Refactor page content generators

CHDataManagement/Generator/Commands/ModelCommand.swift

@@ -0,0 +1,44 @@
+
+struct ModelCommand: CommandProcessor {
+
+    static let commandType: CommandType = .model
+
+    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: `![model](<file>)`
+     */
+    func process(_ arguments: [String], markdown: Substring) -> String {
+        guard arguments.count == 1 else {
+            invalid(markdown)
+            return ""
+        }
+        let fileId = arguments[0]
+        guard fileId.hasSuffix(".glb") else {
+            invalid(markdown)
+            return ""
+        }
+
+        guard let file = content.file(fileId) else {
+            results.missing(file: fileId, source: "Model command")
+            return ""
+        }
+        results.require(file: file)
+        results.require(header: .modelViewer)
+
+        let description = file.localized(in: language)
+        return ModelViewer(file: file.absoluteUrl, description: description).content
+    }
+
+
+}