use cobs::{decode_in_place, decode_in_place_report};
use serde::Deserialize;

pub(crate) mod deserializer;
pub mod flavors;

use crate::error::{Error, Result};
use deserializer::Deserializer;

/// Deserialize a message of type `T` from a byte slice. The unused portion (if any)
/// of the byte slice is not returned.
pub fn from_bytes<'a, T>(s: &'a [u8]) -> Result<T>
where
    T: Deserialize<'a>,
{
    let mut deserializer = Deserializer::from_bytes(s);
    let t = T::deserialize(&mut deserializer)?;
    Ok(t)
}

/// Deserialize a message of type `T` from a cobs-encoded byte slice.
///
/// The unused portion (if any) of the byte slice is not returned.
/// The used portion of the input slice is modified during deserialization (even if an error is returned).
/// Therefore, if this is not desired, pass a clone of the original slice.
pub fn from_bytes_cobs<'a, T>(s: &'a mut [u8]) -> Result<T>
where
    T: Deserialize<'a>,
{
    let sz = decode_in_place(s).map_err(|_| Error::DeserializeBadEncoding)?;
    from_bytes::<T>(&s[..sz])
}

/// Deserialize a message of type `T` from a cobs-encoded byte slice.
///
/// The unused portion (if any) of the byte slice is returned for further usage.
/// The used portion of the input slice is modified during deserialization (even if an error is returned).
/// Therefore, if this is not desired, pass a clone of the original slice.
pub fn take_from_bytes_cobs<'a, T>(s: &'a mut [u8]) -> Result<(T, &'a mut [u8])>
where
    T: Deserialize<'a>,
{
    let mut report = decode_in_place_report(s).map_err(|_| Error::DeserializeBadEncoding)?;

    // The report does not include terminator bytes. If there is one in the
    // buffer right AFTER the message, also include it.
    if s.get(report.src_used) == Some(&0) {
        report.src_used += 1;
    }

    // First split off the amount used for the "destination", which includes our now
    // decoded message to deserialize
    let (dst_used, dst_unused) = s.split_at_mut(report.dst_used);

    // Then create a slice that includes the unused bytes, but DON'T include the
    // excess bytes that were "shrunk" away from the original message
    let (_unused, src_unused) = dst_unused.split_at_mut(report.src_used - report.dst_used);
    Ok((from_bytes::<T>(dst_used)?, src_unused))
}

/// Deserialize a message of type `T` from a byte slice. The unused portion (if any)
/// of the byte slice is returned for further usage
pub fn take_from_bytes<'a, T>(s: &'a [u8]) -> Result<(T, &'a [u8])>
where
    T: Deserialize<'a>,
{
    let mut deserializer = Deserializer::from_bytes(s);
    let t = T::deserialize(&mut deserializer)?;
    Ok((t, deserializer.finalize()?))
}

/// Deserialize a message of type `T` from a [`embedded_io`](crate::eio::embedded_io)::[`Read`](crate::eio::Read).
#[cfg(any(feature = "embedded-io-04", feature = "embedded-io-06"))]
pub fn from_eio<'a, T, R>(val: (R, &'a mut [u8])) -> Result<(T, (R, &'a mut [u8]))>
where
    T: Deserialize<'a>,
    R: crate::eio::Read + 'a,
{
    let flavor = flavors::io::eio::EIOReader::new(val.0, val.1);
    let mut deserializer = Deserializer::from_flavor(flavor);
    let t = T::deserialize(&mut deserializer)?;
    Ok((t, deserializer.finalize()?))
}

/// Deserialize a message of type `T` from a [`std::io::Read`].
#[cfg(feature = "use-std")]
pub fn from_io<'a, T, R>(val: (R, &'a mut [u8])) -> Result<(T, (R, &'a mut [u8]))>
where
    T: Deserialize<'a>,
    R: std::io::Read + 'a,
{
    let flavor = flavors::io::io::IOReader::new(val.0, val.1);
    let mut deserializer = Deserializer::from_flavor(flavor);
    let t = T::deserialize(&mut deserializer)?;
    Ok((t, deserializer.finalize()?))
}

/// Conveniently deserialize a message of type `T` from a byte slice with a Crc. The unused portion (if any)
/// of the byte slice is not returned.
///
/// See the `de_flavors::crc` module for the complete set of functions.
#[cfg(feature = "use-crc")]
#[cfg_attr(docsrs, doc(cfg(feature = "use-crc")))]
#[inline]
pub fn from_bytes_crc32<'a, T>(s: &'a [u8], digest: crc::Digest<'a, u32>) -> Result<T>
where
    T: Deserialize<'a>,
{
    flavors::crc::from_bytes_u32(s, digest)
}

/// Conveniently deserialize a message of type `T` from a byte slice with a Crc. The unused portion (if any)
/// of the byte slice is returned for further usage
///
/// See the `de_flavors::crc` module for the complete set of functions.
#[cfg(feature = "use-crc")]
#[cfg_attr(docsrs, doc(cfg(feature = "use-crc")))]
#[inline]
pub fn take_from_bytes_crc32<'a, T>(
    s: &'a [u8],
    digest: crc::Digest<'a, u32>,
) -> Result<(T, &'a [u8])>
where
    T: Deserialize<'a>,
{
    flavors::crc::take_from_bytes_u32(s, digest)
}

////////////////////////////////////////////////////////////////////////////////

#[cfg(feature = "heapless")]
#[cfg(test)]
mod test_heapless {
    use super::*;
    use crate::{ser::to_vec, to_vec_cobs, varint::varint_max};
    use core::fmt::Write;
    use core::ops::Deref;
    use heapless::{FnvIndexMap, String, Vec};
    use serde::{Deserialize, Deserializer, Serialize, Serializer};

    #[test]
    fn de_u8() {
        let output: Vec<u8, 1> = to_vec(&0x05u8).unwrap();
        assert_eq!(&[5], output.deref());

        let out: u8 = from_bytes(output.deref()).unwrap();
        assert_eq!(out, 0x05);
    }

    #[test]
    fn de_u16() {
        let output: Vec<u8, { varint_max::<u16>() }> = to_vec(&0xA5C7u16).unwrap();
        assert_eq!(&[0xC7, 0xCB, 0x02], output.deref());

        let out: u16 = from_bytes(output.deref()).unwrap();
        assert_eq!(out, 0xA5C7);
    }

    #[test]
    fn de_u32() {
        let output: Vec<u8, { varint_max::<u32>() }> = to_vec(&0xCDAB3412u32).unwrap();
        assert_eq!(&[0x92, 0xE8, 0xAC, 0xED, 0x0C], output.deref());

        let out: u32 = from_bytes(output.deref()).unwrap();
        assert_eq!(out, 0xCDAB3412u32);
    }

    #[test]
    fn de_u64() {
        let output: Vec<u8, { varint_max::<u64>() }> = to_vec(&0x1234_5678_90AB_CDEFu64).unwrap();
        assert_eq!(
            &[0xEF, 0x9B, 0xAF, 0x85, 0x89, 0xCF, 0x95, 0x9A, 0x12],
            output.deref()
        );

        let out: u64 = from_bytes(output.deref()).unwrap();
        assert_eq!(out, 0x1234_5678_90AB_CDEFu64);
    }

    #[test]
    fn de_u128() {
        let output: Vec<u8, { varint_max::<u128>() }> =
            to_vec(&0x1234_5678_90AB_CDEF_1234_5678_90AB_CDEFu128).unwrap();
        assert_eq!(
            &[
                0xEF, 0x9B, 0xAF, 0x85, 0x89, 0xCF, 0x95, 0x9A, 0x92, 0xDE, 0xB7, 0xDE, 0x8A, 0x92,
                0x9E, 0xAB, 0xB4, 0x24,
            ],
            output.deref()
        );

        let out: u128 = from_bytes(output.deref()).unwrap();
        assert_eq!(out, 0x1234_5678_90AB_CDEF_1234_5678_90AB_CDEFu128);
    }

    #[derive(Debug, Serialize, Deserialize, Eq, PartialEq)]
    struct BasicU8S {
        st: u16,
        ei: u8,
        ote: u128,
        sf: u64,
        tt: u32,
    }

    #[test]
    fn de_struct_unsigned() {
        let data = BasicU8S {
            st: 0xABCD,
            ei: 0xFE,
            ote: 0x1234_4321_ABCD_DCBA_1234_4321_ABCD_DCBA,
            sf: 0x1234_4321_ABCD_DCBA,
            tt: 0xACAC_ACAC,
        };

        const SZ: usize = varint_max::<u16>()
            + 1
            + varint_max::<u128>()
            + varint_max::<u64>()
            + varint_max::<u32>();

        let output: Vec<u8, SZ> = to_vec(&data).unwrap();

        assert_eq!(
            &[
                0xCD, 0xD7, 0x02, 0xFE, 0xBA, 0xB9, 0xB7, 0xDE, 0x9A, 0xE4, 0x90, 0x9A, 0x92, 0xF4,
                0xF2, 0xEE, 0xBC, 0xB5, 0xC8, 0xA1, 0xB4, 0x24, 0xBA, 0xB9, 0xB7, 0xDE, 0x9A, 0xE4,
                0x90, 0x9A, 0x12, 0xAC, 0xD9, 0xB2, 0xE5, 0x0A
            ],
            output.deref()
        );

        let out: BasicU8S = from_bytes(output.deref()).unwrap();
        assert_eq!(out, data);
    }

    #[test]
    fn de_byte_slice() {
        let input: &[u8] = &[1u8, 2, 3, 4, 5, 6, 7, 8];
        let output: Vec<u8, 9> = to_vec(input).unwrap();
        assert_eq!(
            &[0x08, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08],
            output.deref()
        );

        let out: Vec<u8, 128> = from_bytes(output.deref()).unwrap();
        assert_eq!(input, out.deref());

        let mut input: Vec<u8, 1024> = Vec::new();
        for i in 0..1024 {
            input.push((i & 0xFF) as u8).unwrap();
        }
        let output: Vec<u8, 2048> = to_vec(input.deref()).unwrap();
        assert_eq!(&[0x80, 0x08], &output.deref()[..2]);

        assert_eq!(output.len(), 1026);
        for (i, val) in output.deref()[2..].iter().enumerate() {
            assert_eq!((i & 0xFF) as u8, *val);
        }

        let de: Vec<u8, 1024> = from_bytes(output.deref()).unwrap();
        assert_eq!(input.deref(), de.deref());
    }

    #[test]
    fn de_str() {
        let input: &str = "hello, postcard!";
        let output: Vec<u8, 17> = to_vec(input).unwrap();
        assert_eq!(0x10, output.deref()[0]);
        assert_eq!(input.as_bytes(), &output.deref()[1..]);

        let mut input: String<1024> = String::new();
        for _ in 0..256 {
            write!(&mut input, "abcd").unwrap();
        }
        let output: Vec<u8, 2048> = to_vec(input.deref()).unwrap();
        assert_eq!(&[0x80, 0x08], &output.deref()[..2]);

        assert_eq!(output.len(), 1026);
        for ch in output.deref()[2..].chunks(4) {
            assert_eq!("abcd", core::str::from_utf8(ch).unwrap());
        }

        let de: String<1024> = from_bytes(output.deref()).unwrap();
        assert_eq!(input.deref(), de.deref());
    }

    #[allow(dead_code)]
    #[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
    enum BasicEnum {
        Bib,
        Bim,
        Bap,
    }

    #[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
    struct EnumStruct {
        eight: u8,
        sixt: u16,
    }

    #[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
    enum DataEnum {
        Bib(u16),
        Bim(u64),
        Bap(u8),
        Kim(EnumStruct),
        Chi { a: u8, b: u32 },
        Sho(u16, u8),
    }

    #[test]
    fn enums() {
        let output: Vec<u8, 1> = to_vec(&BasicEnum::Bim).unwrap();
        assert_eq!(&[0x01], output.deref());
        let out: BasicEnum = from_bytes(output.deref()).unwrap();
        assert_eq!(out, BasicEnum::Bim);

        let output: Vec<u8, { 1 + varint_max::<u64>() }> =
            to_vec(&DataEnum::Bim(u64::MAX)).unwrap();
        assert_eq!(
            &[0x01, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x01],
            output.deref()
        );

        let output: Vec<u8, { 1 + varint_max::<u16>() }> =
            to_vec(&DataEnum::Bib(u16::MAX)).unwrap();
        assert_eq!(&[0x00, 0xFF, 0xFF, 0x03], output.deref());
        let out: DataEnum = from_bytes(output.deref()).unwrap();
        assert_eq!(out, DataEnum::Bib(u16::MAX));

        let output: Vec<u8, 2> = to_vec(&DataEnum::Bap(u8::MAX)).unwrap();
        assert_eq!(&[0x02, 0xFF], output.deref());
        let out: DataEnum = from_bytes(output.deref()).unwrap();
        assert_eq!(out, DataEnum::Bap(u8::MAX));

        let output: Vec<u8, 8> = to_vec(&DataEnum::Kim(EnumStruct {
            eight: 0xF0,
            sixt: 0xACAC,
        }))
        .unwrap();
        assert_eq!(&[0x03, 0xF0, 0xAC, 0xD9, 0x02], output.deref());
        let out: DataEnum = from_bytes(output.deref()).unwrap();
        assert_eq!(
            out,
            DataEnum::Kim(EnumStruct {
                eight: 0xF0,
                sixt: 0xACAC
            })
        );

        let output: Vec<u8, 8> = to_vec(&DataEnum::Chi {
            a: 0x0F,
            b: 0xC7C7C7C7,
        })
        .unwrap();
        assert_eq!(&[0x04, 0x0F, 0xC7, 0x8F, 0x9F, 0xBE, 0x0C], output.deref());
        let out: DataEnum = from_bytes(output.deref()).unwrap();
        assert_eq!(
            out,
            DataEnum::Chi {
                a: 0x0F,
                b: 0xC7C7C7C7
            }
        );

        let output: Vec<u8, 8> = to_vec(&DataEnum::Sho(0x6969, 0x07)).unwrap();
        assert_eq!(&[0x05, 0xE9, 0xD2, 0x01, 0x07], output.deref());
        let out: DataEnum = from_bytes(output.deref()).unwrap();
        assert_eq!(out, DataEnum::Sho(0x6969, 0x07));
    }

    #[test]
    fn tuples() {
        let output: Vec<u8, 128> = to_vec(&(1u8, 10u32, "Hello!")).unwrap();
        assert_eq!(
            &[1u8, 0x0A, 0x06, b'H', b'e', b'l', b'l', b'o', b'!'],
            output.deref()
        );
        let out: (u8, u32, &str) = from_bytes(output.deref()).unwrap();
        assert_eq!(out, (1u8, 10u32, "Hello!"));
    }

    #[derive(Debug, Eq, PartialEq)]
    pub struct ByteSliceStruct<'a> {
        bytes: &'a [u8],
    }

    impl Serialize for ByteSliceStruct<'_> {
        fn serialize<S>(&self, serializer: S) -> core::result::Result<S::Ok, S::Error>
        where
            S: Serializer,
        {
            // Serialization is generic for all slice types, so the default serialization of byte
            // slices does not use `Serializer::serialize_bytes`.
            serializer.serialize_bytes(self.bytes)
        }
    }

    impl<'a, 'de> Deserialize<'de> for ByteSliceStruct<'a>
    where
        'de: 'a,
    {
        fn deserialize<D>(deserializer: D) -> core::result::Result<Self, D::Error>
        where
            D: Deserializer<'de>,
        {
            // Deserialization of byte slices is specialized for byte slices, so the default
            // deserialization will call `Deserializer::deserialize_bytes`.
            Ok(Self {
                bytes: Deserialize::deserialize(deserializer)?,
            })
        }
    }

    #[test]
    fn bytes() {
        let x: &[u8; 32] = &[0u8; 32];
        let output: Vec<u8, 128> = to_vec(x).unwrap();
        assert_eq!(output.len(), 32);
        let out: [u8; 32] = from_bytes(output.deref()).unwrap();
        assert_eq!(out, [0u8; 32]);

        let x: &[u8] = &[0u8; 32];
        let output: Vec<u8, 128> = to_vec(x).unwrap();
        assert_eq!(output.len(), 33);
        let out: &[u8] = from_bytes(output.deref()).unwrap();
        assert_eq!(out, [0u8; 32]);

        let x = ByteSliceStruct { bytes: &[0u8; 32] };
        let output: Vec<u8, 128> = to_vec(&x).unwrap();
        assert_eq!(output.len(), 33);
        let out: ByteSliceStruct<'_> = from_bytes(output.deref()).unwrap();
        assert_eq!(out, ByteSliceStruct { bytes: &[0u8; 32] });
    }

    #[test]
    fn chars() {
        let x: char = 'a';
        let output: Vec<u8, 5> = to_vec(&x).unwrap();
        assert_eq!(output.len(), 2);
        let out: char = from_bytes(output.deref()).unwrap();
        assert_eq!(out, 'a');
    }

    #[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
    pub struct NewTypeStruct(u32);

    #[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
    pub struct TupleStruct((u8, u16));

    #[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
    pub struct DualTupleStruct(u8, u16);

    #[test]
    fn structs() {
        let output: Vec<u8, 4> = to_vec(&NewTypeStruct(5)).unwrap();
        assert_eq!(&[0x05], output.deref());
        let out: NewTypeStruct = from_bytes(output.deref()).unwrap();
        assert_eq!(out, NewTypeStruct(5));

        let output: Vec<u8, 3> = to_vec(&TupleStruct((0xA0, 0x1234))).unwrap();
        assert_eq!(&[0xA0, 0xB4, 0x24], output.deref());
        let out: TupleStruct = from_bytes(output.deref()).unwrap();
        assert_eq!(out, TupleStruct((0xA0, 0x1234)));

        let output: Vec<u8, 3> = to_vec(&DualTupleStruct(0xA0, 0x1234)).unwrap();
        assert_eq!(&[0xA0, 0xB4, 0x24], output.deref());
        let out: DualTupleStruct = from_bytes(output.deref()).unwrap();
        assert_eq!(out, DualTupleStruct(0xA0, 0x1234));
    }

    #[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
    struct RefStruct<'a> {
        bytes: &'a [u8],
        str_s: &'a str,
    }

    #[test]
    fn ref_struct() {
        let message = "hElLo";
        let bytes = [0x01, 0x10, 0x02, 0x20];
        let output: Vec<u8, 11> = to_vec(&RefStruct {
            bytes: &bytes,
            str_s: message,
        })
        .unwrap();

        assert_eq!(
            &[0x04, 0x01, 0x10, 0x02, 0x20, 0x05, b'h', b'E', b'l', b'L', b'o',],
            output.deref()
        );

        let out: RefStruct<'_> = from_bytes(output.deref()).unwrap();
        assert_eq!(
            out,
            RefStruct {
                bytes: &bytes,
                str_s: message,
            }
        );
    }

    #[test]
    fn unit() {
        let output: Vec<u8, 1> = to_vec(&()).unwrap();
        assert_eq!(output.len(), 0);
        let _: () = from_bytes(output.deref()).unwrap();
    }

    #[test]
    fn heapless_data() {
        let mut input: Vec<u8, 4> = Vec::new();
        input.extend_from_slice(&[0x01, 0x02, 0x03, 0x04]).unwrap();
        let output: Vec<u8, 5> = to_vec(&input).unwrap();
        assert_eq!(&[0x04, 0x01, 0x02, 0x03, 0x04], output.deref());
        let out: Vec<u8, 4> = from_bytes(output.deref()).unwrap();
        assert_eq!(out, input);

        let mut input: String<8> = String::new();
        write!(&mut input, "helLO!").unwrap();
        let output: Vec<u8, 7> = to_vec(&input).unwrap();
        assert_eq!(&[0x06, b'h', b'e', b'l', b'L', b'O', b'!'], output.deref());
        let out: String<8> = from_bytes(output.deref()).unwrap();
        assert_eq!(input, out);

        let mut input: FnvIndexMap<u8, u8, 4> = FnvIndexMap::new();
        input.insert(0x01, 0x05).unwrap();
        input.insert(0x02, 0x06).unwrap();
        input.insert(0x03, 0x07).unwrap();
        input.insert(0x04, 0x08).unwrap();
        let output: Vec<u8, 100> = to_vec(&input).unwrap();
        assert_eq!(
            &[0x04, 0x01, 0x05, 0x02, 0x06, 0x03, 0x07, 0x04, 0x08],
            output.deref()
        );
        let out: FnvIndexMap<u8, u8, 4> = from_bytes(output.deref()).unwrap();
        assert_eq!(input, out);
    }

    #[test]
    fn cobs_test() {
        let message = "hElLo";
        let bytes = [0x01, 0x00, 0x02, 0x20];
        let input = RefStruct {
            bytes: &bytes,
            str_s: message,
        };

        let output: Vec<u8, 11> = to_vec(&input).unwrap();

        let mut encode_buf = [0u8; 32];
        let sz = cobs::encode(output.deref(), &mut encode_buf);
        let out = from_bytes_cobs::<RefStruct<'_>>(&mut encode_buf[..sz]).unwrap();

        assert_eq!(input, out);
    }

    #[test]
    fn take_from_includes_terminator() {
        // With the null terminator
        let mut output: Vec<u8, 32> = to_vec_cobs(&(4i32, 0u8, 4u64)).unwrap();
        let (val, remain) = take_from_bytes_cobs::<(i32, u8, u64)>(&mut output).unwrap();
        assert_eq!((4, 0, 4), val);
        assert_eq!(remain.len(), 0);

        // without the null terminator
        let mut output: Vec<u8, 32> = to_vec_cobs(&(4i32, 0u8, 4u64)).unwrap();
        assert_eq!(output.pop(), Some(0));
        let (val, remain) = take_from_bytes_cobs::<(i32, u8, u64)>(&mut output).unwrap();
        assert_eq!((4, 0, 4), val);
        assert_eq!(remain.len(), 0);
    }
}

#[cfg(any(feature = "alloc", feature = "use-std"))]
#[cfg(test)]
mod test_alloc {
    extern crate alloc;

    use super::*;

    use alloc::vec;
    use serde::Deserialize;

    #[derive(Debug, Deserialize, PartialEq)]
    struct ZSTStruct;

    #[test]
    fn zst_vec() {
        assert_eq!(from_bytes(&[3]), Ok(vec![ZSTStruct, ZSTStruct, ZSTStruct]));

        assert_eq!(
            from_bytes(&[4]),
            Ok(vec![ZSTStruct, ZSTStruct, ZSTStruct, ZSTStruct])
        );
    }

    #[test]
    fn vec() {
        assert_eq!(
            from_bytes::<Vec<u8>>(&[8, 255, 255, 255, 0, 0, 0, 0, 0]),
            Ok(vec![255, 255, 255, 0, 0, 0, 0, 0])
        );

        // This won't actually prove anything since tests will likely always be
        // run on devices with larger amounts of memory, but it can't hurt.
        assert_eq!(
            from_bytes::<Vec<u8>>(&[(1 << 7) | 8, 255, 255, 255, 0, 0, 0, 0, 0]),
            Err(Error::DeserializeUnexpectedEnd)
        );
    }
}