teo_runtime/value/
index.rs

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use std::ops;
use indexmap::IndexMap;
use super::value::Value;

// Code from this file is inspired from serde json
// https://github.com/serde-rs/json/blob/master/src/value/index.rs

pub trait Index {
    fn index_into<'v>(&self, v: &'v Value) -> Option<&'v Value>;
    fn index_into_mut<'v>(&self, v: &'v mut Value) -> Option<&'v mut Value>;
    fn index_or_insert<'v>(&self, v: &'v mut Value) -> &'v mut Value;
}

impl Index for usize {

    fn index_into<'v>(&self, v: &'v Value) -> Option<&'v Value> {
        match v {
            Value::Array(vec) => vec.get(*self),
            Value::Tuple(vec) => vec.get(*self),
            _ => None,
        }
    }

    fn index_into_mut<'v>(&self, v: &'v mut Value) -> Option<&'v mut Value> {
        match v {
            Value::Array(vec) => vec.get_mut(*self),
            Value::Tuple(vec) => vec.get_mut(*self),
            _ => None,
        }
    }

    fn index_or_insert<'v>(&self, v: &'v mut Value) -> &'v mut Value {
        match v {
            Value::Array(vec) => {
                let len = vec.len();
                vec.get_mut(*self).unwrap_or_else(|| {
                    panic!(
                        "cannot access index {} of Teon array of length {}",
                        self, len
                    )
                })
            },
            Value::Tuple(vec) => {
                let len = vec.len();
                vec.get_mut(*self).unwrap_or_else(|| {
                    panic!(
                        "cannot access index {} of Teon tuple of length {}",
                        self, len
                    )
                })
            },
            _ => panic!("cannot access index {} of Teon {}", self, v.type_hint()),
        }
    }
}

impl Index for str {

    fn index_into<'v>(&self, v: &'v Value) -> Option<&'v Value> {
        match v {
            Value::Dictionary(map) => map.get(self),
            _ => None,
        }
    }

    fn index_into_mut<'v>(&self, v: &'v mut Value) -> Option<&'v mut Value> {
        match v {
            Value::Dictionary(map) => map.get_mut(self),
            _ => None,
        }
    }

    fn index_or_insert<'v>(&self, v: &'v mut Value) -> &'v mut Value {
        if let Value::Null = v {
            *v = Value::Dictionary(IndexMap::new());
        }
        match v {
            Value::Dictionary(map) => map.entry(self.to_owned()).or_insert(Value::Null),
            _ => panic!("cannot access key {:?} in Teon {}", self, v.type_hint()),
        }
    }
}

impl Index for String {

    fn index_into<'v>(&self, v: &'v Value) -> Option<&'v Value> {
        self[..].index_into(v)
    }

    fn index_into_mut<'v>(&self, v: &'v mut Value) -> Option<&'v mut Value> {
        self[..].index_into_mut(v)
    }

    fn index_or_insert<'v>(&self, v: &'v mut Value) -> &'v mut Value {
        self[..].index_or_insert(v)
    }
}

impl<'a, T> Index for &'a T where T: ?Sized + Index, {

    fn index_into<'v>(&self, v: &'v Value) -> Option<&'v Value> {
        (**self).index_into(v)
    }

    fn index_into_mut<'v>(&self, v: &'v mut Value) -> Option<&'v mut Value> {
        (**self).index_into_mut(v)
    }

    fn index_or_insert<'v>(&self, v: &'v mut Value) -> &'v mut Value {
        (**self).index_or_insert(v)
    }
}

impl<I> ops::Index<I> for Value where I: Index {

    type Output = Value;

    fn index(&self, index: I) -> &Value {
        static NULL: Value = Value::Null;
        index.index_into(self).unwrap_or(&NULL)
    }
}

impl<I> ops::IndexMut<I> for Value where I: Index {

    fn index_mut(&mut self, index: I) -> &mut Value {
        index.index_or_insert(self)
    }
}