//! Specialized serialization for flags types using `serde`.

use crate::{

    parser::{self, ParseHex, WriteHex},

    Flags,

};

use core::{fmt, str};

use serde::{

    de::{Error, Visitor},

    Deserialize, Deserializer, Serialize, Serializer,

};

/**

Serialize a set of flags as a human-readable string or their underlying bits.

Any unknown bits will be retained.

*/

pub fn serialize<B: Flags, S: Serializer>(flags: &B, serializer: S) -> Result<S::Ok, S::Error>

where

    B::Bits: WriteHex + Serialize,

{

    // Serialize human-readable flags as a string like `"A | B"`

    if serializer.is_human_readable() {

        serializer.collect_str(&parser::AsDisplay(flags))

    }

    // Serialize non-human-readable flags directly as the underlying bits

    else {

        flags.bits().serialize(serializer)

    }

}

/**

Deserialize a set of flags from a human-readable string or their underlying bits.

Any unknown bits will be retained.

*/

pub fn deserialize<'de, B: Flags, D: Deserializer<'de>>(deserializer: D) -> Result<B, D::Error>

where

    B::Bits: ParseHex + Deserialize<'de>,

{

    if deserializer.is_human_readable() {

        // Deserialize human-readable flags by parsing them from strings like `"A | B"`

        struct FlagsVisitor<B>(core::marker::PhantomData<B>);

        impl<'de, B: Flags> Visitor<'de> for FlagsVisitor<B>

        where

            B::Bits: ParseHex,

        {

            type Value = B;

            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {

                formatter.write_str("a string value of `|` separated flags")

            }

            fn visit_str<E: Error>(self, flags: &str) -> Result<Self::Value, E> {

                parser::from_str(flags).map_err(|e| E::custom(e))

            }

        }

        deserializer.deserialize_str(FlagsVisitor(Default::default()))

    } else {

        // Deserialize non-human-readable flags directly from the underlying bits

        let bits = B::Bits::deserialize(deserializer)?;

        Ok(B::from_bits_retain(bits))

    }

}

#[cfg(test)]

mod tests {

    use serde_test::{assert_tokens, Configure, Token::*};

    bitflags! {

        #[derive(serde_derive::Serialize, serde_derive::Deserialize, Debug, PartialEq, Eq)]

        #[serde(transparent)]

        struct SerdeFlags: u32 {

            const A = 1;

            const B = 2;

            const C = 4;

            const D = 8;

        }

    }

    #[test]

    fn test_serde_bitflags_default() {

        assert_tokens(&SerdeFlags::empty().readable(), &[Str("")]);

        assert_tokens(&SerdeFlags::empty().compact(), &[U32(0)]);

        assert_tokens(&(SerdeFlags::A | SerdeFlags::B).readable(), &[Str("A | B")]);

        assert_tokens(&(SerdeFlags::A | SerdeFlags::B).compact(), &[U32(1 | 2)]);

    }

}