Start implementing f-droid catalog; add parsing of atom releases feed

Author: marcprux

Sources/FairExpo/AtomFeed.swift

@@ -0,0 +1,96 @@
+import Swift
+import FairCore
+import Universal
+import struct Foundation.Data
+
+/// An Atom web feed
+public struct AtomFeed {
+    public var id: String?
+    public var title: String?
+    public var updated: String?
+    public var links: [Link]
+    public var entries: [Entry]
+
+    /// Attempts to initialze the AtomFeed with the given atom data, which must be valid XML.
+    public init(xmlData data: Data) throws {
+        try self.init(node: XMLNode.parse(data: data, options: [.reportNamespacePrefixes]))
+    }
+
+    private init(node: XMLNode) throws {
+        guard let root = node.elementChildren.first,
+              root.elementName == "feed" else {
+            throw Errors.noAtomRoot
+        }
+
+        let entries = root.elementChildren
+
+        let elements = entries.dictionary(keyedBy: \.elementName)
+        self.id = elements["id"]?.childContentTrimmed
+        self.title = elements["title"]?.childContentTrimmed
+        self.updated = elements["updated"]?.childContentTrimmed
+
+        self.entries = try entries.filter({ $0.elementName == "entry" }).map(Entry.init)
+        self.links = try entries.filter({ $0.elementName == "link" }).map(Link.init)
+    }
+
+    public struct Link {
+        public var type: String?
+        public var rel: String?
+        public var href: String?
+
+        public init(node: XMLNode) throws {
+            let dict = node.elementDictionary(attributes: true, childNodes: false)
+            self.type = dict["type"]
+            self.rel = dict["rel"]
+            self.href = dict["href"]
+        }
+    }
+
+    public struct Author {
+        public var name: String?
+
+        public init(node: XMLNode) throws {
+            let entries = node.elementChildren
+            self.name = entries.filter({ $0.elementName == "name" }).first?.stringContent
+        }
+    }
+
+    public struct Content {
+        public var type: String?
+        public var contents: String?
+
+        public init(node: XMLNode) throws {
+            let dict = node.elementDictionary(attributes: true, childNodes: false)
+            self.type = dict["type"]
+            self.contents = node.stringContent
+        }
+    }
+
+    public struct Entry {
+        public var id: String?
+        public var title: String?
+        public var updated: String?
+        public var links: [Link]?
+        public var authors: [Author]?
+        public var contents: [Content]?
+
+        public init(node: XMLNode) throws {
+            let elements = node.elementChildren.dictionary(keyedBy: \.elementName)
+
+            self.id = elements["id"]?.childContentTrimmed
+            self.title = elements["title"]?.childContentTrimmed
+            self.updated = elements["updated"]?.childContentTrimmed
+
+            self.links = try node.elementChildren.filter({ $0.elementName == "link" }).map(Link.init)
+            self.authors = try node.elementChildren.filter({ $0.elementName == "author" }).map(Author.init)
+            self.contents = try node.elementChildren.filter({ $0.elementName == "content" }).map(Content.init)
+        }
+    }
+
+    public enum Errors : Error {
+        case noAtomRoot
+        case rootEntriesInvalid
+        case noChannelTitle
+        case noChannelLink
+    }
+}