#[cfg(all(feature = "client", feature = "http1"))]

use bytes::BytesMut;

use http::header::HeaderValue;

#[cfg(all(feature = "http2", feature = "client"))]

use http::Method;

#[cfg(any(feature = "client", all(feature = "server", feature = "http2")))]

use http::{

    header::{ValueIter, CONTENT_LENGTH},

    HeaderMap,

};

#[cfg(feature = "http1")]

pub(super) fn connection_keep_alive(value: &HeaderValue) -> bool {

    connection_has(value, "keep-alive")

}

#[cfg(feature = "http1")]

pub(super) fn connection_close(value: &HeaderValue) -> bool {

    connection_has(value, "close")

}

#[cfg(feature = "http1")]

fn connection_has(value: &HeaderValue, needle: &str) -> bool {

    if let Ok(s) = value.to_str() {

        for val in s.split(',') {

            if val.trim().eq_ignore_ascii_case(needle) {

                return true;

            }

        }

    }

    false

}

#[cfg(all(feature = "http1", feature = "server"))]

pub(super) fn content_length_parse(value: &HeaderValue) -> Option<u64> {

    from_digits(value.as_bytes())

}

#[cfg(any(feature = "client", all(feature = "server", feature = "http2")))]

pub(super) fn content_length_parse_all(headers: &HeaderMap) -> Option<u64> {

    content_length_parse_all_values(headers.get_all(CONTENT_LENGTH).into_iter())

}

#[cfg(any(feature = "client", all(feature = "server", feature = "http2")))]

pub(super) fn content_length_parse_all_values(values: ValueIter<'_, HeaderValue>) -> Option<u64> {

    // If multiple Content-Length headers were sent, everything can still

    // be alright if they all contain the same value, and all parse

    // correctly. If not, then it's an error.

    let mut content_length: Option<u64> = None;

    for h in values {

        if let Ok(line) = h.to_str() {

            for v in line.split(',') {

                if let Some(n) = from_digits(v.trim().as_bytes()) {

                    if content_length.is_none() {

                        content_length = Some(n)

                    } else if content_length != Some(n) {

                        return None;

                    }

                } else {

                    return None;

                }

            }

        } else {

            return None;

        }

    }

    content_length

}

fn from_digits(bytes: &[u8]) -> Option<u64> {

    // cannot use FromStr for u64, since it allows a signed prefix

    let mut result = 0u64;

    const RADIX: u64 = 10;

    if bytes.is_empty() {

        return None;

    }

    for &b in bytes {

        // can't use char::to_digit, since we haven't verified these bytes

        // are utf-8.

        match b {

            b'0'..=b'9' => {

                result = result.checked_mul(RADIX)?;

                result = result.checked_add((b - b'0') as u64)?;

            }

            _ => {

                // not a DIGIT, get outta here!

                return None;

            }

        }

    }

    Some(result)

}

#[cfg(all(feature = "http2", feature = "client"))]

pub(super) fn method_has_defined_payload_semantics(method: &Method) -> bool {

    !matches!(

        *method,

        Method::GET | Method::HEAD | Method::DELETE | Method::CONNECT

    )

}

#[cfg(feature = "http2")]

pub(super) fn set_content_length_if_missing(headers: &mut HeaderMap, len: u64) {

    headers

        .entry(CONTENT_LENGTH)

        .or_insert_with(|| HeaderValue::from(len));

}

#[cfg(all(feature = "client", feature = "http1"))]

pub(super) fn transfer_encoding_is_chunked(headers: &HeaderMap) -> bool {

    is_chunked(headers.get_all(http::header::TRANSFER_ENCODING).into_iter())

}

#[cfg(all(feature = "client", feature = "http1"))]

pub(super) fn is_chunked(mut encodings: ValueIter<'_, HeaderValue>) -> bool {

    // chunked must always be the last encoding, according to spec

    if let Some(line) = encodings.next_back() {

        return is_chunked_(line);

    }

    false

}

#[cfg(feature = "http1")]

pub(super) fn is_chunked_(value: &HeaderValue) -> bool {

    // chunked must always be the last encoding, according to spec

    if let Ok(s) = value.to_str() {

        if let Some(encoding) = s.rsplit(',').next() {

            return encoding.trim().eq_ignore_ascii_case("chunked");

        }

    }

    false

}

#[cfg(all(feature = "client", feature = "http1"))]

pub(super) fn add_chunked(mut entry: http::header::OccupiedEntry<'_, HeaderValue>) {

    const CHUNKED: &str = "chunked";

    if let Some(line) = entry.iter_mut().next_back() {

        // + 2 for ", "

        let new_cap = line.as_bytes().len() + CHUNKED.len() + 2;

        let mut buf = BytesMut::with_capacity(new_cap);

        buf.extend_from_slice(line.as_bytes());

        buf.extend_from_slice(b", ");

        buf.extend_from_slice(CHUNKED.as_bytes());

        *line = HeaderValue::from_maybe_shared(buf.freeze())

            .expect("original header value plus ascii is valid");

        return;

    }

    entry.insert(HeaderValue::from_static(CHUNKED));

}