use std::fmt;
use std::str::FromStr;

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

/// # [4.4.3.6. EXT-X-I-FRAMES-ONLY]
/// The [ExtXIFramesOnly] tag indicates that each [Media Segment] in the
/// Playlist describes a single I-frame. I-frames are encoded video
/// frames, whose decoding does not depend on any other frame. I-frame
/// Playlists can be used for trick play, such as fast forward, rapid
/// reverse, and scrubbing.
///
/// Its format is:
/// ```text
/// #EXT-X-I-FRAMES-ONLY
/// ```
///
/// [Media Segment]: crate::MediaSegment
/// [4.4.3.6. EXT-X-I-FRAMES-ONLY]:
/// https://tools.ietf.org/html/draft-pantos-hls-rfc8216bis-04#section-4.4.3.6
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct ExtXIFramesOnly;

impl ExtXIFramesOnly {
    pub(crate) const PREFIX: &'static str = "#EXT-X-I-FRAMES-ONLY";
}

impl RequiredVersion for ExtXIFramesOnly {
    fn required_version(&self) -> ProtocolVersion {
        ProtocolVersion::V4
    }
}

impl fmt::Display for ExtXIFramesOnly {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        Self::PREFIX.fmt(f)
    }
}

impl FromStr for ExtXIFramesOnly {
    type Err = Error;

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

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_display() {
        assert_eq!(
            ExtXIFramesOnly.to_string(),
            "#EXT-X-I-FRAMES-ONLY".to_string(),
        )
    }

    #[test]
    fn test_parser() {
        assert_eq!(ExtXIFramesOnly, "#EXT-X-I-FRAMES-ONLY".parse().unwrap(),)
    }

    #[test]
    fn test_required_version() {
        assert_eq!(ExtXIFramesOnly.required_version(), ProtocolVersion::V4)
    }
}