use chrono::{DateTime, Utc};
use http::header::{HeaderMap, HeaderName, HeaderValue, InvalidHeaderValue, AUTHORIZATION};

use crate::{
    ALGORITHM_FIELD, ALGORITHM_VALUE, CREATED_FIELD, EXPIRES_FIELD, HEADERS_FIELD, KEY_ID_FIELD,
    SIGNATURE_FIELD,
};

const SIGNATURE_HEADER: &'static str = "Signature";

pub struct Signed {
    signature: String,
    sig_headers: Vec<String>,
    created: DateTime<Utc>,
    expires: DateTime<Utc>,
    key_id: String,
}

pub struct Unsigned {
    pub(crate) signing_string: String,
    pub(crate) sig_headers: Vec<String>,
    pub(crate) created: DateTime<Utc>,
    pub(crate) expires: DateTime<Utc>,
}

impl Signed {
    pub fn signature_header(self, hm: &mut HeaderMap) -> Result<(), InvalidHeaderValue> {
        hm.insert(
            AUTHORIZATION,
            HeaderValue::from_str(&format!("Signature {}", self.into_header()))?,
        );
        Ok(())
    }

    pub fn authorization_header(self, hm: &mut HeaderMap) -> Result<(), InvalidHeaderValue> {
        hm.insert(
            HeaderName::from_static(SIGNATURE_HEADER),
            HeaderValue::from_str(&self.into_header())?,
        );
        Ok(())
    }

    fn into_header(self) -> String {
        let header_parts = [
            (KEY_ID_FIELD, self.key_id),
            (ALGORITHM_FIELD, ALGORITHM_VALUE.to_owned()),
            (CREATED_FIELD, self.created.timestamp().to_string()),
            (EXPIRES_FIELD, self.expires.timestamp().to_string()),
            (HEADERS_FIELD, self.sig_headers.join(" ")),
            (SIGNATURE_FIELD, self.signature),
        ];

        header_parts
            .iter()
            .map(|(k, v)| format!("{}=\"{}\"", k, v))
            .collect::<Vec<_>>()
            .join(",")
    }
}

impl Unsigned {
    pub fn sign<F, E>(self, key_id: String, f: F) -> Result<Signed, E>
    where
        F: FnOnce(&str) -> Result<Vec<u8>, E>,
    {
        (f)(&self.signing_string).map(|v| Signed {
            signature: base64::encode(&v),
            sig_headers: self.sig_headers,
            created: self.created,
            expires: self.expires,
            key_id,
        })
    }
}