Ensure custom exposure mode is supported

Reviewed-on: #6
Reviewed-by: Ivan Malison <ivanmalison@gmail.com>

package/ios/CameraView+RecordVideo.swift

@@ -50,4 +50,12 @@ extension CameraView: AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureAud
   func resumeRecording(promise: Promise) {
     cameraSession.resumeRecording(promise: promise)
   }
+  
+  func lockExposure(promise: Promise) {
+    cameraSession.lockCurrentExposure(promise: promise)
+  }
+  
+  func unlockExposure(promise: Promise) {
+    cameraSession.unlockCurrentExposure(promise: promise)
+  }
 }

package/ios/CameraViewManager.m

@@ -86,5 +86,13 @@ RCT_EXTERN_METHOD(focus
                   : (NSDictionary*)point resolve
                   : (RCTPromiseResolveBlock)resolve reject
                   : (RCTPromiseRejectBlock)reject);
+RCT_EXTERN_METHOD(lockCurrentExposure
+                  : (nonnull NSNumber*)node resolve
+                  : (RCTPromiseResolveBlock)resolve reject
+                  : (RCTPromiseRejectBlock)reject);
+RCT_EXTERN_METHOD(unlockCurrentExposure
+                  : (nonnull NSNumber*)node resolve
+                  : (RCTPromiseResolveBlock)resolve reject
+                  : (RCTPromiseRejectBlock)reject);
 
 @end

package/ios/CameraViewManager.swift

@@ -111,6 +111,18 @@ final class CameraViewManager: RCTViewManager {
     }
   }
   
+  @objc
+  final func lockCurrentExposure(_ node: NSNumber, resolve: @escaping RCTPromiseResolveBlock, reject: @escaping RCTPromiseRejectBlock) {
+    let component = getCameraView(withTag: node)
+    component.lockExposure(promise: Promise(resolver: resolve, rejecter: reject))
+  }
+  
+  @objc
+  final func unlockCurrentExposure(_ node: NSNumber, resolve: @escaping RCTPromiseResolveBlock, reject: @escaping RCTPromiseRejectBlock) {
+    let component = getCameraView(withTag: node)
+    component.unlockExposure(promise: Promise(resolver: resolve, rejecter: reject))
+  }
+
   // MARK: Private
 
   private func getCameraView(withTag tag: NSNumber) -> CameraView {

package/ios/Core/CameraSession+Video.swift

@@ -191,4 +191,68 @@ extension CameraSession {
       }
     }
   }
+
+  func lockCurrentExposure(promise: Promise) {
+    CameraQueues.cameraQueue.async {
+      withPromise(promise) {
+        guard let captureDevice = AVCaptureDevice.default(for: .video) else {
+          print("No capture device available")
+          return
+        }
+
+        guard captureDevice.isExposureModeSupported(.custom) else {
+          ReactLogger.log(level: .info, message: "Custom exposure mode not supported")
+          return
+        }
+        do {
+          // Lock the device for configuration
+          try captureDevice.lockForConfiguration()
+
+          // Get the current exposure duration and ISO
+          let currentExposureDuration = captureDevice.exposureDuration
+          let currentISO = captureDevice.iso
+
+          // Check if the device supports custom exposure settings
+          if captureDevice.isExposureModeSupported(.custom) {
+            // Lock the current exposure and ISO by setting custom exposure mode
+            captureDevice.setExposureModeCustom(duration: currentExposureDuration, iso: currentISO, completionHandler: nil)
+            ReactLogger.log(level: .info, message: "Exposure and ISO locked at current values")
+          } else {
+            ReactLogger.log(level: .info, message:"Custom exposure mode not supported")
+          }
+
+          // Unlock the device after configuration
+          captureDevice.unlockForConfiguration()
+
+        } catch {
+          ReactLogger.log(level: .warning, message:"Error locking exposure: \(error)")
+        }
+
+        return nil
+      }
+    }
+  }
+
+  func unlockCurrentExposure(promise: Promise) {
+    CameraQueues.cameraQueue.async {
+      withPromise(promise) {
+        guard let captureDevice = AVCaptureDevice.default(for: .video) else {
+          print("No capture device available")
+          return
+        }
+
+        do {
+          if captureDevice.isExposureModeSupported(.autoExpose) {
+            try captureDevice.lockForConfiguration()
+            captureDevice.exposureMode = .continuousAutoExposure
+            captureDevice.unlockForConfiguration()
+          }
+        } catch {
+          ReactLogger.log(level: .warning, message:"Error unlocking exposure: \(error)")
+        }
+
+        return nil
+      }
+    }
+  }
 }

package/src/Camera.tsx

@@ -319,6 +319,22 @@ export class Camera extends React.PureComponent<CameraProps, CameraState> {
       throw tryParseNativeCameraError(e)
     }
   }
+
+  public async lockCurrentExposure(): Promise<void> {
+    try {
+      return await CameraModule.lockCurrentExposure(this.handle)
+    } catch (e) {
+      throw tryParseNativeCameraError(e)
+    }
+  }
+
+  public async unlockCurrentExposure(): Promise<void> {
+    try {
+      return await CameraModule.unlockCurrentExposure(this.handle)
+    } catch (e) {
+      throw tryParseNativeCameraError(e)
+    }
+  }
   //#endregion
 
   //#region Static Functions (NativeModule)