Initial draft of fieldset builder

components/datetime/src/builder.rs

@@ -0,0 +1,236 @@
+// 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::fieldsets::{self, enums::*};
+use crate::options::*;
+
+/// An enumeration over all possible date and calendar period field sets
+/// without options.
+///
+/// This is a builder enum. See [`builder`](crate::fieldsets::builder).
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[non_exhaustive]
+pub enum DateFields {
+    /// The day of the month, as in
+    /// “on the 1st”.
+    D,
+    /// The month and day of the month, as in
+    /// “January 1st”.
+    MD,
+    /// The year, month, and day of the month, as in
+    /// “January 1st, 2000”.
+    YMD,
+    /// The day of the month and day of the week, as in
+    /// “Saturday 1st”.
+    DE,
+    /// The month, day of the month, and day of the week, as in
+    /// “Saturday, January 1st”.
+    MDE,
+    /// The year, month, day of the month, and day of the week, as in
+    /// “Saturday, January 1st, 2000”.
+    YMDE,
+    /// The day of the week alone, as in
+    /// “Saturday”.
+    E,
+    /// A standalone month, as in
+    /// “January”.
+    M,
+    /// A month and year, as in
+    /// “January 2000”.
+    YM,
+    /// A year, as in
+    /// “2000”.
+    Y,
+}
+
+/// An enumeration over all possible time zone styles.
+///
+/// This is a builder enum. See [`builder`](crate::fieldsets::builder).
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[non_exhaustive]
+pub enum ZoneStyle {
+    /// The long specific non-location format, as in
+    /// “Pacific Daylight Time”.
+    Z,
+    /// The short specific non-location format, as in
+    /// “PDT”.
+    Zs,
+    /// The long offset format, as in
+    /// “GMT−8:00”.
+    O,
+    /// The short offset format, as in
+    /// “GMT−8”.
+    Os,
+    /// The long generic non-location format, as in
+    /// “Pacific Time”.
+    V,
+    /// The short generic non-location format, as in
+    /// “PT”.
+    Vs,
+    /// The location format, as in
+    /// “Los Angeles time”.
+    L,
+}
+
+#[derive(Debug, displaydoc::Display)]
+#[non_exhaustive]
+pub enum BuilderError {
+    /// The specified fields are incompatible with the desired field set
+    InvalidFields,
+    /// The specified options are incompatible with the specified field set
+    InvalidOptions,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Default)]
+#[non_exhaustive]
+pub struct FieldSetBuilder {
+    pub length: Option<Length>,
+    pub date_fields: Option<DateFields>,
+    pub time_precision: Option<TimePrecision>,
+    pub zone_style: Option<ZoneStyle>,
+    pub alignment: Option<Alignment>,
+    pub year_style: Option<YearStyle>,
+}
+
+const DEFAULT_LENGTH: Length = Length::Medium;
+
+impl FieldSetBuilder {
+    pub fn build_date(mut self) -> Result<DateFieldSet, BuilderError> {
+        let date_field_set = match self.date_fields.take() {
+            Some(DateFields::D) => {
+                DateFieldSet::D(fieldsets::D::take_from_builder(&mut self, DEFAULT_LENGTH))
+            }
+            Some(DateFields::MD) => {
+                DateFieldSet::MD(fieldsets::MD::take_from_builder(&mut self, DEFAULT_LENGTH))
+            }
+            Some(DateFields::YMD) => {
+                DateFieldSet::YMD(fieldsets::YMD::take_from_builder(&mut self, DEFAULT_LENGTH))
+            }
+            Some(DateFields::DE) => {
+                DateFieldSet::DE(fieldsets::DE::take_from_builder(&mut self, DEFAULT_LENGTH))
+            }
+            Some(DateFields::MDE) => {
+                DateFieldSet::MDE(fieldsets::MDE::take_from_builder(&mut self, DEFAULT_LENGTH))
+            }
+            Some(DateFields::YMDE) => DateFieldSet::YMDE(fieldsets::YMDE::take_from_builder(
+                &mut self,
+                DEFAULT_LENGTH,
+            )),
+            Some(DateFields::E) => {
+                DateFieldSet::E(fieldsets::E::take_from_builder(&mut self, DEFAULT_LENGTH))
+            }
+            Some(DateFields::M) | Some(DateFields::YM) | Some(DateFields::Y) | None => {
+                return Err(BuilderError::InvalidFields)
+            }
+        };
+        self.check_options_consumed()?;
+        Ok(date_field_set)
+    }
+
+    pub fn build_time(mut self) -> Result<TimeFieldSet, BuilderError> {
+        let time_field_set =
+            TimeFieldSet::T(fieldsets::T::take_from_builder(&mut self, DEFAULT_LENGTH));
+        self.check_options_consumed()?;
+        Ok(time_field_set)
+    }
+
+    pub fn build_datetime(mut self) -> Result<CompositeDateTimeFieldSet, BuilderError> {
+        let datetime_field_set = match (self.date_fields.take(), self.time_precision.is_some()) {
+            (Some(DateFields::D), false) => CompositeDateTimeFieldSet::Date(DateFieldSet::D(
+                fieldsets::D::take_from_builder(&mut self, DEFAULT_LENGTH),
+            )),
+            (Some(DateFields::MD), false) => CompositeDateTimeFieldSet::Date(DateFieldSet::MD(
+                fieldsets::MD::take_from_builder(&mut self, DEFAULT_LENGTH),
+            )),
+            (Some(DateFields::YMD), false) => CompositeDateTimeFieldSet::Date(DateFieldSet::YMD(
+                fieldsets::YMD::take_from_builder(&mut self, DEFAULT_LENGTH),
+            )),
+            (Some(DateFields::DE), false) => CompositeDateTimeFieldSet::Date(DateFieldSet::DE(
+                fieldsets::DE::take_from_builder(&mut self, DEFAULT_LENGTH),
+            )),
+            (Some(DateFields::MDE), false) => CompositeDateTimeFieldSet::Date(DateFieldSet::MDE(
+                fieldsets::MDE::take_from_builder(&mut self, DEFAULT_LENGTH),
+            )),
+            (Some(DateFields::YMDE), false) => CompositeDateTimeFieldSet::Date(DateFieldSet::YMDE(
+                fieldsets::YMDE::take_from_builder(&mut self, DEFAULT_LENGTH),
+            )),
+            (Some(DateFields::E), false) => CompositeDateTimeFieldSet::Date(DateFieldSet::E(
+                fieldsets::E::take_from_builder(&mut self, DEFAULT_LENGTH),
+            )),
+            (Some(DateFields::M), false) => {
+                CompositeDateTimeFieldSet::CalendarPeriod(CalendarPeriodFieldSet::M(
+                    fieldsets::M::take_from_builder(&mut self, DEFAULT_LENGTH),
+                ))
+            }
+            (Some(DateFields::YM), false) => {
+                CompositeDateTimeFieldSet::CalendarPeriod(CalendarPeriodFieldSet::YM(
+                    fieldsets::YM::take_from_builder(&mut self, DEFAULT_LENGTH),
+                ))
+            }
+            (Some(DateFields::Y), false) => {
+                CompositeDateTimeFieldSet::CalendarPeriod(CalendarPeriodFieldSet::Y(
+                    fieldsets::Y::take_from_builder(&mut self, DEFAULT_LENGTH),
+                ))
+            }
+            (Some(DateFields::D), true) => {
+                CompositeDateTimeFieldSet::DateTime(DateAndTimeFieldSet::DT(
+                    fieldsets::DT::take_from_builder(&mut self, DEFAULT_LENGTH),
+                ))
+            }
+            (Some(DateFields::MD), true) => {
+                CompositeDateTimeFieldSet::DateTime(DateAndTimeFieldSet::MDT(
+                    fieldsets::MDT::take_from_builder(&mut self, DEFAULT_LENGTH),
+                ))
+            }
+            (Some(DateFields::YMD), true) => {
+                CompositeDateTimeFieldSet::DateTime(DateAndTimeFieldSet::YMDT(
+                    fieldsets::YMDT::take_from_builder(&mut self, DEFAULT_LENGTH),
+                ))
+            }
+            (Some(DateFields::DE), true) => {
+                CompositeDateTimeFieldSet::DateTime(DateAndTimeFieldSet::DET(
+                    fieldsets::DET::take_from_builder(&mut self, DEFAULT_LENGTH),
+                ))
+            }
+            (Some(DateFields::MDE), true) => {
+                CompositeDateTimeFieldSet::DateTime(DateAndTimeFieldSet::MDET(
+                    fieldsets::MDET::take_from_builder(&mut self, DEFAULT_LENGTH),
+                ))
+            }
+            (Some(DateFields::YMDE), true) => {
+                CompositeDateTimeFieldSet::DateTime(DateAndTimeFieldSet::YMDET(
+                    fieldsets::YMDET::take_from_builder(&mut self, DEFAULT_LENGTH),
+                ))
+            }
+            (Some(DateFields::E), true) => {
+                CompositeDateTimeFieldSet::DateTime(DateAndTimeFieldSet::ET(
+                    fieldsets::ET::take_from_builder(&mut self, DEFAULT_LENGTH),
+                ))
+            }
+            (None, true) => CompositeDateTimeFieldSet::Time(TimeFieldSet::T(
+                fieldsets::T::take_from_builder(&mut self, DEFAULT_LENGTH),
+            )),
+            (Some(DateFields::M), true)
+            | (Some(DateFields::YM), true)
+            | (Some(DateFields::Y), true)
+            | (None, false) => {
+                return Err(BuilderError::InvalidFields);
+            }
+        };
+        self.check_options_consumed()?;
+        Ok(datetime_field_set)
+    }
+
+    pub fn build(self) -> Result<CompositeFieldSet, BuilderError> {
+        todo!()
+    }
+
+    fn check_options_consumed(self) -> Result<(), BuilderError> {
+        if self != Self::default() {
+            Err(BuilderError::InvalidOptions)
+        } else {
+            Ok(())
+        }
+    }
+}

components/datetime/src/fieldsets.rs

@@ -49,6 +49,8 @@
 //! assert_eq!(field_set_1, field_set_2);
 //! ```
 
+#[path = "builder.rs"]
+pub mod builder;
 #[path = "dynamic.rs"]
 pub mod enums;
 
@@ -236,6 +238,18 @@ macro_rules! impl_marker_with_options {
                     $(time_precision: yes_to!(options.time_precision, $timeprecision_yes),)?
                 }
             }
+            #[allow(unused)]
+            pub(crate) fn take_from_builder(
+                options: &mut builder::FieldSetBuilder,
+                default_length: Length
+            ) -> Self {
+                Self {
+                    $(length: yes_to!(options.length.take().unwrap_or(default_length), $sample_length),)?
+                    $(alignment: yes_to!(options.alignment.take(), $alignment_yes),)?
+                    $(year_style: yes_to!(options.year_style.take(), $yearstyle_yes),)?
+                    $(time_precision: yes_to!(options.time_precision.take(), $timeprecision_yes),)?
+                }
+            }
         }
         $(
             impl $type {