daterange: support relative terms

Support relative terms when writing date ranges in the search and filter
commands with the -d flag. Syntax is inspired by the notmuch search
terms.

Terms can be written with spaces or underscores for a better
readability, so both "this_week" and "this week" are allowed. Terms are
not case-sensitive.

Some terms can be prefixed with either "this" or "last" where applicable
("this" is assumed by default if omitted):

- "today", "yesterday"
- ("this"|"last") "year", "month", "week"
- all weekdays (e.g. "Tuesday", "last_wed")
- all months  (e.g. "January", "last_feb")

Note that "month" should always be spelled out to prevent a possible
ambiguity with "Monday".

Weekdays and months do not need to be written out completely, i.e.
"February..March" and "Feb..Mar" are both understood.

Relative date terms can be used with the <N (year|month|week|day)>
syntax where N is a positive integer indicating the number of time units
in the past from today. The units can be abbreviated with a single
letter, e.g. "1w 1d.." is the same as "1 week 1 day..".

More examples:
:filter -d yesterday
:filter -d last_monday..
:filter -d mon..sat
:filter -d 1y1m1w1d..
:search -d this_week "PATCH aerc"

Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

4 files changed, 475 insertions, 5 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6c6a1d92..f356122c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   defined in their environment.`
 - Override the subject prefix prefix for replies pattern with
   `subject-re-pattern`.
+- Search/filter by absolute and relative date ranges with the `-d` flag.
 
 ### Fixed
 
diff --git a/doc/aerc-search.1.scd b/doc/aerc-search.1.scd
index 51e93ade..8349874b 100644
--- a/doc/aerc-search.1.scd
+++ b/doc/aerc-search.1.scd
@@ -44,6 +44,25 @@ aerc-search - search and filter patterns and options for *aerc*(1)
 		Search for messages within a particular date range defined as
 		\[start, end) where the dates are in the YYYY-MM-DD format.
 
+		Relative dates can be used to specify a date range. Spaces and
+		underscores are allowed to improve readability:
+
+		*today*, *yesterday*
+
+		*(this|last) (year|month|week)*
+
+		*Weekdays*, *Monthnames*
+			Can also be abbreviate, so Monday..Tuesday can written
+			as Mon..Tue and February..March as Feb..Mar.
+
+		_<N>_ *(y[ear]|m[onth]|w[eek]|d[ay])*
+			_<N>_ is a positive integer that represents the number
+			of the time units in the past. Mutiple relative terms
+			can will be accumulated. The units can also be
+			abbreviated by a single letter such that yesterday would
+			correspond to _1d_ (equivalent to _1 day_ or _1_day_)
+			and _8 days ago_ would be either _1w1d_ or _8d_.
+
 # NOTMUCH
 
 *search* _query_...
diff --git a/worker/lib/daterange.go b/worker/lib/daterange.go
index c996392c..b08bf177 100644
--- a/worker/lib/daterange.go
+++ b/worker/lib/daterange.go
@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"strings"
 	"time"
+
+	"git.sr.ht/~rjarry/aerc/log"
 )
 
 const dateFmt = "2006-01-02"
@@ -16,13 +18,16 @@ const dateFmt = "2006-01-02"
 //
 // ParseDateRange can also parse open-ended ranges, i.e. start.. or ..end are
 // allowed.
+//
+// Relative date terms (such as "1 week 1 day" or "1w 1d") can be used, too.
 func ParseDateRange(s string) (start, end time.Time, err error) {
-	s = strings.ReplaceAll(s, " ", "")
+	s = cleanInput(s)
+	s = ensureRangeOp(s)
 	i := strings.Index(s, "..")
 	switch {
 	case i < 0:
 		// single date
-		start, err = time.Parse(dateFmt, s)
+		start, err = translate(s)
 		if err != nil {
 			err = fmt.Errorf("failed to parse date: %w", err)
 			return
@@ -35,7 +40,7 @@ func ParseDateRange(s string) (start, end time.Time, err error) {
 			err = fmt.Errorf("no date found")
 			return
 		}
-		end, err = time.Parse(dateFmt, s[2:])
+		end, err = translate(s[2:])
 		if err != nil {
 			err = fmt.Errorf("failed to parse date: %w", err)
 			return
@@ -43,7 +48,7 @@ func ParseDateRange(s string) (start, end time.Time, err error) {
 
 	case i > 0:
 		// start date first
-		start, err = time.Parse(dateFmt, s[:i])
+		start, err = translate(s[:i])
 		if err != nil {
 			err = fmt.Errorf("failed to parse date: %w", err)
 			return
@@ -52,7 +57,7 @@ func ParseDateRange(s string) (start, end time.Time, err error) {
 			return
 		}
 		// and end dates if available
-		end, err = time.Parse(dateFmt, s[(i+2):])
+		end, err = translate(s[(i + 2):])
 		if err != nil {
 			err = fmt.Errorf("failed to parse date: %w", err)
 			return
@@ -61,3 +66,406 @@ func ParseDateRange(s string) (start, end time.Time, err error) {
 
 	return
 }
+
+type dictFunc = func(bool) time.Time
+
+// dict is a dictionary to translate words to dates. Map key must be at least 3
+// characters for matching purposes.
+var dict map[string]dictFunc = map[string]dictFunc{
+	"today": func(_ bool) time.Time {
+		return time.Now()
+	},
+	"yesterday": func(_ bool) time.Time {
+		return time.Now().AddDate(0, 0, -1)
+	},
+	"week": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -7
+		}
+		return time.Now().AddDate(0, 0,
+			daydiff(time.Monday)+diff)
+	},
+	"month": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(0, diff, -t.Day()+1)
+	},
+	"year": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff, 0, -t.YearDay()+1)
+	},
+	"monday": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -7
+		}
+		return time.Now().AddDate(0, 0,
+			daydiff(time.Monday)+diff)
+	},
+	"tuesday": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -7
+		}
+		return time.Now().AddDate(0, 0,
+			daydiff(time.Tuesday)+diff)
+	},
+	"wednesday": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -7
+		}
+		return time.Now().AddDate(0, 0,
+			daydiff(time.Wednesday)+diff)
+	},
+	"thursday": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -7
+		}
+		return time.Now().AddDate(0, 0,
+			daydiff(time.Thursday)+diff)
+	},
+	"friday": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -7
+		}
+		return time.Now().AddDate(0, 0,
+			daydiff(time.Friday)+diff)
+	},
+	"saturday": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -7
+		}
+		return time.Now().AddDate(0, 0,
+			daydiff(time.Saturday)+diff)
+	},
+	"sunday": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -7
+		}
+		return time.Now().AddDate(0, 0,
+			daydiff(time.Sunday)+diff)
+	},
+	"january": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.January), -t.Day()+1)
+	},
+	"february": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.February), -t.Day()+1)
+	},
+	"march": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.March), -t.Day()+1)
+	},
+	"april": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.April), -t.Day()+1)
+	},
+	"may": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.May), -t.Day()+1)
+	},
+	"june": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.June), -t.Day()+1)
+	},
+	"july": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.July), -t.Day()+1)
+	},
+	"august": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.August), -t.Day()+1)
+	},
+	"september": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.September), -t.Day()+1)
+	},
+	"october": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.October), -t.Day()+1)
+	},
+	"november": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.November), -t.Day()+1)
+	},
+	"december": func(this bool) time.Time {
+		diff := 0
+		if !this {
+			diff = -1
+		}
+		t := time.Now()
+		return t.AddDate(diff,
+			monthdiff(time.December), -t.Day()+1)
+	},
+}
+
+func daydiff(d time.Weekday) int {
+	daydiff := d - time.Now().Weekday()
+	if daydiff > 0 {
+		return int(daydiff) - 7
+	}
+	return int(daydiff)
+}
+
+func monthdiff(d time.Month) int {
+	monthdiff := d - time.Now().Month()
+	if monthdiff > 0 {
+		return int(monthdiff) - 12
+	}
+	return int(monthdiff)
+}
+
+// translate translates regular time words into date strings
+func translate(s string) (time.Time, error) {
+	if s == "" {
+		return time.Now(), fmt.Errorf("empty string")
+	}
+	log.Tracef("input: %s", s)
+	s0 := s
+
+	// if next characters is integer, then parse a relative date
+	if '0' <= s[0] && s[0] <= '9' && hasUnit(s) {
+		relDate, err := ParseRelativeDate(s)
+		if err != nil {
+			log.Errorf("could not parse relative date from '%s': %v",
+				s0, err)
+		} else {
+			log.Tracef("relative date: translated to %v from %s",
+				relDate, s0)
+			return bod(relDate.Apply(time.Now())), nil
+		}
+	}
+
+	// consult dictionary for terms translation
+	s, this, hasPrefix := handlePrefix(s)
+	for term, dateFn := range dict {
+		if term == "month" && !hasPrefix {
+			continue
+		}
+		if strings.Contains(term, s) {
+			log.Tracef("dictionary: translated to %s from %s",
+				term, s0)
+			return bod(dateFn(this)), nil
+		}
+	}
+
+	// this is a regular date, parse it in the normal format
+	log.Infof("parse: translates %s to regular format", s0)
+	return time.Parse(dateFmt, s)
+}
+
+// bod returns the begin of the day
+func bod(t time.Time) time.Time {
+	y, m, d := t.Date()
+	return time.Date(y, m, d, 0, 0, 0, 0, t.Location())
+}
+
+func handlePrefix(s string) (string, bool, bool) {
+	var hasPrefix bool
+	this := true
+	if strings.HasPrefix(s, "this") {
+		hasPrefix = true
+		s = strings.TrimPrefix(s, "this")
+	}
+	if strings.HasPrefix(s, "last") {
+		hasPrefix = true
+		this = false
+		s = strings.TrimPrefix(s, "last")
+	}
+	return s, this, hasPrefix
+}
+
+func cleanInput(s string) string {
+	s = strings.ToLower(s)
+	s = strings.ReplaceAll(s, " ", "")
+	s = strings.ReplaceAll(s, "_", "")
+	return s
+}
+
+// RelDate is the relative date in the past, e.g. yesterday would be
+// represented as RelDate{0,0,1}.
+type RelDate struct {
+	Year  uint
+	Month uint
+	Day   uint
+}
+
+func (d RelDate) Apply(t time.Time) time.Time {
+	return t.AddDate(-int(d.Year), -int(d.Month), -int(d.Day))
+}
+
+// ParseRelativeDate parses a string of relative terms into a DateAdd.
+//
+// Syntax: N (year|month|week|day) ..
+//
+// The following are valid inputs:
+// 5weeks1day
+// 5w1d
+//
+// Adapted from the Go stdlib in src/time/format.go
+func ParseRelativeDate(s string) (RelDate, error) {
+	s0 := s
+	s = cleanInput(s)
+	var da RelDate
+	for s != "" {
+		var n uint
+
+		var err error
+
+		// expect an integer
+		if !('0' <= s[0] && s[0] <= '9') {
+			return da, fmt.Errorf("not a valid relative term: %s",
+				s0)
+		}
+
+		// consume integer
+		n, s, err = leadingInt(s)
+		if err != nil {
+			return da, fmt.Errorf("cannot read integer in %s",
+				s0)
+		}
+
+		// consume the units
+		i := 0
+		for ; i < len(s); i++ {
+			c := s[i]
+			if '0' <= c && c <= '9' {
+				break
+			}
+		}
+		if i == 0 {
+			return da, fmt.Errorf("missing unit in %s", s0)
+		}
+
+		u := s[:i]
+		s = s[i:]
+		switch u[0] {
+		case 'y':
+			da.Year += n
+		case 'm':
+			da.Month += n
+		case 'w':
+			da.Day += 7 * n
+		case 'd':
+			da.Day += n
+		default:
+			return da, fmt.Errorf("unknown unit %s in %s", u, s0)
+		}
+
+	}
+
+	return da, nil
+}
+
+func hasUnit(s string) (has bool) {
+	for _, u := range "ymwd" {
+		if strings.Contains(s, string(u)) {
+			return true
+		}
+	}
+	return false
+}
+
+// leadingInt parses and returns the leading integer in s.
+//
+// Adapted from the Go stdlib in src/time/format.go
+func leadingInt(s string) (x uint, rem string, err error) {
+	i := 0
+	for ; i < len(s); i++ {
+		c := s[i]
+		if c < '0' || c > '9' {
+			break
+		}
+		x = x*10 + uint(c) - '0'
+	}
+	return x, s[i:], nil
+}
+
+func ensureRangeOp(s string) string {
+	if strings.Contains(s, "..") {
+		return s
+	}
+	s0 := s
+	for _, m := range []string{"this", "last"} {
+		for _, u := range []string{"year", "month", "week"} {
+			term := m + u
+			if strings.Contains(s, term) {
+				if m == "last" {
+					return s0 + "..this" + u
+				} else {
+					return s0 + ".."
+				}
+			}
+		}
+	}
+	return s0
+}
diff --git a/worker/lib/daterange_test.go b/worker/lib/daterange_test.go
index 983f99a0..807e7ac7 100644
--- a/worker/lib/daterange_test.go
+++ b/worker/lib/daterange_test.go
@@ -1,6 +1,7 @@
 package lib_test
 
 import (
+	"reflect"
 	"testing"
 	"time"
 
@@ -53,3 +54,44 @@ func TestParseDateRange(t *testing.T) {
 		}
 	}
 }
+
+func TestParseRelativeDate(t *testing.T) {
+	tests := []struct {
+		s    string
+		want lib.RelDate
+	}{
+		{
+			s:    "5 weeks 1 day",
+			want: lib.RelDate{Year: 0, Month: 0, Day: 5*7 + 1},
+		},
+		{
+			s:    "5_weeks 1_day",
+			want: lib.RelDate{Year: 0, Month: 0, Day: 5*7 + 1},
+		},
+		{
+			s:    "5weeks1day",
+			want: lib.RelDate{Year: 0, Month: 0, Day: 5*7 + 1},
+		},
+		{
+			s:    "5w1d",
+			want: lib.RelDate{Year: 0, Month: 0, Day: 5*7 + 1},
+		},
+		{
+			s:    "5y4m3w1d",
+			want: lib.RelDate{Year: 5, Month: 4, Day: 3*7 + 1},
+		},
+	}
+
+	for _, test := range tests {
+		da, err := lib.ParseRelativeDate(test.s)
+		if err != nil {
+			t.Errorf("ParseRelativeDate return error for %s: %v",
+				test.s, err)
+		}
+
+		if !reflect.DeepEqual(da, test.want) {
+			t.Errorf("results don't match. expected %v, got %v",
+				test.want, da)
+		}
+	}
+}