use std::iter::FromIterator;

use http::{HeaderValue, Method};

use crate::util::FlatCsv;

/// `Allow` header, defined in [RFC7231](https://datatracker.ietf.org/doc/html/rfc7231#section-7.4.1)

///

/// The `Allow` header field lists the set of methods advertised as

/// supported by the target resource.  The purpose of this field is

/// strictly to inform the recipient of valid request methods associated

/// with the resource.

///

/// # ABNF

///

/// ```text

/// Allow = #method

/// ```

///

/// # Example values

/// * `GET, HEAD, PUT`

/// * `OPTIONS, GET, PUT, POST, DELETE, HEAD, TRACE, CONNECT, PATCH, fOObAr`

/// * ``

///

/// # Examples

///

/// ```

/// extern crate http;

/// use headers::Allow;

/// use http::Method;

///

/// let allow = vec![Method::GET, Method::POST]

///     .into_iter()

///     .collect::<Allow>();

/// ```

#[derive(Clone, Debug, PartialEq)]

pub struct Allow(FlatCsv);

derive_header! {

    Allow(_),

    name: ALLOW

}

impl Allow {

    /// Returns an iterator over `Method`s contained within.

    pub fn iter(&self) -> impl Iterator<Item = Method> + '_ {

        self.0.iter().filter_map(|s| s.parse().ok())

    }

}

impl FromIterator<Method> for Allow {

    fn from_iter<I>(iter: I) -> Self

    where

        I: IntoIterator<Item = Method>,

    {

        let flat = iter

            .into_iter()

            .map(|method| {

                method

                    .as_str()

                    .parse::<HeaderValue>()

                    .expect("Method is a valid HeaderValue")

            })

            .collect();

        Allow(flat)

    }

}