Add first source scanning

WebsiteGenerator.xcodeproj/project.pbxproj

@@ -35,6 +35,8 @@
 		E22E87B0289F221A00E51191 /* PrefilledTopBarTemplate.swift in Sources */ = {isa = PBXBuildFile; fileRef = E22E87AF289F221A00E51191 /* PrefilledTopBarTemplate.swift */; };
 		E22E87B2289F296700E51191 /* ThumbnailInfo.swift in Sources */ = {isa = PBXBuildFile; fileRef = E22E87B1289F296700E51191 /* ThumbnailInfo.swift */; };
 		E22E87B6289FF67B00E51191 /* Metadata.swift in Sources */ = {isa = PBXBuildFile; fileRef = E22E87B5289FF67B00E51191 /* Metadata.swift */; };
+		E253C86928AFD86E0076B6D0 /* FileAccess.swift in Sources */ = {isa = PBXBuildFile; fileRef = E253C86828AFD86E0076B6D0 /* FileAccess.swift */; };
+		E253C86B28AFE0980076B6D0 /* Context.swift in Sources */ = {isa = PBXBuildFile; fileRef = E253C86A28AFE0980076B6D0 /* Context.swift */; };
 		E26555E428A2C4FA00BAF496 /* LinkPreviewMetadataProvider.swift in Sources */ = {isa = PBXBuildFile; fileRef = E26555E328A2C4FA00BAF496 /* LinkPreviewMetadataProvider.swift */; };
 		E2C5A5D528A0223C00102A25 /* HeaderTemplate.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2C5A5D428A0223C00102A25 /* HeaderTemplate.swift */; };
 		E2C5A5D728A022C500102A25 /* TemplateFactory.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2C5A5D628A022C500102A25 /* TemplateFactory.swift */; };
@@ -55,6 +57,14 @@
 		E2F8FA2628ACD64500632026 /* PageVideoTemplate.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2F8FA2528ACD64500632026 /* PageVideoTemplate.swift */; };
 		E2F8FA2828ACD84400632026 /* VideoType.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2F8FA2728ACD84400632026 /* VideoType.swift */; };
 		E2F8FA2B28AD0BD200632026 /* Splash in Frameworks */ = {isa = PBXBuildFile; productRef = E2F8FA2A28AD0BD200632026 /* Splash */; };
+		E2F8FA2D28AD2F5300632026 /* GenericMetadata.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2F8FA2C28AD2F5300632026 /* GenericMetadata.swift */; };
+		E2F8FA3028AD450B00632026 /* PageState.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2F8FA2F28AD450B00632026 /* PageState.swift */; };
+		E2F8FA3228AD456C00632026 /* GenericMetadata+Localized.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2F8FA3128AD456C00632026 /* GenericMetadata+Localized.swift */; };
+		E2F8FA3428AD6F3400632026 /* Element.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2F8FA3328AD6F3400632026 /* Element.swift */; };
+		E2F8FA3628AE233600632026 /* Element+LocalizedMetadata.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2F8FA3528AE233600632026 /* Element+LocalizedMetadata.swift */; };
+		E2F8FA3828AE27A500632026 /* ContentError.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2F8FA3728AE27A500632026 /* ContentError.swift */; };
+		E2F8FA3A28AE313A00632026 /* ErrorOutput.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2F8FA3928AE313A00632026 /* ErrorOutput.swift */; };
+		E2F8FA3C28AE685C00632026 /* Decodable+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2F8FA3B28AE685C00632026 /* Decodable+Extensions.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXCopyFilesBuildPhase section */
@@ -98,6 +108,8 @@
 		E22E87AF289F221A00E51191 /* PrefilledTopBarTemplate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PrefilledTopBarTemplate.swift; sourceTree = "<group>"; };
 		E22E87B1289F296700E51191 /* ThumbnailInfo.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ThumbnailInfo.swift; sourceTree = "<group>"; };
 		E22E87B5289FF67B00E51191 /* Metadata.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Metadata.swift; sourceTree = "<group>"; };
+		E253C86828AFD86E0076B6D0 /* FileAccess.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FileAccess.swift; sourceTree = "<group>"; };
+		E253C86A28AFE0980076B6D0 /* Context.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Context.swift; sourceTree = "<group>"; };
 		E26555E328A2C4FA00BAF496 /* LinkPreviewMetadataProvider.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LinkPreviewMetadataProvider.swift; sourceTree = "<group>"; };
 		E2C5A5D428A0223C00102A25 /* HeaderTemplate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = HeaderTemplate.swift; sourceTree = "<group>"; };
 		E2C5A5D628A022C500102A25 /* TemplateFactory.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TemplateFactory.swift; sourceTree = "<group>"; };
@@ -117,6 +129,14 @@
 		E2F8FA2328ACD0A800632026 /* PageImageTemplate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PageImageTemplate.swift; sourceTree = "<group>"; };
 		E2F8FA2528ACD64500632026 /* PageVideoTemplate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PageVideoTemplate.swift; sourceTree = "<group>"; };
 		E2F8FA2728ACD84400632026 /* VideoType.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = VideoType.swift; sourceTree = "<group>"; };
+		E2F8FA2C28AD2F5300632026 /* GenericMetadata.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GenericMetadata.swift; sourceTree = "<group>"; };
+		E2F8FA2F28AD450B00632026 /* PageState.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PageState.swift; sourceTree = "<group>"; };
+		E2F8FA3128AD456C00632026 /* GenericMetadata+Localized.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "GenericMetadata+Localized.swift"; sourceTree = "<group>"; };
+		E2F8FA3328AD6F3400632026 /* Element.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Element.swift; sourceTree = "<group>"; };
+		E2F8FA3528AE233600632026 /* Element+LocalizedMetadata.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Element+LocalizedMetadata.swift"; sourceTree = "<group>"; };
+		E2F8FA3728AE27A500632026 /* ContentError.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ContentError.swift; sourceTree = "<group>"; };
+		E2F8FA3928AE313A00632026 /* ErrorOutput.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ErrorOutput.swift; sourceTree = "<group>"; };
+		E2F8FA3B28AE685C00632026 /* Decodable+Extensions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Decodable+Extensions.swift"; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -151,6 +171,7 @@
 		E22E8761289D84C300E51191 /* WebsiteGenerator */ = {
 			isa = PBXGroup;
 			children = (
+				E2F8FA2E28AD44FF00632026 /* Generic */,
 				E22E8762289D84C300E51191 /* main.swift */,
 				E22E87A1289F0BF000E51191 /* Content */,
 				E22E87A2289F0C6200E51191 /* Generators */,
@@ -170,6 +191,7 @@
 			children = (
 				E22E879A289EE02F00E51191 /* Optional+Extensions.swift */,
 				E22E87AD289F1E0000E51191 /* String+Extensions.swift */,
+				E2F8FA3B28AE685C00632026 /* Decodable+Extensions.swift */,
 			);
 			path = Extensions;
 			sourceTree = "<group>";
@@ -257,6 +279,22 @@
 			path = Filled;
 			sourceTree = "<group>";
 		};
+		E2F8FA2E28AD44FF00632026 /* Generic */ = {
+			isa = PBXGroup;
+			children = (
+				E253C86A28AFE0980076B6D0 /* Context.swift */,
+				E2F8FA2C28AD2F5300632026 /* GenericMetadata.swift */,
+				E2F8FA3128AD456C00632026 /* GenericMetadata+Localized.swift */,
+				E2F8FA2F28AD450B00632026 /* PageState.swift */,
+				E2F8FA3328AD6F3400632026 /* Element.swift */,
+				E2F8FA3528AE233600632026 /* Element+LocalizedMetadata.swift */,
+				E2F8FA3728AE27A500632026 /* ContentError.swift */,
+				E2F8FA3928AE313A00632026 /* ErrorOutput.swift */,
+				E253C86828AFD86E0076B6D0 /* FileAccess.swift */,
+			);
+			path = Generic;
+			sourceTree = "<group>";
+		};
 /* End PBXGroup section */
 
 /* Begin PBXNativeTarget section */
@@ -325,9 +363,11 @@
 			files = (
 				E2C5A5D728A022C500102A25 /* TemplateFactory.swift in Sources */,
 				E22E8772289D8C2700E51191 /* IndexPageGenerator.swift in Sources */,
+				E2F8FA3A28AE313A00632026 /* ErrorOutput.swift in Sources */,
 				E22E876E289D868100E51191 /* Site+LocalizedMetadata.swift in Sources */,
 				E2C5A5D528A0223C00102A25 /* HeaderTemplate.swift in Sources */,
 				E22E876C289D855D00E51191 /* ThumbnailStyle.swift in Sources */,
+				E2F8FA2D28AD2F5300632026 /* GenericMetadata.swift in Sources */,
 				E22E8798289EA42C00E51191 /* FileProcessor.swift in Sources */,
 				E26555E428A2C4FA00BAF496 /* LinkPreviewMetadataProvider.swift in Sources */,
 				E22E87AA289F1AEE00E51191 /* PageHeadGenerator.swift in Sources */,
@@ -336,6 +376,7 @@
 				E2D55EDF28A2AD4F00B9453E /* LinkPreviewMetadata.swift in Sources */,
 				E22E876A289D84FD00E51191 /* Section+Metadata.swift in Sources */,
 				E2F8FA2028AB72D900632026 /* PlaceholderTemplate.swift in Sources */,
+				E2F8FA3428AD6F3400632026 /* Element.swift in Sources */,
 				E22E87AE289F1E0000E51191 /* String+Extensions.swift in Sources */,
 				E22E879E289EFDFC00E51191 /* OverviewPageGenerator.swift in Sources */,
 				E22E8793289E7EC700E51191 /* Page+LocalizedMetadata.swift in Sources */,
@@ -346,6 +387,7 @@
 				E22E87A4289F0C7000E51191 /* SiteGenerator.swift in Sources */,
 				E22E87AC289F1D3700E51191 /* Template.swift in Sources */,
 				E22E87A0289F008200E51191 /* ThumbnailListGenerator.swift in Sources */,
+				E2F8FA3028AD450B00632026 /* PageState.swift in Sources */,
 				E22E8784289DCD5E00E51191 /* Section+LocalizedMetadata.swift in Sources */,
 				E22E8789289DDF5700E51191 /* Page+Metadata.swift in Sources */,
 				E2C5A5EC28A055E900102A25 /* SiteElement.swift in Sources */,
@@ -364,11 +406,17 @@
 				E22E8795289E81D700E51191 /* FileSystem.swift in Sources */,
 				E2C5A5D928A023FA00102A25 /* PageHeadTemplate.swift in Sources */,
 				E22E8763289D84C300E51191 /* main.swift in Sources */,
+				E253C86B28AFE0980076B6D0 /* Context.swift in Sources */,
 				E22E879B289EE02F00E51191 /* Optional+Extensions.swift in Sources */,
 				E22E877A289DA9F900E51191 /* Site.swift in Sources */,
+				E2F8FA3228AD456C00632026 /* GenericMetadata+Localized.swift in Sources */,
 				E22E87B2289F296700E51191 /* ThumbnailInfo.swift in Sources */,
+				E2F8FA3C28AE685C00632026 /* Decodable+Extensions.swift in Sources */,
 				E2F8FA2428ACD0A800632026 /* PageImageTemplate.swift in Sources */,
 				E22E8787289DDF4C00E51191 /* Page.swift in Sources */,
+				E2F8FA3828AE27A500632026 /* ContentError.swift in Sources */,
+				E2F8FA3628AE233600632026 /* Element+LocalizedMetadata.swift in Sources */,
+				E253C86928AFD86E0076B6D0 /* FileAccess.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

WebsiteGenerator.xcodeproj/xcuserdata/ch.xcuserdatad/xcdebugger/Breakpoints_v2.xcbkptlist

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Bucket
+   uuid = "A4ABB69A-4D7A-40A2-832F-5B0B63325500"
+   type = "1"
+   version = "2.0">
+</Bucket>

WebsiteGenerator/Content/LinkPreviewMetadata.swift

@@ -10,7 +10,7 @@ struct LinkPreviewMetadata {
     /**
      The title to use for the link preview.
 
-     If `nil` is specified, then the localized element title is used.
+     If `nil` is specified, then the localized element `title` is used.
      */
     let title: String?
 
@@ -23,8 +23,8 @@ struct LinkPreviewMetadata {
 
     /**
      The description text for the link preview.
-     - Note: If `nil` is specified, then first the (localized) element subtitle is used.
+     - Note: If `nil` is specified, then first the (localized) element `subtitle` is used.
-     If this is `nil` too, then the localized description of the element is used.
+     If this is `nil` too, then the localized `description` of the element is used.
      */
     let description: String?
 }

WebsiteGenerator/Content/Site.swift

@@ -29,8 +29,8 @@ struct Site {
         print("Loaded site with \(elements.count) sections and \(metadata.languages.count) languages")
 
         // Create example metadata
-        _ = try? Page.Metadata(in: folder)
+        //_ = try? Page.Metadata(in: folder)
-        _ = try? Section.Metadata(in: folder)
+        //_ = try? Section.Metadata(in: folder)
     }
 }
 

WebsiteGenerator/Extensions/Decodable+Extensions.swift

@@ -0,0 +1,8 @@
+import Foundation
+
+extension JSONDecoder {
+
+    func decode<T>(from data: Data) throws -> T where T: Decodable {
+        try self.decode(T.self, from: data)
+    }
+}

WebsiteGenerator/Extensions/Optional+Extensions.swift

@@ -9,4 +9,20 @@ extension Optional {
         }
         return nil
     }
+
+    @discardableResult
+    func ifNil(_ closure: () -> Void) -> Self {
+        if self == nil {
+            closure()
+        }
+        return self
+    }
+
+    @discardableResult
+    func ifNotNil(_ closure: () -> Void) -> Self {
+        if self != nil {
+            closure()
+        }
+        return self
+    }
 }

WebsiteGenerator/FileSystem.swift

@@ -42,6 +42,9 @@ extension URL {
         FileSystem.fm.fileExists(atPath: path)
     }
 
+    /**
+     Delete the file at the url.
+     */
     func delete() throws {
         try FileSystem.fm.removeItem(at: self)
     }

WebsiteGenerator/Generic/ContentError.swift

@@ -0,0 +1,27 @@
+import Foundation
+
+struct ContentError: Error {
+
+    let reason: String
+
+    let source: String
+
+    let error: Error?
+}
+
+extension Optional {
+
+    func unwrapped(or error: ContentError) throws -> Wrapped {
+        guard case let .some(value) = self else {
+            throw error
+        }
+        return value
+    }
+
+    func unwrapOrFail(_ reason: String, source: String, error: Error? = nil) throws -> Wrapped {
+        guard case let .some(value) = self else {
+            throw ContentError(reason: reason, source: source, error: error)
+        }
+        return value
+    }
+}

WebsiteGenerator/Generic/Context.swift

@@ -0,0 +1,14 @@
+import Foundation
+
+final class Context {
+
+    let validation: ErrorOutput
+
+    let fileSystem: FileAccess
+
+    init(inputFolder: URL, outputFolder: URL) {
+        let validation = ErrorOutput()
+        self.validation = validation
+        self.fileSystem = FileAccess(in: inputFolder, errorOutput: validation)
+    }
+}

WebsiteGenerator/Generic/Element+LocalizedMetadata.swift

@@ -0,0 +1,223 @@
+import Foundation
+
+extension Element {
+
+    /**
+     Metadata localized for a specific language.
+     */
+    struct LocalizedMetadata {
+
+        static let moreLinkDefaultText = "DefaultMoreText"
+
+        /**
+         The language for which the content is specified.
+         - Note: This field is mandatory
+         */
+        let language: String
+
+        /**
+         - Note: This field is mandatory
+         The title used in the page header.
+         */
+        let title: String
+
+        /**
+         The subtitle used in the page header.
+         */
+        let subtitle: String?
+
+        /**
+         The description text used in the page header.
+         */
+        let description: String?
+
+        /**
+         The title to use for the link preview.
+
+         If `nil` is specified, then the localized element `title` is used.
+         */
+        let linkPreviewTitle: String
+
+        /**
+         The file name of the link preview image.
+         - Note: The image must be located in the element folder.
+         - Note: If `nil` is specified, then the (localized) thumbnail is used.
+         */
+        let linkPreviewImage: String
+
+        /**
+         The description text for the link preview.
+         - Note: If `nil` is specified, then first the (localized) element `subtitle` is used.
+         If this is `nil` too, then the localized `description` of the element is used.
+         */
+        let linkPreviewDescription: String
+
+        /**
+         The text on the link to show the section page when previewing multiple sections on an overview page.
+         - Note: If this value is inherited from the parent, if it is not defined. There must be at least one
+         element in the path that defines this property.
+         */
+        let moreLinkText: String
+
+        /**
+         The text on the back navigation link of **contained** elements.
+
+         This text does not appear on the section page, but on the pages contained within the section.
+         - Note: If this property is not specified, then the `defaultBackLinkText` is used
+         */
+        let backLinkText: String
+
+        /**
+         The text to show as a title for placeholder boxes
+
+         Placeholders are included in missing pages.
+         - Note: If no value is specified, then this property is inherited from the parent. The root element must specify this property.
+         */
+        let placeholderTitle: String
+
+        /**
+         The text to show as a description for placeholder boxes
+
+         Placeholders are included in missing pages.
+         - Note: If no value is specified, then this property is inherited from the parent. The root element must specify this property.
+         */
+        let placeholderText: String
+
+        /**
+         An optional suffix to add to the title on a page.
+
+         This can be useful to express a different author, project grouping, etc.
+         */
+        let titleSuffix: String?
+
+        /**
+         An optional suffix to add to the thumbnail title of a page.
+
+         This can be useful to express a different author, project grouping, etc.
+         */
+        let thumbnailSuffix: String?
+
+        /**
+         A text to place in the top right corner of a large thumbnail.
+
+         The text should be a very short string to fit into the corner, like `soon`, or `draft`
+
+         - Note: This property is ignored if `thumbnailStyle` is not `large`.
+         */
+        let cornerText: String?
+
+        /**
+         The external url to use instead of automatically generating the page.
+
+         This property can be used for links to other parts of the site, like additional services.
+         It can also be set to manually write a page.
+         */
+        let externalUrl: String?
+    }
+}
+
+extension Element.LocalizedMetadata {
+
+    init?(atRoot folder: URL, data: GenericMetadata.LocalizedMetadata, with context: Context) {
+        let validation = context.validation
+        // Go through all elements and check them for completeness
+        // In the end, check that all required elements are present
+        var isComplete = true
+        func markAsIncomplete() {
+            isComplete = false
+        }
+        let source = "root"
+        self.language = validation
+            .required(data.language, name: "language", source: source)
+            .ifNil(markAsIncomplete) ?? ""
+        self.title = validation
+            .required(data.title, name: "title", source: source)
+            .ifNil(markAsIncomplete) ?? ""
+        self.subtitle = data.subtitle
+        self.description = data.description
+        self.linkPreviewTitle = data.linkPreviewTitle ?? data.title ?? ""
+        self.linkPreviewImage = validation
+            .linkPreviewThumbnail(customFile: data.linkPreviewImage, for: language, in: folder, source: source) ?? ""
+        let linkPreviewDescription = data.linkPreviewDescription ?? data.subtitle ?? data.description
+        self.linkPreviewDescription = validation
+            .required(linkPreviewDescription, name: "linkPreviewDescription", source: source)
+            .ifNil(markAsIncomplete) ?? ""
+        self.moreLinkText = data.moreLinkText ?? Element.LocalizedMetadata.moreLinkDefaultText
+        self.backLinkText = validation
+            .required(data.backLinkText, name: "backLinkText", source: source)
+            .ifNil(markAsIncomplete) ?? ""
+        self.placeholderTitle = validation
+            .required(data.placeholderTitle, name: "placeholderTitle", source: source)
+            .ifNil(markAsIncomplete) ?? ""
+        self.placeholderText = validation
+            .required(data.placeholderText, name: "placeholderText", source: source)
+            .ifNil(markAsIncomplete) ?? ""
+        self.titleSuffix = data.titleSuffix
+        self.thumbnailSuffix = validation.unused(data.thumbnailSuffix, "thumbnailSuffix", source: source)
+        self.cornerText = validation.unused(data.cornerText, "cornerText", source: source)
+        self.externalUrl = validation.unexpected(data.externalUrl, name: "externalUrl", source: source)
+
+        guard isComplete else {
+            return nil
+        }
+    }
+
+    init?(folder: URL, data: GenericMetadata.LocalizedMetadata, source: String, parent: Element.LocalizedMetadata, with context: Context) {
+        let validation = context.validation
+        // Go through all elements and check them for completeness
+        // In the end, check that all required elements are present
+        var isComplete = true
+        func markAsIncomplete() {
+            isComplete = false
+        }
+        self.language = parent.language
+        self.title = validation
+            .required(data.title, name: "title", source: source)
+            .ifNil(markAsIncomplete) ?? ""
+        self.subtitle = data.subtitle
+        self.description = data.description
+        self.linkPreviewTitle = data.linkPreviewTitle ?? data.title ?? ""
+        self.linkPreviewImage = validation
+            .linkPreviewThumbnail(customFile: data.linkPreviewImage, for: language, in: folder, source: source) ?? ""
+        let linkPreviewDescription = data.linkPreviewDescription ?? data.subtitle ?? data.description
+        self.linkPreviewDescription = validation
+            .required(linkPreviewDescription, name: "linkPreviewDescription", source: source)
+            .ifNil(markAsIncomplete) ?? ""
+        self.moreLinkText = validation.moreLinkText(data.moreLinkText, parent: parent.moreLinkText, source: source)
+        self.backLinkText = data.backLinkText ?? parent.backLinkText
+        self.placeholderTitle = data.placeholderTitle ?? parent.placeholderTitle
+        self.placeholderText = data.placeholderText ?? parent.placeholderText
+        self.titleSuffix = data.titleSuffix
+        self.thumbnailSuffix = data.thumbnailSuffix
+        self.cornerText = data.cornerText
+        self.externalUrl = data.externalUrl
+
+        guard isComplete else {
+            return nil
+        }
+    }
+}
+
+// MARK: Thumbnails
+
+extension Element {
+
+    static let defaultThumbnailName = "thumbnail.jpg"
+
+    static func localizedThumbnailName(for language: String) -> String {
+        "thumbnail-\(language).jpg"
+    }
+
+    static func findThumbnail(for language: String, in folder: URL) -> String? {
+        let localizedThumbnail = localizedThumbnailName(for: language)
+        let localizedThumbnailUrl = folder.appendingPathComponent(localizedThumbnail)
+        if localizedThumbnailUrl.exists {
+            return localizedThumbnail
+        }
+        let defaultThumbnailUrl = folder.appendingPathComponent(defaultThumbnailName)
+        if defaultThumbnailUrl.exists {
+            return defaultThumbnailName
+        }
+        return nil
+    }
+}

WebsiteGenerator/Generic/Element.swift

@@ -0,0 +1,237 @@
+import Foundation
+
+struct Element {
+
+    static let overviewItemCountDefault = 6
+
+    /**
+     The author of the content.
+
+     If no author is set, then the author from the parent element is used.
+     */
+    let author: String
+
+    /**
+     The title used in the top bar of the website, next to the logo.
+
+     This title can be HTML content, and only the root level value is used.
+     */
+    let topBarTitle: String
+
+    /**
+     The url where the site will be deployed.
+
+     This value is required to build absolute links for link previews.
+
+     - Note: Only the root level value is used.
+     - Note: The path does not need to contain a trailing slash.
+     */
+    let deployedBaseUrl: String
+
+    /**
+     The (start) date of the element.
+
+     The date is printed on content pages and may also used for sorting elements,
+     depending on the `useManualSorting` property of the parent.
+     */
+    let date: Date?
+
+    /**
+     The end date of the element.
+
+     This property can be used to specify a date range for a content page.
+     */
+    let endDate: Date?
+
+    /**
+     The deployment state of the page.
+
+     - Note: This property defaults to ``PageState.standard`
+     */
+    let state: PageState
+
+    /**
+     The sort index of the page for manual sorting.
+
+     - Note: This property is only used (and must be set) if `useManualSorting` option of the parent is set.
+     */
+    let sortIndex: Int?
+
+    /**
+     All files which may occur in content but is stored externally.
+
+     Missing files which would otherwise produce a warning are ignored when included here.
+     - Note: This property defaults to an empty set.
+     */
+    let externalFiles: Set<String>
+
+    /**
+     Specifies additional files which should be copied to the destination when generating the content.
+     - Note: This property defaults to an empty set.
+     */
+    let requiredFiles: Set<String>
+
+    /**
+     The style of thumbnail to use when generating overviews.
+
+     - Note: This property is only relevant for sections.
+     - Note: This property is inherited from the parent if not specified.
+     */
+    let thumbnailStyle: ThumbnailStyle
+
+    /**
+     Sort the child elements by their `sortIndex` property when generating overviews, instead of using the `date`.
+
+     - Note: This property is only relevant for sections.
+     - Note: This property defaults to `false`
+     */
+    let useManualSorting: Bool
+
+    /**
+     The number of items to show when generating overviews of this element.
+     - Note: This property is only relevant for sections.
+     - Note: This property is inherited from the parent if not specified.
+     */
+    let overviewItemCount: Int
+
+    /**
+     The localized metadata for each language.
+     */
+    let languages: [LocalizedMetadata]
+
+    /**
+     All elements contained within the element.
+
+     If the element is a section, then this property contains the pages or subsections within.
+     */
+    var elements: [Element] = []
+
+    /**
+     The url of the element's folder in the source hierarchy.
+     - Note: This property is essentially the root folder of the site, appended with the value of the ``path`` property.
+     */
+    let inputFolder: URL
+
+    /**
+     The path to the element's folder in the source hierarchy (without a leading slash).
+     */
+    let path: String
+
+    /**
+     Create the root element of a site.
+
+     The root element will recursively move into subfolders and build the site content
+     by looking for metadata files in each subfolder.
+     - Parameter folder: The root folder of the site content.
+     - Parameter context: The context to create the element (validation, file access, etc.)
+     */
+    init?(atRoot folder: URL, with context: Context) throws {
+        let validation = context.validation
+        self.inputFolder = folder
+        self.path = ""
+
+        let source = "root"
+        guard let metadata = try GenericMetadata(path: nil, with: context) else {
+            return nil
+        }
+
+        self.author = validation.required(metadata.author, name: "author", source: source) ?? "author"
+        self.topBarTitle = validation
+            .required(metadata.topBarTitle, name: "topBarTitle", source: source) ?? "My Website"
+        self.deployedBaseUrl = validation
+            .required(metadata.deployedBaseUrl, name: "deployedBaseUrl", source: source) ?? "https://example.com"
+        self.date = validation.unused(metadata.date, "date", source: source)
+        self.endDate = validation.unused(metadata.endDate, "endDate", source: source)
+        self.state = validation.state(metadata.state, source: source)
+        self.sortIndex = validation.unused(metadata.sortIndex, "sortIndex", source: source)
+        self.externalFiles = metadata.externalFiles ?? []
+        self.requiredFiles = metadata.requiredFiles ?? []
+        self.thumbnailStyle = validation.unused(metadata.thumbnailStyle, "thumbnailStyle", source: source) ?? .large
+        self.useManualSorting = validation.unused(metadata.useManualSorting, "useManualSorting", source: source) ?? true
+        self.overviewItemCount = metadata.overviewItemCount ?? Element.overviewItemCountDefault
+        self.languages = validation.required(metadata.languages, name: "languages", source: source)?
+            .compactMap { language in
+                    .init(atRoot: folder, data: language, with: context)
+            } ?? []
+        try self.readElements(in: folder, source: nil, with: context)
+    }
+
+    mutating func readElements(in folder: URL, source: String?, with context: Context) throws {
+        let subFolders: [URL]
+        do {
+            subFolders = try FileSystem.folders(in: folder)
+        } catch {
+            context.validation.add(error: "Failed to read subfolders", source: source ?? "root", error: error)
+            return
+        }
+        self.elements = try subFolders.compactMap { subFolder in
+            let s = (source.unwrapped { $0 + "/" } ?? "") + subFolder.lastPathComponent
+            return try Element(parent: self, folder: subFolder, with: context, source: s)
+        }
+    }
+
+    init?(parent: Element, folder: URL, with: Context, source: String) throws {
+        let validation = context.validation
+        self.inputFolder = folder
+        self.path = source
+
+        guard let metadata = try GenericMetadata(path: source, with: context) else {
+            return nil
+        }
+        self.author = metadata.author ?? parent.author
+        self.topBarTitle = validation
+            .unused(metadata.topBarTitle, "topBarTitle", source: source) ?? parent.topBarTitle
+        self.deployedBaseUrl = validation
+            .unused(metadata.deployedBaseUrl, "deployedBaseUrl", source: source) ?? parent.deployedBaseUrl
+        let date = validation.date(from: metadata.date, property: "date", source: source).ifNil {
+            if !parent.useManualSorting {
+                validation.add(error: "No 'date', but parent defines 'useManualSorting' = false", source: source)
+            }
+        }
+        self.date = date
+        self.endDate = validation.date(from: metadata.endDate, property: "endDate", source: source).ifNotNil {
+            if date == nil {
+                validation.add(warning: "Set 'endDate', but no 'date'", source: source)
+            }
+        }
+        self.state = validation.state(metadata.state, source: source)
+        self.sortIndex = metadata.sortIndex.ifNil {
+            if parent.useManualSorting {
+                validation.add(error: "No 'sortIndex', but parent defines 'useManualSorting' = true", source: source)
+            }
+        }
+        // TODO: Propagate external files from the parent if subpath matches?
+        self.externalFiles = metadata.externalFiles ?? []
+        self.requiredFiles = metadata.requiredFiles ?? []
+        self.thumbnailStyle = validation.thumbnailStyle(metadata.state, source: source)
+        self.useManualSorting = metadata.useManualSorting ?? false
+        self.overviewItemCount = metadata.overviewItemCount ?? parent.overviewItemCount
+        self.languages = parent.languages.compactMap { parentData in
+            guard let data = metadata.languages?.first(where: { $0.language == parentData.language }) else {
+                validation.add(info: "Language '\(parentData.language)' not found", source: source)
+                return nil
+            }
+            return .init(folder: folder, data: data, source: source, parent: parentData, with: context)
+        }
+        // Check that each 'language' tag is present, and that all languages appear in the parent
+        validation.required(metadata.languages, name: "languages", source: source)?
+            .compactMap { validation.required($0.language, name: "language", source: source) }
+            .filter { language in
+                !parent.languages.contains { $0.language == language }
+            }
+            .forEach {
+                validation.add(warning: "Language '\($0)' not found in parent, so not generated", source: source)
+            }
+        try self.readElements(in: folder, source: source, with: context)
+    }
+}
+
+// MARK: Debug
+
+extension Element {
+
+    func printTree(indentation: String = "") {
+        print(indentation + "/" + path)
+        elements.forEach { $0.printTree(indentation: indentation + "  ") }
+    }
+}

WebsiteGenerator/Generic/ErrorOutput.swift

@@ -0,0 +1,137 @@
+import Foundation
+
+final class ErrorOutput {
+
+    init() {
+
+    }
+
+    func add(error: ContentError) {
+        print("[ERROR] Reason: \(error.reason), Source: \(error.source), Error: \(error.error?.localizedDescription ?? "nil")")
+    }
+
+    func add(error reason: String, source: String, error: Error? = nil) {
+        add(error: .init(reason: reason, source: source, error: error))
+    }
+
+    func add(warning: ContentError) {
+        print("[WARNING] Reason: \(warning.reason), Source: \(warning.source), Error: \(warning.error?.localizedDescription ?? "nil")")
+    }
+
+    func add(warning reason: String, source: String, error: Error? = nil) {
+        add(warning: .init(reason: reason, source: source, error: error))
+    }
+
+    func add(info: ContentError) {
+        print("[INFO] Reason: \(info.reason), Source: \(info.source), Error: \(info.error?.localizedDescription ?? "nil")")
+    }
+
+    func add(info reason: String, source: String, error: Error? = nil) {
+        add(info: .init(reason: reason, source: source, error: error))
+    }
+
+    @discardableResult
+    func unused<T, R>(_ value: Optional<T>, _ name: String, source: String) -> Optional<R> {
+        if value != nil {
+            add(info: "Unused property '\(name)'", source: source)
+        }
+        return nil
+    }
+
+    func unknown(property: String, source: String) {
+        add(info: "Unknown property '\(property)'", source: source)
+    }
+
+    func required<T>(_ value: Optional<T>, name: String, source: String) -> Optional<T> {
+        guard let value = value else {
+            add(error: "Missing property '\(name)'", source: source)
+            return nil
+        }
+        return value
+    }
+
+    func unexpected<T>(_ value: Optional<T>, name: String, source: String) -> Optional<T> {
+        if let value = value {
+            add(error: "Unexpected property '\(name)' = '\(value)'", source: source)
+            return nil
+        }
+        return nil
+    }
+
+    func missing(_ file: String, requiredBy source: String) {
+        print("[ERROR] Missing file '\(file)' required by \(source)")
+    }
+
+    func failedToOpen(_ file: String, requiredBy source: String, error: Error?) {
+        print("[ERROR] Failed to open file '\(file)' required by \(source): \(error?.localizedDescription ?? "No error provided")")
+    }
+
+    func state(_ raw: String?, source: String) -> PageState {
+        guard let raw = raw else {
+            return .standard
+        }
+        guard let state = PageState(rawValue: raw) else {
+            add(warning: "Invalid 'state' '\(raw)', using 'standard'", source: source)
+            return .standard
+        }
+        return state
+    }
+
+    func thumbnailStyle(_ raw: String?, source: String) -> ThumbnailStyle {
+        guard let raw = raw else {
+            return .large
+        }
+        guard let style = ThumbnailStyle(rawValue: raw) else {
+            add(warning: "Invalid 'thumbnailStyle' '\(raw)', using 'large'", source: source)
+            return .large
+        }
+        return style
+    }
+
+    func linkPreviewThumbnail(customFile: String?, for language: String, in folder: URL, source: String) -> String? {
+        if let customFile = customFile {
+            #warning("Allow absolute urls for link preview thumbnails")
+            let customFileUrl = folder.appendingPathComponent(customFile)
+            guard customFileUrl.exists else {
+                missing(customFile, requiredBy: "property 'linkPreviewImage' in metadata of \(source)")
+                return nil
+            }
+            return customFile
+        }
+        guard let thumbnail = Element.findThumbnail(for: language, in: folder) else {
+            // Link preview images are not necessarily required
+            return nil
+        }
+        return thumbnail
+    }
+
+    func moreLinkText(_ elementText: String?, parent parentText: String?, source: String) -> String {
+        if let elementText = elementText {
+            return elementText
+        }
+        let standard = Element.LocalizedMetadata.moreLinkDefaultText
+        guard let parentText = parentText, parentText != standard else {
+            add(error: "Missing property 'moreLinkText'", source: source)
+            return standard
+        }
+
+        return parentText
+    }
+
+    func date(from string: String?, property: String, source: String) -> Date? {
+        guard let string = string else {
+            return nil
+        }
+        guard let date = ErrorOutput.metadataDate.date(from: string) else {
+            add(warning: "Invalid date string '\(string)' for property '\(property)'", source: source)
+            return nil
+        }
+        return date
+    }
+
+    private static let metadataDate: DateFormatter = {
+        let df = DateFormatter()
+        df.dateFormat = "dd.MM.yy"
+        return df
+    }()
+}

WebsiteGenerator/Generic/FileAccess.swift

@@ -0,0 +1,146 @@
+import Foundation
+
+enum FileAccessError: Error {
+    case failedToReadFile(String, Error)
+}
+
+final class FileAccess {
+
+    static let accessTimesFileName = "access.json"
+
+    let errorOutput: ErrorOutput
+
+    let sourceFolder: URL
+
+    private let source = "FileAccess"
+
+    private var modificationTimeCacheFile: URL {
+        sourceFolder.appendingPathComponent(FileAccess.accessTimesFileName)
+    }
+
+    /**
+     The time stamps of last modified times for all accessed source files.
+
+     The key is the relative path to the file from the source
+     */
+    private var sourceLastModifiedTimes: [String : Date] = [:]
+
+    private var changedFiles: Set<String> = []
+
+    init(in root: URL, errorOutput: ErrorOutput) {
+        self.sourceFolder = root
+        self.errorOutput = errorOutput
+
+        loadSavedModificationTimes()
+    }
+
+    private func loadSavedModificationTimes() {
+        let url = modificationTimeCacheFile
+        guard url.exists else {
+            errorOutput.add(info: "No file modification times loaded, regarding all content as new", source: source)
+            return
+        }
+        let data: Data
+        do {
+            data = try Data(contentsOf: url)
+        } catch {
+            errorOutput.add(
+                warning: "File modification times data not read, regarding all content as new",
+                source: source,
+                error: error)
+            return
+        }
+        do {
+            self.sourceLastModifiedTimes = try JSONDecoder().decode(from: data)
+        } catch {
+            errorOutput.add(
+                warning: "File modification times not decoded, regarding all content as new",
+                source: source,
+                error: error)
+            try? url.delete()
+            return
+        }
+    }
+
+    private func didAccess(inputPath: String, modified lastModified: Date, source: String) {
+        guard let previousDate = sourceLastModifiedTimes[inputPath] else {
+            // File not processed before, so mark as changed
+            changedFiles.insert(inputPath)
+            return
+        }
+        guard lastModified > previousDate else {
+            // File is unchanged
+            return
+        }
+        changedFiles.insert(inputPath)
+    }
+
+    private func lastModifiedTime(of url: URL) -> Date? {
+        guard url.exists else {
+            return nil
+        }
+        do {
+            let attributes = try FileManager.default.attributesOfItem(atPath: url.path)
+            guard let date = attributes[.modificationDate] as? Date else {
+                errorOutput.add(warning: "Failed to read modification time of \(url.path)", source: source)
+                return nil
+            }
+            return date
+        } catch {
+            errorOutput.add(warning: "Failed to read file attributes of \(url.path)", source: source)
+            return nil
+        }
+    }
+
+    func loadStringContent(inputPath: String) throws -> String? {
+        try load(inputPath: inputPath, String.init)
+    }
+
+    func loadDataContent(inputPath: String) throws -> Data? {
+        try load(inputPath: inputPath) { try Data(contentsOf: $0) }
+    }
+
+    private func load<T>(inputPath: String, _ closure: (URL) throws -> T) rethrows -> T? {
+        let url = sourceFolder.appendingPathComponent(inputPath)
+        guard let modifiedDate = lastModifiedTime(of: url) else {
+            sourceLastModifiedTimes[inputPath] = nil
+            return nil
+        }
+        do {
+            let content = try closure(url)
+            didAccess(inputPath: inputPath, modified: modifiedDate, source: source)
+            return content
+        } catch {
+            throw FileAccessError.failedToReadFile(inputPath, error)
+        }
+    }
+
+    func didGenerateAllFiles() {
+        for file in changedFiles {
+            let url = sourceFolder.appendingPathComponent(file)
+            guard let date = lastModifiedTime(of: url) else {
+                continue
+            }
+            sourceLastModifiedTimes[file] = date
+        }
+        do {
+            let data = try JSONEncoder().encode(sourceLastModifiedTimes)
+            try data.write(to: modificationTimeCacheFile)
+        } catch {
+            errorOutput.add(warning: "Failed to save modification times", source: source, error: error)
+        }
+    }
+
+    func printChangedFilesOverview() {
+        let count = changedFiles.count
+        guard count > 0 else {
+            print("No files modified")
+            return
+        }
+        print("\(count) files modified:")
+        changedFiles.prefix(10).forEach { print("  " + $0) }
+        if count > 10 {
+            print("  ...")
+        }
+    }
+}

WebsiteGenerator/Generic/GenericMetadata+Localized.swift

@@ -0,0 +1,203 @@
+import Foundation
+
+extension GenericMetadata {
+
+    /**
+     Metadata localized for a specific language.
+     */
+    struct LocalizedMetadata {
+
+        /**
+         The language for which the content is specified.
+         - Note: This field is mandatory
+         */
+        let language: String?
+
+        /**
+         - Note: This field is mandatory
+         The title used in the page header.
+         */
+        let title: String?
+
+        /**
+         The subtitle used in the page header.
+         */
+        let subtitle: String?
+
+        /**
+         The description text used in the page header
+         */
+        let description: String?
+
+        /**
+         The title to use for the link preview.
+
+         If `nil` is specified, then the localized element `title` is used.
+         */
+        let linkPreviewTitle: String?
+
+        /**
+         The file name of the link preview image.
+         - Note: The image must be located in the element folder.
+         - Note: If `nil` is specified, then the (localized) thumbnail is used.
+         */
+        let linkPreviewImage: String?
+
+        /**
+         The description text for the link preview.
+         - Note: If `nil` is specified, then first the (localized) element `subtitle` is used.
+         If this is `nil` too, then the localized `description` of the element is used.
+         */
+        let linkPreviewDescription: String?
+
+        /**
+         The text on the link to show the section page when previewing multiple sections on an overview page.
+         - Note: If this value is inherited from the parent, if it is not defined. There must be at least one
+         element in the path that defines this property.
+         */
+        let moreLinkText: String?
+
+        /**
+         The text on the back navigation link of **contained** elements.
+
+         This text does not appear on the section page, but on the pages contained within the section.
+         - Note: If this property is not specified, then the root `backLinkText` is used.
+         - Note: The root element must specify this property.
+         */
+        let backLinkText: String?
+
+        /**
+         The text to show as a title for placeholder boxes
+
+         Placeholders are included in missing pages.
+         - Note: If no value is specified, then this property is inherited from the parent. The root element must specify this property.
+         */
+        let placeholderTitle: String?
+
+        /**
+         The text to show as a description for placeholder boxes
+
+         Placeholders are included in missing pages.
+         - Note: If no value is specified, then this property is inherited from the parent. The root element must specify this property.
+         */
+        let placeholderText: String?
+
+        /**
+         An optional suffix to add to the title on a page.
+
+         This can be useful to express a different author, project grouping, etc.
+         */
+        let titleSuffix: String?
+
+        /**
+         An optional suffix to add to the thumbnail title of a page.
+
+         This can be useful to express a different author, project grouping, etc.
+         */
+        let thumbnailSuffix: String?
+
+        /**
+         A text to place in the top right corner of a large thumbnail.
+
+         The text should be a very short string to fit into the corner, like `soon`, or `draft`
+
+         - Note: This property is ignored if `thumbnailStyle` is not `large`.
+         */
+        let cornerText: String?
+
+        /**
+         The external url to use instead of automatically generating the page.
+
+         This property can be used for links to other parts of the site, like additional services.
+         It can also be set to manually write a page.
+         */
+        let externalUrl: String?
+    }
+}
+
+extension GenericMetadata.LocalizedMetadata: Codable {
+
+    private static var knownKeyList: [CodingKeys] {
+        [
+            .language,
+            .title,
+            .subtitle,
+            .description,
+            .linkPreviewTitle,
+            .linkPreviewImage,
+            .linkPreviewDescription,
+            .moreLinkText,
+            .backLinkText,
+            .placeholderTitle,
+            .placeholderText
+        ]
+    }
+
+    static var knownKeys: Set<String> {
+        Set(knownKeyList.map { $0.stringValue })
+    }
+}
+
+extension GenericMetadata.LocalizedMetadata {
+
+    /**
+     The mandatory minimum for a site element.
+     */
+    static var mandatory: GenericMetadata.LocalizedMetadata {
+        .init(
+            language: "",
+            title: "",
+            subtitle: nil,
+            description: nil,
+            linkPreviewTitle: nil,
+            linkPreviewImage: nil,
+            linkPreviewDescription: nil,
+            moreLinkText: nil,
+            backLinkText: nil,
+            placeholderTitle: nil,
+            placeholderText: nil,
+            titleSuffix: nil,
+            thumbnailSuffix: nil,
+            cornerText: nil,
+            externalUrl: nil)
+    }
+
+    /**
+     The mandatory minimum for the root element of a site.
+     */
+    static var mandatoryAtRoot: GenericMetadata.LocalizedMetadata {
+        .init(language: "",
+              title: "",
+              subtitle: nil,
+              description: nil,
+              linkPreviewTitle: nil,
+              linkPreviewImage: nil,
+              linkPreviewDescription: nil,
+              moreLinkText: nil,
+              backLinkText: "",
+              placeholderTitle: "",
+              placeholderText: "",
+              titleSuffix: nil,
+              thumbnailSuffix: nil,
+              cornerText: nil,
+              externalUrl: nil)
+    }
+
+    static var full: GenericMetadata.LocalizedMetadata {
+        .init(language: "",
+              title: "",
+              subtitle: "",
+              description: "",
+              linkPreviewTitle: "",
+              linkPreviewImage: "",
+              linkPreviewDescription: "",
+              moreLinkText: "",
+              backLinkText: "",
+              placeholderTitle: "",
+              placeholderText: "",
+              titleSuffix: "",
+              thumbnailSuffix: "",
+              cornerText: "",
+              externalUrl: "")
+    }
+}

WebsiteGenerator/Generic/GenericMetadata.swift

@@ -0,0 +1,176 @@
+import Foundation
+
+/**
+ The metadata for all site elements.
+ */
+struct GenericMetadata {
+
+    /**
+     The name of the metadata file contained in the folder of each site element.
+     */
+    static let metadataFileName = "metadata.json"
+
+    /**
+     The author of the content.
+
+     If no author is set, then the author from the parent element is used.
+     */
+    let author: String?
+
+    /**
+     The title used in the top bar of the website, next to the logo.
+
+     This title can be HTML content, and only the root level value is used.
+     */
+    let topBarTitle: String?
+
+    /**
+     The url where the site will be deployed.
+
+     This value is required to build absolute links for link previews.
+
+     - Note: Only the root level value is used.
+     - Note: The path does not need to contain a trailing slash.
+     */
+    let deployedBaseUrl: String?
+
+    /**
+     The (start) date of the element.
+
+     The date is printed on content pages and may also used for sorting elements,
+     depending on the `useManualSorting` property of the parent.
+     */
+    let date: String?
+
+    /**
+     The end date of the element.
+
+     This property can be used to specify a date range for a content page.
+     */
+    let endDate: String?
+
+    /**
+     The deployment state of the page.
+
+     - Note: This property defaults to ``PageState.standard`
+     */
+    let state: String?
+
+    /**
+     The sort index of the page for manual sorting.
+
+     - Note: This property is only used (and must be set) if `useManualSorting` option of the parent is set.
+     */
+    let sortIndex: Int?
+
+    /**
+     All files which may occur in content but is stored externally.
+
+     Missing files which would otherwise produce a warning are ignored when included here.
+     - Note: This property defaults to an empty set.
+     */
+    let externalFiles: Set<String>?
+
+    /**
+     Specifies additional files which should be copied to the destination when generating the content.
+     - Note: This property defaults to an empty set.
+     */
+    let requiredFiles: Set<String>?
+
+    /**
+     The style of thumbnail to use when generating overviews.
+
+     - Note: This property is only relevant for sections.
+     - Note: This property is inherited from the parent if not specified.
+     */
+    let thumbnailStyle: ThumbnailStyle?
+
+    /**
+     Sort the child elements by their `sortIndex` property when generating overviews, instead of using the `date`.
+
+     - Note: This property is only relevant for sections.
+     - Note: This property defaults to `false`
+     */
+    let useManualSorting: Bool?
+
+    /**
+     The number of items to show when generating overviews of this element.
+     - Note: This property is only relevant for sections.
+     - Note: This property is inherited from the parent if not specified.
+     */
+    let overviewItemCount: Int?
+
+    /**
+     The localized metadata for each language.
+     */
+    let languages: [LocalizedMetadata]?
+}
+
+extension GenericMetadata: Codable {
+
+    private static var knownKeyList: [CodingKeys] {
+        [
+            .author,
+            .topBarTitle,
+            .deployedBaseUrl,
+            .date,
+            .endDate,
+            .state,
+            .sortIndex,
+            .externalFiles,
+            .requiredFiles,
+            .thumbnailStyle,
+            .useManualSorting,
+            .overviewItemCount,
+            .languages
+        ]
+    }
+
+    static var knownKeys: Set<String> {
+        Set(knownKeyList.map { $0.stringValue })
+    }
+}
+
+extension GenericMetadata {
+
+    /**
+     Decode metadata in a folder.
+
+     - Parameter path: The path to the element folder, relative to the source root
+     - Parameter context: The context for the element (validation, file access, etc.)
+     - Note: The decoding routine also checks for unknown properties, and writes them to the output.
+     */
+    init?(path: String?, with context: Context) throws {
+        let source = path ?? "root"
+        let metadataPath = (path.unwrapped { $0 + "/" } ?? "") + GenericMetadata.metadataFileName
+        guard let data = try context.fileSystem.loadDataContent(inputPath: metadataPath) else {
+            return nil
+        }
+        
+        let decoder = JSONDecoder()
+        
+        let knownKeys = GenericMetadata.knownKeys
+        let knownLocalizedKeys = LocalizedMetadata.knownKeys
+        decoder.keyDecodingStrategy = .custom { keys in
+            let key = keys.last!
+            // Only one key means we are decoding the generic metadata
+            guard keys.count > 1 else {
+                if !knownKeys.contains(key.stringValue) {
+                    context.validation.unknown(property: key.stringValue, source: source)
+                }
+                return key
+            }
+            // Two levels means we're decoding the localized metadata
+            if !knownLocalizedKeys.contains(key.stringValue) {
+                context.validation.unknown(property: key.stringValue, source: source)
+            }
+            return key
+        }
+        do {
+            self = try decoder.decode(from: data)
+        } catch {
+            context.validation.failedToOpen(GenericMetadata.metadataFileName, requiredBy: source, error: error)
+            return nil
+        }
+    }
+}

WebsiteGenerator/Generic/PageState.swift

@@ -0,0 +1,18 @@
+import Foundation
+
+enum PageState: String {
+    /**
+     Generate the page, and show it in overviews of the parent.
+     */
+    case standard
+
+    /**
+     Generate the page, but don't provide links in overviews.
+     */
+    case draft
+
+    /**
+     Generate the page, but don't include it in overviews of the parent.
+     */
+    case hide
+}

WebsiteGenerator/main.swift

@@ -2,6 +2,26 @@ import Foundation
 
 let contentDirectory = URL(fileURLWithPath: "/Users/ch/Projects/MakerSpace")
 let outputDirectory = URL(fileURLWithPath: "/Users/ch/Projects/MakerSpace/Site")
+
+let context = Context(inputFolder: contentDirectory, outputFolder: outputDirectory)
+
+let siteData: Element
+do {
+    guard let element = try Element(atRoot: contentDirectory, with: context) else {
+        exit(0)
+    }
+    siteData = element
+} catch {
+    print(error)
+    exit(0)
+}
+
+siteData.printTree()
+context.fileSystem.printChangedFilesOverview()
+context.fileSystem.didGenerateAllFiles()
+
+exit(0)
+
 let files = FileProcessor(
     inputFolder: contentDirectory, outputFolder: outputDirectory)