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node_modules/expo-image/ios/ContentPosition.swift

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+import ExpoModulesCore
+
+/**
+ Represents a position value that might be either `Double` or `String`.
+ */
+typealias ContentPositionValue = Either<Double, String>
+
+/**
+ Specifies the alignment of the image within the container's box.
+ - Note: Its intention is to behave like the CSS [`object-position`](https://developer.mozilla.org/en-US/docs/Web/CSS/object-position) property.
+ */
+struct ContentPosition: Record {
+  static let center = Self()
+
+  @Field
+  var top: ContentPositionValue?
+
+  @Field
+  var bottom: ContentPositionValue?
+
+  @Field
+  var right: ContentPositionValue?
+
+  @Field
+  var left: ContentPositionValue?
+
+  /**
+   Returns a horizontal content offset based on the `left` or `right` field.
+   */
+  func offsetX(contentWidth: Double, containerWidth: Double) -> Double {
+    let diff = containerWidth - contentWidth
+
+    if let leftDistance = distance(from: left) {
+      return -diff / 2 + leftDistance
+    }
+    if let rightDistance = distance(from: right) {
+      return diff / 2 - rightDistance
+    }
+    if let factor = factor(from: left) {
+      return -diff / 2 + diff * factor
+    }
+    if let factor = factor(from: right) {
+      return diff / 2 - diff * factor
+    }
+    return 0
+  }
+
+  /**
+   Returns a vertical content offset based on the `top` or `bottom` field.
+   */
+  func offsetY(contentHeight: Double, containerHeight: Double) -> Double {
+    let diff = containerHeight - contentHeight
+
+    if let topDistance = distance(from: top) {
+      return -diff / 2 + topDistance
+    }
+    if let bottomDistance = distance(from: bottom) {
+      return diff / 2 - bottomDistance
+    }
+    if let factor = factor(from: top) {
+      return -diff / 2 + diff * factor
+    }
+    if let factor = factor(from: bottom) {
+      return diff / 2 - diff * factor
+    }
+    return 0
+  }
+
+  /**
+   A `CGPoint` with horizontal and vertical content offsets.
+   */
+  func offset(contentSize: CGSize, containerSize: CGSize) -> CGPoint {
+    return CGPoint(
+      x: offsetX(contentWidth: contentSize.width, containerWidth: containerSize.width),
+      y: offsetY(contentHeight: contentSize.height, containerHeight: containerSize.height)
+    )
+  }
+}
+
+/**
+ Returns a static offset from the given position value or `nil` when it cannot be cast to a `Double`.
+ */
+private func distance(from value: ContentPositionValue?) -> Double? {
+  if let value: Double = value?.get() {
+    return value
+  }
+  if let value: String = value?.get() {
+    return Double(value)
+  }
+  return nil
+}
+
+/**
+ Returns a factor from the percentage value from the given position.
+ The value must be a string containing a number and `%` character, or equal to `"center"` which is an equivalent to `50%`.
+ */
+private func factor(from value: ContentPositionValue?) -> Double? {
+  guard let value: String = value?.get() else {
+    return nil
+  }
+  if value == "center" {
+    return 0.5
+  }
+  guard value.contains("%"), let percentage = Double(value.replacingOccurrences(of: "%", with: "")) else {
+    return nil
+  }
+  return percentage / 100
+}