feat(core): Add "relative dates"

core/datepatterns.txt

@@ -20,6 +20,18 @@ weekday monthname day[ hour24:min[:sec]] fullyear
 year monthname day[ hour12:min[:sec] meridiem[ offset]][ adbc]
 year monthname day[ hour24:min[:sec][ offset]][ adbc]
 
-# Today dates
+# Relative dates
+today
+today:adddays
+today:-subdays
+today[:[adddays][-subdays]] hour12:min[:sec] meridiem[ offset]
+today[:[adddays][-subdays]] hour24:min[:sec][ offset]
+hour12:min[:sec] meridiem[ offset]
+hour24:min[:sec][ offset]
+
+today:'W'addweeks
+today:'W'subweeks
+today[:'W'[addweeks][-subweeks]] hour12:min[:sec] meridiem[ offset]
+today[:'W'[addweeks][-subweeks]] hour24:min[:sec][ offset]
 hour12:min[:sec] meridiem[ offset]
 hour24:min[:sec][ offset]

core/src/parsing/datetime.rs

@@ -6,7 +6,7 @@ use crate::ast::{DatePattern, DateToken};
 use crate::loader::Context;
 use crate::types::{BaseUnit, BigInt, BigRat, Dimensionality, GenericDateTime, Number, Numeric};
 use chrono::format::Parsed;
-use chrono::{DateTime, Duration, FixedOffset, Local, TimeZone, Weekday};
+use chrono::{DateTime, Datelike, Days, Duration, FixedOffset, Local, TimeZone, Weekday};
 use chrono_tz::Tz;
 use std::iter::Peekable;
 use std::str::FromStr;
@@ -303,6 +303,81 @@ where
                 }
                 x => Err(format!("Expected weekday, got {}", ts(x))),
             },
+            "today" => match tok {
+                Some(DateToken::Literal(ref s)) if s == "today" => {
+                    let date = Local::now().date_naive();
+                    *out = Parsed::new();
+                    out.year = Some(date.year());
+                    out.month = Some(date.month());
+                    out.day = Some(date.day());
+                    Ok(())
+                },
+                x => Err(format!("Expected `today`, got {}", ts(x))),
+            },
+            "adddays" => numeric_match(tok.as_ref(), "adddays", 0, 0..=i32::MAX).and_then(|days| {
+                let date = out.to_naive_date().expect("The parser should parse only correct dates and handle invalid cases by itself, chrono should not error here");
+                let add = Days::new(days as u64);
+                match date.checked_add_days(add) {
+                    Some(date) => {
+                        *out = Parsed::new();
+                        out.year = Some(date.year());
+                        out.month = Some(date.month());
+                        out.day = Some(date.day());
+                        Ok(())
+                    },
+                    None => {
+                        Err(format!("Expected valid date, out of bounds"))
+                    }
+                }
+            }),
+            "subdays" => numeric_match(tok.as_ref(), "subdays", 0, 0..=i32::MAX).and_then(|days| {
+                let date = out.to_naive_date().expect("The parser should parse only correct dates and handle invalid cases by itself, chrono should not error here");
+                let sub = Days::new(days as u64);
+                match date.checked_sub_days(sub) {
+                    Some(date) => {
+                        *out = Parsed::new();
+                        out.year = Some(date.year());
+                        out.month = Some(date.month());
+                        out.day = Some(date.day());
+                        Ok(())
+                    },
+                    None => {
+                        Err(format!("Expected valid date, out of bounds"))
+                    }
+                }
+            }),
+            "addweeks" => numeric_match(tok.as_ref(), "addweeks", 0, 0..=(i32::MAX / 7)).and_then(|weeks| {
+                let date = out.to_naive_date().expect("The parser should parse only correct dates and handle invalid cases by itself, chrono should not error here");
+                let add = Days::new(7 * weeks as u64);
+                match date.checked_add_days(add) {
+                    Some(date) => {
+                        *out = Parsed::new();
+                        out.year = Some(date.year());
+                        out.month = Some(date.month());
+                        out.day = Some(date.day());
+                        Ok(())
+                    },
+                    None => {
+                        Err(format!("Expected valid date, out of bounds"))
+                    }
+                }
+            }),
+            "subweeks" => numeric_match(tok.as_ref(), "subweeks", 0, 0..=(i32::MAX / 7)).and_then(|weeks| {
+                let date = out.to_naive_date().expect("The parser should parse only correct dates and handle invalid cases by itself, chrono should not error here");
+                let sub = Days::new(7 * weeks as u64);
+                match date.checked_sub_days(sub) {
+                    Some(date) => {
+                        *out = Parsed::new();
+                        out.year = Some(date.year());
+                        out.month = Some(date.month());
+                        out.day = Some(date.day());
+                        Ok(())
+                    },
+                    None => {
+                        Err(format!("Expected valid date, out of bounds"))
+                    }
+                }
+            }),
             x => Err(format!("Unknown match pattern `{}`", x)),
         },
         Some(&DatePattern::Optional(ref pats)) => {

docs/rink-dates.5.adoc

@@ -94,6 +94,26 @@ The valid keywords are:
 	Makes English weekday names, case insensitive. Recognizes 3-letter
 	names (like mon, tue, wed) and full names.
 
+**today**::
+	Specifies a relative date. Resets the date to the current date in the
+	local timezone, with time at 00:00.
+
+**adddays**::
+	Matches a number of days. Can be any number of digits. Adds that amount
+	of days to the date relative to **today**.
+
+**subdays**::
+	Matches a number of days. Can be any number of digits. Subtracts that
+	amount of days from the date relative to **today**.
+
+**addweeks**::
+	Matches a number of weeks. Can be any number of digits. Adds that
+	amount of weeks to the date relative to **today**.
+
+**subweeks**::
+	Matches a number of weeks. Can be any number of digits. Subtracts that
+	amount of weeks from the date relative to **today**.
+
 **`-`**::
 	Matches a literal `-` character.