use core::fmt;
use serde::{de, ser};

use super::DateTime;
use crate::naive::datetime::serde::serde_from;
#[cfg(feature = "clock")]
use crate::offset::Local;
use crate::offset::{FixedOffset, TimeZone, Utc};

#[doc(hidden)]
#[derive(Debug)]
pub struct SecondsTimestampVisitor;

#[doc(hidden)]
#[derive(Debug)]
pub struct NanoSecondsTimestampVisitor;

#[doc(hidden)]
#[derive(Debug)]
pub struct MicroSecondsTimestampVisitor;

#[doc(hidden)]
#[derive(Debug)]
pub struct MilliSecondsTimestampVisitor;

/// Serialize into a rfc3339 time string
///
/// See [the `serde` module](./serde/index.html) for alternate
/// serializations.
impl<Tz: TimeZone> ser::Serialize for DateTime<Tz> {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: ser::Serializer,
    {
        struct FormatWrapped<'a, D: 'a> {
            inner: &'a D,
        }

        impl<'a, D: fmt::Debug> fmt::Display for FormatWrapped<'a, D> {
            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                self.inner.fmt(f)
            }
        }

        // Debug formatting is correct RFC3339, and it allows Zulu.
        serializer.collect_str(&FormatWrapped { inner: &self })
    }
}

struct DateTimeVisitor;

impl<'de> de::Visitor<'de> for DateTimeVisitor {
    type Value = DateTime<FixedOffset>;

    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        formatter.write_str("a formatted date and time string or a unix timestamp")
    }

    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
    where
        E: de::Error,
    {
        value.parse().map_err(E::custom)
    }
}

/// Deserialize a value that optionally includes a timezone offset in its
/// string representation
///
/// The value to be deserialized must be an rfc3339 string.
///
/// See [the `serde` module](./serde/index.html) for alternate
/// deserialization formats.
impl<'de> de::Deserialize<'de> for DateTime<FixedOffset> {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        deserializer.deserialize_str(DateTimeVisitor)
    }
}

/// Deserialize into a UTC value
///
/// The value to be deserialized must be an rfc3339 string.
///
/// See [the `serde` module](./serde/index.html) for alternate
/// deserialization formats.
impl<'de> de::Deserialize<'de> for DateTime<Utc> {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        deserializer.deserialize_str(DateTimeVisitor).map(|dt| dt.with_timezone(&Utc))
    }
}

/// Deserialize a value that includes no timezone in its string
/// representation
///
/// The value to be deserialized must be an rfc3339 string.
///
/// See [the `serde` module](./serde/index.html) for alternate
/// serialization formats.
#[cfg(feature = "clock")]
impl<'de> de::Deserialize<'de> for DateTime<Local> {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        deserializer.deserialize_str(DateTimeVisitor).map(|dt| dt.with_timezone(&Local))
    }
}

/// Ser/de to/from timestamps in nanoseconds
///
/// Intended for use with `serde`'s `with` attribute.
///
/// # Example:
///
/// ```rust
/// # use chrono::{TimeZone, DateTime, Utc};
/// # use serde_derive::{Deserialize, Serialize};
/// use chrono::serde::ts_nanoseconds;
/// #[derive(Deserialize, Serialize)]
/// struct S {
///     #[serde(with = "ts_nanoseconds")]
///     time: DateTime<Utc>
/// }
///
/// let time = Utc.ymd(2018, 5, 17).and_hms_nano(02, 04, 59, 918355733);
/// let my_s = S {
///     time: time.clone(),
/// };
///
/// let as_string = serde_json::to_string(&my_s)?;
/// assert_eq!(as_string, r#"{"time":1526522699918355733}"#);
/// let my_s: S = serde_json::from_str(&as_string)?;
/// assert_eq!(my_s.time, time);
/// # Ok::<(), serde_json::Error>(())
/// ```
pub mod ts_nanoseconds {
    use core::fmt;
    use serde::{de, ser};

    use crate::offset::TimeZone;
    use crate::{DateTime, Utc};

    use super::{serde_from, NanoSecondsTimestampVisitor};

    /// Serialize a UTC datetime into an integer number of nanoseconds since the epoch
    ///
    /// Intended for use with `serde`s `serialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{TimeZone, DateTime, Utc};
    /// # use serde_derive::Serialize;
    /// use chrono::serde::ts_nanoseconds::serialize as to_nano_ts;
    /// #[derive(Serialize)]
    /// struct S {
    ///     #[serde(serialize_with = "to_nano_ts")]
    ///     time: DateTime<Utc>
    /// }
    ///
    /// let my_s = S {
    ///     time: Utc.ymd(2018, 5, 17).and_hms_nano(02, 04, 59, 918355733),
    /// };
    /// let as_string = serde_json::to_string(&my_s)?;
    /// assert_eq!(as_string, r#"{"time":1526522699918355733}"#);
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn serialize<S>(dt: &DateTime<Utc>, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: ser::Serializer,
    {
        serializer.serialize_i64(dt.timestamp_nanos())
    }

    /// Deserialize a [`DateTime`] from a nanosecond timestamp
    ///
    /// Intended for use with `serde`s `deserialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{DateTime, Utc};
    /// # use serde_derive::Deserialize;
    /// use chrono::serde::ts_nanoseconds::deserialize as from_nano_ts;
    /// #[derive(Deserialize)]
    /// struct S {
    ///     #[serde(deserialize_with = "from_nano_ts")]
    ///     time: DateTime<Utc>
    /// }
    ///
    /// let my_s: S = serde_json::from_str(r#"{ "time": 1526522699918355733 }"#)?;
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn deserialize<'de, D>(d: D) -> Result<DateTime<Utc>, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        d.deserialize_i64(NanoSecondsTimestampVisitor)
    }

    impl<'de> de::Visitor<'de> for NanoSecondsTimestampVisitor {
        type Value = DateTime<Utc>;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            formatter.write_str("a unix timestamp in nanoseconds")
        }

        /// Deserialize a timestamp in nanoseconds since the epoch
        fn visit_i64<E>(self, value: i64) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            serde_from(
                Utc.timestamp_opt(value / 1_000_000_000, (value % 1_000_000_000) as u32),
                &value,
            )
        }

        /// Deserialize a timestamp in nanoseconds since the epoch
        fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            serde_from(
                Utc.timestamp_opt((value / 1_000_000_000) as i64, (value % 1_000_000_000) as u32),
                &value,
            )
        }
    }
}

/// Ser/de to/from optional timestamps in nanoseconds
///
/// Intended for use with `serde`'s `with` attribute.
///
/// # Example:
///
/// ```rust
/// # use chrono::{TimeZone, DateTime, Utc};
/// # use serde_derive::{Deserialize, Serialize};
/// use chrono::serde::ts_nanoseconds_option;
/// #[derive(Deserialize, Serialize)]
/// struct S {
///     #[serde(with = "ts_nanoseconds_option")]
///     time: Option<DateTime<Utc>>
/// }
///
/// let time = Some(Utc.ymd(2018, 5, 17).and_hms_nano(02, 04, 59, 918355733));
/// let my_s = S {
///     time: time.clone(),
/// };
///
/// let as_string = serde_json::to_string(&my_s)?;
/// assert_eq!(as_string, r#"{"time":1526522699918355733}"#);
/// let my_s: S = serde_json::from_str(&as_string)?;
/// assert_eq!(my_s.time, time);
/// # Ok::<(), serde_json::Error>(())
/// ```
pub mod ts_nanoseconds_option {
    use core::fmt;
    use serde::{de, ser};

    use crate::{DateTime, Utc};

    use super::NanoSecondsTimestampVisitor;

    /// Serialize a UTC datetime into an integer number of nanoseconds since the epoch or none
    ///
    /// Intended for use with `serde`s `serialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{TimeZone, DateTime, Utc};
    /// # use serde_derive::Serialize;
    /// use chrono::serde::ts_nanoseconds_option::serialize as to_nano_tsopt;
    /// #[derive(Serialize)]
    /// struct S {
    ///     #[serde(serialize_with = "to_nano_tsopt")]
    ///     time: Option<DateTime<Utc>>
    /// }
    ///
    /// let my_s = S {
    ///     time: Some(Utc.ymd(2018, 5, 17).and_hms_nano(02, 04, 59, 918355733)),
    /// };
    /// let as_string = serde_json::to_string(&my_s)?;
    /// assert_eq!(as_string, r#"{"time":1526522699918355733}"#);
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn serialize<S>(opt: &Option<DateTime<Utc>>, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: ser::Serializer,
    {
        match *opt {
            Some(ref dt) => serializer.serialize_some(&dt.timestamp_nanos()),
            None => serializer.serialize_none(),
        }
    }

    /// Deserialize a `DateTime` from a nanosecond timestamp or none
    ///
    /// Intended for use with `serde`s `deserialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{DateTime, Utc};
    /// # use serde_derive::Deserialize;
    /// use chrono::serde::ts_nanoseconds_option::deserialize as from_nano_tsopt;
    /// #[derive(Deserialize)]
    /// struct S {
    ///     #[serde(deserialize_with = "from_nano_tsopt")]
    ///     time: Option<DateTime<Utc>>
    /// }
    ///
    /// let my_s: S = serde_json::from_str(r#"{ "time": 1526522699918355733 }"#)?;
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn deserialize<'de, D>(d: D) -> Result<Option<DateTime<Utc>>, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        d.deserialize_option(OptionNanoSecondsTimestampVisitor)
    }

    struct OptionNanoSecondsTimestampVisitor;

    impl<'de> de::Visitor<'de> for OptionNanoSecondsTimestampVisitor {
        type Value = Option<DateTime<Utc>>;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            formatter.write_str("a unix timestamp in nanoseconds or none")
        }

        /// Deserialize a timestamp in nanoseconds since the epoch
        fn visit_some<D>(self, d: D) -> Result<Self::Value, D::Error>
        where
            D: de::Deserializer<'de>,
        {
            d.deserialize_i64(NanoSecondsTimestampVisitor).map(Some)
        }

        /// Deserialize a timestamp in nanoseconds since the epoch
        fn visit_none<E>(self) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            Ok(None)
        }

        /// Deserialize a timestamp in nanoseconds since the epoch
        fn visit_unit<E>(self) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            Ok(None)
        }
    }
}

/// Ser/de to/from timestamps in microseconds
///
/// Intended for use with `serde`'s `with` attribute.
///
/// # Example:
///
/// ```rust
/// # use chrono::{TimeZone, DateTime, Utc};
/// # use serde_derive::{Deserialize, Serialize};
/// use chrono::serde::ts_microseconds;
/// #[derive(Deserialize, Serialize)]
/// struct S {
///     #[serde(with = "ts_microseconds")]
///     time: DateTime<Utc>
/// }
///
/// let time = Utc.ymd(2018, 5, 17).and_hms_micro(02, 04, 59, 918355);
/// let my_s = S {
///     time: time.clone(),
/// };
///
/// let as_string = serde_json::to_string(&my_s)?;
/// assert_eq!(as_string, r#"{"time":1526522699918355}"#);
/// let my_s: S = serde_json::from_str(&as_string)?;
/// assert_eq!(my_s.time, time);
/// # Ok::<(), serde_json::Error>(())
/// ```
pub mod ts_microseconds {
    use core::fmt;
    use serde::{de, ser};

    use super::{serde_from, MicroSecondsTimestampVisitor};
    use crate::offset::TimeZone;
    use crate::{DateTime, Utc};

    /// Serialize a UTC datetime into an integer number of microseconds since the epoch
    ///
    /// Intended for use with `serde`s `serialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{TimeZone, DateTime, Utc};
    /// # use serde_derive::Serialize;
    /// use chrono::serde::ts_microseconds::serialize as to_micro_ts;
    /// #[derive(Serialize)]
    /// struct S {
    ///     #[serde(serialize_with = "to_micro_ts")]
    ///     time: DateTime<Utc>
    /// }
    ///
    /// let my_s = S {
    ///     time: Utc.ymd(2018, 5, 17).and_hms_micro(02, 04, 59, 918355),
    /// };
    /// let as_string = serde_json::to_string(&my_s)?;
    /// assert_eq!(as_string, r#"{"time":1526522699918355}"#);
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn serialize<S>(dt: &DateTime<Utc>, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: ser::Serializer,
    {
        serializer.serialize_i64(dt.timestamp_micros())
    }

    /// Deserialize a `DateTime` from a microsecond timestamp
    ///
    /// Intended for use with `serde`s `deserialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{DateTime, Utc};
    /// # use serde_derive::Deserialize;
    /// use chrono::serde::ts_microseconds::deserialize as from_micro_ts;
    /// #[derive(Deserialize)]
    /// struct S {
    ///     #[serde(deserialize_with = "from_micro_ts")]
    ///     time: DateTime<Utc>
    /// }
    ///
    /// let my_s: S = serde_json::from_str(r#"{ "time": 1526522699918355 }"#)?;
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn deserialize<'de, D>(d: D) -> Result<DateTime<Utc>, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        d.deserialize_i64(MicroSecondsTimestampVisitor)
    }

    impl<'de> de::Visitor<'de> for MicroSecondsTimestampVisitor {
        type Value = DateTime<Utc>;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            formatter.write_str("a unix timestamp in microseconds")
        }

        /// Deserialize a timestamp in milliseconds since the epoch
        fn visit_i64<E>(self, value: i64) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            serde_from(
                Utc.timestamp_opt(value / 1_000_000, ((value % 1_000_000) * 1_000) as u32),
                &value,
            )
        }

        /// Deserialize a timestamp in milliseconds since the epoch
        fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            serde_from(
                Utc.timestamp_opt((value / 1_000_000) as i64, ((value % 1_000_000) * 1_000) as u32),
                &value,
            )
        }
    }
}

/// Ser/de to/from optional timestamps in microseconds
///
/// Intended for use with `serde`'s `with` attribute.
///
/// # Example:
///
/// ```rust
/// # use chrono::{TimeZone, DateTime, Utc};
/// # use serde_derive::{Deserialize, Serialize};
/// use chrono::serde::ts_microseconds_option;
/// #[derive(Deserialize, Serialize)]
/// struct S {
///     #[serde(with = "ts_microseconds_option")]
///     time: Option<DateTime<Utc>>
/// }
///
/// let time = Some(Utc.ymd(2018, 5, 17).and_hms_micro(02, 04, 59, 918355));
/// let my_s = S {
///     time: time.clone(),
/// };
///
/// let as_string = serde_json::to_string(&my_s)?;
/// assert_eq!(as_string, r#"{"time":1526522699918355}"#);
/// let my_s: S = serde_json::from_str(&as_string)?;
/// assert_eq!(my_s.time, time);
/// # Ok::<(), serde_json::Error>(())
/// ```
pub mod ts_microseconds_option {
    use core::fmt;
    use serde::{de, ser};

    use super::MicroSecondsTimestampVisitor;
    use crate::{DateTime, Utc};

    /// Serialize a UTC datetime into an integer number of microseconds since the epoch or none
    ///
    /// Intended for use with `serde`s `serialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{TimeZone, DateTime, Utc};
    /// # use serde_derive::Serialize;
    /// use chrono::serde::ts_microseconds_option::serialize as to_micro_tsopt;
    /// #[derive(Serialize)]
    /// struct S {
    ///     #[serde(serialize_with = "to_micro_tsopt")]
    ///     time: Option<DateTime<Utc>>
    /// }
    ///
    /// let my_s = S {
    ///     time: Some(Utc.ymd(2018, 5, 17).and_hms_micro(02, 04, 59, 918355)),
    /// };
    /// let as_string = serde_json::to_string(&my_s)?;
    /// assert_eq!(as_string, r#"{"time":1526522699918355}"#);
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn serialize<S>(opt: &Option<DateTime<Utc>>, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: ser::Serializer,
    {
        match *opt {
            Some(ref dt) => serializer.serialize_some(&dt.timestamp_micros()),
            None => serializer.serialize_none(),
        }
    }

    /// Deserialize a `DateTime` from a microsecond timestamp or none
    ///
    /// Intended for use with `serde`s `deserialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{DateTime, Utc};
    /// # use serde_derive::Deserialize;
    /// use chrono::serde::ts_microseconds_option::deserialize as from_micro_tsopt;
    /// #[derive(Deserialize)]
    /// struct S {
    ///     #[serde(deserialize_with = "from_micro_tsopt")]
    ///     time: Option<DateTime<Utc>>
    /// }
    ///
    /// let my_s: S = serde_json::from_str(r#"{ "time": 1526522699918355 }"#)?;
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn deserialize<'de, D>(d: D) -> Result<Option<DateTime<Utc>>, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        d.deserialize_option(OptionMicroSecondsTimestampVisitor)
    }

    struct OptionMicroSecondsTimestampVisitor;

    impl<'de> de::Visitor<'de> for OptionMicroSecondsTimestampVisitor {
        type Value = Option<DateTime<Utc>>;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            formatter.write_str("a unix timestamp in microseconds or none")
        }

        /// Deserialize a timestamp in microseconds since the epoch
        fn visit_some<D>(self, d: D) -> Result<Self::Value, D::Error>
        where
            D: de::Deserializer<'de>,
        {
            d.deserialize_i64(MicroSecondsTimestampVisitor).map(Some)
        }

        /// Deserialize a timestamp in microseconds since the epoch
        fn visit_none<E>(self) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            Ok(None)
        }

        /// Deserialize a timestamp in microseconds since the epoch
        fn visit_unit<E>(self) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            Ok(None)
        }
    }
}

/// Ser/de to/from timestamps in milliseconds
///
/// Intended for use with `serde`s `with` attribute.
///
/// # Example
///
/// ```rust
/// # use chrono::{TimeZone, DateTime, Utc};
/// # use serde_derive::{Deserialize, Serialize};
/// use chrono::serde::ts_milliseconds;
/// #[derive(Deserialize, Serialize)]
/// struct S {
///     #[serde(with = "ts_milliseconds")]
///     time: DateTime<Utc>
/// }
///
/// let time = Utc.ymd(2018, 5, 17).and_hms_milli(02, 04, 59, 918);
/// let my_s = S {
///     time: time.clone(),
/// };
///
/// let as_string = serde_json::to_string(&my_s)?;
/// assert_eq!(as_string, r#"{"time":1526522699918}"#);
/// let my_s: S = serde_json::from_str(&as_string)?;
/// assert_eq!(my_s.time, time);
/// # Ok::<(), serde_json::Error>(())
/// ```
pub mod ts_milliseconds {
    use core::fmt;
    use serde::{de, ser};

    use super::{serde_from, MilliSecondsTimestampVisitor};
    use crate::offset::TimeZone;
    use crate::{DateTime, Utc};

    /// Serialize a UTC datetime into an integer number of milliseconds since the epoch
    ///
    /// Intended for use with `serde`s `serialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{TimeZone, DateTime, Utc};
    /// # use serde_derive::Serialize;
    /// use chrono::serde::ts_milliseconds::serialize as to_milli_ts;
    /// #[derive(Serialize)]
    /// struct S {
    ///     #[serde(serialize_with = "to_milli_ts")]
    ///     time: DateTime<Utc>
    /// }
    ///
    /// let my_s = S {
    ///     time: Utc.ymd(2018, 5, 17).and_hms_milli(02, 04, 59, 918),
    /// };
    /// let as_string = serde_json::to_string(&my_s)?;
    /// assert_eq!(as_string, r#"{"time":1526522699918}"#);
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn serialize<S>(dt: &DateTime<Utc>, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: ser::Serializer,
    {
        serializer.serialize_i64(dt.timestamp_millis())
    }

    /// Deserialize a `DateTime` from a millisecond timestamp
    ///
    /// Intended for use with `serde`s `deserialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{DateTime, Utc};
    /// # use serde_derive::Deserialize;
    /// use chrono::serde::ts_milliseconds::deserialize as from_milli_ts;
    /// #[derive(Deserialize)]
    /// struct S {
    ///     #[serde(deserialize_with = "from_milli_ts")]
    ///     time: DateTime<Utc>
    /// }
    ///
    /// let my_s: S = serde_json::from_str(r#"{ "time": 1526522699918 }"#)?;
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn deserialize<'de, D>(d: D) -> Result<DateTime<Utc>, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        d.deserialize_i64(MilliSecondsTimestampVisitor).map(|dt| dt.with_timezone(&Utc))
    }

    impl<'de> de::Visitor<'de> for MilliSecondsTimestampVisitor {
        type Value = DateTime<Utc>;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            formatter.write_str("a unix timestamp in milliseconds")
        }

        /// Deserialize a timestamp in milliseconds since the epoch
        fn visit_i64<E>(self, value: i64) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            serde_from(Utc.timestamp_opt(value / 1000, ((value % 1000) * 1_000_000) as u32), &value)
        }

        /// Deserialize a timestamp in milliseconds since the epoch
        fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            serde_from(
                Utc.timestamp_opt((value / 1000) as i64, ((value % 1000) * 1_000_000) as u32),
                &value,
            )
        }
    }
}

/// Ser/de to/from optional timestamps in milliseconds
///
/// Intended for use with `serde`s `with` attribute.
///
/// # Example
///
/// ```rust
/// # use chrono::{TimeZone, DateTime, Utc};
/// # use serde_derive::{Deserialize, Serialize};
/// use chrono::serde::ts_milliseconds_option;
/// #[derive(Deserialize, Serialize)]
/// struct S {
///     #[serde(with = "ts_milliseconds_option")]
///     time: Option<DateTime<Utc>>
/// }
///
/// let time = Some(Utc.ymd(2018, 5, 17).and_hms_milli(02, 04, 59, 918));
/// let my_s = S {
///     time: time.clone(),
/// };
///
/// let as_string = serde_json::to_string(&my_s)?;
/// assert_eq!(as_string, r#"{"time":1526522699918}"#);
/// let my_s: S = serde_json::from_str(&as_string)?;
/// assert_eq!(my_s.time, time);
/// # Ok::<(), serde_json::Error>(())
/// ```
pub mod ts_milliseconds_option {
    use core::fmt;
    use serde::{de, ser};

    use super::MilliSecondsTimestampVisitor;
    use crate::{DateTime, Utc};

    /// Serialize a UTC datetime into an integer number of milliseconds since the epoch or none
    ///
    /// Intended for use with `serde`s `serialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{TimeZone, DateTime, Utc};
    /// # use serde_derive::Serialize;
    /// use chrono::serde::ts_milliseconds_option::serialize as to_milli_tsopt;
    /// #[derive(Serialize)]
    /// struct S {
    ///     #[serde(serialize_with = "to_milli_tsopt")]
    ///     time: Option<DateTime<Utc>>
    /// }
    ///
    /// let my_s = S {
    ///     time: Some(Utc.ymd(2018, 5, 17).and_hms_milli(02, 04, 59, 918)),
    /// };
    /// let as_string = serde_json::to_string(&my_s)?;
    /// assert_eq!(as_string, r#"{"time":1526522699918}"#);
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn serialize<S>(opt: &Option<DateTime<Utc>>, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: ser::Serializer,
    {
        match *opt {
            Some(ref dt) => serializer.serialize_some(&dt.timestamp_millis()),
            None => serializer.serialize_none(),
        }
    }

    /// Deserialize a `DateTime` from a millisecond timestamp or none
    ///
    /// Intended for use with `serde`s `deserialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{TimeZone, DateTime, Utc};
    /// # use serde_derive::Deserialize;
    /// use chrono::serde::ts_milliseconds_option::deserialize as from_milli_tsopt;
    ///
    /// #[derive(Deserialize, PartialEq, Debug)]
    /// #[serde(untagged)]
    /// enum E<T> {
    ///     V(T),
    /// }
    ///
    /// #[derive(Deserialize, PartialEq, Debug)]
    /// struct S {
    ///     #[serde(default, deserialize_with = "from_milli_tsopt")]
    ///     time: Option<DateTime<Utc>>
    /// }
    ///
    /// let my_s: E<S> = serde_json::from_str(r#"{ "time": 1526522699918 }"#)?;
    /// assert_eq!(my_s, E::V(S { time: Some(Utc.timestamp(1526522699, 918000000)) }));
    /// let s: E<S> = serde_json::from_str(r#"{ "time": null }"#)?;
    /// assert_eq!(s, E::V(S { time: None }));
    /// let t: E<S> = serde_json::from_str(r#"{}"#)?;
    /// assert_eq!(t, E::V(S { time: None }));
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn deserialize<'de, D>(d: D) -> Result<Option<DateTime<Utc>>, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        d.deserialize_option(OptionMilliSecondsTimestampVisitor)
            .map(|opt| opt.map(|dt| dt.with_timezone(&Utc)))
    }

    struct OptionMilliSecondsTimestampVisitor;

    impl<'de> de::Visitor<'de> for OptionMilliSecondsTimestampVisitor {
        type Value = Option<DateTime<Utc>>;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            formatter.write_str("a unix timestamp in milliseconds or none")
        }

        /// Deserialize a timestamp in milliseconds since the epoch
        fn visit_some<D>(self, d: D) -> Result<Self::Value, D::Error>
        where
            D: de::Deserializer<'de>,
        {
            d.deserialize_i64(MilliSecondsTimestampVisitor).map(Some)
        }

        /// Deserialize a timestamp in milliseconds since the epoch
        fn visit_none<E>(self) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            Ok(None)
        }

        /// Deserialize a timestamp in milliseconds since the epoch
        fn visit_unit<E>(self) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            Ok(None)
        }
    }
}

/// Ser/de to/from timestamps in seconds
///
/// Intended for use with `serde`'s `with` attribute.
///
/// # Example:
///
/// ```rust
/// # use chrono::{TimeZone, DateTime, Utc};
/// # use serde_derive::{Deserialize, Serialize};
/// use chrono::serde::ts_seconds;
/// #[derive(Deserialize, Serialize)]
/// struct S {
///     #[serde(with = "ts_seconds")]
///     time: DateTime<Utc>
/// }
///
/// let time = Utc.ymd(2015, 5, 15).and_hms(10, 0, 0);
/// let my_s = S {
///     time: time.clone(),
/// };
///
/// let as_string = serde_json::to_string(&my_s)?;
/// assert_eq!(as_string, r#"{"time":1431684000}"#);
/// let my_s: S = serde_json::from_str(&as_string)?;
/// assert_eq!(my_s.time, time);
/// # Ok::<(), serde_json::Error>(())
/// ```
pub mod ts_seconds {
    use core::fmt;
    use serde::{de, ser};

    use super::{serde_from, SecondsTimestampVisitor};
    use crate::offset::TimeZone;
    use crate::{DateTime, Utc};

    /// Serialize a UTC datetime into an integer number of seconds since the epoch
    ///
    /// Intended for use with `serde`s `serialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{TimeZone, DateTime, Utc};
    /// # use serde_derive::Serialize;
    /// use chrono::serde::ts_seconds::serialize as to_ts;
    /// #[derive(Serialize)]
    /// struct S {
    ///     #[serde(serialize_with = "to_ts")]
    ///     time: DateTime<Utc>
    /// }
    ///
    /// let my_s = S {
    ///     time: Utc.ymd(2015, 5, 15).and_hms(10, 0, 0),
    /// };
    /// let as_string = serde_json::to_string(&my_s)?;
    /// assert_eq!(as_string, r#"{"time":1431684000}"#);
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn serialize<S>(dt: &DateTime<Utc>, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: ser::Serializer,
    {
        serializer.serialize_i64(dt.timestamp())
    }

    /// Deserialize a `DateTime` from a seconds timestamp
    ///
    /// Intended for use with `serde`s `deserialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{DateTime, Utc};
    /// # use serde_derive::Deserialize;
    /// use chrono::serde::ts_seconds::deserialize as from_ts;
    /// #[derive(Deserialize)]
    /// struct S {
    ///     #[serde(deserialize_with = "from_ts")]
    ///     time: DateTime<Utc>
    /// }
    ///
    /// let my_s: S = serde_json::from_str(r#"{ "time": 1431684000 }"#)?;
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn deserialize<'de, D>(d: D) -> Result<DateTime<Utc>, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        d.deserialize_i64(SecondsTimestampVisitor)
    }

    impl<'de> de::Visitor<'de> for SecondsTimestampVisitor {
        type Value = DateTime<Utc>;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            formatter.write_str("a unix timestamp in seconds")
        }

        /// Deserialize a timestamp in seconds since the epoch
        fn visit_i64<E>(self, value: i64) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            serde_from(Utc.timestamp_opt(value, 0), &value)
        }

        /// Deserialize a timestamp in seconds since the epoch
        fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            serde_from(Utc.timestamp_opt(value as i64, 0), &value)
        }
    }
}

/// Ser/de to/from optional timestamps in seconds
///
/// Intended for use with `serde`'s `with` attribute.
///
/// # Example:
///
/// ```rust
/// # use chrono::{TimeZone, DateTime, Utc};
/// # use serde_derive::{Deserialize, Serialize};
/// use chrono::serde::ts_seconds_option;
/// #[derive(Deserialize, Serialize)]
/// struct S {
///     #[serde(with = "ts_seconds_option")]
///     time: Option<DateTime<Utc>>
/// }
///
/// let time = Some(Utc.ymd(2015, 5, 15).and_hms(10, 0, 0));
/// let my_s = S {
///     time: time.clone(),
/// };
///
/// let as_string = serde_json::to_string(&my_s)?;
/// assert_eq!(as_string, r#"{"time":1431684000}"#);
/// let my_s: S = serde_json::from_str(&as_string)?;
/// assert_eq!(my_s.time, time);
/// # Ok::<(), serde_json::Error>(())
/// ```
pub mod ts_seconds_option {
    use core::fmt;
    use serde::{de, ser};

    use super::SecondsTimestampVisitor;
    use crate::{DateTime, Utc};

    /// Serialize a UTC datetime into an integer number of seconds since the epoch or none
    ///
    /// Intended for use with `serde`s `serialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{TimeZone, DateTime, Utc};
    /// # use serde_derive::Serialize;
    /// use chrono::serde::ts_seconds_option::serialize as to_tsopt;
    /// #[derive(Serialize)]
    /// struct S {
    ///     #[serde(serialize_with = "to_tsopt")]
    ///     time: Option<DateTime<Utc>>
    /// }
    ///
    /// let my_s = S {
    ///     time: Some(Utc.ymd(2015, 5, 15).and_hms(10, 0, 0)),
    /// };
    /// let as_string = serde_json::to_string(&my_s)?;
    /// assert_eq!(as_string, r#"{"time":1431684000}"#);
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn serialize<S>(opt: &Option<DateTime<Utc>>, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: ser::Serializer,
    {
        match *opt {
            Some(ref dt) => serializer.serialize_some(&dt.timestamp()),
            None => serializer.serialize_none(),
        }
    }

    /// Deserialize a `DateTime` from a seconds timestamp or none
    ///
    /// Intended for use with `serde`s `deserialize_with` attribute.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # use chrono::{DateTime, Utc};
    /// # use serde_derive::Deserialize;
    /// use chrono::serde::ts_seconds_option::deserialize as from_tsopt;
    /// #[derive(Deserialize)]
    /// struct S {
    ///     #[serde(deserialize_with = "from_tsopt")]
    ///     time: Option<DateTime<Utc>>
    /// }
    ///
    /// let my_s: S = serde_json::from_str(r#"{ "time": 1431684000 }"#)?;
    /// # Ok::<(), serde_json::Error>(())
    /// ```
    pub fn deserialize<'de, D>(d: D) -> Result<Option<DateTime<Utc>>, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        d.deserialize_option(OptionSecondsTimestampVisitor)
    }

    struct OptionSecondsTimestampVisitor;

    impl<'de> de::Visitor<'de> for OptionSecondsTimestampVisitor {
        type Value = Option<DateTime<Utc>>;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            formatter.write_str("a unix timestamp in seconds or none")
        }

        /// Deserialize a timestamp in seconds since the epoch
        fn visit_some<D>(self, d: D) -> Result<Self::Value, D::Error>
        where
            D: de::Deserializer<'de>,
        {
            d.deserialize_i64(SecondsTimestampVisitor).map(Some)
        }

        /// Deserialize a timestamp in seconds since the epoch
        fn visit_none<E>(self) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            Ok(None)
        }

        /// Deserialize a timestamp in seconds since the epoch
        fn visit_unit<E>(self) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            Ok(None)
        }
    }
}

#[test]
fn test_serde_serialize() {
    super::test_encodable_json(serde_json::to_string, serde_json::to_string);
}

#[cfg(feature = "clock")]
#[test]
fn test_serde_deserialize() {
    super::test_decodable_json(
        |input| serde_json::from_str(input),
        |input| serde_json::from_str(input),
        |input| serde_json::from_str(input),
    );
}

#[test]
fn test_serde_bincode() {
    // Bincode is relevant to test separately from JSON because
    // it is not self-describing.
    use bincode::{deserialize, serialize};

    let dt = Utc.ymd(2014, 7, 24).and_hms(12, 34, 6);
    let encoded = serialize(&dt).unwrap();
    let decoded: DateTime<Utc> = deserialize(&encoded).unwrap();
    assert_eq!(dt, decoded);
    assert_eq!(dt.offset(), decoded.offset());
}
