1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101

use std::fmt::{self, Debug};

use liquid_error;
use liquid_value::Value;

/// Expected return type of a `Filter`.
pub type FilterResult = Result<Value, liquid_error::Error>;

/// A trait for creating custom tags. This is a simple type alias for a function.
///
/// This function will be called whenever the parser encounters a tag and returns
/// a new [Renderable](trait.Renderable.html) based on its parameters. The received parameters
/// specify the name of the tag, the argument [Tokens](lexer/enum.Token.html) passed to
/// the tag and the global [`Language`](struct.Language.html).
pub trait FilterValue: Send + Sync + FilterValueClone + Debug {
    /// Filter `input` based on `arguments`.
    fn filter(&self, input: &Value, arguments: &[Value]) -> FilterResult;
}

/// Support cloning of `Box<FilterValue>`.
pub trait FilterValueClone {
    /// Cloning of `dyn FilterValue`.
    fn clone_box(&self) -> Box<FilterValue>;
}

impl<T> FilterValueClone for T
where
    T: 'static + FilterValue + Clone,
{
    fn clone_box(&self) -> Box<FilterValue> {
        Box::new(self.clone())
    }
}

impl Clone for Box<FilterValue> {
    fn clone(&self) -> Box<FilterValue> {
        self.clone_box()
    }
}

/// Function signature that can act as a `FilterValue`.
pub type FnFilterValue = fn(&Value, &[Value]) -> FilterResult;

#[derive(Clone)]
struct FnValueFilter {
    filter: FnFilterValue,
}

impl FnValueFilter {
    fn new(filter: FnFilterValue) -> Self {
        Self { filter }
    }
}

impl FilterValue for FnValueFilter {
    fn filter(&self, input: &Value, arguments: &[Value]) -> FilterResult {
        (self.filter)(input, arguments)
    }
}

impl Debug for FnValueFilter {
    #[inline]
    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        writeln!(formatter, "fn filter")
    }
}

#[derive(Clone, Debug)]
enum EnumValueFilter {
    Fun(FnValueFilter),
    Heap(Box<FilterValue>),
}

/// Custom `Box<FilterValue>` with a `FnFilterValue` optimization.
#[derive(Clone, Debug)]
pub struct BoxedValueFilter {
    filter: EnumValueFilter,
}

impl FilterValue for BoxedValueFilter {
    fn filter(&self, input: &Value, arguments: &[Value]) -> FilterResult {
        match self.filter {
            EnumValueFilter::Fun(ref f) => f.filter(input, arguments),
            EnumValueFilter::Heap(ref f) => f.filter(input, arguments),
        }
    }
}

impl From<fn(&Value, &[Value]) -> FilterResult> for BoxedValueFilter {
    fn from(filter: FnFilterValue) -> BoxedValueFilter {
        let filter = EnumValueFilter::Fun(FnValueFilter::new(filter));
        Self { filter }
    }
}

impl From<Box<FilterValue>> for BoxedValueFilter {
    fn from(filter: Box<FilterValue>) -> BoxedValueFilter {
        let filter = EnumValueFilter::Heap(filter);
        Self { filter }
    }
}