From 2a5855992e96940fdcba90e66132fdf0db1b41a2 Mon Sep 17 00:00:00 2001
From: Paul Buetow <paul@buetow.org>
Date: Mon, 13 Apr 2026 08:01:10 +0300
Subject: n2: extract Pebble-free fasting logic module

---
 src/c/fastforge_logic.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 src/c/fastforge_logic.c

(limited to 'src/c/fastforge_logic.c')

diff --git a/src/c/fastforge_logic.c b/src/c/fastforge_logic.c
new file mode 100644
index 0000000..64fe776
--- /dev/null
+++ b/src/c/fastforge_logic.c
@@ -0,0 +1,88 @@
+#include "fastforge_logic.h"
+
+#if defined(__has_include)
+#if __has_include(<pebble.h>)
+#include <pebble.h>
+#endif
+#endif
+
+#include <stdio.h>
+#include <time.h>
+
+time_t entry_duration_seconds(const FastEntry *entry) {
+  if (!entry || entry->start_time == 0 || entry->end_time <= entry->start_time) {
+    return 0;
+  }
+  return entry->end_time - entry->start_time;
+}
+
+uint8_t stage_level_for_elapsed(time_t elapsed_seconds) {
+  if (elapsed_seconds >= 24 * 3600) {
+    return 3;
+  }
+  if (elapsed_seconds >= 18 * 3600) {
+    return 2;
+  }
+  if (elapsed_seconds >= 12 * 3600) {
+    return 1;
+  }
+  return 0;
+}
+
+const char *stage_text_for_elapsed(time_t elapsed_seconds) {
+  if (elapsed_seconds >= 24 * 3600) {
+    return "DEEP KETOSIS";
+  }
+  if (elapsed_seconds >= 18 * 3600) {
+    return "EARLY KETOSIS";
+  }
+  if (elapsed_seconds >= 12 * 3600) {
+    return "FAT BURN";
+  }
+  return "GLYCOGEN";
+}
+
+void format_hhmmss(time_t seconds, char *buffer, size_t size) {
+  if (seconds < 0) {
+    seconds = 0;
+  }
+  snprintf(buffer, size, "%02d:%02d:%02d",
+           (int)(seconds / 3600),
+           (int)((seconds % 3600) / 60),
+           (int)(seconds % 60));
+}
+
+void format_duration_hours_minutes(time_t seconds, char *buffer, size_t size) {
+  if (seconds < 0) {
+    seconds = 0;
+  }
+  int hours = (int)(seconds / 3600);
+  int minutes = (int)((seconds % 3600) / 60);
+  snprintf(buffer, size, "%dh %02dm", hours, minutes);
+}
+
+time_t local_day_start(time_t timestamp) {
+  if (timestamp <= 0) {
+    return 0;
+  }
+
+  struct tm tm_copy;
+  struct tm *tm_info = localtime(&timestamp);
+  if (!tm_info) {
+    return 0;
+  }
+
+  tm_copy = *tm_info;
+  tm_copy.tm_hour = 0;
+  tm_copy.tm_min = 0;
+  tm_copy.tm_sec = 0;
+  tm_copy.tm_isdst = -1;
+  return mktime(&tm_copy);
+}
+
+bool running_fast_is_at_target(const FastEntry *entry, time_t now) {
+  if (!entry || entry->start_time == 0 || entry->end_time != 0 || entry->target_minutes == 0) {
+    return false;
+  }
+  return now >= entry->start_time + (time_t)entry->target_minutes * 60;
+}
-- 
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