use crate::registry::Registry;
use crate::{registry, Context, ContextSelectionSet, QueryError, Result, ID};
use graphql_parser::query::{Field, Value};
use std::borrow::Cow;
use std::future::Future;
use std::pin::Pin;

/// 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())
    }

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

    /// Returns a `GlobalID` that is unique among all types.
    fn global_id(id: ID) -> ID {
        base64::encode(format!("{}:{}", Self::type_name(), id)).into()
    }

    /// Parse `GlobalID`.
    fn from_global_id(id: ID) -> Result<ID> {
        let v: Vec<&str> = id.splitn(2, ':').collect();
        if v.len() != 2 {
            return Err(QueryError::InvalidGlobalID.into());
        }
        if v[0] != Self::type_name() {
            return Err(QueryError::InvalidGlobalIDType {
                expect: Self::type_name().to_string(),
                actual: v[0].to_string(),
            }
            .into());
        }
        Ok(v[1].to_string().into())
    }
}

/// Represents a GraphQL input value
pub trait InputValueType: Type + Sized {
    /// Parse from `Value`
    fn parse(value: &Value) -> Option<Self>;
}

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

#[allow(missing_docs)]
pub type BoxFieldFuture<'a> =
    Pin<Box<dyn Future<Output = Result<(String, serde_json::Value)>> + 'a + Send>>;

/// Represents a GraphQL object
#[async_trait::async_trait]
pub trait ObjectType: OutputValueType {
    /// This function returns true of type `EmptyMutation` only
    #[doc(hidden)]
    fn is_empty() -> bool {
        false
    }

    /// Resolves a field value and outputs it as a json value `serde_json::Value`.
    async fn resolve_field(&self, ctx: &Context<'_>, field: &Field) -> Result<serde_json::Value>;

    /// Collect the fields with the `name` inline object
    fn collect_inline_fields<'a>(
        &'a self,
        name: &str,
        _ctx: ContextSelectionSet<'a>,
        _futures: &mut Vec<BoxFieldFuture<'a>>,
    ) -> Result<()> {
        anyhow::bail!(QueryError::UnrecognizedInlineFragment {
            object: Self::type_name().to_string(),
            name: name.to_string(),
        });
    }
}

/// Represents a GraphQL input object
pub trait InputObjectType: InputValueType {}

/// Represents a GraphQL scalar
///
/// You can implement the trait to create a custom scalar.
///
/// # Examples
///
/// ```rust
/// use async_graphql::*;
///
/// struct MyInt(i32);
///
/// impl Scalar for MyInt {
///     fn type_name() -> &'static str {
///         "MyInt"
///     }
///
///     fn parse(value: &Value) -> Option<Self> {
///         if let Value::Int(n) = value {
///             Some(MyInt(n.as_i64().unwrap() as i32))
///         } else {
///             None
///         }
///     }
///
///     fn to_json(&self) -> Result<serde_json::Value> {
///         Ok(self.0.into())
///     }
/// }
///
/// impl_scalar!(MyInt); // // Don't forget this one
/// ```
pub trait Scalar: Sized + Send {
    /// The type name of a scalar.
    fn type_name() -> &'static str;

    /// The description of a scalar.
    fn description() -> Option<&'static str> {
        None
    }

    /// Parse a scalar value, return `Some(Self)` if successful, otherwise return `None`.
    fn parse(value: &Value) -> Option<Self>;

    /// Checks for a valid scalar value.
    ///
    /// The default implementation is to try to parse it, and in some cases you can implement this on your own to improve performance.
    fn is_valid(value: &Value) -> bool {
        Self::parse(value).is_some()
    }

    /// Convert the scalar value to json value.
    fn to_json(&self) -> Result<serde_json::Value>;
}

#[macro_export]
#[doc(hidden)]
macro_rules! impl_scalar_internal {
    ($ty:ty) => {
        impl crate::Type for $ty {
            fn type_name() -> std::borrow::Cow<'static, str> {
                std::borrow::Cow::Borrowed(<$ty as crate::Scalar>::type_name())
            }

            fn create_type_info(registry: &mut crate::registry::Registry) -> String {
                registry.create_type::<$ty, _>(|_| crate::registry::Type::Scalar {
                    name: <$ty as crate::Scalar>::type_name().to_string(),
                    description: <$ty>::description(),
                    is_valid: |value| <$ty as crate::Scalar>::is_valid(value),
                })
            }
        }

        impl crate::InputValueType for $ty {
            fn parse(value: &crate::Value) -> Option<Self> {
                <$ty as crate::Scalar>::parse(value)
            }
        }

        #[allow(clippy::ptr_arg)]
        #[async_trait::async_trait]
        impl crate::OutputValueType for $ty {
            async fn resolve(
                value: &Self,
                _: &crate::ContextSelectionSet<'_>,
            ) -> crate::Result<serde_json::Value> {
                value.to_json()
            }
        }
    };
}

/// After implementing the `Scalar` trait, you must call this macro to implement some additional traits.
#[macro_export]
macro_rules! impl_scalar {
    ($ty:ty) => {
        impl async_graphql::Type for $ty {
            fn type_name() -> std::borrow::Cow<'static, str> {
                std::borrow::Cow::Borrowed(<$ty as async_graphql::Scalar>::type_name())
            }

            fn create_type_info(registry: &mut async_graphql::registry::Registry) -> String {
                registry.create_type::<$ty, _>(|_| async_graphql::registry::Type::Scalar {
                    name: <$ty as async_graphql::Scalar>::type_name().to_string(),
                    description: <$ty>::description(),
                    is_valid: |value| <$ty as async_graphql::Scalar>::is_valid(value),
                })
            }
        }

        impl async_graphql::InputValueType for $ty {
            fn parse(value: &async_graphql::Value) -> Option<Self> {
                <$ty as async_graphql::Scalar>::parse(value)
            }
        }

        #[allow(clippy::ptr_arg)]
        #[async_graphql::async_trait::async_trait]
        impl async_graphql::OutputValueType for $ty {
            async fn resolve(
                value: &Self,
                _: &async_graphql::ContextSelectionSet<'_>,
            ) -> async_graphql::Result<serde_json::Value> {
                value.to_json()
            }
        }
    };
}

impl<T: Type + Send + Sync> 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> OutputValueType for &T {
    #[allow(clippy::trivially_copy_pass_by_ref)]
    async fn resolve(value: &Self, ctx: &ContextSelectionSet<'_>) -> Result<serde_json::Value> {
        T::resolve(*value, ctx).await
    }
}