Print date as dd/mm or mm/dd depending on the user locale

Overkill, but this was a nice weekend project :-)

Fixes: https://todo.sr.ht/~taiite/senpai/107

3 files changed, 60 insertions, 9 deletions

diff --git a/go.mod b/go.mod
index 6bc57ac..2c304cd 100644
--- a/go.mod
+++ b/go.mod
@@ -4,7 +4,7 @@ go 1.16
 
 require (
 	git.sr.ht/~emersion/go-scfg v0.0.0-20201019143924-142a8aa629fc
-	github.com/gdamore/encoding v1.0.0
+	github.com/delthas/go-localeinfo v0.0.0-20221115102303-5a7785a1acc1
 	github.com/gdamore/tcell/v2 v2.5.4-0.20221017224006-ede1dd5ee680
 	github.com/mattn/go-runewidth v0.0.14
 	golang.org/x/net v0.0.0-20220722155237-a158d28d115b
diff --git a/go.sum b/go.sum
index cb2a317..afa9274 100644
--- a/go.sum
+++ b/go.sum
@@ -2,6 +2,8 @@ git.sr.ht/~emersion/go-scfg v0.0.0-20201019143924-142a8aa629fc h1:51BD67xFX+bozd
 git.sr.ht/~emersion/go-scfg v0.0.0-20201019143924-142a8aa629fc/go.mod h1:t+Ww6SR24yYnXzEWiNlOY0AFo5E9B73X++10lrSpp4U=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/delthas/go-localeinfo v0.0.0-20221115102303-5a7785a1acc1 h1:sCu9bac1vv1LMBOsnUymZsi4iTO5PBQqn2Z3KJiGXXg=
+github.com/delthas/go-localeinfo v0.0.0-20221115102303-5a7785a1acc1/go.mod h1:sG54BxlyQgIskYURLrg7mvhoGBe0Qq12DNtYRALwNa4=
 github.com/gdamore/encoding v1.0.0 h1:+7OoQ1Bc6eTm5niUzBa0Ctsh6JbMW6Ra+YNuAtDBdko=
 github.com/gdamore/encoding v1.0.0/go.mod h1:alR0ol34c49FCSBLjhosxzcPHQbf2trDkoo5dl+VrEg=
 github.com/gdamore/tcell/v2 v2.5.4-0.20221017224006-ede1dd5ee680 h1:bCjGvZsZNvhzJZ+gDmXpKdDPyf358nSPqepaTI1AsMQ=
diff --git a/ui/draw_utils.go b/ui/draw_utils.go
index 3d04f11..62f2d79 100644
--- a/ui/draw_utils.go
+++ b/ui/draw_utils.go
@@ -2,8 +2,12 @@ package ui
 
 import (
 	"fmt"
+	"strings"
+	"sync"
 	"time"
 
+	"github.com/delthas/go-localeinfo"
+
 	"github.com/gdamore/tcell/v2"
 )
 
@@ -42,17 +46,62 @@ func printNumber(screen tcell.Screen, x *int, y int, st tcell.Style, n int) {
 	printString(screen, x, y, s)
 }
 
+var dateConfig sync.Once
+var dateMonthFirst bool
+
+func loadDateInfo() {
+	// Very overkill, but I like it :)
+	// Try to extract from the user locale whether they'd rather have the date
+	// printed as dd/mm or mm/dd.
+	// If we're not sure, print dd/mm.
+	l, err := localeinfo.NewLocale("")
+	if err != nil {
+		return
+	}
+	format := l.DateFormat()
+	dayIndex := -1
+	for _, s := range []string{"%d", "%e"} {
+		dayIndex = strings.Index(format, s)
+		if dayIndex >= 0 {
+			break
+		}
+	}
+	if dayIndex == -1 {
+		return
+	}
+	monthIndex := -1
+	for _, s := range []string{"%m", "%b", "%B"} {
+		monthIndex = strings.Index(format, s)
+		if monthIndex >= 0 {
+			break
+		}
+	}
+	if monthIndex == -1 {
+		return
+	}
+	if monthIndex < dayIndex {
+		dateMonthFirst = true
+	}
+}
+
 func printDate(screen tcell.Screen, x int, y int, st tcell.Style, t time.Time) {
+	dateConfig.Do(loadDateInfo)
 	_, m, d := t.Date()
-	d0 := rune(d/10) + '0'
-	d1 := rune(d%10) + '0'
-	m0 := rune(m/10) + '0'
-	m1 := rune(m%10) + '0'
-	screen.SetContent(x+0, y, d0, nil, st)
-	screen.SetContent(x+1, y, d1, nil, st)
+	var left, right int
+	if dateMonthFirst {
+		left, right = int(m), d
+	} else {
+		left, right = d, int(m)
+	}
+	l0 := rune(left/10) + '0'
+	l1 := rune(left%10) + '0'
+	r0 := rune(right/10) + '0'
+	r1 := rune(right%10) + '0'
+	screen.SetContent(x+0, y, l0, nil, st)
+	screen.SetContent(x+1, y, l1, nil, st)
 	screen.SetContent(x+2, y, '/', nil, st)
-	screen.SetContent(x+3, y, m0, nil, st)
-	screen.SetContent(x+4, y, m1, nil, st)
+	screen.SetContent(x+3, y, r0, nil, st)
+	screen.SetContent(x+4, y, r1, nil, st)
 }
 
 func printTime(screen tcell.Screen, x int, y int, st tcell.Style, t time.Time) {