Margin Calendar: a Google Calendar client for desktop and phone

Tauri 2, React 19 and zustand on the front, Rust behind. Rust owns auth,
all HTTP to Google, the SQLite store, the sync loop, recurrence expansion
and timezone maths. TypeScript owns rendering and never talks to Google,
which keeps the content security policy locked to ipc:.

Week, day and agenda views, and no month view: it would be a second layout
engine, and the fit and fold logic that makes a day fit the window without
scrolling is the whole point of the app.

Runs on macOS, Linux, Android and iOS. Desktop catches Google's OAuth
redirect on a loopback port. A phone cannot, and Google rejects loopback
for mobile client types anyway, so it redirects to a custom URI scheme and
needs its own public OAuth clients, which docs/mobile.md covers. Refresh
tokens are sealed with XChaCha20-Poly1305 in the app data directory on
every platform, with no OS credential store in the picture.

On a phone the chrome becomes a top bar and a bottom tab bar, overlays
become sheets, hover affordances become taps, and dragging out an event
waits for a long press. Navigation moves one day at a time everywhere,
a swipe included.

src-tauri/gen/android/buildSrc/build.gradle.kts

@@ -0,0 +1,23 @@
+plugins {
+    `kotlin-dsl`
+}
+
+gradlePlugin {
+    plugins {
+        create("pluginsForCoolKids") {
+            id = "rust"
+            implementationClass = "RustPlugin"
+        }
+    }
+}
+
+repositories {
+    google()
+    mavenCentral()
+}
+
+dependencies {
+    compileOnly(gradleApi())
+    implementation("com.android.tools.build:gradle:8.11.0")
+}
+

src-tauri/gen/android/buildSrc/src/main/java/studio/margin/calendar/kotlin/BuildTask.kt

@@ -0,0 +1,68 @@
+import java.io.File
+import org.apache.tools.ant.taskdefs.condition.Os
+import org.gradle.api.DefaultTask
+import org.gradle.api.GradleException
+import org.gradle.api.logging.LogLevel
+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.TaskAction
+
+open class BuildTask : DefaultTask() {
+    @Input
+    var rootDirRel: String? = null
+    @Input
+    var target: String? = null
+    @Input
+    var release: Boolean? = null
+
+    @TaskAction
+    fun assemble() {
+        val executable = """pnpm""";
+        try {
+            runTauriCli(executable)
+        } catch (e: Exception) {
+            if (Os.isFamily(Os.FAMILY_WINDOWS)) {
+                // Try different Windows-specific extensions
+                val fallbacks = listOf(
+                    "$executable.exe",
+                    "$executable.cmd",
+                    "$executable.bat",
+                )
+                
+                var lastException: Exception = e
+                for (fallback in fallbacks) {
+                    try {
+                        runTauriCli(fallback)
+                        return
+                    } catch (fallbackException: Exception) {
+                        lastException = fallbackException
+                    }
+                }
+                throw lastException
+            } else {
+                throw e;
+            }
+        }
+    }
+
+    fun runTauriCli(executable: String) {
+        val rootDirRel = rootDirRel ?: throw GradleException("rootDirRel cannot be null")
+        val target = target ?: throw GradleException("target cannot be null")
+        val release = release ?: throw GradleException("release cannot be null")
+        val args = listOf("tauri", "android", "android-studio-script");
+
+        project.exec {
+            workingDir(File(project.projectDir, rootDirRel))
+            executable(executable)
+            args(args)
+            if (project.logger.isEnabled(LogLevel.DEBUG)) {
+                args("-vv")
+            } else if (project.logger.isEnabled(LogLevel.INFO)) {
+                args("-v")
+            }
+            if (release) {
+                args("--release")
+            }
+            args(listOf("--target", target))
+        }.assertNormalExitValue()
+    }
+}

src-tauri/gen/android/buildSrc/src/main/java/studio/margin/calendar/kotlin/RustPlugin.kt

@@ -0,0 +1,85 @@
+import com.android.build.api.dsl.ApplicationExtension
+import org.gradle.api.DefaultTask
+import org.gradle.api.Plugin
+import org.gradle.api.Project
+import org.gradle.kotlin.dsl.configure
+import org.gradle.kotlin.dsl.get
+
+const val TASK_GROUP = "rust"
+
+open class Config {
+    lateinit var rootDirRel: String
+}
+
+open class RustPlugin : Plugin<Project> {
+    private lateinit var config: Config
+
+    override fun apply(project: Project) = with(project) {
+        config = extensions.create("rust", Config::class.java)
+
+        val defaultAbiList = listOf("arm64-v8a", "armeabi-v7a", "x86", "x86_64");
+        val abiList = (findProperty("abiList") as? String)?.split(',') ?: defaultAbiList
+
+        val defaultArchList = listOf("arm64", "arm", "x86", "x86_64");
+        val archList = (findProperty("archList") as? String)?.split(',') ?: defaultArchList
+
+        val targetsList = (findProperty("targetList") as? String)?.split(',') ?: listOf("aarch64", "armv7", "i686", "x86_64")
+
+        extensions.configure<ApplicationExtension> {
+            @Suppress("UnstableApiUsage")
+            flavorDimensions.add("abi")
+            productFlavors {
+                create("universal") {
+                    dimension = "abi"
+                    ndk {
+                        abiFilters += abiList
+                    }
+                }
+                defaultArchList.forEachIndexed { index, arch ->
+                    create(arch) {
+                        dimension = "abi"
+                        ndk {
+                            abiFilters.add(defaultAbiList[index])
+                        }
+                    }
+                }
+            }
+        }
+
+        afterEvaluate {
+            for (profile in listOf("debug", "release")) {
+                val profileCapitalized = profile.replaceFirstChar { it.uppercase() }
+                val buildTask = tasks.maybeCreate(
+                    "rustBuildUniversal$profileCapitalized",
+                    DefaultTask::class.java
+                ).apply {
+                    group = TASK_GROUP
+                    description = "Build dynamic library in $profile mode for all targets"
+                }
+
+                tasks["mergeUniversal${profileCapitalized}JniLibFolders"].dependsOn(buildTask)
+
+                for (targetPair in targetsList.withIndex()) {
+                    val targetName = targetPair.value
+                    val targetArch = archList[targetPair.index]
+                    val targetArchCapitalized = targetArch.replaceFirstChar { it.uppercase() }
+                    val targetBuildTask = project.tasks.maybeCreate(
+                        "rustBuild$targetArchCapitalized$profileCapitalized",
+                        BuildTask::class.java
+                    ).apply {
+                        group = TASK_GROUP
+                        description = "Build dynamic library in $profile mode for $targetArch"
+                        rootDirRel = config.rootDirRel
+                        target = targetName
+                        release = profile == "release"
+                    }
+
+                    buildTask.dependsOn(targetBuildTask)
+                    tasks["merge$targetArchCapitalized${profileCapitalized}JniLibFolders"].dependsOn(
+                        targetBuildTask
+                    )
+                }
+            }
+        }
+    }
+}