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use crate::pack::{Pack, PackError};
use bytes::{Buf, BufMut, Bytes};
use serde::{de::Visitor, Deserialize, Deserializer, Serialize, Serializer};
use std::{
    borrow::Borrow,
    cmp::{Eq, Ord, Ordering, PartialEq, PartialOrd},
    convert::AsRef,
    fmt,
    hash::{Hash, Hasher},
    ops::Deref,
    str,
};

/// This is a thin wrapper around a Bytes that guarantees that it's contents are
/// well formed unicode.
#[derive(Clone)]
pub struct Chars(Bytes);

impl Chars {
    pub fn new() -> Chars {
        Chars(Bytes::new())
    }

    pub fn from_bytes(bytes: Bytes) -> Result<Chars, str::Utf8Error> {
        str::from_utf8(&bytes)?;
        Ok(Chars(bytes))
    }

    pub unsafe fn from_bytes_unchecked(bytes: Bytes) -> Chars {
        Chars(bytes)
    }

    pub fn len(&self) -> usize {
        self.0.len()
    }

    pub fn bytes(&self) -> &[u8] {
        &*self.0
    }

    pub fn to_vec(&self) -> Vec<u8> {
        self.0.to_vec()
    }
}

impl Serialize for Chars {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        serializer.serialize_str(&**self)
    }
}

struct CharsVis;

impl<'de> Visitor<'de> for CharsVis {
    type Value = Chars;

    fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "expected a string")
    }

    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
    where
        E: serde::de::Error,
    {
        Ok(Chars::from(v))
    }

    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
    where
        E: serde::de::Error,
    {
        Ok(Chars::from(String::from(v)))
    }
}

impl<'de> Deserialize<'de> for Chars {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        deserializer.deserialize_string(CharsVis)
    }
}

impl PartialEq for Chars {
    fn eq(&self, other: &Chars) -> bool {
        self.as_ref() == other.as_ref()
    }
}

impl Eq for Chars {}

impl PartialOrd for Chars {
    fn partial_cmp(&self, other: &Chars) -> Option<Ordering> {
        self.as_ref().partial_cmp(other.as_ref())
    }
}

impl Ord for Chars {
    fn cmp(&self, other: &Self) -> Ordering {
        self.as_ref().cmp(other.as_ref())
    }
}

impl Hash for Chars {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.as_ref().hash(state)
    }
}

impl AsRef<str> for Chars {
    fn as_ref(&self) -> &str {
        unsafe { str::from_utf8_unchecked(&self.0) }
    }
}

impl Pack for Chars {
    fn encoded_len(&self) -> usize {
        Pack::encoded_len(&self.0)
    }

    fn encode(&self, buf: &mut impl BufMut) -> Result<(), PackError> {
        Pack::encode(&self.0, buf)
    }

    fn decode(buf: &mut impl Buf) -> Result<Self, PackError> {
        match Chars::from_bytes(<Bytes as Pack>::decode(buf)?) {
            Ok(c) => Ok(c),
            Err(_) => Err(PackError::InvalidFormat),
        }
    }
}

impl From<&'static str> for Chars {
    fn from(src: &'static str) -> Chars {
        Chars(Bytes::from(src.as_bytes()))
    }
}

impl From<String> for Chars {
    fn from(src: String) -> Chars {
        Chars(Bytes::from(src))
    }
}

impl Into<String> for &Chars {
    fn into(self) -> String {
        self.as_ref().into()
    }
}

impl Into<String> for Chars {
    fn into(self) -> String {
        self.as_ref().into()
    }
}

impl Deref for Chars {
    type Target = str;

    fn deref(&self) -> &str {
        unsafe { str::from_utf8_unchecked(&*self.0) }
    }
}

impl Borrow<str> for Chars {
    fn borrow(&self) -> &str {
        &*self
    }
}

impl fmt::Display for Chars {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Display::fmt(&**self, f)
    }
}

impl fmt::Debug for Chars {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Debug::fmt(&**self, f)
    }
}