From b0fd3bf373abe05f23b71d3dc49edde75506e5fa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9o=20LUDWIG?= <contact@theoludwig.fr>
Date: Tue, 8 Oct 2024 08:47:16 +0200
Subject: [PATCH] feat(date): add `date_get_age`

Fixes #7
---
 lib/date.c       |  8 ++++++++
 lib/date.h       |  9 +++++++++
 test/date_test.c | 27 +++++++++++++++++++++++++++
 test/date_test.h |  2 ++
 4 files changed, 46 insertions(+)

diff --git a/lib/date.c b/lib/date.c
index 5b077b2..3e22204 100644
--- a/lib/date.c
+++ b/lib/date.c
@@ -329,3 +329,11 @@ struct date *date_get_now_local() {
 
   return date;
 }
+
+uint16_t date_get_age(struct date *birth_date, struct date *current_date) {
+  uint16_t age = current_date->year - birth_date->year;
+  if (current_date->month < birth_date->month || (current_date->month == birth_date->month && current_date->day < birth_date->day)) {
+    age--;
+  }
+  return age;
+}
diff --git a/lib/date.h b/lib/date.h
index dceb869..8a80bde 100644
--- a/lib/date.h
+++ b/lib/date.h
@@ -338,4 +338,13 @@ struct date *date_get_now_utc();
  */
 struct date *date_get_now_local();
 
+/**
+ * @brief Calculates the age of a person based on their birth date.
+ *
+ * @param birth_date
+ * @return uint16_t
+ * @since v5.1.0
+ */
+uint16_t date_get_age(struct date *birth_date, struct date *current_date);
+
 #endif
diff --git a/test/date_test.c b/test/date_test.c
index ba03d8b..28181d1 100644
--- a/test/date_test.c
+++ b/test/date_test.c
@@ -8,6 +8,7 @@ void date_test() {
   date_get_is_leap_year_test();
   date_duration_seconds_between_2_dates_test();
   date_to_utc_test();
+  date_get_age_test();
 }
 
 void date_copy_test() {
@@ -162,3 +163,29 @@ void date_to_utc_test() {
   free(iso_string);
   free(date);
 }
+
+void date_get_age_test() {
+  struct date *birth_date = date_from_iso_string("1980-02-20T00:00:00.000Z");
+  struct date *current_date = date_from_iso_string("2018-03-20T00:00:00.000Z");
+  assert(date_get_age(birth_date, current_date) == 38);
+  free(birth_date);
+  free(current_date);
+
+  birth_date = date_from_iso_string("1980-07-20T00:00:00.000Z");
+  current_date = date_from_iso_string("2018-03-20T00:00:00.000Z");
+  assert(date_get_age(birth_date, current_date) == 37);
+  free(birth_date);
+  free(current_date);
+
+  birth_date = date_from_iso_string("1980-03-20T00:00:00.000Z");
+  current_date = date_from_iso_string("2018-03-20T00:00:00.000Z");
+  assert(date_get_age(birth_date, current_date) == 38);
+  free(birth_date);
+  free(current_date);
+
+  birth_date = date_from_iso_string("1980-03-25T00:00:00.000Z");
+  current_date = date_from_iso_string("2018-03-20T00:00:00.000Z");
+  assert(date_get_age(birth_date, current_date) == 37);
+  free(birth_date);
+  free(current_date);
+}
diff --git a/test/date_test.h b/test/date_test.h
index d3ec9b7..a415018 100644
--- a/test/date_test.h
+++ b/test/date_test.h
@@ -21,4 +21,6 @@ void date_duration_seconds_between_2_dates_test();
 
 void date_to_utc_test();
 
+void date_get_age_test();
+
 #endif