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//! Contexts are elements that can be polled to verify wether their inner state is still considered
//! valid or not.

/// Trait for Contexts
pub trait ContractContext {
    /// Check wether the clauses are still met, true by default.
    fn poll_valid(&self) -> bool {
        true
    }
}

/// Kinds of ContextErrors
#[derive(Debug)]
pub enum ContextErrorKind {
    /// Context has expired for this current Contract
    ExpiredContext,
}

/// Error Type for Context Related Errors
#[derive(Debug)]
pub struct ContextError {
    kind: ContextErrorKind,
}

impl ContextError {
    /// Build a ContextError from a ContextErrorKind
    pub fn from(kind: ContextErrorKind) -> Self {
        Self { kind }
    }
}

impl std::fmt::Display for ContextError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        use ContextErrorKind::*;
        let error = match &self.kind {
            k @ ExpiredContext => {
                format!("{:?}: context is no longer available in this contract", k)
            }
        };
        write!(f, "{}", error)
    }
}

impl std::error::Error for ContextError {}

impl ContractContext for bool {
    fn poll_valid(&self) -> bool {
        *self
    }
}

impl ContractContext for () {}

impl ContractContext for u8 {}
impl ContractContext for u16 {}
impl ContractContext for u32 {}
impl ContractContext for u64 {}
impl ContractContext for u128 {}
impl ContractContext for usize {}

impl ContractContext for i8 {}
impl ContractContext for i16 {}
impl ContractContext for i32 {}
impl ContractContext for i64 {}
impl ContractContext for i128 {}
impl ContractContext for isize {}

/// Empty context to use if you want non-voidable contracts that produce no value.
#[derive(Copy, Clone)]
pub struct DefaultContext;

impl ContractContext for DefaultContext {}

impl Default for DefaultContext {
    fn default() -> Self {
        Self::new()
    }
}

impl DefaultContext {
    pub fn new() -> Self {
        Self
    }
}

/// Generic comparaison contexts
pub mod cmp {
    use super::ContractContext;

    /// Context to compare the equality of two elements
    pub struct EqContext<A, B>(pub A, pub B);

    impl<A, B> ContractContext for EqContext<A, B>
    where
        A: PartialEq<B>,
    {
        fn poll_valid(&self) -> bool {
            self.0 == self.1
        }
    }

    /// Context to compare the inequality of two elements
    pub struct NqContext<A, B>(pub A, pub B);

    impl<A, B> ContractContext for NqContext<A, B>
    where
        A: PartialEq<B>,
    {
        fn poll_valid(&self) -> bool {
            self.0 != self.1
        }
    }

    /// Context to compare the less than ordering of two elements
    pub struct LtContext<A>(pub A, pub A);

    impl<A> ContractContext for LtContext<A>
    where
        A: Ord,
    {
        fn poll_valid(&self) -> bool {
            self.0 < self.1
        }
    }

    /// Context to compare the less or equal ordering of two elements
    pub struct LeContext<A>(pub A, pub A);

    impl<A> ContractContext for LeContext<A>
    where
        A: Ord,
    {
        fn poll_valid(&self) -> bool {
            self.0 <= self.1
        }
    }

    /// Context to compare the greater than ordering of two elements
    pub struct GtContext<A>(pub A, pub A);

    impl<A> ContractContext for GtContext<A>
    where
        A: Ord,
    {
        fn poll_valid(&self) -> bool {
            self.0 > self.1
        }
    }

    /// Context to compare the greater or equal ordering of two elements
    pub struct GeContext<A>(pub A, pub A);

    impl<A> ContractContext for GeContext<A>
    where
        A: Ord,
    {
        fn poll_valid(&self) -> bool {
            self.0 > self.1
        }
    }
}