//! A container representing a moment in ISO-8601 format Time
use std::{cmp::Ordering, fmt, str::FromStr};

mod error;
mod parser;
pub use {error::Error, parser::Parser};

#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};
use x509_parser::der_parser::ber::ber_read_element_header;

#[derive(Clone, Copy, Debug, PartialEq)]
#[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
pub enum Sign {
    Positive,
    Negative,
}

impl fmt::Display for Sign {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Positive => write!(f, "+"),
            Self::Negative => write!(f, "-"),
        }
    }
}

impl TryFrom<char> for Sign {
    type Error = Error;

    fn try_from(value: char) -> Result<Self, Self::Error> {
        match value {
            '+' => Ok(Self::Positive),
            '-' => Ok(Self::Negative),
            _ => Err(Error::InvalidOffset),
        }
    }
}

#[derive(Clone, Copy, Debug, PartialEq)]
#[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
pub struct Offset {
    pub sign: Sign,
    pub hours: u8,
    pub minutes: Option<u8>,
}

impl fmt::Display for Offset {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if let Some(m) = self.minutes {
            write!(f, "{}{:02}:{m:02}", self.sign, self.hours)
        } else {
            write!(f, "{}{:02}", self.sign, self.hours)
        }
    }
}

#[derive(Clone, Copy, Debug, PartialEq)]
#[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
pub enum TimeZone {
    UTC,
    Offset(Offset),
}

impl fmt::Display for TimeZone {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::UTC => write!(f, "Z"),
            Self::Offset(o) => write!(f, "{o}"),
        }
    }
}

#[derive(Clone, Copy, Debug, PartialEq)]
#[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
pub struct DateTime {
    pub year: u32,
    pub month: u8,
    pub day: u8,
    pub hour: Option<u8>,
    pub minute: Option<u8>,
    pub second: Option<u8>,
    pub tz: Option<TimeZone>,
}

impl fmt::Display for DateTime {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{:04}", self.year)?;
        'blk: {
            for field in &[self.month, self.day] {
                write!(f, "-{field:02}")?;
            }
            if let Some(h) = self.hour {
                write!(f, "T{h:02}")?;
            } else {
                break 'blk;
            }
            for field in &[self.minute, self.second] {
                if let Some(field) = field {
                    write!(f, ":{field:02}")?;
                } else {
                    break 'blk;
                }
            }
        }
        if let Some(ref tz) = self.tz {
            write!(f, "{tz}")
        } else {
            Ok(())
        }
    }
}

impl PartialOrd for DateTime {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        let a = self.normalize()?;
        let b = other.normalize()?;
        (a.year, a.month, a.day, a.hour, a.minute, a.second)
            .partial_cmp(&(b.year, b.month, b.day, b.hour, b.minute, b.second))
    }
}

impl FromStr for DateTime {
    type Err = Error;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Parser::new(s).parse()
    }
}

impl DateTime {
    pub fn normalize(&self) -> Option<Self> {
        if self.tz == Some(TimeZone::UTC) {
            Some(*self)
        } else {
            if let Some(TimeZone::Offset(tz)) = self.tz {
                let hour = if let Some(hour) = self.hour {
                    match tz.sign {
                        Sign::Positive => Some(hour + tz.hours),
                        Sign::Negative => Some(hour - tz.hours),
                    }
                } else {
                    None
                };
                let minute = 'blk: {
                    if let Some(minutes) = self.minute {
                        if let Some(o) = tz.minutes {
                            match tz.sign {
                                Sign::Positive => break 'blk Some(minutes + o),
                                Sign::Negative => break 'blk Some(minutes - o),
                            }
                        }
                    }
                    None
                };
                Some(DateTime {
                    hour,
                    minute,
                    ..*self
                })
            } else {
                None
            }
        }
    }
}

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

    #[test]
    fn fmt_full() {
        let dt = DateTime {
            year: 2023,
            month: 5,
            day: 7,
            hour: Some(9),
            minute: Some(3),
            second: Some(8),
            tz: Some(TimeZone::Offset(Offset {
                sign: Sign::Positive,
                hours: 5,
                minutes: Some(15),
            })),
        };
        assert_eq!(dt.to_string(), "2023-05-07T09:03:08+05:15");
    }

    #[test]
    fn fmt_partial_offset() {
        let dt = DateTime {
            year: 2023,
            month: 5,
            day: 7,
            hour: Some(9),
            minute: Some(3),
            second: Some(8),
            tz: Some(TimeZone::Offset(Offset {
                sign: Sign::Negative,
                hours: 5,
                minutes: None,
            })),
        };
        assert_eq!(dt.to_string(), "2023-05-07T09:03:08-05");
    }

    #[test]
    fn fmt_utc() {
        let dt = DateTime {
            year: 2023,
            month: 5,
            day: 7,
            hour: Some(9),
            minute: Some(3),
            second: Some(8),
            tz: Some(TimeZone::UTC),
        };
        assert_eq!(dt.to_string(), "2023-05-07T09:03:08Z");
    }

    #[test]
    fn fmt_no_tz() {
        let dt = DateTime {
            year: 2023,
            month: 5,
            day: 7,
            hour: Some(9),
            minute: Some(3),
            second: Some(8),
            tz: None,
        };
        assert_eq!(dt.to_string(), "2023-05-07T09:03:08");
    }

    #[test]
    fn fmt_no_seconds() {
        let dt = DateTime {
            year: 2023,
            month: 5,
            day: 7,
            hour: Some(9),
            minute: Some(3),
            second: None,
            tz: Some(TimeZone::UTC),
        };
        assert_eq!(dt.to_string(), "2023-05-07T09:03Z");
    }

    #[test]
    fn fmt_no_minutes() {
        let dt = DateTime {
            year: 2023,
            month: 5,
            day: 7,
            hour: Some(9),
            minute: None,
            second: Some(50),
            tz: Some(TimeZone::UTC),
        };
        assert_eq!(dt.to_string(), "2023-05-07T09Z");
    }

    #[test]
    fn fmt_no_time() {
        let dt = DateTime {
            year: 2023,
            month: 5,
            day: 7,
            hour: None,
            minute: None,
            second: Some(50),
            tz: Some(TimeZone::UTC),
        };
        assert_eq!(dt.to_string(), "2023-05-07Z");
    }

    #[test]
    fn ordering() {
        let mut dates = vec![
            "2023-06-10T10:01:52Z",
            "2023-06-10T08:01:52+05",
            "2023-06-10T11:30:30-05:15",
        ];
        dates.sort_by(|a, b| a.partial_cmp(b).unwrap());
        assert_eq!(
            dates,
            vec![
                "2023-06-10T08:01:52+05",
                "2023-06-10T10:01:52Z",
                "2023-06-10T11:30:30-05:15",
            ]
        )
    }
}