json_decode/
decoders.rs

use super::{DecodeError, Decoder};
use std::convert::{TryFrom, TryInto};
use std::iter::FromIterator;
use std::marker::PhantomData;

pub type BoxDecoder<'a, T> = Box<dyn Decoder<'a, T> + 'a + Send + Sync>;

pub fn field<'a, T>(field_name: &str, decoder: BoxDecoder<'a, T>) -> BoxDecoder<'a, T>
where
    T: 'a,
{
    Box::new(FieldDecoder {
        field_name: field_name.to_string(),
        inner_decoder: decoder,
    })
}

pub struct FieldDecoder<'a, DecodesTo> {
    field_name: String,
    inner_decoder: BoxDecoder<'a, DecodesTo>,
}

impl<'a, DecodesTo> Decoder<'a, DecodesTo> for FieldDecoder<'a, DecodesTo> {
    fn decode(&self, value: &serde_json::Value) -> Result<DecodesTo, DecodeError> {
        match value {
            serde_json::Value::Object(map) => map
                .get(&self.field_name)
                .ok_or_else(|| {
                    DecodeError::MissingField(self.field_name.clone(), value.to_string())
                })
                .and_then(|inner_value| (*self.inner_decoder).decode(inner_value)),
            _ => Err(DecodeError::IncorrectType(
                "Object".to_string(),
                value.to_string(),
            )),
        }
    }
}

pub fn string() -> BoxDecoder<'static, String> {
    Box::new(StringDecoder {})
}

pub struct StringDecoder {}

impl<'a> Decoder<'a, String> for StringDecoder {
    fn decode(&self, value: &serde_json::Value) -> Result<String, DecodeError> {
        match value {
            serde_json::Value::String(s) => Ok(s.clone()),
            _ => Err(DecodeError::IncorrectType(
                "String".to_string(),
                value.to_string(),
            )),
        }
    }
}

pub fn integer<I: TryFrom<i64>>() -> BoxDecoder<'static, I>
where
    I: 'static + Send + Sync,
{
    Box::new(IntDecoder {
        phantom: PhantomData,
    })
}

pub struct IntDecoder<I: TryFrom<i64>> {
    phantom: PhantomData<I>,
}

impl<'a, I> Decoder<'a, I> for IntDecoder<I>
where
    I: TryFrom<i64>,
{
    fn decode(&self, value: &serde_json::Value) -> Result<I, DecodeError> {
        match value {
            serde_json::Value::Number(n) => {
                let int64 = n
                    .as_i64()
                    .ok_or_else(|| DecodeError::InvalidInteger(value.to_string()))?;

                Ok(int64.try_into().map_err(|_| {
                    DecodeError::IntegerOverflow(value.to_string(), std::any::type_name::<I>())
                })?)
            }
            _ => Err(DecodeError::IncorrectType(
                "Number".to_string(),
                value.to_string(),
            )),
        }
    }
}

pub fn unsigned_integer<'a, I: TryFrom<u64>>() -> Box<dyn Decoder<'a, I> + 'a>
where
    I: 'a,
{
    Box::new(UIntDecoder {
        phantom: PhantomData,
    })
}

pub struct UIntDecoder<I: TryFrom<u64>> {
    phantom: PhantomData<I>,
}

impl<'a, I> Decoder<'a, I> for UIntDecoder<I>
where
    I: TryFrom<u64>,
{
    fn decode(&self, value: &serde_json::Value) -> Result<I, DecodeError> {
        match value {
            serde_json::Value::Number(n) => {
                let uint64 = n
                    .as_u64()
                    .ok_or_else(|| DecodeError::InvalidInteger(value.to_string()))?;

                Ok(uint64.try_into().map_err(|_| {
                    DecodeError::IntegerOverflow(value.to_string(), std::any::type_name::<I>())
                })?)
            }
            _ => Err(DecodeError::IncorrectType(
                "Number".to_string(),
                value.to_string(),
            )),
        }
    }
}

pub fn float<F: From<f64>>() -> BoxDecoder<'static, F>
where
    F: 'static + Send + Sync,
{
    Box::new(FloatDecoder {
        phantom: PhantomData,
    })
}

pub struct FloatDecoder<I: From<f64>> {
    phantom: PhantomData<I>,
}

// TODO: Probably don't need from - just force f64 etc.
impl<'a, I> Decoder<'a, I> for FloatDecoder<I>
where
    I: From<f64>,
{
    fn decode(&self, value: &serde_json::Value) -> Result<I, DecodeError> {
        match value {
            serde_json::Value::Number(n) => n
                .as_f64()
                .map(Into::into)
                .ok_or_else(|| DecodeError::InvalidInteger(value.to_string())),
            _ => Err(DecodeError::IncorrectType(
                "Number".to_string(),
                value.to_string(),
            )),
        }
    }
}

pub fn boolean() -> BoxDecoder<'static, bool> {
    Box::new(BooleanDecoder {})
}

pub struct BooleanDecoder {}

impl<'a> Decoder<'a, bool> for BooleanDecoder {
    fn decode(&self, value: &serde_json::Value) -> Result<bool, DecodeError> {
        match value {
            serde_json::Value::Bool(b) => Ok(*b),
            _ => Err(DecodeError::IncorrectType(
                "Boolean".to_string(),
                value.to_string(),
            )),
        }
    }
}

pub fn option<'a, DecodesTo>(
    decoder: BoxDecoder<'a, DecodesTo>,
) -> BoxDecoder<'a, Option<DecodesTo>>
where
    DecodesTo: 'a + Send + Sync,
{
    Box::new(OptionDecoder {
        inner_decoder: decoder,
    })
}

pub struct OptionDecoder<'a, DecodesTo> {
    inner_decoder: BoxDecoder<'a, DecodesTo>,
}

impl<'a, DecodesTo> Decoder<'a, Option<DecodesTo>> for OptionDecoder<'a, DecodesTo>
where
    DecodesTo: 'a,
{
    fn decode(&self, value: &serde_json::Value) -> Result<Option<DecodesTo>, DecodeError> {
        match value {
            serde_json::Value::Null => Ok(None),
            _ => self.inner_decoder.decode(value).map(Some),
        }
    }
}

// TODO: Difficulties using this due to type inference problems
// look to re-work the interface somehow
pub fn list<'a, Item, Collection>(decoder: BoxDecoder<'a, Item>) -> BoxDecoder<'a, Collection>
where
    Collection: FromIterator<Item> + 'a + Send + Sync,
    Item: 'a,
{
    Box::new(ListDecoder {
        inner_decoder: decoder,
        phantom: PhantomData,
    })
}

pub struct ListDecoder<'a, Item, DecodesTo: FromIterator<Item>> {
    phantom: PhantomData<DecodesTo>,
    inner_decoder: BoxDecoder<'a, Item>,
}

impl<'a, Item, DecodesTo> Decoder<'a, DecodesTo> for ListDecoder<'a, Item, DecodesTo>
where
    DecodesTo: FromIterator<Item>,
{
    fn decode(&self, value: &serde_json::Value) -> Result<DecodesTo, DecodeError> {
        match value {
            serde_json::Value::Array(vec) => vec
                .iter()
                .map(|item| (*self.inner_decoder).decode(item))
                .collect(),
            _ => Err(DecodeError::IncorrectType(
                "Array".to_string(),
                value.to_string(),
            )),
        }
    }
}

// TODO: Do we need the lifetimes here
pub fn map<'a, F, T1, NewDecodesTo>(func: F, d1: BoxDecoder<'a, T1>) -> BoxDecoder<'a, NewDecodesTo>
where
    F: (Fn(T1) -> NewDecodesTo) + 'a + Send + Sync,
    NewDecodesTo: 'a,
    T1: 'a,
{
    Box::new(DecoderFn1 {
        func: Box::new(func),
        decoder: d1,
    })
}

pub struct DecoderFn1<'a, DecodesTo, Argument1> {
    func: Box<dyn Fn(Argument1) -> DecodesTo + 'a + Send + Sync>,
    decoder: BoxDecoder<'a, Argument1>,
}

impl<'a, DecodesTo, Argument1> Decoder<'a, DecodesTo> for DecoderFn1<'a, DecodesTo, Argument1> {
    fn decode(&self, value: &serde_json::Value) -> Result<DecodesTo, DecodeError> {
        let arg0 = self.decoder.decode(value)?;
        Ok((*self.func)(arg0))
    }
}

pub fn serde<T>() -> BoxDecoder<'static, T>
where
    for<'de> T: serde::Deserialize<'de> + 'static + Send + Sync,
{
    Box::new(SerdeDecoder {
        phantom: PhantomData,
    })
}

pub struct SerdeDecoder<T> {
    phantom: PhantomData<T>,
}

impl<'a, DecodesTo> Decoder<'a, DecodesTo> for SerdeDecoder<DecodesTo>
where
    for<'de> DecodesTo: serde::Deserialize<'de>,
{
    fn decode(&self, value: &serde_json::Value) -> Result<DecodesTo, DecodeError> {
        // TODO: Figure out if we can get rid of this clone somehow?
        serde_json::from_value(value.clone()).map_err(|e| DecodeError::SerdeError(e.to_string()))
    }
}

pub fn json() -> BoxDecoder<'static, serde_json::Value> {
    Box::new(JsonDecoder {})
}

pub struct JsonDecoder {}

impl<'a> Decoder<'a, serde_json::Value> for JsonDecoder {
    fn decode(&self, value: &serde_json::Value) -> Result<serde_json::Value, DecodeError> {
        // TODO: Figure out if we can get rid of this clone somehow?
        Ok(value.clone())
    }
}

pub fn succeed<'a, V>(value: V) -> BoxDecoder<'a, V>
where
    V: Clone + Send + Sync + 'a,
{
    Box::new(SucceedDecoder { value })
}

pub struct SucceedDecoder<V> {
    value: V,
}

impl<'a, V> Decoder<'a, V> for SucceedDecoder<V>
where
    V: Clone + Send + Sync + 'a,
{
    fn decode(&self, _value: &serde_json::Value) -> Result<V, DecodeError> {
        // Be nice to figure out a way to avoid this clone...
        Ok(self.value.clone())
    }
}

pub fn fail<V>(error: impl Into<String>) -> BoxDecoder<'static, V> {
    // TODO: Might be nice to get this using a std::Error but it was
    // surprisingly tricky.  For now just using a String instead.
    Box::new(FailDecoder {
        error: error.into(),
    })
}

pub struct FailDecoder {
    error: String,
}

impl<'a, V> Decoder<'a, V> for FailDecoder {
    fn decode(&self, _value: &serde_json::Value) -> Result<V, DecodeError> {
        // Be nice to figure out a way to avoid this clone...
        Err(DecodeError::Other(self.error.clone()))
    }
}

pub fn and_then<'a, F, T, NewDecodesTo>(
    func: F,
    d: BoxDecoder<'a, T>,
) -> BoxDecoder<'a, NewDecodesTo>
where
    F: (Fn(T) -> BoxDecoder<'a, NewDecodesTo>) + 'a + Send + Sync,
    NewDecodesTo: 'a,
    T: 'a,
{
    Box::new(DecoderAndThen {
        func: Box::new(func),
        decoder: d,
    })
}

pub struct DecoderAndThen<'a, DecodesTo, Argument> {
    func: Box<dyn Fn(Argument) -> BoxDecoder<'a, DecodesTo> + 'a + Send + Sync>,
    decoder: BoxDecoder<'a, Argument>,
}

impl<'a, DecodesTo, Argument> Decoder<'a, DecodesTo> for DecoderAndThen<'a, DecodesTo, Argument> {
    fn decode(&self, value: &serde_json::Value) -> Result<DecodesTo, DecodeError> {
        let func_param = self.decoder.decode(value)?;
        let inner_decoder = (*self.func)(func_param);
        let res = inner_decoder.decode(value)?;
        Ok(res)
    }
}
json_decode/decoders.rs

json_decode/
decoders.rs
