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use crate::error::{Error, ErrorKind, ResultExt};
use crate::headers::{self, AsHeaders, HeaderName, HeaderValue};
use std::convert::From;
use std::fmt;
use std::str::FromStr;

#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub struct Range {
    pub start: u64,
    pub end: u64,
}

impl Range {
    pub fn new(start: u64, end: u64) -> Range {
        Range { start, end }
    }

    pub fn len(&self) -> u64 {
        self.end - self.start
    }

    pub fn is_empty(&self) -> bool {
        self.end == self.start
    }
}

impl AsHeaders for Range {
    type Iter = std::vec::IntoIter<(HeaderName, HeaderValue)>;

    fn as_headers(&self) -> Self::Iter {
        let mut headers = vec![(headers::MS_RANGE, format!("{self}").into())];
        if self.len() < 1024 * 1024 * 4 {
            headers.push((
                headers::RANGE_GET_CONTENT_CRC64,
                HeaderValue::from_static("true"),
            ));
        }
        headers.into_iter()
    }
}

impl From<std::ops::Range<u64>> for Range {
    fn from(r: std::ops::Range<u64>) -> Self {
        Self {
            start: r.start,
            end: r.end,
        }
    }
}

impl From<std::ops::Range<i32>> for Range {
    fn from(r: std::ops::Range<i32>) -> Self {
        Self {
            start: r.start as u64,
            end: r.end as u64,
        }
    }
}

impl From<std::ops::Range<usize>> for Range {
    fn from(r: std::ops::Range<usize>) -> Self {
        Self {
            start: r.start as u64,
            end: r.end as u64,
        }
    }
}

impl FromStr for Range {
    type Err = Error;
    fn from_str(s: &str) -> crate::Result<Range> {
        let v = s.split('/').collect::<Vec<&str>>();
        if v.len() != 2 {
            return Err(Error::with_message(ErrorKind::Other, || {
                format!(
                    "expected token \"{}\" not found when parsing Range from \"{}\"",
                    "/", s
                )
            }));
        }

        let cp_start = v[0].parse::<u64>().map_kind(ErrorKind::DataConversion)?;
        let cp_end = v[1].parse::<u64>().map_kind(ErrorKind::DataConversion)? + 1;

        Ok(Range {
            start: cp_start,
            end: cp_end,
        })
    }
}

impl fmt::Display for Range {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "bytes={}-{}", self.start, self.end - 1)
    }
}

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

    #[test]
    fn test_range_parse() {
        let range = "1000/2000".parse::<Range>().unwrap();

        assert_eq!(range.start, 1000);
        assert_eq!(range.end, 2001);
    }

    #[test]
    fn test_range_parse_panic_1() {
        "abba/2000".parse::<Range>().unwrap_err();
    }

    #[test]
    fn test_range_parse_panic_2() {
        "1000-2000".parse::<Range>().unwrap_err();
    }

    #[test]
    fn test_range_display() {
        let range = Range {
            start: 100,
            end: 501,
        };

        let txt = format!("{range}");

        assert_eq!(txt, "bytes=100-500");
    }
}