From 72dea9c869eba6976efc1b6134b0fcae42d1df22 Mon Sep 17 00:00:00 2001
From: Eric Betts <bettse@fastmail.fm>
Date: Sat, 7 Mar 2026 13:04:13 -0800
Subject: [PATCH] Add trace log ref #30

---
 trace_log.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 trace_log.h | 34 +++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 trace_log.c
 create mode 100644 trace_log.h

diff --git a/trace_log.c b/trace_log.c
new file mode 100644
index 0000000..4b3240a
--- /dev/null
+++ b/trace_log.c
@@ -0,0 +1,62 @@
+#include "trace_log.h"
+
+#ifdef SEADER_ENABLE_TRACE_LOG
+
+#include <storage/storage.h>
+#include <toolbox/stream/buffered_file_stream.h>
+
+static void seader_trace_write(FS_OpenMode open_mode, const char* line) {
+    Storage* storage = furi_record_open(RECORD_STORAGE);
+    storage_simply_mkdir(storage, STORAGE_APP_DATA_PATH_PREFIX);
+
+    Stream* stream = buffered_file_stream_alloc(storage);
+    if(buffered_file_stream_open(stream, SEADER_TRACE_FILE_NAME, FSAM_READ_WRITE, open_mode)) {
+        stream_seek(stream, 0, StreamOffsetFromEnd);
+        stream_write(stream, (const uint8_t*)line, strlen(line));
+    }
+
+    buffered_file_stream_close(stream);
+    stream_free(stream);
+    furi_record_close(RECORD_STORAGE);
+}
+
+void seader_trace_reset(void) {
+    seader_trace_write(FSOM_CREATE_ALWAYS, "");
+}
+
+void seader_trace(const char* tag, const char* fmt, ...) {
+    char message[192];
+    va_list args;
+    va_start(args, fmt);
+    vsnprintf(message, sizeof(message), fmt, args);
+    va_end(args);
+
+    char line[224];
+    snprintf(line, sizeof(line), "[%s] %s\n", tag, message);
+    seader_trace_write(FSOM_OPEN_ALWAYS, line);
+}
+
+void seader_trace_hex(const char* tag, const char* prefix, const uint8_t* data, size_t len) {
+    if(!data || len == 0) {
+        seader_trace(tag, "%s <empty>", prefix);
+        return;
+    }
+
+    /* Keep trace lines bounded; enough to diagnose short RF exchanges. */
+    const size_t max_bytes = 32;
+    size_t trace_len = len > max_bytes ? max_bytes : len;
+
+    char hex[(max_bytes * 2) + 1];
+    for(size_t i = 0; i < trace_len; i++) {
+        snprintf(hex + (i * 2), sizeof(hex) - (i * 2), "%02x", data[i]);
+    }
+    hex[trace_len * 2] = '\0';
+
+    if(trace_len < len) {
+        seader_trace(tag, "%s len=%u data=%s...", prefix, (unsigned)len, hex);
+    } else {
+        seader_trace(tag, "%s len=%u data=%s", prefix, (unsigned)len, hex);
+    }
+}
+
+#endif
diff --git a/trace_log.h b/trace_log.h
new file mode 100644
index 0000000..cda847f
--- /dev/null
+++ b/trace_log.h
@@ -0,0 +1,34 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef SEADER_ENABLE_TRACE_LOG
+
+/* Define SEADER_ENABLE_TRACE_LOG in the app build to enable SD-card tracing. */
+
+#define SEADER_TRACE_FILE_NAME APP_DATA_PATH("trace.log")
+
+void seader_trace_reset(void);
+void seader_trace(const char* tag, const char* fmt, ...);
+void seader_trace_hex(const char* tag, const char* prefix, const uint8_t* data, size_t len);
+
+#else
+
+static inline void seader_trace_reset(void) {
+}
+
+static inline void seader_trace(const char* tag, const char* fmt, ...) {
+    (void)tag;
+    (void)fmt;
+}
+
+static inline void
+    seader_trace_hex(const char* tag, const char* prefix, const uint8_t* data, size_t len) {
+    (void)tag;
+    (void)prefix;
+    (void)data;
+    (void)len;
+}
+
+#endif