Refactor page content generators

CHDataManagement/Generator/Commands/PageLinkCommand.swift

@@ -0,0 +1,61 @@
+
+struct PageLinkCommand: CommandProcessor {
+
+    static let commandType: CommandType = .pageLink
+
+    let content: Content
+
+    let results: PageGenerationResults
+
+    let language: ContentLanguage
+
+    init(content: Content, results: PageGenerationResults, language: ContentLanguage) {
+        self.content = content
+        self.results = results
+        self.language = language
+    }
+
+    /**
+     Format: `![page](<pageId>)`
+     */
+    func process(_ arguments: [String], markdown: Substring) -> String {
+        guard arguments.count == 1 else {
+            invalid(markdown)
+            return ""
+        }
+        let pageId = arguments[0]
+
+        guard let page = content.page(pageId) else {
+            results.missing(page: pageId, source: "Page link command")
+            return ""
+        }
+        guard !page.isDraft else {
+            // Prevent linking to unpublished content
+            return ""
+        }
+
+        results.linked(to: page)
+
+        let localized = page.localized(in: language)
+        let url = page.absoluteUrl(in: language)
+        let title = localized.linkPreviewTitle ?? localized.title
+        let description = localized.linkPreviewDescription ?? ""
+        let image = makePageImage(item: localized)
+
+        return RelatedPageLink(
+            title: title,
+            description: description,
+            url: url,
+            image: image)
+            .content
+    }
+
+    private func makePageImage(item: LinkPreviewItem) -> ImageSet? {
+        item.linkPreviewImage.map { image in
+            let size = content.settings.pages.pageLinkImageSize
+            let imageSet = image.imageSet(width: size, height: size, language: language)
+            results.require(imageSet: imageSet)
+            return imageSet
+        }
+    }
+}