feat(spike): add the M1 settings spike app and make targets

A separate throwaway app (own app ID, no permissions) that shows what the
Garmin Connect app delivers per settings field and writes values back, to
measure the undocumented settings limits on the real phone and watch.
Includes length-marked test strings, `make spike` / `make spike-sim`,
`make vectors`, and step-by-step instructions in docs/SETTINGS_SPIKE.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 144 insertions, 0 deletions

diff --git a/spike/settings/source/SpikeReport.mc b/spike/settings/source/SpikeReport.mc
new file mode 100644
index 0000000..09f27fa
--- /dev/null
+++ b/spike/settings/source/SpikeReport.mc
@@ -0,0 +1,144 @@
+// Author:  cirakg & claude ai
+// Summary: Reads every spike setting, measures lengths and characters, writes the status back, builds the screen lines.
+//
+// Per text field it reports: length in characters and UTF-8 bytes, the first
+// 12 and last 8 characters (the test strings start with "N=<length>|" and
+// end with "END", so truncation is obvious), and which of the characters
+// & < > \ " { } % and non-ASCII it contains.
+//
+// Write-back test: on every settings change the watch writes a status line
+// into the read-only "statusField" and clears "secretField". Opening the
+// settings on the phone afterwards shows whether the phone displays values
+// the watch wrote.
+
+import Toybox.Application;
+import Toybox.Application.Properties;
+import Toybox.Lang;
+import Toybox.System;
+
+module SpikeKeys {
+    const TEXT_FIELDS = ["text1", "text2", "text3", "text4", "text5", "text6", "text7", "text8"];
+    const SECRET = "secretField";
+    const STATUS = "statusField";
+    const OTHER_FIELDS = ["switchField", "listField", "numberField", "longField"];
+    const HEAD_CHARS = 12;
+    const TAIL_CHARS = 8;
+    const ASCII_BACKSLASH = 92;
+    const ASCII_QUOTE = 34;
+}
+
+class SpikeReport {
+
+    // Lines for SpikeView, rebuilt by analyse().
+    var lines as Array<String> = [] as Array<String>;
+    // onSettingsChanged calls since the app started, and the time of the last.
+    var changeCount as Number = 0;
+    var lastChange as String = "never";
+    // Totals over the eight text fields, from the latest analysis.
+    var totalChars as Number = 0;
+    var totalBytes as Number = 0;
+    // Length of the password field when it was last read (before clearing).
+    var passwordReceived as Number = 0;
+    // The status line the watch wrote last ("" before the first change).
+    var lastWriteBack as String = "";
+
+    function initialize() {
+    }
+
+    // On start: no write-back, just show what the last sync delivered.
+    function analyseOnStart() as Void {
+        passwordReceived = readString(SpikeKeys.SECRET).length();
+        analyse();
+    }
+
+    // Settings were saved on the phone: measure, write back, show.
+    function settingsChanged() as Void {
+        changeCount++;
+        lastChange = clockText();
+        passwordReceived = readString(SpikeKeys.SECRET).length();
+        analyse();
+        lastWriteBack = "seen " + totalChars + " chars at " + lastChange + ", change #" + changeCount;
+        Properties.setValue(SpikeKeys.STATUS, lastWriteBack);
+        Properties.setValue(SpikeKeys.SECRET, "");
+        analyse();
+    }
+
+    // Rebuild every screen line from the current property values.
+    function analyse() as Void {
+        lines = [] as Array<String>;
+        totalChars = 0;
+        totalBytes = 0;
+        var fieldLines = [] as Array<String>;
+        for (var i = 0; i < SpikeKeys.TEXT_FIELDS.size(); i++) {
+            describeText(fieldLines, "T" + (i + 1), readString(SpikeKeys.TEXT_FIELDS[i]));
+        }
+        lines.add("Settings spike");
+        lines.add("Changes seen: " + changeCount);
+        lines.add("Last change: " + lastChange);
+        lines.add("Total: " + totalChars + " chars, " + totalBytes + " B");
+        lines.addAll(fieldLines);
+        lines.add("Password: got " + passwordReceived + " chars,");
+        lines.add("  now " + readString(SpikeKeys.SECRET).length() + " (watch clears it)");
+        for (var i = 0; i < SpikeKeys.OTHER_FIELDS.size(); i++) {
+            lines.add(SpikeKeys.OTHER_FIELDS[i] + ": " + valueText(SpikeKeys.OTHER_FIELDS[i]));
+        }
+        lines.add("Status now: " + readString(SpikeKeys.STATUS));
+        lines.add("Wrote: " + (lastWriteBack.equals("") ? "nothing yet" : lastWriteBack));
+    }
+
+    // Length, ends and special characters of one text field.
+    private function describeText(out as Array<String>, label as String, value as String) as Void {
+        var chars = value.length();
+        var bytes = value.toUtf8Array().size();
+        totalChars += chars;
+        totalBytes += bytes;
+        out.add(label + ": " + chars + " chars, " + bytes + " B");
+        if (chars == 0) {
+            return;
+        }
+        var head = part(value, 0, chars < SpikeKeys.HEAD_CHARS ? chars : SpikeKeys.HEAD_CHARS);
+        var tailStart = chars > SpikeKeys.TAIL_CHARS ? chars - SpikeKeys.TAIL_CHARS : 0;
+        out.add("  " + head + " .. " + part(value, tailStart, chars));
+        out.add("  has: " + specialsIn(value, chars != bytes));
+    }
+
+    // Which of the characters the plan worries about occur in the value.
+    private function specialsIn(value as String, nonAscii as Boolean) as String {
+        var probes = [
+            "&", "<", ">", SpikeKeys.ASCII_BACKSLASH.toChar().toString(),
+            SpikeKeys.ASCII_QUOTE.toChar().toString(), "{", "}", "%"
+        ];
+        var found = "";
+        for (var i = 0; i < probes.size(); i++) {
+            if (value.find(probes[i]) != null) {
+                found += probes[i] + " ";
+            }
+        }
+        if (nonAscii) {
+            found += "non-ASCII";
+        }
+        return found.equals("") ? "none" : found;
+    }
+
+    // A property as a String; anything missing or of another type reads as "".
+    private function readString(key as String) as String {
+        var value = Properties.getValue(key);
+        return value instanceof String ? value : "";
+    }
+
+    // Any property as display text.
+    private function valueText(key as String) as String {
+        // getValue throws for unknown keys and never returns null for declared ones.
+        return Properties.getValue(key).toString() as String;
+    }
+
+    private function part(value as String, startIndex as Number, endIndex as Number) as String {
+        var result = value.substring(startIndex, endIndex);
+        return result == null ? "" : result;
+    }
+
+    private function clockText() as String {
+        var time = System.getClockTime();
+        return time.hour.format("%02d") + ":" + time.min.format("%02d") + ":" + time.sec.format("%02d");
+    }
+}