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use sha::{
    sha256::Sha256,
    sha512::Sha512,
    utils::{Digest, DigestExt},
};

use std::{
    fmt,
    collections::HashMap,
    io::Result as IoResult
};

use crate::Uri;

/// The SIP Authentication schema.
#[derive(Debug, PartialEq, Clone, Copy)]
pub enum AuthSchema {
    Digest,
}

impl fmt::Display for AuthSchema {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            AuthSchema::Digest => write!(f, "Digest"),
        }
    }
}

/// AuthHeader used for headers such as Authorization
/// or WWWAuthenticate.
#[derive(Debug, PartialEq, Clone)]
pub struct AuthHeader(pub AuthSchema, pub HashMap<String, String>);

impl fmt::Display for AuthHeader {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self.0)?;
        for (index, (key, value)) in self.1.iter().enumerate() {
            if index == 0 && key == &"qop".to_string() {
                write!(f, "{}={}", key, value)?;
            } else if index == 0 && key == &"auth".to_string() {
                write!(f, "{}={:08}", key, value)?;
            } else if index == 0 {
                write!(f, " {}=\"{}\"", key, value)?;
            } else if key == &"qop".to_string() {
                write!(f, ", {}={}", key, value)?;
            } else if key == &"auth".to_string() {
                write!(f, ", {}={:08}", key, value)?;
            } else {
                write!(f, ", {}=\"{}\"", key, value)?;
            }
        }
        Ok(())
    }
}

/// Context struct used when calculating the Auth Headers.
pub struct AuthContext<'a> {
    pub user: &'a str,
    pub pass: &'a str,
    pub nc: u32,
    pub uri: &'a Uri,
}

impl AuthHeader {

    /// Perform the authenticate action.
    pub fn authenticate<'a>(&self, ctx: AuthContext<'a>) -> IoResult<AuthHeader> {
        match self.0 {
            AuthSchema::Digest => self.handle_digest_auth(ctx),
        }
    }

    /// Perform the Digest auth method.
    fn handle_digest_auth<'a>(&self, ctx: AuthContext<'a>) -> IoResult<AuthHeader> {
        let qop = self
            .1
            .get("qop")
            .expect("Auth header does not contain a qop field");
        match qop.as_ref() {
            "auth" => self.handle_digest_qop_auth(ctx),
            qop => panic!("unknown auth qop: {}", qop),
        }
    }

    /// Decides witch authorization algorythm to use.
    fn handle_digest_qop_auth<'a>(&self, ctx: AuthContext<'a>) -> IoResult<AuthHeader> {
        let alg = self
            .1
            .get("algorithm")
            .map(|item| item.to_string())
            .unwrap_or_else(|| "md5".to_string());
        match alg.as_ref() {
            "md5" | "MD5" => self.handle_md5_digest_auth(ctx),
            "sha-256" | "SHA-256" => self.handle_sha256_digest_auth(ctx),
            "sha-512-256" | "SHA-512-256" => self.handle_sha512_digest_auth(ctx),
            alg => panic!("Unknown Auth alogirithm: {}", alg),
        }
    }

    /// Handle the MD5 digest auth method.
    fn handle_md5_digest_auth<'a>(&self, ctx: AuthContext<'a>) -> IoResult<AuthHeader> {
        let realm = self
            .1
            .get("realm")
            .expect("Auth header does not contain a realm");
        let nonce = self
            .1
            .get("nonce")
            .expect("Auth header does not contain a nonce");
        let mut map: HashMap<String, String> = HashMap::new();
        let cnonce = self.generate_cnonce();
        map.insert("username".into(), ctx.user.to_string());
        map.insert("nonce".into(), nonce.to_string());
        map.insert("realm".into(), realm.clone());
        map.insert("uri".into(), format!("{}", ctx.uri));
        map.insert("qop".into(), self.1.get("qop").unwrap().clone());
        map.insert("algorithm".into(), "MD5".into());
        map.insert("cnonce".into(), format!("{:x}", cnonce));
        map.insert("nc".into(), format!("{:08}", ctx.nc));
        let ha1 = md5::compute(&format!("{}:{}:{}", ctx.user, realm, ctx.pass));
        let ha2 = md5::compute(format!("REGISTER:{}", ctx.uri));
        let digest = format!(
            "{:x}:{}:{:08}:{:x}:auth:{:x}",
            ha1, nonce, ctx.nc, cnonce, ha2
        );
        let pass = md5::compute(digest);
        map.insert("response".into(), format!("{:x}", pass));
        Ok(AuthHeader(AuthSchema::Digest, map))
    }
 
    /// Handle sha256 Digest auth method.
    fn handle_sha256_digest_auth<'a>(&self, ctx: AuthContext<'a>) -> IoResult<AuthHeader> {
        let realm = self
            .1
            .get("realm")
            .expect("Auth header does not contain a realm");
        let nonce = self
            .1
            .get("nonce")
            .expect("Auth header does not contain a nonce");
        let opaque = self
            .1
            .get("opaque")
            .expect("Auth header does not contain a opaque");
        let mut map: HashMap<String, String> = HashMap::new();
        let cnonce = self.generate_cnonce();
        map.insert("username".into(), ctx.user.to_string());
        map.insert("nonce".into(), nonce.to_string());
        map.insert("realm".into(), realm.clone());
        map.insert("uri".into(), format!("{}", ctx.uri));
        map.insert("qop".into(), self.1.get("qop").unwrap().clone());
        map.insert("algorithm".into(), "SHA-512-256".into());
        map.insert("cnonce".into(), format!("{:x}", cnonce));
        map.insert("nc".into(), format!("{:08}", ctx.nc));
        map.insert("opaque".into(), opaque.into());
        let mut ha1_hasher = Sha256::default();
        let ha1 = ha1_hasher.digest(format!("{}:{}:{}", ctx.user, realm, ctx.pass).as_ref());
        let mut ha2_hasher = Sha256::default();
        let ha2 = ha2_hasher.digest(format!("REGISTER:{}", ctx.uri).as_ref());
        let digest = format!(
            "{}:{}:{:08}:{:x}:auth:{}",
            ha1.to_hex(),
            nonce,
            ctx.nc,
            cnonce,
            ha2.to_hex()
        );
        let pass = md5::compute(digest);
        map.insert("response".into(), format!("{:x}", pass));
        Ok(AuthHeader(AuthSchema::Digest, map))
    }

    /// Handle sha512 auth method.
    fn handle_sha512_digest_auth<'a>(&self, ctx: AuthContext<'a>) -> IoResult<AuthHeader> {
        let realm = self
            .1
            .get("realm")
            .expect("Auth header does not contain a realm");
        let nonce = self
            .1
            .get("nonce")
            .expect("Auth header does not contain a nonce");
        let opaque = self
            .1
            .get("opaque")
            .expect("Auth header does not contain a opaque");
        let mut map: HashMap<String, String> = HashMap::new();
        let cnonce = self.generate_cnonce();
        map.insert("username".into(), ctx.user.to_string());
        map.insert("nonce".into(), nonce.to_string());
        map.insert("realm".into(), realm.clone());
        map.insert("uri".into(), format!("{}", ctx.uri));
        map.insert("qop".into(), self.1.get("qop").unwrap().clone());
        map.insert("algorithm".into(), "SHA-512".into());
        map.insert("cnonce".into(), format!("{:x}", cnonce));
        map.insert("nc".into(), format!("{:08}", ctx.nc));
        map.insert("opaque".into(), opaque.into());
        let mut ha1_hasher = Sha512::default();
        let ha1 = ha1_hasher.digest(format!("{}:{}:{}", ctx.user, realm, ctx.pass).as_ref());
        let mut ha2_hasher = Sha512::default();
        let ha2 = ha2_hasher.digest(format!("REGISTER:{}", ctx.uri).as_ref());
        let digest = format!(
            "{}:{}:{:08}:{:x}:auth:{}",
            ha1.to_hex(),
            nonce,
            ctx.nc,
            cnonce,
            ha2.to_hex()
        );
        let pass = md5::compute(digest);
        map.insert("response".into(), format!("{:x}", pass));
        Ok(AuthHeader(AuthSchema::Digest, map))
    }

    /// Generate the nonce used during authorization.
    fn generate_cnonce(&self) -> md5::Digest {
        md5::compute(rand::random::<[u8; 16]>())
    }
}