use std::{
    fmt,
    time::{Duration, SystemTime},
};

use rb_sys::{rb_time_new, rb_time_timeval, rb_time_utc_offset, timeval, VALUE};

use crate::{
    api::Ruby,
    error::{protect, Error},
    into_value::IntoValue,
    object::Object,
    r_typed_data::RTypedData,
    try_convert::TryConvert,
    value::{
        private::{self, ReprValue as _},
        Fixnum, ReprValue, Value,
    },
};

/// # `Time`
///
/// Functions to create and work with Ruby `Time` objects.
///
/// See also the [`Time`] type.
impl Ruby {
    /// Create a new `Time` in the local timezone.
    ///
    /// # Examples
    ///
    /// ```
    /// use magnus::{rb_assert, Error, Ruby};
    ///
    /// fn example(ruby: &Ruby) -> Result<(), Error> {
    ///     let t = ruby.time_new(1654013280, 0)?;
    ///
    ///     rb_assert!(ruby, r#"t == Time.new(2022, 5, 31, 9, 8, 0, "-07:00")"#, t);
    ///
    ///     Ok(())
    /// }
    /// # Ruby::init(example).unwrap()
    /// ```
    pub fn time_new(&self, seconds: i64, microseconds: i64) -> Result<Time, Error> {
        protect(|| unsafe {
            Time::from_rb_value_unchecked(rb_time_new(
                seconds.try_into().unwrap(),
                microseconds.try_into().unwrap(),
            ))
        })
    }
}

/// Wrapper type for a Value known to be an instance of Ruby's Time class.
///
/// See the [`ReprValue`] and [`Object`] traits for additional methods
/// available on this type. See [`Ruby`](Ruby#time) for methods to create a
/// `Time`.
#[derive(Clone, Copy)]
#[repr(transparent)]
pub struct Time(RTypedData);

impl Time {
    /// Return `Some(Time)` if `val` is a `Time`, `None` otherwise.
    ///
    /// # Examples
    ///
    /// ```
    /// use magnus::eval;
    /// # let _cleanup = unsafe { magnus::embed::init() };
    ///
    /// assert!(magnus::Time::from_value(eval("Time.now").unwrap()).is_some());
    /// assert!(magnus::Time::from_value(eval("0").unwrap()).is_none());
    /// ```
    #[inline]
    pub fn from_value(val: Value) -> Option<Self> {
        RTypedData::from_value(val)
            .filter(|_| val.is_kind_of(Ruby::get_with(val).class_time()))
            .map(Self)
    }

    #[inline]
    pub(crate) unsafe fn from_rb_value_unchecked(val: VALUE) -> Self {
        Self(RTypedData::from_rb_value_unchecked(val))
    }

    /// Returns the timezone offset of `self` from UTC in seconds.
    ///
    /// # Examples
    ///
    /// ```
    /// use magnus::{Error, Ruby, Time};
    ///
    /// fn example(ruby: &Ruby) -> Result<(), Error> {
    ///     let t: Time = ruby.eval(r#"Time.new(2022, 5, 31, 9, 8, 0, "-07:00")"#)?;
    ///
    ///     assert_eq!(t.utc_offset(), -25_200);
    ///
    ///     Ok(())
    /// }
    /// # Ruby::init(example).unwrap()
    /// ```
    pub fn utc_offset(self) -> i64 {
        unsafe { Fixnum::from_rb_value_unchecked(rb_time_utc_offset(self.as_rb_value())).to_i64() }
    }
}

impl fmt::Display for Time {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", unsafe { self.to_s_infallible() })
    }
}

impl fmt::Debug for Time {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.inspect())
    }
}

impl IntoValue for Time {
    #[inline]
    fn into_value_with(self, _: &Ruby) -> Value {
        self.0.as_value()
    }
}

impl IntoValue for SystemTime {
    #[inline]
    fn into_value_with(self, ruby: &Ruby) -> Value {
        match self.duration_since(Self::UNIX_EPOCH) {
            Ok(duration) => ruby
                .time_new(
                    duration.as_secs().try_into().unwrap(),
                    duration.subsec_micros().try_into().unwrap(),
                )
                .unwrap()
                .as_value(),
            Err(_) => {
                let duration = Self::UNIX_EPOCH.duration_since(self).unwrap();
                ruby.time_new(
                    -i64::try_from(duration.as_secs()).unwrap(),
                    -i64::try_from(duration.subsec_micros()).unwrap(),
                )
                .unwrap()
                .as_value()
            }
        }
    }
}

impl Object for Time {}

unsafe impl private::ReprValue for Time {}

impl ReprValue for Time {}

impl TryConvert for Time {
    fn try_convert(val: Value) -> Result<Self, Error> {
        Self::from_value(val).ok_or_else(|| {
            Error::new(
                Ruby::get_with(val).exception_type_error(),
                format!("no implicit conversion of {} into Time", unsafe {
                    val.classname()
                },),
            )
        })
    }
}

impl TryConvert for SystemTime {
    fn try_convert(val: Value) -> Result<Self, Error> {
        let mut timeval = timeval {
            tv_sec: 0,
            tv_usec: 0,
        };
        protect(|| unsafe {
            timeval = rb_time_timeval(val.as_rb_value());
            Ruby::get_unchecked().qnil()
        })?;
        if timeval.tv_sec >= 0 && timeval.tv_usec >= 0 {
            let mut duration = Duration::from_secs(timeval.tv_sec as _);
            duration += Duration::from_micros(timeval.tv_usec as _);
            Ok(Self::UNIX_EPOCH + duration)
        } else {
            Err(Error::new(
                Ruby::get_with(val).exception_arg_error(),
                "time must not be negative",
            ))
        }
    }
}