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use std::borrow::Cow;

use crate::parser::types::Field;
use crate::registry::Registry;
use crate::{
    registry, ContainerType, ContextSelectionSet, InputValueResult, Positioned, Result,
    ServerResult, Value,
};

#[doc(hidden)]
pub trait Description {
    fn description() -> &'static str;
}

/// Represents a GraphQL type.
///
/// All GraphQL types implement this trait, such as `Scalar`, `Object`, `Union` ...
pub trait Type {
    /// Type the name.
    fn type_name() -> Cow<'static, str>;

    /// Qualified typename.
    fn qualified_type_name() -> String {
        format!("{}!", Self::type_name())
    }

    /// Introspection type name
    ///
    /// Is the return value of field `__typename`, the interface and union should return the current type, and the others return `Type::type_name`.
    fn introspection_type_name(&self) -> Cow<'static, str> {
        Self::type_name()
    }

    /// Create type information in the registry and return qualified typename.
    fn create_type_info(registry: &mut registry::Registry) -> String;
}

/// Represents a GraphQL input value.
pub trait InputValueType: Type + Sized {
    /// Parse from `Value`. None represents undefined.
    fn parse(value: Option<Value>) -> InputValueResult<Self>;

    /// Convert to a `Value` for introspection.
    fn to_value(&self) -> Value;
}

/// Represents a GraphQL output value.
#[async_trait::async_trait]
pub trait OutputValueType: Type {
    /// Resolve an output value to `async_graphql::Value`.
    async fn resolve(
        &self,
        ctx: &ContextSelectionSet<'_>,
        field: &Positioned<Field>,
    ) -> ServerResult<Value>;
}

impl<T: Type + Send + Sync + ?Sized> Type for &T {
    fn type_name() -> Cow<'static, str> {
        T::type_name()
    }

    fn create_type_info(registry: &mut Registry) -> String {
        T::create_type_info(registry)
    }
}

#[async_trait::async_trait]
impl<T: OutputValueType + Send + Sync + ?Sized> OutputValueType for &T {
    #[allow(clippy::trivially_copy_pass_by_ref)]
    async fn resolve(
        &self,
        ctx: &ContextSelectionSet<'_>,
        field: &Positioned<Field>,
    ) -> ServerResult<Value> {
        T::resolve(*self, ctx, field).await
    }
}

impl<T: Type> Type for Result<T> {
    fn type_name() -> Cow<'static, str> {
        T::type_name()
    }

    fn qualified_type_name() -> String {
        T::qualified_type_name()
    }

    fn create_type_info(registry: &mut registry::Registry) -> String {
        T::create_type_info(registry)
    }
}

#[async_trait::async_trait]
impl<T: OutputValueType + Sync> OutputValueType for Result<T> {
    async fn resolve(
        &self,
        ctx: &ContextSelectionSet<'_>,
        field: &Positioned<Field>,
    ) -> ServerResult<Value> {
        match self {
            Ok(value) => Ok(value.resolve(ctx, field).await?),
            Err(err) => Err(err.clone().into_server_error().at(field.pos)),
        }
    }
}

/// A GraphQL object.
pub trait ObjectType: ContainerType {}

#[async_trait::async_trait]
impl<T: ObjectType + Send + Sync> ObjectType for &T {}

/// A GraphQL interface.
pub trait InterfaceType: ContainerType {}

/// A GraphQL interface.
pub trait UnionType: ContainerType {}

/// A GraphQL input object.
pub trait InputObjectType: InputValueType {}