use std::{any::Any, convert::Infallible};

use thiserror::Error;

use crate::{header::HeaderMap, status::StatusCodeError, Body, Extensions, StatusCode, Version};

/// Represents an HTTP response
///
/// An HTTP response consists of a head and a potentially optional body. The body
/// component is generic, enabling arbitrary types to represent the HTTP body.
/// For example, the body could be `Vec<u8>`, a `Stream` of byte chunks, or a
/// value that has been deserialized.
///
/// Typically you'll work with responses on the client side as the result of
/// sending a `Request` and on the server you'll be generating a `Response` to
/// send back to the client.
///
/// # Examples
///
/// Creating a `Response` to return
///
/// ```
/// use axol_http::{Request, Response, StatusCode};
///
/// fn respond_to(req: Request<()>) -> axol_http::Result<Response<()>> {
///     let mut builder = Response::builder()
///         .header("Foo", "Bar")
///         .status(StatusCode::OK);
///
///     if req.headers().contains_key("Another-Header") {
///         builder = builder.header("Another-Header", "Ack");
///     }
///
///     builder.body(())
/// }
/// ```
///
/// A simple 404 handler
///
/// ```
/// use axol_http::{Request, Response, StatusCode};
///
/// fn not_found(_req: Request<()>) -> axol_http::Result<Response<()>> {
///     Response::builder()
///         .status(StatusCode::NOT_FOUND)
///         .body(())
/// }
/// ```
///
/// Or otherwise inspecting the result of a request:
///
/// ```no_run
/// use axol_http::{Request, Response};
///
/// fn get(url: &str) -> axol_http::Result<Response<()>> {
///     // ...
/// # panic!()
/// }
///
/// let response = get("https://www.rust-lang.org/").unwrap();
///
/// if !response.status().is_success() {
///     panic!("failed to get a successful response status!");
/// }
///
/// if let Some(date) = response.headers().get("Date") {
///     // we've got a `Date` header!
/// }
///
/// let body = response.body();
/// // ...
/// ```
///
/// Deserialize a response of bytes via json:
///
/// ```
/// # extern crate serde;
/// # extern crate serde_json;
/// # extern crate http;
/// use axol_http::Response;
/// use serde::de;
///
/// fn deserialize<T>(res: Response<Vec<u8>>) -> serde_json::Result<Response<T>>
///     where for<'de> T: de::Deserialize<'de>,
/// {
///     let (parts, body) = res.into_parts();
///     let body = serde_json::from_slice(&body)?;
///     Ok(Response::from_parts(parts, body))
/// }
/// #
/// # fn main() {}
/// ```
///
/// Or alternatively, serialize the body of a response to json
///
/// ```
/// # extern crate serde;
/// # extern crate serde_json;
/// # extern crate http;
/// use axol_http::Response;
/// use serde::ser;
///
/// fn serialize<T>(res: Response<T>) -> serde_json::Result<Response<Vec<u8>>>
///     where T: ser::Serialize,
/// {
///     let (parts, body) = res.into_parts();
///     let body = serde_json::to_vec(&body)?;
///     Ok(Response::from_parts(parts, body))
/// }
/// #
/// # fn main() {}
/// ```
#[derive(Debug, Default)]
pub struct Response {
    /// The response's status
    pub status: StatusCode,

    /// The response's version
    pub version: Version,

    /// The response's headers
    pub headers: HeaderMap,

    /// The response's extensions
    pub extensions: Extensions,

    /// The response's body
    pub body: Body,
}

/// Component parts of an HTTP `Response`
///
/// The HTTP response head consists of a status, version, and a set of
/// header fields.
#[derive(Debug, Default)]
pub struct ResponseParts {
    /// The response's status
    pub status: StatusCode,

    /// The response's version
    pub version: Version,

    /// The response's headers
    pub headers: HeaderMap,

    /// The response's extensions
    pub extensions: Extensions,
}

impl ResponseParts {
    pub fn as_ref(&mut self) -> ResponsePartsRef<'_> {
        ResponsePartsRef {
            status: &mut self.status,
            version: &mut self.version,
            headers: &mut self.headers,
            extensions: &mut self.extensions,
        }
    }
}

impl Response {
    pub fn parts_mut(&mut self) -> ResponsePartsRef<'_> {
        ResponsePartsRef {
            status: &mut self.status,
            version: &mut self.version,
            headers: &mut self.headers,
            extensions: &mut self.extensions,
        }
    }
}

#[derive(Debug)]
pub struct ResponsePartsRef<'a> {
    /// The response's status
    pub status: &'a mut StatusCode,

    /// The response's version
    pub version: &'a mut Version,

    /// The response's headers
    pub headers: &'a mut HeaderMap,

    /// The response's extensions
    pub extensions: &'a mut Extensions,
}

impl ResponseParts {
    /// Creates a new default instance of `ResponseParts`
    pub fn new() -> ResponseParts {
        Default::default()
    }
}

#[derive(Error, Debug)]
pub enum ResponseBuilderError {
    #[error("")]
    Infallible(#[from] Infallible),
    #[error("status code error: {0}")]
    StatusCode(#[from] StatusCodeError),
    // #[error("http error: {0}")]
    // Http(#[from] HttpError),
}

/// An HTTP response builder
///
/// This type can be used to construct an instance of `Response` through a
/// builder-like pattern.
#[derive(Debug)]
pub struct Builder {
    inner: Result<Response, ResponseBuilderError>,
}

impl Response {
    /// Creates a new builder-style object to manufacture a `Response`
    ///
    /// This method returns an instance of `Builder` which can be used to
    /// create a `Response`.
    ///
    /// # Examples
    ///
    /// ```
    /// # use axol_http::*;
    /// let response = Response::builder()
    ///     .status(200)
    ///     .header("X-Custom-Foo", "Bar")
    ///     .body(())
    ///     .unwrap();
    /// ```
    pub fn builder() -> Builder {
        Builder::new()
    }

    /// Creates a new blank `Response` with the body
    ///
    /// The component ports of this response will be set to their default, e.g.
    /// the ok status, no headers, etc.
    ///
    /// # Examples
    ///
    /// ```
    /// # use axol_http::*;
    /// let response = Response::new("hello world");
    ///
    /// assert_eq!(response.status(), StatusCode::OK);
    /// assert_eq!(*response.body(), "hello world");
    /// ```
    pub fn new(body: impl Into<Body>) -> Response {
        Self::from_parts(Default::default(), body)
    }

    /// Creates a new `Response` with the given head and body
    ///
    /// # Examples
    ///
    /// ```
    /// # use axol_http::*;
    /// let response = Response::new("hello world");
    /// let (mut parts, body) = response.into_parts();
    ///
    /// parts.status = StatusCode::BAD_REQUEST;
    /// let response = Response::from_parts(parts, body);
    ///
    /// assert_eq!(response.status(), StatusCode::BAD_REQUEST);
    /// assert_eq!(*response.body(), "hello world");
    /// ```
    pub fn from_parts(parts: ResponseParts, body: impl Into<Body>) -> Response {
        Response {
            status: parts.status,
            version: parts.version,
            headers: parts.headers,
            extensions: parts.extensions,
            body: body.into(),
        }
    }

    /// Consumes the response returning the head and body parts.
    ///
    /// # Examples
    ///
    /// ```
    /// # use axol_http::*;
    /// let response: Response<()> = Response::default();
    /// let (parts, body) = response.into_parts();
    /// assert_eq!(parts.status, StatusCode::OK);
    /// ```
    pub fn into_parts(self) -> (ResponseParts, Body) {
        (
            ResponseParts {
                status: self.status,
                version: self.version,
                headers: self.headers,
                extensions: self.extensions,
            },
            self.body,
        )
    }

    /// Sets status code of response
    pub fn with_status(mut self, status: StatusCode) -> Self {
        self.status = status;
        self
    }
}

impl Builder {
    /// Creates a new default instance of `Builder` to construct either a
    /// `Head` or a `Response`.
    ///
    /// # Examples
    ///
    /// ```
    /// # use axol_http::*;
    ///
    /// let response = response::Builder::new()
    ///     .status(200)
    ///     .body(())
    ///     .unwrap();
    /// ```
    pub fn new() -> Builder {
        Builder::default()
    }

    /// Set the HTTP status for this response.
    ///
    /// This function will configure the HTTP status code of the `Response` that
    /// will be returned from `Builder::build`.
    ///
    /// By default this is `200`.
    ///
    /// # Examples
    ///
    /// ```
    /// # use axol_http::*;
    ///
    /// let response = Response::builder()
    ///     .status(200)
    ///     .body(())
    ///     .unwrap();
    /// ```
    pub fn status<T>(self, status: T) -> Builder
    where
        StatusCode: TryFrom<T>,
        <StatusCode as TryFrom<T>>::Error: Into<StatusCodeError>,
    {
        self.and_then(move |mut head| {
            head.status = TryFrom::try_from(status).map_err(Into::into)?;
            Ok(head)
        })
    }

    /// Set the HTTP version for this response.
    ///
    /// This function will configure the HTTP version of the `Response` that
    /// will be returned from `Builder::build`.
    ///
    /// By default this is HTTP/1.1
    ///
    /// # Examples
    ///
    /// ```
    /// # use axol_http::*;
    ///
    /// let response = Response::builder()
    ///     .version(Version::HTTP_2)
    ///     .body(())
    ///     .unwrap();
    /// ```
    pub fn version(self, version: Version) -> Builder {
        self.and_then(move |mut head| {
            head.version = version;
            Ok(head)
        })
    }

    /// Appends a header to this response builder.
    ///
    /// This function will append the provided key/value as a header to the
    /// internal `HeaderMap` being constructed. Essentially this is equivalent
    /// to calling `HeaderMap::append`.
    ///
    /// # Examples
    ///
    /// ```
    /// # use axol_http::*;
    /// # use axol_http::header::HeaderValue;
    ///
    /// let response = Response::builder()
    ///     .header("Content-Type", "text/html")
    ///     .header("X-Custom-Foo", "bar")
    ///     .header("content-length", 0)
    ///     .body(())
    ///     .unwrap();
    /// ```
    pub fn header(self, name: impl AsRef<str>, value: impl Into<String>) -> Builder {
        self.and_then(move |mut head| {
            head.headers.insert(name, value);
            Ok(head)
        })
    }

    /// Get header on this response builder.
    ///
    /// When builder has error returns None.
    ///
    /// # Example
    ///
    /// ```
    /// # use axol_http::Response;
    /// # use axol_http::header::HeaderValue;
    /// let res = Response::builder()
    ///     .header("Accept", "text/html")
    ///     .header("X-Custom-Foo", "bar");
    /// let headers = res.headers_ref().unwrap();
    /// assert_eq!( headers["Accept"], "text/html" );
    /// assert_eq!( headers["X-Custom-Foo"], "bar" );
    /// ```
    pub fn headers_ref(&self) -> Option<&HeaderMap> {
        self.inner.as_ref().ok().map(|h| &h.headers)
    }

    /// Get header on this response builder.
    /// when builder has error returns None
    ///
    /// # Example
    ///
    /// ```
    /// # use axol_http::*;
    /// # use axol_http::header::HeaderValue;
    /// # use axol_http::response::Builder;
    /// let mut res = Response::builder();
    /// {
    ///   let headers = res.headers_mut().unwrap();
    ///   headers.insert("Accept", HeaderValue::from_static("text/html"));
    ///   headers.insert("X-Custom-Foo", HeaderValue::from_static("bar"));
    /// }
    /// let headers = res.headers_ref().unwrap();
    /// assert_eq!( headers["Accept"], "text/html" );
    /// assert_eq!( headers["X-Custom-Foo"], "bar" );
    /// ```
    pub fn headers_mut(&mut self) -> Option<&mut HeaderMap> {
        self.inner.as_mut().ok().map(|h| &mut h.headers)
    }

    /// Adds an extension to this builder
    ///
    /// # Examples
    ///
    /// ```
    /// # use axol_http::*;
    ///
    /// let response = Response::builder()
    ///     .extension("My Extension")
    ///     .body(())
    ///     .unwrap();
    ///
    /// assert_eq!(response.extensions().get::<&'static str>(),
    ///            Some(&"My Extension"));
    /// ```
    pub fn extension<T>(self, extension: T) -> Builder
    where
        T: Any + Send + Sync + 'static,
    {
        self.and_then(move |head| {
            head.extensions.insert(extension);
            Ok(head)
        })
    }

    /// Get a reference to the extensions for this response builder.
    ///
    /// If the builder has an error, this returns `None`.
    ///
    /// # Example
    ///
    /// ```
    /// # use axol_http::Response;
    /// let res = Response::builder().extension("My Extension").extension(5u32);
    /// let extensions = res.extensions_ref().unwrap();
    /// assert_eq!(extensions.get::<&'static str>(), Some(&"My Extension"));
    /// assert_eq!(extensions.get::<u32>(), Some(&5u32));
    /// ```
    pub fn extensions_ref(&self) -> Option<&Extensions> {
        self.inner.as_ref().ok().map(|h| &h.extensions)
    }

    /// Get a mutable reference to the extensions for this response builder.
    ///
    /// If the builder has an error, this returns `None`.
    ///
    /// # Example
    ///
    /// ```
    /// # use axol_http::Response;
    /// let mut res = Response::builder().extension("My Extension");
    /// let mut extensions = res.extensions_mut().unwrap();
    /// assert_eq!(extensions.get::<&'static str>(), Some(&"My Extension"));
    /// extensions.insert(5u32);
    /// assert_eq!(extensions.get::<u32>(), Some(&5u32));
    /// ```
    pub fn extensions_mut(&mut self) -> Option<&mut Extensions> {
        self.inner.as_mut().ok().map(|h| &mut h.extensions)
    }

    /// "Consumes" this builder, using the provided `body` to return a
    /// constructed `Response`.
    ///
    /// # Errors
    ///
    /// This function may return an error if any previously configured argument
    /// failed to parse or get converted to the internal representation. For
    /// example if an invalid `head` was specified via `header("Foo",
    /// "Bar\r\n")` the error will be returned when this function is called
    /// rather than when `header` was called.
    ///
    /// # Examples
    ///
    /// ```
    /// # use axol_http::*;
    ///
    /// let response = Response::builder()
    ///     .body(())
    ///     .unwrap();
    /// ```
    pub fn body(self, body: impl Into<Body>) -> Result<Response, ResponseBuilderError> {
        self.inner.map(move |mut head| {
            head.body = body.into();
            head
        })
    }

    // private

    fn and_then<F>(self, func: F) -> Self
    where
        F: FnOnce(Response) -> Result<Response, ResponseBuilderError>,
    {
        Builder {
            inner: self.inner.and_then(func),
        }
    }
}

impl Default for Builder {
    fn default() -> Builder {
        Builder {
            inner: Ok(Default::default()),
        }
    }
}