Add metal detector guide with new format

app/src/main/java/com/kylecorry/trail_sense/tools/guide/infrastructure/Guides.kt

@@ -4,13 +4,16 @@ import android.content.Context
 import android.hardware.Sensor
 import com.kylecorry.andromeda.sense.Sensors
 import com.kylecorry.trail_sense.R
+import com.kylecorry.trail_sense.shared.sensors.SensorService
 import com.kylecorry.trail_sense.tools.guide.domain.UserGuide
 import com.kylecorry.trail_sense.tools.guide.domain.UserGuideCategory
 
 object Guides {
 
     fun guides(context: Context): List<UserGuideCategory> {
 
+        val hasCompass = SensorService(context).hasCompass()
+
         val general = UserGuideCategory(
             context.getString(R.string.general), listOf(
                 UserGuide(
@@ -78,6 +81,11 @@ object Guides {
                     null,
                     R.raw.packing_lists
                 ),
+                if (hasCompass) UserGuide(
+                    context.getString(R.string.tool_metal_detector_title),
+                    null,
+                    R.raw.guide_tool_metal_detector
+                ) else null,
                 UserGuide(
                     context.getString(R.string.clinometer_title),
                     context.getString(R.string.tool_clinometer_summary),

app/src/main/java/com/kylecorry/trail_sense/tools/ui/Tools.kt

@@ -266,6 +266,7 @@ object Tools {
                 R.drawable.ic_tool_metal_detector,
                 R.id.action_action_experimental_tools_to_fragmentToolMetalDetector,
                 ToolCategory.Other,
+                guideId = R.raw.guide_tool_metal_detector
             ) else null,
             Tool(
                 29,

app/src/main/res/raw/guide_tool_metal_detector.md

@@ -0,0 +1,34 @@
+## Calibration
+Calibrating the metal detector improves the accuracy of readings. To calibrate:
+
+1. Hold your phone 2-3 inches (5-8 cm) above the ground with the screen facing up.
+2. Press 'Calibrate'.
+3. Recalibrate occasionally for accuracy.
+
+The detector automatically calibrates when started.
+
+## Detecting Metal
+The detector only finds magnetic metals like iron. To detect metal:
+
+1. After calibrating, hold your phone 2-3 inches (5-8 cm) above the area to scan with the screen facing up.
+2. Slowly move your phone, keeping the distance and orientation consistent.
+3. When metal is detected, the phone will vibrate and indicate detection.
+
+## Understanding Readings
+The graph shows magnetic field strength over time. Metal causes spikes up or down. If spikes occur that don't trigger the metal detector, lower the threshold to increase sensitivity.
+
+Readings at the top of the screen show field strength in microteslas (uT).
+
+## Threshold
+Lower threshold values increase sensitivity. Higher values decrease it. Adjust with the on-screen slider.
+
+## High Sensitivity Mode
+This removes noise filtering for maximum sensitivity. The graph becomes noisier and false positives occur more frequently. Enable with the 'High sensitivity' switch.
+
+## Metal Direction (experimental)
+This experimental feature attempts to indicate metal direction with two on-screen dots. One points towards the metal and the other away from it. Unfortunately, it's uncertain which is which. Move your phone towards one dot; if the number in the center increases, you are getting closer. If the dots swap, it likely means you just passed over the metal. This requires a gyroscope sensor.
+
+Enable it on Settings > Experimental > Show metal direction.
+
+## Use Cases
+Find dropped magnetic metal objects like keys or knives. Cannot detect coins or jewelry.