error = BipackError;

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

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

impl<'a, S: BipackSink> ser::SerializeTupleVariant for &'a mut Serializer<S> {
    type Ok = ();
    type Error = BipackError;

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

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

impl<'a, S: BipackSink> ser::SerializeMap for &'a mut Serializer<S> {
    type Ok = ();
    type Error = BipackError;

    // 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<'a, S: BipackSink> ser::SerializeStruct for &'a mut Serializer<S> {
    type Ok = ();
    type Error = BipackError;

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

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

impl<'a, S: BipackSink> ser::SerializeStructVariant for &'a mut Serializer<S> {
    type Ok = ();
    type Error = BipackError;

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

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

#[cfg(test)]
mod test {
    use std::collections::HashMap;
    use std::string::FromUtf8Error;

    use serde::Serialize;

    use crate::bipack_source::{BipackError, BipackSource, SliceSource};
    use crate::error;
    use crate::ser::to_bytes;
    use crate::tools::{to_dump, to_hex};

    #[test]
    fn test_struct() -> Result<(), BipackError> {
        #[derive(Serialize)]
        struct Test {
            int: u32,
            seq: Vec<&'static str>,
        }

        let test = Test {
            int: 17,
            seq: vec!["a", "b"],
        };
        let x = to_bytes(&test).unwrap();
        println!("!:\n{}", to_dump(&x));
        // let y = x.clone();
        // let z = x.clone();
        let mut src = SliceSource::from(&x);
        assert_eq!(test.int, src.get_unsigned()? as u32);
        assert_eq!(test.seq.len(), src.get_unsigned()? as usize);
        assert_eq!(test.seq[0], src.get_str()?);
        assert_eq!(test.seq[1], src.get_str()?);
        Ok(())
    }

    #[test]
    fn test_enum() -> Result<(), FromUtf8Error> {
        #[derive(Serialize)]
        enum E {
            Unit,
            Unit2,
            Newtype(u32),
            Tuple(u32, u32),
            Struct { a: u32 },
        }

        let u = E::Unit;
        println!("u:{}", to_dump(to_bytes(&u).unwrap().as_slice()));
        assert_eq!("00", to_hex(to_bytes(&u).unwrap())?);
        let u2 = E::Unit2;
        println!("u:{}", to_dump(to_bytes(&u2).unwrap().as_slice()));
        let nt = E::Newtype(17);
        println!("u:{}", to_dump(to_bytes(&nt).unwrap().as_slice()));
        assert_eq!("08 44", to_hex(to_bytes(&nt).unwrap())?);
        let t = E::Tuple(7, 17);
        println!("u:{}", to_dump(to_bytes(&t).unwrap().as_slice()));
        assert_eq!("0c 1c 44", to_hex(to_bytes(&t).unwrap())?);
        let t = E::Struct { a: 17 };
        println!("u:{}", to_dump(to_bytes(&t).unwrap().as_slice()));
        assert_eq!("10 44", to_hex(to_bytes(&t).unwrap())?);
        // let expected = r#""Unit""#;
        // assert_eq!(to_string(&u).unwrap(), expected);
        //
        // let n = E::Newtype(1);
        // let expected = r#"{"Newtype":1}"#;
        // assert_eq!(to_string(&n).unwrap(), expected);
        //
        // let t = E::Tuple(1, 2);
        // let expected = r#"{"Tuple":[1,2]}"#;
        // assert_eq!(to_string(&t).unwrap(), expected);
        //
        // let s = E::Struct { a: 1 };
        // let expected = r#"{"Struct":{"a":1}}"#;
        // assert_eq!(to_string(&s).unwrap(), expected);
        Ok(())
    }

    #[test]
    fn test_map() -> error::Result<()> {
        let mut src = HashMap::new();
        // src.insert("foo", 1);
        src.insert("foo", 42);
        src.insert("bar", 1);
        src.insert("baz", 17);
        let packed = to_bytes(&src)?;
        println!("{}", to_dump(&packed));
        Ok(())
    }
}