use std::fmt;
use std::ops::{Deref, DerefMut};
use std::str::FromStr;

use crate::types::{DecryptionKey, EncryptionMethod, ProtocolVersion, RequiredVersion};
use crate::utils::tag;
use crate::Error;

/// # [4.3.4.5. EXT-X-SESSION-KEY]
/// The [ExtXSessionKey] tag allows encryption keys from [Media Playlist]s
/// to be specified in a [Master Playlist]. This allows the client to
/// preload these keys without having to read the [Media Playlist]s
/// first.
///
/// Its format is:
/// ```text
/// #EXT-X-SESSION-KEY:<attribute-list>
/// ```
///
/// [Media Playlist]: crate::MediaPlaylist
/// [Master Playlist]: crate::MasterPlaylist
/// [4.3.4.5. EXT-X-SESSION-KEY]: https://tools.ietf.org/html/rfc8216#section-4.3.4.5
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct ExtXSessionKey(DecryptionKey);

impl ExtXSessionKey {
    pub(crate) const PREFIX: &'static str = "#EXT-X-SESSION-KEY:";

    /// Makes a new [ExtXSessionKey] tag.
    ///
    /// # Panic
    /// An [ExtXSessionKey] should only be used, if the segments of the stream are encrypted.
    /// Therefore this function will panic, if the `method` is [EncryptionMethod::None].
    ///
    /// # Example
    /// ```
    /// # use hls_m3u8::tags::ExtXSessionKey;
    /// use hls_m3u8::types::EncryptionMethod;
    ///
    /// let session_key = ExtXSessionKey::new(
    ///     EncryptionMethod::Aes128,
    ///     "https://www.example.com/"
    /// );
    /// ```
    pub fn new<T: ToString>(method: EncryptionMethod, uri: T) -> Self {
        if method == EncryptionMethod::None {
            panic!("The EncryptionMethod is not allowed to be None");
        }

        Self(DecryptionKey::new(method, uri))
    }
}

impl RequiredVersion for ExtXSessionKey {
    fn required_version(&self) -> ProtocolVersion {
        self.0.required_version()
    }
}

impl fmt::Display for ExtXSessionKey {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        if self.0.method == EncryptionMethod::None {
            return Err(fmt::Error);
        }
        write!(f, "{}{}", Self::PREFIX, self.0)
    }
}

impl FromStr for ExtXSessionKey {
    type Err = Error;

    fn from_str(input: &str) -> Result<Self, Self::Err> {
        let input = tag(input, Self::PREFIX)?;
        Ok(Self(input.parse()?))
    }
}

impl Deref for ExtXSessionKey {
    type Target = DecryptionKey;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl DerefMut for ExtXSessionKey {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

#[cfg(test)]
mod test {
    use super::*;
    use crate::types::{EncryptionMethod, KeyFormat};

    #[test]
    fn test_display() {
        let mut key = ExtXSessionKey::new(
            EncryptionMethod::Aes128,
            "https://www.example.com/hls-key/key.bin",
        );
        key.set_iv(Some([
            16, 239, 143, 117, 140, 165, 85, 17, 85, 132, 187, 91, 60, 104, 127, 82,
        ]));

        assert_eq!(
            key.to_string(),
            "#EXT-X-SESSION-KEY:METHOD=AES-128,\
             URI=\"https://www.example.com/hls-key/key.bin\",\
             IV=0x10ef8f758ca555115584bb5b3c687f52"
                .to_string()
        );
    }

    #[test]
    fn test_parser() {
        assert_eq!(
            r#"#EXT-X-SESSION-KEY:METHOD=AES-128,URI="https://priv.example.com/key.php?r=52""#
                .parse::<ExtXSessionKey>()
                .unwrap(),
            ExtXSessionKey::new(
                EncryptionMethod::Aes128,
                "https://priv.example.com/key.php?r=52"
            )
        );

        let mut key = ExtXSessionKey::new(
            EncryptionMethod::Aes128,
            "https://www.example.com/hls-key/key.bin",
        );
        key.set_iv(Some([
            16, 239, 143, 117, 140, 165, 85, 17, 85, 132, 187, 91, 60, 104, 127, 82,
        ]));

        assert_eq!(
            "#EXT-X-SESSION-KEY:METHOD=AES-128,\
             URI=\"https://www.example.com/hls-key/key.bin\",\
             IV=0X10ef8f758ca555115584bb5b3c687f52"
                .parse::<ExtXSessionKey>()
                .unwrap(),
            key
        );

        key.set_key_format(Some(KeyFormat::Identity));

        assert_eq!(
            "#EXT-X-SESSION-KEY:\
             METHOD=AES-128,\
             URI=\"https://www.example.com/hls-key/key.bin\",\
             IV=0x10ef8f758ca555115584bb5b3c687f52,\
             KEYFORMAT=\"identity\""
                .parse::<ExtXSessionKey>()
                .unwrap(),
            key
        )
    }

    #[test]
    fn test_required_version() {
        assert_eq!(
            ExtXSessionKey::new(EncryptionMethod::Aes128, "https://www.example.com/")
                .required_version(),
            ProtocolVersion::V1
        );
    }

    #[test]
    #[should_panic]
    // ExtXSessionKey::new should panic, if the provided
    // EncryptionMethod is None!
    fn test_new_panic() {
        ExtXSessionKey::new(EncryptionMethod::None, "");
    }

    #[test]
    #[should_panic]
    fn test_display_err() {
        ExtXSessionKey(DecryptionKey::new(EncryptionMethod::None, "")).to_string();
    }

    #[test]
    fn test_deref() {
        let key = ExtXSessionKey::new(EncryptionMethod::Aes128, "https://www.example.com/");

        assert_eq!(key.method(), EncryptionMethod::Aes128);
        assert_eq!(key.uri(), &Some("https://www.example.com/".into()));
    }

    #[test]
    fn test_deref_mut() {
        let mut key = ExtXSessionKey::new(EncryptionMethod::Aes128, "https://www.example.com/");

        key.set_method(EncryptionMethod::None);
        assert_eq!(key.method(), EncryptionMethod::None);
        key.set_uri(Some("https://www.github.com/"));
        assert_eq!(key.uri(), &Some("https://www.github.com/".into()));
    }
}