use axum::http::{HeaderName, HeaderValue, Uri, header, request::Parts};
use itertools::Itertools;
use url::Url;

/// Fields from a "Forwarded" header per [RFC7239 sec 4](https://www.rfc-editor.org/rfc/rfc7239#section-4)
#[derive(Debug, Clone)]
pub struct ForwardedHeader {
    pub for_field: Vec<String>,
    pub by: Option<String>,
    pub host: Option<String>,
    pub proto: Option<String>,
}

impl ForwardedHeader {
    /// Return the 'for' headers as a list of [std::net::IpAddr]'s.
    pub fn for_as_ipaddr(self) -> Vec<std::net::IpAddr> {
        self.for_field
            .iter()
            .filter_map(|ip| {
                if ip.contains(']') {
                    // this is an IPv6 address, get what's between the []
                    ip.split(']')
                        .next()?
                        .split('[')
                        .next_back()?
                        .parse::<std::net::IpAddr>()
                        .ok()
                } else {
                    ip.parse::<std::net::IpAddr>().ok()
                }
            })
            .collect::<Vec<std::net::IpAddr>>()
    }
}

/// This parses the Forwarded header, and returns a list of the IPs in the
/// "for=" fields. Per [RFC7239 sec 4](https://www.rfc-editor.org/rfc/rfc7239#section-4)
impl TryFrom<HeaderValue> for ForwardedHeader {
    type Error = String;
    fn try_from(forwarded: HeaderValue) -> Result<ForwardedHeader, String> {
        ForwardedHeader::try_from(&forwarded)
    }
}

/// This parses the Forwarded header, and returns a list of the IPs in the
/// "for=" fields. Per [RFC7239 sec 4](https://www.rfc-editor.org/rfc/rfc7239#section-4)
impl TryFrom<&HeaderValue> for ForwardedHeader {
    type Error = String;
    fn try_from(forwarded: &HeaderValue) -> Result<ForwardedHeader, String> {
        let mut for_field: Vec<String> = Vec::new();
        let mut by: Option<String> = None;
        let mut host: Option<String> = None;
        let mut proto: Option<String> = None;
        // first get the k=v pairs
        forwarded
            .to_str()
            .map_err(|err| err.to_string())?
            .split(';')
            .for_each(|s| {
                let s = s.trim().to_lowercase();
                // The for value can look like this:
                // for=192.0.2.43, for=198.51.100.17
                // so we need to handle this case
                if s.starts_with("for=") || s.starts_with("for =") {
                    // we have a valid thing to grab
                    let chunks: Vec<String> = s
                        .split(',')
                        .filter_map(|chunk| {
                            chunk.trim().split('=').next_back().map(|c| c.to_string())
                        })
                        .collect::<Vec<String>>();
                    for_field.extend(chunks);
                } else if s.starts_with("by=") {
                    by = s.split('=').next_back().map(|c| c.to_string());
                } else if s.starts_with("host=") {
                    host = s.split('=').next_back().map(|c| c.to_string());
                } else if s.starts_with("proto=") {
                    proto = s.split('=').next_back().map(|c| c.to_string());
                } else {
                    // probably need to work out what to do here
                }
            });

        Ok(ForwardedHeader {
            for_field,
            by,
            host,
            proto,
        })
    }
}

#[derive(Clone, Debug)]
pub struct ForwardedRelatedInfo {
    pub forwarded: Option<ForwardedHeader>,
    pub x_forwarded_proto: Option<String>,
    pub x_forwarded_host: Option<String>,
    pub x_forwarded_for: Option<Vec<String>>,
    pub host: Option<String>,
    pub uri: Uri,
    pub origin: Option<String>,
}

impl ForwardedRelatedInfo {
    pub fn from_request_parts(request_parts: &Parts) -> ForwardedRelatedInfo {
        let headers = &request_parts.headers;
        let forwarded = headers
            .get(header::FORWARDED)
            .and_then(|s| ForwardedHeader::try_from(s.clone()).ok());

        let x_forwarded_proto = headers
            .get(HeaderName::from_static("x-forwarded-proto"))
            .and_then(|s| s.to_str().map(String::from).ok());

        let x_forwarded_host = headers
            .get(HeaderName::from_static("x-forwarded-host"))
            .and_then(|s| s.to_str().map(String::from).ok());

        let x_forwarded_for = headers
            .get(HeaderName::from_static("x-forwarded-for"))
            .and_then(|s| s.to_str().ok())
            .and_then(|s| {
                let l = s.split(",").map(|s| s.trim().to_string()).collect_vec();
                if l.is_empty() { None } else { Some(l) }
            });

        let host = headers
            .get(header::HOST)
            .and_then(|s| s.to_str().map(String::from).ok());

        let origin = headers
            .get(header::ORIGIN)
            .and_then(|s| s.to_str().map(String::from).ok());

        ForwardedRelatedInfo {
            host,
            x_forwarded_for,
            x_forwarded_host,
            x_forwarded_proto,
            forwarded,
            uri: request_parts.uri.clone(),
            origin,
        }
    }

    pub fn resolved_protocol(&self) -> Option<&str> {
        self.forwarded
            .as_ref()
            .and_then(|s| s.proto.as_deref())
            .or(self.x_forwarded_proto.as_deref())
            .or(self.uri.scheme_str())
    }

    pub fn resolved_host(&self) -> Option<&str> {
        self.forwarded
            .as_ref()
            .and_then(|s| s.host.as_deref())
            .or(self.x_forwarded_host.as_deref())
            .or(self.uri.host())
    }

    pub fn resolved_origin(&self) -> Option<Url> {
        if let (Some(protocol), Some(host)) = (self.resolved_protocol(), self.resolved_host()) {
            let origin = format!("{protocol}://{host}");
            Url::parse(&origin).ok()
        } else {
            None
        }
    }
}