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#![allow(clippy::used_underscore_binding)]

use derive_more::{Display, Error};
use std::any::{Any, TypeId};

#[cfg(feature = "rc")]
macro_rules! feature_unique {
    ({ $($common:tt)* }, { $($rc:tt)* }, { $($_arc:tt)* }) => {
        $($common)*
        $($rc)*
    };
}

#[cfg(feature = "arc")]
macro_rules! feature_unique {
    ({ $($common:tt)* }, { $($_rc:tt)* }, { $($arc:tt)* }) => {
        $($common)*
        $($arc)*
    };
}

feature_unique!(
    {
        /// A reference-counted pointer holding a service. The pointer type is
        /// determined by the feature flags passed to this crate.
        ///
        /// - **rc**: Pointer type is `Rc<T>`
        /// - **arc**: Pointer type is `Arc<T>`
    },
    {
        pub type Svc<T> = std::rc::Rc<T>;
    },
    {
        pub type Svc<T> = std::sync::Arc<T>;
    }
);

feature_unique!(
    {
        /// A reference-counted service pointer holding an instance of `dyn
        /// Any`.
    },
    {
        pub type DynSvc = Svc<dyn Any>;
    },
    {
        pub type DynSvc = Svc<dyn Any + Send + Sync>;
    }
);

feature_unique!(
    {
        /// Implemented automatically on types that are capable of being a
        /// service.
    },
    {
        pub trait Service: Any {}
        impl<T: ?Sized + Any> Service for T {}
    },
    {
        pub trait Service: Any + Send + Sync {}
        impl<T: ?Sized + Any + Send + Sync> Service for T {}
    }
);

/// A result from attempting to inject dependencies into a service and
/// construct an instance of it.
pub type InjectResult<T> = Result<T, InjectError>;

/// Type information about a service.
#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
pub struct ServiceInfo {
    id: TypeId,
    name: &'static str,
}

impl ServiceInfo {
    /// Creates a [`ServiceInfo`] for the given type.
    #[must_use]
    pub fn of<T: ?Sized + Any>() -> Self {
        ServiceInfo {
            id: TypeId::of::<T>(),
            name: std::any::type_name::<T>(),
        }
    }

    /// Gets the [`TypeId`] for this service.
    #[must_use]
    pub fn id(&self) -> TypeId {
        self.id
    }

    /// Gets the type name of this service.
    #[must_use]
    pub fn name(&self) -> &'static str {
        self.name
    }
}

/// An error that has occurred during creation of a service.
#[derive(Debug, Display, Error)]
#[display(fmt = "an error occurred during injection: {}")]
pub enum InjectError {
    /// Failed to find a provider for the requested type.
    #[display(fmt = "{} has no provider", "service_info.name()")]
    MissingProvider {
        /// The service that was requested.
        service_info: ServiceInfo,
    },

    /// A provider for a dependency of the requested service is missing.
    #[display(fmt = "{} is missing a dependency", "service_info.name()")]
    MissingDependency {
        /// The service that was requested.
        service_info: ServiceInfo,

        /// The dependency that is missing a provider.
        dependency_info: ServiceInfo,
    },

    /// A cycle was detected during activation of a service.
    #[display(
        fmt = "a cycle was detected during activation of {} [{}]",
        "service_info.name()",
        "fmt_cycle(cycle)"
    )]
    CycleDetected {
        /// The service that was requested.
        service_info: ServiceInfo,

        /// The chain of services that were requested during resolution of this
        /// service.
        cycle: Vec<ServiceInfo>,
    },

    /// The requested implementer is not valid for the requested service.
    #[display(
        fmt = "{} is not registered as an implementer of {}",
        "implementation.name()",
        "service_info.name()"
    )]
    InvalidImplementation {
        /// The service that was requested.
        service_info: ServiceInfo,

        /// The implementation that was requested for this service.
        implementation: ServiceInfo,
    },

    /// The registered provider returned the wrong service type.
    #[display(fmt = "the registered provider returned the wrong type")]
    InvalidProvider {
        /// The service that was requested.
        service_info: ServiceInfo,
    },

    /// The requested service has too many providers registered.
    #[display(
        fmt = "the requested service has {} providers registered (did you mean to request a Services<T> instead?)",
        providers
    )]
    MultipleProviders {
        /// The service that was requested.
        service_info: ServiceInfo,
        /// The number of providers registered for that service.
        providers: usize,
    },

    /// An unexpected error has occurred. This is usually caused by a bug in
    /// the library itself.
    #[display(
        fmt = "an unexpected error occurred (please report this): {}",
        _0
    )]
    InternalError(#[error(ignore)] String),
}

fn fmt_cycle(cycle: &[ServiceInfo]) -> String {
    let mut joined = String::new();
    for item in cycle.iter().rev() {
        if !joined.is_empty() {
            joined.push_str(" -> ");
        }
        joined.push_str(item.name());
    }
    joined
}