feat: add torch plugin for iOS and Android (#3551)

* feat(barcode-scanner): add torch toggle

* feat: torch plugin

* fix

---------

Co-authored-by: Lucas Nogueira <lucas@tauri.app>

plugins/torch/src/error.rs

@@ -0,0 +1,28 @@
+// Copyright 2019-2023 Tauri Programme within The Commons Conservancy
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: MIT
+
+use serde::{Serialize, ser::Serializer};
+
+/// Alias for the result type returned by this crate's functions.
+pub type Result<T> = std::result::Result<T, Error>;
+
+/// The error type returned by this crate's APIs. Serialized as its [`Display`](std::fmt::Display)
+/// string when it crosses the IPC boundary.
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    /// Failed to run a command on the mobile plugin implementation (Kotlin on Android, Swift on
+    /// iOS). This includes the native side rejecting the call, e.g. because the device has no
+    /// torch or the camera is held by another app.
+    #[error(transparent)]
+    PluginInvoke(#[from] tauri::plugin::mobile::PluginInvokeError),
+}
+
+impl Serialize for Error {
+    fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(self.to_string().as_ref())
+    }
+}

plugins/torch/src/lib.rs

@@ -0,0 +1,117 @@
+// Copyright 2019-2023 Tauri Programme within The Commons Conservancy
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: MIT
+
+//! Control the device flashlight (torch).
+//!
+//! - Supported platforms: Android and iOS.
+//!
+//! On Android the torch keeps working while the
+//! [barcode scanner](https://docs.rs/tauri-plugin-barcode-scanner) plugin holds the camera.
+
+#![cfg(mobile)]
+
+use serde::Deserialize;
+use tauri::{
+    Manager, Runtime,
+    plugin::{Builder, PluginHandle, TauriPlugin},
+};
+
+mod error;
+
+pub use error::{Error, Result};
+
+#[cfg(target_os = "android")]
+const PLUGIN_IDENTIFIER: &str = "app.tauri.torch";
+
+#[cfg(target_os = "ios")]
+tauri::ios_plugin_binding!(init_plugin_torch);
+
+#[derive(Deserialize)]
+struct AvailableResponse {
+    available: bool,
+}
+
+#[derive(Deserialize)]
+struct EnabledResponse {
+    enabled: bool,
+}
+
+/// Access to the torch APIs.
+pub struct Torch<R: Runtime>(PluginHandle<R>);
+
+impl<R: Runtime> Torch<R> {
+    /// Turns the torch on.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`Error::PluginInvoke`] if the device has no torch, the torch is temporarily
+    /// unavailable (e.g. the device is overheating) or the camera is held by another app.
+    pub fn enable(&self) -> Result<()> {
+        self.0.run_mobile_plugin("enable", ()).map_err(Into::into)
+    }
+
+    /// Turns the torch off.
+    ///
+    /// # Errors
+    ///
+    /// Same as [`Self::enable`].
+    pub fn disable(&self) -> Result<()> {
+        self.0.run_mobile_plugin("disable", ()).map_err(Into::into)
+    }
+
+    /// Flips the torch and returns its new state (`true` when it is now on).
+    ///
+    /// # Errors
+    ///
+    /// Same as [`Self::enable`].
+    pub fn toggle(&self) -> Result<bool> {
+        self.0
+            .run_mobile_plugin::<EnabledResponse>("toggle", ())
+            .map(|r| r.enabled)
+            .map_err(Into::into)
+    }
+
+    /// Whether the device has a torch.
+    pub fn is_available(&self) -> Result<bool> {
+        self.0
+            .run_mobile_plugin::<AvailableResponse>("isAvailable", ())
+            .map(|r| r.available)
+            .map_err(Into::into)
+    }
+
+    /// Whether the torch is currently on. Reads the hardware state, so it also reflects the torch
+    /// being turned off by the system or another app.
+    pub fn is_enabled(&self) -> Result<bool> {
+        self.0
+            .run_mobile_plugin::<EnabledResponse>("isEnabled", ())
+            .map(|r| r.enabled)
+            .map_err(Into::into)
+    }
+}
+
+/// Extensions to [`tauri::App`], [`tauri::AppHandle`], [`tauri::WebviewWindow`], [`tauri::Webview`] and [`tauri::Window`] to access the torch APIs.
+pub trait TorchExt<R: Runtime> {
+    /// Returns the [`Torch`] instance managed by the app.
+    fn torch(&self) -> &Torch<R>;
+}
+
+impl<R: Runtime, T: Manager<R>> crate::TorchExt<R> for T {
+    fn torch(&self) -> &Torch<R> {
+        self.state::<Torch<R>>().inner()
+    }
+}
+
+/// Initializes the plugin.
+pub fn init<R: Runtime>() -> TauriPlugin<R> {
+    Builder::new("torch")
+        .setup(|app, api| {
+            #[cfg(target_os = "android")]
+            let handle = api.register_android_plugin(PLUGIN_IDENTIFIER, "TorchPlugin")?;
+            #[cfg(target_os = "ios")]
+            let handle = api.register_ios_plugin(init_plugin_torch)?;
+            app.manage(Torch(handle));
+            Ok(())
+        })
+        .build()
+}