// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// Copyright by contributors to this project.
// SPDX-License-Identifier: (Apache-2.0 OR MIT)

use crate::{client::MlsError, time::MlsTime};
use mls_rs_codec::{MlsDecode, MlsEncode, MlsSize};

#[derive(Clone, Debug, PartialEq, Eq, MlsSize, MlsEncode, MlsDecode, Default)]
#[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[non_exhaustive]
pub struct Lifetime {
    pub not_before: u64,
    pub not_after: u64,
}

impl Lifetime {
    pub fn new(not_before: u64, not_after: u64) -> Lifetime {
        Lifetime {
            not_before,
            not_after,
        }
    }

    pub fn seconds(s: u64) -> Result<Self, MlsError> {
        #[cfg(feature = "std")]
        let not_before = MlsTime::now().seconds_since_epoch();
        #[cfg(not(feature = "std"))]
        // There is no clock on no_std, this is here just so that we can run tests.
        let not_before = 3600u64;

        let not_after = not_before.checked_add(s).ok_or(MlsError::TimeOverflow)?;

        Ok(Lifetime {
            // Subtract 1 hour to address time difference between machines
            not_before: not_before - 3600,
            not_after,
        })
    }

    pub fn days(d: u32) -> Result<Self, MlsError> {
        Self::seconds((d * 86400) as u64)
    }

    pub fn years(y: u8) -> Result<Self, MlsError> {
        Self::days(365 * y as u32)
    }

    pub(crate) fn within_lifetime(&self, time: MlsTime) -> bool {
        let since_epoch = time.seconds_since_epoch();
        since_epoch >= self.not_before && since_epoch <= self.not_after
    }
}

#[cfg(test)]
mod tests {
    use core::time::Duration;

    use super::*;
    use assert_matches::assert_matches;

    #[test]
    fn test_lifetime_overflow() {
        let res = Lifetime::seconds(u64::MAX);
        assert_matches!(res, Err(MlsError::TimeOverflow))
    }

    #[test]
    fn test_seconds() {
        let seconds = 10;
        let lifetime = Lifetime::seconds(seconds).unwrap();
        assert_eq!(lifetime.not_after - lifetime.not_before, 3610);
    }

    #[test]
    fn test_days() {
        let days = 2;
        let lifetime = Lifetime::days(days).unwrap();

        assert_eq!(
            lifetime.not_after - lifetime.not_before,
            86400u64 * days as u64 + 3600
        );
    }

    #[test]
    fn test_years() {
        let years = 2;
        let lifetime = Lifetime::years(years).unwrap();

        assert_eq!(
            lifetime.not_after - lifetime.not_before,
            86400 * 365 * years as u64 + 3600
        );
    }

    #[test]
    fn test_bounds() {
        let test_lifetime = Lifetime {
            not_before: 5,
            not_after: 10,
        };

        assert!(!test_lifetime
            .within_lifetime(MlsTime::from_duration_since_epoch(Duration::from_secs(4))));

        assert!(!test_lifetime
            .within_lifetime(MlsTime::from_duration_since_epoch(Duration::from_secs(11))));

        assert!(test_lifetime
            .within_lifetime(MlsTime::from_duration_since_epoch(Duration::from_secs(5))));

        assert!(test_lifetime
            .within_lifetime(MlsTime::from_duration_since_epoch(Duration::from_secs(10))));

        assert!(test_lifetime
            .within_lifetime(MlsTime::from_duration_since_epoch(Duration::from_secs(6))));
    }
}