Add initial TOTP watch face impl

Vendor code from https://github.com/Netthaw/TOTP-MCU to do the
heavy lifting of computing SHA-1 and HMAC and the rest of TOTP

Also implement a date_time to unix timestamp method

movement/lib/TOTP-MCU

@@ -0,0 +1 @@
+Subproject commit 646474a8757e1fca490792e81082b2ad89b966a3

movement/make/Makefile

@@ -16,6 +16,7 @@ INCLUDES += \
   -I../watch_faces/complications/ \
   -I../watch_faces/thermistor/ \
   -I../watch_faces/demos/ \
+  -I../lib/TOTP-MCU/ \
 
 # If you add any other source files you wish to compile, add them after ../app.c
 # Note that you will need to add a backslash at the end of any line you wish to continue, i.e.
@@ -24,6 +25,8 @@ INCLUDES += \
 #   ../drivers/lis2dh.c \
 #   ../watch_faces/fitness/step_count_face.c
 SRCS += \
+  ../lib/TOTP-MCU/sha1.c \
+  ../lib/TOTP-MCU/TOTP.c \
   ../movement.c \
   ../watch_faces/clock/simple_clock_face.c \
   ../watch_faces/settings/preferences_face.c \
@@ -37,6 +40,7 @@ SRCS += \
   ../watch_faces/complications/beats_face.c \
   ../watch_faces/complications/day_one_face.c \
   ../watch_faces/complications/stopwatch_face.c \
+  ../watch_faces/complications/totp_face.c \
 
 # Leave this line at the bottom of the file; it has all the targets for making your project.
 include $(TOP)/rules.mk

movement/movement_config.h

@@ -12,6 +12,7 @@
 #include "day_one_face.h"
 #include "voltage_face.h"
 #include "stopwatch_face.h"
+#include "totp_face.h"
 
 const watch_face_t watch_faces[] = {
     simple_clock_face,

movement/watch_faces/complications/totp_face.c

@@ -0,0 +1,137 @@
+/**
+ * 
+ * TODO:
+ * - this ONLY works if watch is set to UTC, probably worth including a TZ offset setting since it can be used by beats as well
+ * - show how long code is valid for in upper right corner of LCD
+ * - optimize code so that we don't calculating a new unix timestamp every second AND a new TOTP code
+ * - Support for multiple codes
+ */
+#include <stdlib.h>
+#include <string.h>
+#include "totp_face.h"
+#include "watch.h"
+#include "TOTP.h"
+
+// test key: JBSWY3DPEHPK3PXP
+// Use https://cryptii.com/pipes/base32-to-hex to convert base32 to hex
+// Use https://totp.danhersam.com/ to generate test codes for verification
+uint8_t hmacKey[] = {0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x21, 0xde, 0xad, 0xbe, 0xef};               // Secret key
+
+void totp_face_setup(movement_settings_t *settings, void ** context_ptr) {
+    (void) settings;
+    (void) context_ptr;
+    TOTP(hmacKey, sizeof(hmacKey), 30);
+}
+
+void totp_face_activate(movement_settings_t *settings, void *context) {
+    (void) settings;
+    (void) context;
+}
+
+/**
+ * @brief Get unix timestamp from component parts
+ * 
+ * @param year 
+ * @param month 
+ * @param day 
+ * @param hour 
+ * @param minute 
+ * @param second 
+ * @return uint32_t 
+ * 
+ * Based on code by Josh Haberman for upb
+ * from https://blog.reverberate.org/2020/05/12/optimizing-date-algorithms.html
+ * 
+ * Essentially we need to calculate how many days have occured since year 0
+ * including leap years! The following code does some clever calculations
+ * of the number of february's then offsets based on how many leap years
+ * there have been
+ * 
+ * Once we have the number of days in the year, it's easy enough to add how
+ * many days have happened in the current year, then convert that to seconds
+ */
+uint32_t current_unix_time(uint32_t year, uint32_t month, uint32_t day,
+                            uint32_t hour, uint32_t minute, uint32_t second) {
+    uint16_t DAYS_SO_FAR[] = {
+        0,   // Jan
+        31,  // Feb
+        59,  // March
+        90,  // April
+        120, // May
+        151, // June
+        181, // July
+        212, // August
+        243, // September
+        273, // October
+        304, // November
+        334  // December
+    };
+
+
+    uint32_t year_adj = year + 4800;
+    uint32_t febs = year_adj - (month <= 2 ? 1 : 0);  /* Februaries since base. */
+    uint32_t leap_days = 1 + (febs / 4) - (febs / 100) + (febs / 400);
+    uint32_t days = 365 * year_adj + leap_days + DAYS_SO_FAR[month - 1] + day - 1;
+    days -= 2472692;  /* Adjust to Unix epoch. */
+
+    uint32_t timestamp = days * 86400;
+    timestamp += hour * 3600;
+    timestamp += minute * 60;
+    timestamp += second;
+
+    return timestamp;
+}
+
+uint32_t current_unix_time_from_rtc() {
+    watch_date_time date_time = watch_rtc_get_date_time();
+    return current_unix_time(
+        date_time.unit.year + 2020, // year is stored starting in 2020
+        date_time.unit.month,
+        date_time.unit.day,
+        date_time.unit.hour,
+        date_time.unit.minute,
+        date_time.unit.second
+    );
+}
+
+bool totp_face_loop(movement_event_t event, movement_settings_t *settings, void *context) {
+    (void) settings;
+    (void) context;
+
+    char buf[14];
+    watch_date_time date_time = watch_rtc_get_date_time();
+
+    uint32_t ts;
+    uint32_t code;
+    switch (event.event_type) {
+        case EVENT_ACTIVATE:
+        case EVENT_TICK:
+            ts = current_unix_time_from_rtc();
+            code = getCodeFromTimestamp(ts);
+            sprintf(buf, "2f  %lu", code); 
+
+            watch_display_string(buf, 0);
+            break;
+        case EVENT_MODE_BUTTON_UP:
+            movement_move_to_next_face();
+            break;
+        case EVENT_LIGHT_BUTTON_DOWN:
+            movement_illuminate_led();
+            break;
+        case EVENT_TIMEOUT:
+            // go home
+            break;
+        case EVENT_ALARM_BUTTON_DOWN:
+        case EVENT_ALARM_BUTTON_UP:
+        case EVENT_ALARM_LONG_PRESS:
+        default:
+            break;
+    }
+
+    return true;
+}
+
+void totp_face_resign(movement_settings_t *settings, void *context) {
+    (void) settings;
+    (void) context;
+}

movement/watch_faces/complications/totp_face.h

@@ -0,0 +1,19 @@
+#ifndef TOTP_FACE_H_
+#define TOTP_FACE_H_
+
+#include "movement.h"
+
+void totp_face_setup(movement_settings_t *settings, void ** context_ptr);
+void totp_face_activate(movement_settings_t *settings, void *context);
+bool totp_face_loop(movement_event_t event, movement_settings_t *settings, void *context);
+void totp_face_resign(movement_settings_t *settings, void *context);
+
+static const watch_face_t totp_face = {
+    totp_face_setup,
+    totp_face_activate,
+    totp_face_loop,
+    totp_face_resign,
+    NULL
+};
+
+#endif // TOTP_FACE_H_