Introduce Spotless and apply formatting to entire project

.github/workflows/test.yml

@@ -34,7 +34,10 @@ jobs:
           echo BACKTRACE_CORONER_TOKEN=\"${{ secrets.BACKTRACE_CORONER_TOKEN }}\" >> ./local.properties
 
       - name: Accept Android SDK licences
-        run: yes | "${ANDROID_HOME}/cmdline-tools/latest/bin/sdkmanager" --licenses    
+        run: yes | "${ANDROID_HOME}/cmdline-tools/latest/bin/sdkmanager" --licenses
+
+      - name: Check Code Style
+        run: ./gradlew spotlessCheck
 
       - name: Build and check
         run: ./gradlew assembleDebug assembleDebugAndroidTest build check

.pre-commit-config.yaml

@@ -0,0 +1,22 @@
+repos:
+  - repo: local
+    hooks:
+      - id: start-hook
+        name: start-hook
+        entry: echo 'Start pre-commit'
+        language: system
+        stages: [pre-commit]
+        pass_filenames: false
+## TODO: before merge - remove above and uncomment below
+#      - id: spotless-apply
+#        name: Spotless Apply
+#        entry: ./gradlew spotlessApply
+#        language: system
+#        stages: [pre-commit]
+#        pass_filenames: false
+#      - id: spotless-check
+#        name: Spotless Check
+#        entry: ./gradlew spotlessCheck
+#        language: system
+#        stages: [pre-commit]
+#        pass_filenames: false

CONTRIBUTING.md

@@ -1,27 +1,31 @@
 # Contributing
-Thank you for considering contributing to Backtrace Android SDK library. Here are some guidelines to help you get started:
-
-### Getting Started
-
-1. **Clone the Repository**
-    - Clone the repository to your local machine using:
-      ```bash
-      git clone https://github.com/backtrace-labs/backtrace-android.git
-      ```
-
-2. **Create a Branch**
-    - It's good practice to create a new branch for each feature or bugfix, if you have jira ticket put ticket number as branch prefix:
-      ```bash
-      git checkout -b jira-ticket/your-feature-name
-      ```
+Thank you for your interest in contributing to the Backtrace Android SDK. Please review the following guidelines to help you get started.
+
+## Getting Started
+
+1. **Clone the repository**
+   ```bash
+   git clone https://github.com/backtrace-labs/backtrace-android.git
+   ```
+
+2. **Install pre-commit**
+   ```bash
+   pip install pre-commit
+   pre-commit install
+   ```
+
+3. **Create a branch** - it's good practice to create a new branch for each feature or bugfix, if you have jira ticket put ticket number as branch prefix:
+   ```bash
+   git checkout -b jira-ticket/your-feature-name
+   ```
 
-3. **Update submodules**
-```bash
-git submodule update --recursive --remote
-git submodule update --init --recursive
-```
-
-### Coding Guidelines
+4. **Update submodules**
+   ```bash
+   git submodule update --recursive --remote
+   git submodule update --init --recursive
+   ```
+   
+## Coding Guidelines
 
 1. **Code Formatting**
     - Make sure that your code is properly formatted using the default Android Studio formatter.
@@ -34,7 +38,7 @@ git submodule update --init --recursive
 3. **Write Tests**
     - Ensure that you write tests for the new functionality or changes made. This helps maintain the integrity of the project.
 
-### Commit and Push
+## Commit and Push
 
 1. **Commit Your Changes**
     - Write clear and concise commit messages. Follow the convention of using the imperative mood in the subject line.
@@ -48,7 +52,7 @@ git submodule update --init --recursive
       git push origin jira-ticket/your-feature-name
       ```
 
-### Create a Pull Request
+## Create a Pull Request
 
 1. **Submit a Pull Request**
     - Go to the repository on GitHub and click on the `New Pull Request` button.
@@ -57,8 +61,33 @@ git submodule update --init --recursive
 2. **Review Process**
     - One of the project maintainers will review your pull request. Please be responsive to any comments or suggestions made.
 
-### Additional Notes
+## Additional Notes
 
 - Ensure that your code follows the existing code style and structure.
 - Keep your branch up to date with the latest changes from the `master` branch to avoid merge conflicts.
 
+
+## Code Formatting
+
+This project uses **[Spotless](https://github.com/diffplug/spotless)** (a code formatting plugin) integrated with **[pre-commit](https://pre-commit.com/)** to ensure consistent code style and automatic formatting before each commit.
+
+### Setup Instructions
+
+1. Run Spotless check
+This verifies that your code meets the project’s formatting standards.
+   ```bash
+   ./gradlew spotlessCheck
+   ```
+
+2. (Optional) Automatically reformat code
+If formatting issues are found, you can automatically fix them with:
+   ```bash
+   ./gradlew spotlessApply   
+   ```
+
+**Notes**
+- The pre-commit hook ensures code formatting is validated automatically before commits are created.
+- You can manually trigger all pre-commit checks at any time with:
+   ```bash
+   pre-commit run --all-files
+   ```

build.gradle

@@ -13,6 +13,58 @@ buildscript {
     }
 }
 
+plugins {
+    id 'com.diffplug.spotless' version '8.0.0' apply false
+}
+
+def spotlessExcludes = [
+        '.github/**',
+        '.gradle/**',
+        '.idea/**',
+        'build/**',
+        '**/cpp/**',
+        '**/jniLibs/**',
+        '**/build/**',
+        '**/build-*/**',
+        '**/.cxx/**',
+        '**/generated/**'
+]
+
+subprojects {
+    apply plugin: 'com.diffplug.spotless'
+    spotless {
+        java {
+            target '**/*.java'
+            targetExclude spotlessExcludes
+            palantirJavaFormat()
+            removeUnusedImports()
+            trimTrailingWhitespace()
+            endWithNewline()
+        }
+        json {
+            target '**/*.json'
+            targetExclude spotlessExcludes
+            simple()
+        }
+
+        format 'gradle', {
+            target '**/*.gradle'
+            targetExclude spotlessExcludes
+            leadingTabsToSpaces(4)
+            trimTrailingWhitespace()
+            endWithNewline()
+        }
+
+
+        format 'misc', {
+            target '*.md', '.gitignore'
+            targetExclude spotlessExcludes
+            trimTrailingWhitespace()
+            endWithNewline()
+        }
+    }
+}
+
 allprojects {
     repositories {
         google()