Implement a formatter for relative dates.

Signed-off-by: Adrien Destugues <[email protected]>

It can give results such as "in 2 hours", "2 days ago", etc.
This is different from BDurationFormat which will just say "1 hour, 2
minute and 36 seconds"

headers/os/locale/RelativeDateTimeFormat.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2017, Haiku, Inc. All Rights Reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Akshay Agarwal <[email protected]>
+ */
+#ifndef _B_RELATIVE_DATE_TIME_FORMAT_H_
+#define _B_RELATIVE_DATE_TIME_FORMAT_H_
+
+
+#include <Format.h>
+#include <SupportDefs.h>
+
+
+class BString;
+
+#ifndef U_ICU_NAMESPACE
+  #define U_ICU_NAMESPACE icu
+#endif
+namespace U_ICU_NAMESPACE {
+	class GregorianCalendar;
+	class RelativeDateTimeFormatter;
+}
+
+
+class BRelativeDateTimeFormat: public BFormat {
+	typedef BFormat				Inherited;
+public:
+								BRelativeDateTimeFormat();
+								BRelativeDateTimeFormat(const BLanguage& language,
+									const BFormattingConventions& conventions);
+								BRelativeDateTimeFormat(const BRelativeDateTimeFormat& other);
+			virtual				~BRelativeDateTimeFormat();
+
+			status_t			Format(BString& string, const time_t timeValue) const;
+
+private:
+			U_ICU_NAMESPACE::RelativeDateTimeFormatter*	fFormatter;
+			U_ICU_NAMESPACE::GregorianCalendar*	fCalendar;
+};
+
+
+#endif	// _B_RELATIVE_DATE_TIME_FORMAT_H_

src/kits/locale/Jamfile

@@ -34,6 +34,7 @@ local sources =
 	TimeUnitFormat.cpp
 	Format.cpp # Used by some of the above.
 	UnicodeChar.cpp # Already used in FirstBootPrompt.
+	RelativeDateTimeFormat.cpp
 	;
 
 local architectureObject ;

src/kits/locale/RelativeDateTimeFormat.cpp

@@ -0,0 +1,163 @@
+/*
+ * Copyright 2017, Haiku, Inc. All Rights Reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Akshay Agarwal <[email protected]>
+ */
+
+
+#include <unicode/uversion.h>
+#include <RelativeDateTimeFormat.h>
+
+#include <stdlib.h>
+#include <time.h>
+
+#include <unicode/gregocal.h>
+#include <unicode/reldatefmt.h>
+#include <unicode/utypes.h>
+
+#include <ICUWrapper.h>
+
+#include <Language.h>
+#include <Locale.h>
+#include <LocaleRoster.h>
+#include <TimeUnitFormat.h>
+
+
+static const URelativeDateTimeUnit kTimeUnitToRelativeDateTime[] = {
+	UDAT_REL_UNIT_YEAR,
+	UDAT_REL_UNIT_MONTH,
+	UDAT_REL_UNIT_WEEK,
+	UDAT_REL_UNIT_DAY,
+	UDAT_REL_UNIT_HOUR,
+	UDAT_REL_UNIT_MINUTE,
+	UDAT_REL_UNIT_SECOND,
+};
+
+
+static const UCalendarDateFields kTimeUnitToICUDateField[] = {
+	UCAL_YEAR,
+	UCAL_MONTH,
+	UCAL_WEEK_OF_MONTH,
+	UCAL_DAY_OF_WEEK,
+	UCAL_HOUR_OF_DAY,
+	UCAL_MINUTE,
+	UCAL_SECOND,
+};
+
+
+BRelativeDateTimeFormat::BRelativeDateTimeFormat()
+	: Inherited()
+{
+	Locale icuLocale(fLanguage.Code());
+	UErrorCode icuStatus = U_ZERO_ERROR;
+
+	fFormatter = new RelativeDateTimeFormatter(icuLocale, icuStatus);
+	if (fFormatter == NULL) {
+		fInitStatus = B_NO_MEMORY;
+		return;
+	}
+
+	fCalendar = new GregorianCalendar(icuStatus);
+	if (fCalendar == NULL) {
+		fInitStatus = B_NO_MEMORY;
+		return;
+	}
+
+	if (!U_SUCCESS(icuStatus))
+		fInitStatus = B_ERROR;
+}
+
+
+BRelativeDateTimeFormat::BRelativeDateTimeFormat(const BLanguage& language,
+	const BFormattingConventions& conventions)
+	: Inherited(language, conventions)
+{
+	Locale icuLocale(fLanguage.Code());
+	UErrorCode icuStatus = U_ZERO_ERROR;
+
+	fFormatter = new RelativeDateTimeFormatter(icuLocale, icuStatus);
+	if (fFormatter == NULL) {
+		fInitStatus = B_NO_MEMORY;
+		return;
+	}
+
+	fCalendar = new GregorianCalendar(icuStatus);
+	if (fCalendar == NULL) {
+		fInitStatus = B_NO_MEMORY;
+		return;
+	}
+
+	if (!U_SUCCESS(icuStatus))
+		fInitStatus = B_ERROR;
+}
+
+
+BRelativeDateTimeFormat::BRelativeDateTimeFormat(const BRelativeDateTimeFormat& other)
+	: Inherited(other),
+	fFormatter(other.fFormatter != NULL
+		? new RelativeDateTimeFormatter(*other.fFormatter) : NULL),
+	fCalendar(other.fCalendar != NULL
+		? new GregorianCalendar(*other.fCalendar) : NULL)
+{
+	if ((fFormatter == NULL && other.fFormatter != NULL)
+		|| (fCalendar == NULL && other.fCalendar != NULL))
+		fInitStatus = B_NO_MEMORY;
+}
+
+
+BRelativeDateTimeFormat::~BRelativeDateTimeFormat()
+{
+	delete fFormatter;
+	delete fCalendar;
+}
+
+
+status_t
+BRelativeDateTimeFormat::Format(BString& string,
+	const time_t timeValue) const
+{
+	if (fFormatter == NULL)
+		return B_NO_INIT;
+
+	time_t currentTime = time(NULL);
+
+	UErrorCode icuStatus = U_ZERO_ERROR;
+	fCalendar->setTime((UDate)currentTime * 1000, icuStatus);
+	if (!U_SUCCESS(icuStatus))
+		return B_ERROR;
+
+	UDate UTimeValue = (UDate)timeValue * 1000;
+
+	int delta = 0;
+	int offset = 1;
+	URelativeDateTimeUnit unit = UDAT_REL_UNIT_SECOND;
+
+	for (int timeUnit = 0; timeUnit <= B_TIME_UNIT_LAST; ++timeUnit) {
+		delta = fCalendar->fieldDifference(UTimeValue,
+			kTimeUnitToICUDateField[timeUnit], icuStatus);
+
+		if (!U_SUCCESS(icuStatus))
+			return B_ERROR;
+
+		if (abs(delta) >= offset) {
+			unit = kTimeUnitToRelativeDateTime[timeUnit];
+			break;
+		}
+	}
+
+	UnicodeString unicodeResult;
+
+	// Note: icu::RelativeDateTimeFormatter::formatNumeric() is a part of ICU Draft API
+	// and may be changed in the future versions and was introduced in ICU 57.
+	fFormatter->formatNumeric(delta, unit, unicodeResult, icuStatus);
+
+	if (!U_SUCCESS(icuStatus))
+		return B_ERROR;
+
+	BStringByteSink byteSink(&string);
+	unicodeResult.toUTF8(byteSink);
+
+	return B_OK;
+}