// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).

use crate::provider::semantic_skeletons::DatetimePatternsGlueV1;
use crate::scaffold::*;

/// Struct for combining date/time fields with zone fields.
///
/// This struct produces "composite field sets" as defined in UTS 35.
/// See [`fieldsets`](crate::fieldsets).
///
/// # Examples
///
/// The only way to construct a combo field set (in this case, weekday with location-based zone):
///
/// ```
/// use icu::datetime::fieldsets::{zone::Location, Combo, E};
///
/// let field_set = E::long().with_zone(Location);
/// ```
///
/// Format the weekday, hour, and location-based zone:
///
/// ```
/// use icu::datetime::fieldsets::{self, zone, Combo};
/// use icu::datetime::input::ZonedDateTime;
/// use icu::datetime::DateTimeFormatter;
/// use icu::locale::locale;
/// use icu::time::zone::IanaParser;
/// use writeable::assert_writeable_eq;
///
/// // Note: Combo type can be elided, but it is shown here for demonstration
/// let formatter =
///     DateTimeFormatter::<Combo<fieldsets::ET, zone::Location>>::try_new(
///         locale!("en-US").into(),
///         fieldsets::E::short()
///             .with_time_hm()
///             .with_zone(zone::Location),
///     )
///     .unwrap();
///
/// let zdt = ZonedDateTime::try_location_only_from_str(
///     "2024-10-18T15:44[America/Los_Angeles]",
///     formatter.calendar(),
///     IanaParser::new(),
/// )
/// .unwrap();
///
/// assert_writeable_eq!(
///     formatter.format(&zdt),
///     "Fri, 3:44 PM Los Angeles Time"
/// );
/// ```
///
/// Same thing with a fixed calendar formatter:
///
/// ```
/// use icu::calendar::Gregorian;
/// use icu::datetime::fieldsets::{self, zone, Combo};
/// use icu::datetime::input::ZonedDateTime;
/// use icu::datetime::FixedCalendarDateTimeFormatter;
/// use icu::locale::locale;
/// use icu::time::zone::IanaParser;
/// use writeable::assert_writeable_eq;
///
/// // Note: Combo type can be elided, but it is shown here for demonstration
/// let formatter = FixedCalendarDateTimeFormatter::<
///     _,
///     Combo<fieldsets::ET, zone::Location>,
/// >::try_new(
///     locale!("en-US").into(),
///     fieldsets::E::short()
///         .with_time_hm()
///         .with_zone(zone::Location),
/// )
/// .unwrap();
///
/// let zdt = ZonedDateTime::try_location_only_from_str(
///     "2024-10-18T15:44[America/Los_Angeles]",
///     Gregorian,
///     IanaParser::new(),
/// )
/// .unwrap();
///
/// assert_writeable_eq!(
///     formatter.format(&zdt),
///     "Fri, 3:44 PM Los Angeles Time"
/// );
/// ```
///
/// Mix a dynamic [`DateFieldSet`](crate::fieldsets::enums::DateFieldSet)
/// with a static time zone:
///
/// ```
/// use icu::datetime::fieldsets::{
///     enums::DateFieldSet, zone::GenericShort, Combo, YMD,
/// };
/// use icu::datetime::input::ZonedDateTime;
/// use icu::datetime::DateTimeFormatter;
/// use icu::locale::locale;
/// use icu::time::zone::IanaParser;
/// use writeable::assert_writeable_eq;
///
/// // Note: Combo type can be elided, but it is shown here for demonstration
/// let formatter =
///     DateTimeFormatter::<Combo<DateFieldSet, GenericShort>>::try_new(
///         locale!("en-US").into(),
///         DateFieldSet::YMD(YMD::long()).with_zone(GenericShort),
///     )
///     .unwrap();
///
/// let zdt = ZonedDateTime::try_location_only_from_str(
///     "2024-10-18T15:44[America/Los_Angeles]",
///     formatter.calendar(),
///     IanaParser::new(),
/// )
/// .unwrap();
///
/// assert_writeable_eq!(formatter.format(&zdt), "October 18, 2024 PT");
/// ```
///
/// Format with a time of day and long time zone:
///
/// ```
/// # #[cfg(all(feature = "unstable", feature = "ixdtf"))] {
/// use icu::datetime::fieldsets::{zone::SpecificLong, T};
/// use icu::datetime::NoCalendarFormatter;
/// use icu::locale::locale;
/// use icu::time::zone::iana::IanaParser;
/// use icu::time::ZonedTime;
/// use writeable::assert_writeable_eq;
///
/// let formatter = NoCalendarFormatter::try_new(
///     locale!("en-US").into(),
///     T::medium().with_zone(SpecificLong),
/// )
/// .unwrap();
///
/// let zoned_time = ZonedTime::try_strict_from_str(
///     "15:44:00-07:00[America/Los_Angeles]",
///     IanaParser::new(),
/// )
/// .unwrap();
///
/// assert_writeable_eq!(
///     formatter.format(&zoned_time),
///     "3:44:00 PM Pacific Daylight Time"
/// );
/// # }
/// ```
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub struct Combo<DT, Z> {
    date_time_field_set: DT,
    zone_field_set: Z,
}

impl<DT, Z> Combo<DT, Z> {
    #[inline]
    pub(crate) const fn new(date_time_field_set: DT, zone_field_set: Z) -> Self {
        Self {
            date_time_field_set,
            zone_field_set,
        }
    }
}

impl<DT, Z> UnstableSealed for Combo<DT, Z> {}

impl<DT, Z> Combo<DT, Z> {
    #[inline]
    pub(crate) fn dt(self) -> DT {
        self.date_time_field_set
    }
    #[inline]
    pub(crate) fn z(self) -> Z {
        self.zone_field_set
    }
}

impl<DT, Z> DateTimeNamesMarker for Combo<DT, Z>
where
    DT: DateTimeNamesMarker,
    Z: DateTimeNamesMarker,
{
    type YearNames = DT::YearNames;
    type MonthNames = DT::MonthNames;
    type WeekdayNames = DT::WeekdayNames;
    type DayPeriodNames = DT::DayPeriodNames;
    type ZoneEssentials = Z::ZoneEssentials;
    type ZoneLocations = Z::ZoneLocations;
    type ZoneLocationsRoot = Z::ZoneLocationsRoot;
    type ZoneExemplars = Z::ZoneExemplars;
    type ZoneExemplarsRoot = Z::ZoneExemplarsRoot;
    type ZoneGenericLong = Z::ZoneGenericLong;
    type ZoneGenericShort = Z::ZoneGenericShort;
    type ZoneStandardLong = Z::ZoneStandardLong;
    type ZoneSpecificLong = Z::ZoneSpecificLong;
    type ZoneSpecificShort = Z::ZoneSpecificShort;
    type MetazoneLookup = Z::MetazoneLookup;
}

impl<DT, Z> DateTimeMarkers for Combo<DT, Z>
where
    DT: DateTimeMarkers,
    Z: DateTimeMarkers,
{
    type D = DT::D;
    type T = DT::T;
    type Z = Z::Z;
    type GluePatternV1 = datetime_marker_helper!(@glue, yes);
}
