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//! Contains the `DepartureTime` enum and its associated traits. It is used to
//! specify when the user would like to depart for traffic modelling and transit
//! directions.

use crate::directions::error::Error as DirectionsError;
use crate::error::Error as GoogleMapsError;
use chrono::DateTime;
use chrono::NaiveDateTime;
use serde::{Deserialize, Serialize};

// -----------------------------------------------------------------------------
//
/// Specifies the desired [time of
/// departure](https://developers.google.com/maps/documentation/directions/intro#optional-parameters).
///
/// You can specify the time or alternatively you can specify a value of now,
/// which sets the departure time to the current time (correct to the nearest
/// second).
///
/// * For requests where the travel mode is transit: You can optionally specify
/// one of `departure_time` or `arrival_time`. If neither time is specified, the
/// `departure_time` defaults to now (that is, the departure time defaults to
/// the current time).
///
/// * For requests where the travel mode is driving: You can specify the
/// `departure_time` to receive a route and trip duration (response field:
/// `duration_in_traffic`) that take traffic conditions into account. This
/// option is only available if the request contains a valid API key, or a valid
/// Google Maps Platform Premium Plan client ID and signature. The
/// `departure_time` must be set to the current time or some time in the future.
/// It cannot be in the past.
///
/// **Note**: If departure time is not specified, choice of route and duration
/// are based on road network and average time-independent traffic conditions.
/// Results for a given request may vary over time due to changes in the road
/// network, updated average traffic conditions, and the distributed nature of
/// the service. Results may also vary between nearly-equivalent routes at any
/// time or frequency.

#[derive(Clone, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize, Deserialize)]
#[repr(u8)]
pub enum DepartureTime {
    /// You can specify a value of now, which sets the departure time to the
    /// current time (correct to the nearest second).
    #[default]
    Now = 0,
    /// Specifies the desired time of departure.
    At(NaiveDateTime) = 1,
} // enum

// -----------------------------------------------------------------------------

impl std::convert::From<&DepartureTime> for String {
    /// Converts a `DepartureTime` enum to a `String` that contains a [departure
    /// time](https://developers.google.com/maps/documentation/directions/intro#optional-parameters).
    fn from(departure_time: &DepartureTime) -> Self {
        match departure_time {
            DepartureTime::Now => Self::from("now"),
            DepartureTime::At(departure_time) => departure_time.and_utc().timestamp().to_string(),
        } // match
    } // fn
} // impl

// -----------------------------------------------------------------------------

impl std::fmt::Display for DepartureTime {
    /// Converts a `DepartureTime` enum to a `String` that contains a [departure
    /// time](https://developers.google.com/maps/documentation/directions/intro#optional-parameters).
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "{departure_time}", departure_time = String::from(self))
    } // fn
} // impl

// -----------------------------------------------------------------------------

impl std::convert::TryFrom<&str> for DepartureTime {
    // Error definitions are contained in the
    // `google_maps\src\directions\error.rs` module.
    type Error = GoogleMapsError;
    /// Converts `String` that contains a [departure
    /// time](https://developers.google.com/maps/documentation/directions/intro#optional-parameters)
    /// to a `DepartureTime` enum.
    fn try_from(departure_time: &str) -> Result<Self, Self::Error> {
        if departure_time == "now" {
            Ok(Self::Now)
        } else {
            match departure_time.parse::<i64>() {
                Ok(integer) => match DateTime::from_timestamp(integer, 0) {
                    Some(date_time) => Ok(Self::At(date_time.naive_utc())),
                    None => Err(DirectionsError::InvalidDepartureTime(
                        departure_time.to_string(),
                    ))?,
                }, // Ok
                Err(_error) => Err(DirectionsError::InvalidDepartureTime(
                    departure_time.to_string(),
                ))?,
            } // match
        } // if
    } // fn
} // impl

// -----------------------------------------------------------------------------

impl std::str::FromStr for DepartureTime {
    // Error definitions are contained in the
    // `google_maps\src\directions\error.rs` module.
    type Err = GoogleMapsError;
    /// Converts `String` that contains a [departure
    /// time](https://developers.google.com/maps/documentation/directions/intro#optional-parameters)
    /// to a `DepartureTime` enum.
    fn from_str(departure_time: &str) -> Result<Self, Self::Err> {
        Self::try_from(departure_time)
    } // fn
} // impl

// -----------------------------------------------------------------------------

impl DepartureTime {
    /// Formats a `DepartureTime` enum into a string that is presentable to the
    /// end user.
    #[must_use]
    pub fn display(&self) -> String {
        match self {
            Self::Now => "Now".to_string(),
            Self::At(departure_time) => {
                format!("At {}", departure_time.format("At %F %r"))
            }
        } // match
    } // fn
} // impl