use gotham::{
	hyper::body::Bytes,
	mime::{Mime, APPLICATION_JSON}
};
#[cfg(feature = "openapi")]
use openapi_type::OpenapiType;
use serde::{de::DeserializeOwned, Serialize};
use std::error::Error;

#[cfg(not(feature = "openapi"))]
pub trait ResourceType {}

#[cfg(not(feature = "openapi"))]
impl<T> ResourceType for T {}

#[cfg(feature = "openapi")]
pub trait ResourceType: OpenapiType {}

#[cfg(feature = "openapi")]
impl<T: OpenapiType> ResourceType for T {}

/// A type that can be used inside a response body. Implemented for every type that is
/// serializable with serde. If the `openapi` feature is used, it must also be of type
/// [OpenapiType].
pub trait ResponseBody: ResourceType + Serialize {}

impl<T: ResourceType + Serialize> ResponseBody for T {}

/// This trait should be implemented for every type that can be built from an HTTP request body
/// plus its media type.
///
/// For most use cases it is sufficient to derive this trait, you usually don't need to manually
/// implement this. Therefore, make sure that the first variable of your struct can be built from
/// [Bytes], and the second one can be build from [Mime]. If you have any additional variables, they
/// need to be [Default]. This is an example of such a struct:
///
/// ```rust
/// # use gotham::mime::{self, Mime};
/// # use gotham_restful::{FromBody, RequestBody};
/// #[derive(FromBody, RequestBody)]
/// #[supported_types(mime::IMAGE_GIF, mime::IMAGE_JPEG, mime::IMAGE_PNG)]
/// struct RawImage {
/// 	content: Vec<u8>,
/// 	content_type: Mime
/// }
/// ```
pub trait FromBody: Sized {
	/// The error type returned by the conversion if it was unsuccessfull. When using the derive
	/// macro, there is no way to trigger an error, so [std::convert::Infallible] is used here.
	/// However, this might change in the future.
	type Err: Error;

	/// Perform the conversion.
	fn from_body(body: Bytes, content_type: Mime) -> Result<Self, Self::Err>;
}

impl<T: DeserializeOwned> FromBody for T {
	type Err = serde_json::Error;

	fn from_body(body: Bytes, _content_type: Mime) -> Result<Self, Self::Err> {
		serde_json::from_slice(&body)
	}
}

/// A type that can be used inside a request body. Implemented for every type that is deserializable
/// with serde. If the `openapi` feature is used, it must also be of type [OpenapiType].
///
/// If you want a non-deserializable type to be used as a request body, e.g. because you'd like to
/// get the raw data, you can derive it for your own type. All you need is to have a type implementing
/// [FromBody] and optionally a list of supported media types:
///
/// ```rust
/// # use gotham::mime::{self, Mime};
/// # use gotham_restful::{FromBody, RequestBody};
/// #[derive(FromBody, RequestBody)]
/// #[supported_types(mime::IMAGE_GIF, mime::IMAGE_JPEG, mime::IMAGE_PNG)]
/// struct RawImage {
/// 	content: Vec<u8>,
/// 	content_type: Mime
/// }
/// ```
pub trait RequestBody: ResourceType + FromBody {
	/// Return all types that are supported as content types. Use `None` if all types are supported.
	fn supported_types() -> Option<Vec<Mime>> {
		None
	}
}

impl<T: ResourceType + DeserializeOwned> RequestBody for T {
	fn supported_types() -> Option<Vec<Mime>> {
		Some(vec![APPLICATION_JSON])
	}
}
