Prepare v0.4 release and open source docs

Sources/IHatePDFsCore/PDFDocumentBookmarks.swift

@@ -0,0 +1,61 @@
+import Foundation
+
+public struct PDFDocumentBookmark {
+    public var id: String
+    public var pageIndex: Int
+    public var pageLabel: String
+    public var title: String
+    public var createdAt: Date
+
+    public init(
+        id: String = UUID().uuidString,
+        pageIndex: Int,
+        pageLabel: String,
+        title: String,
+        createdAt: Date = Date()
+    ) {
+        self.id = id
+        self.pageIndex = pageIndex
+        self.pageLabel = pageLabel
+        self.title = title
+        self.createdAt = createdAt
+    }
+}
+
+public enum PDFDocumentBookmarks {
+    public static func sorted(_ bookmarks: [PDFDocumentBookmark]) -> [PDFDocumentBookmark] {
+        preferredBookmark(in: bookmarks).map { [$0] } ?? []
+    }
+
+    public static func upsert(
+        _ bookmark: PDFDocumentBookmark,
+        in _: [PDFDocumentBookmark]
+    ) -> [PDFDocumentBookmark] {
+        [bookmark]
+    }
+
+    public static func removing(id: String, from bookmarks: [PDFDocumentBookmark]) -> [PDFDocumentBookmark] {
+        sorted(bookmarks.filter { $0.id != id })
+    }
+
+    public static func bookmark(on pageIndex: Int, in bookmarks: [PDFDocumentBookmark]) -> PDFDocumentBookmark? {
+        sorted(bookmarks).first { $0.pageIndex == pageIndex }
+    }
+
+    public static func clamped(
+        _ bookmarks: [PDFDocumentBookmark],
+        pageCount: Int
+    ) -> [PDFDocumentBookmark] {
+        guard pageCount > 0 else { return [] }
+        return sorted(bookmarks.filter { (0..<pageCount).contains($0.pageIndex) })
+    }
+
+    private static func preferredBookmark(in bookmarks: [PDFDocumentBookmark]) -> PDFDocumentBookmark? {
+        bookmarks.max {
+            if $0.createdAt != $1.createdAt {
+                return $0.createdAt < $1.createdAt
+            }
+            return $0.pageIndex < $1.pageIndex
+        }
+    }
+}