use crate::{Result, Tag};

use alloc::format;

#[cfg(not(feature = "std"))]

use alloc::string::ToString;

use core::fmt;

#[cfg(feature = "datetime")]

use time::OffsetDateTime;

#[derive(Clone, Copy, Debug, Eq, PartialEq, PartialOrd, Ord)]

pub enum ASN1TimeZone {

    /// No timezone provided

    Undefined,

    /// Coordinated universal time

    Z,

    /// Local zone, with offset to coordinated universal time

    ///

    /// `(offset_hour, offset_minute)`

    Offset(i8, i8),

}

#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]

pub struct ASN1DateTime {

    pub year: u32,

    pub month: u8,

    pub day: u8,

    pub hour: u8,

    pub minute: u8,

    pub second: u8,

    pub millisecond: Option<u16>,

    pub tz: ASN1TimeZone,

}

impl ASN1DateTime {

    #[allow(clippy::too_many_arguments)]

    pub const fn new(

        year: u32,

        month: u8,

        day: u8,

        hour: u8,

        minute: u8,

        second: u8,

        millisecond: Option<u16>,

        tz: ASN1TimeZone,

    ) -> Self {

        ASN1DateTime {

            year,

            month,

            day,

            hour,

            minute,

            second,

            millisecond,

            tz,

        }

    }

    #[cfg(feature = "datetime")]

    fn to_time_datetime(

        &self,

    ) -> core::result::Result<OffsetDateTime, time::error::ComponentRange> {

        use std::convert::TryFrom;

        use time::{Date, Month, PrimitiveDateTime, Time, UtcOffset};

        let month = Month::try_from(self.month)?;

        let date = Date::from_calendar_date(self.year as i32, month, self.day)?;

        let time = Time::from_hms_milli(

            self.hour,

            self.minute,

            self.second,

            self.millisecond.unwrap_or(0),

        )?;

        let primitive_date = PrimitiveDateTime::new(date, time);

        let offset = match self.tz {

            ASN1TimeZone::Offset(h, m) => UtcOffset::from_hms(h, m, 0)?,

            ASN1TimeZone::Undefined | ASN1TimeZone::Z => UtcOffset::UTC,

        };

        Ok(primitive_date.assume_offset(offset))

    }

    #[cfg(feature = "datetime")]

    pub fn to_datetime(&self) -> Result<OffsetDateTime> {

        use crate::Error;

        self.to_time_datetime().map_err(|_| Error::InvalidDateTime)

    }

}

impl fmt::Display for ASN1DateTime {

    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

        let fractional = match self.millisecond {

            None => "".to_string(),

            Some(v) => format!(".{}", v),

        };

        write!(

            f,

            "{:04}{:02}{:02}{:02}{:02}{:02}{}Z",

            self.year, self.month, self.day, self.hour, self.minute, self.second, fractional,

        )

    }

}

/// Decode 2-digit decimal value

pub(crate) fn decode_decimal(tag: Tag, hi: u8, lo: u8) -> Result<u8> {

    if hi.is_ascii_digit() && lo.is_ascii_digit() {

        Ok((hi - b'0') * 10 + (lo - b'0'))

    } else {

        Err(tag.invalid_value("expected digit"))

    }

}