import Foundation

struct SiteGenerator {

    let templates: TemplateFactory

    init() throws {
        let templatesFolder = files.urlInContentFolder("templates")
        self.templates = try TemplateFactory(templateFolder: templatesFolder)
    }

    func generate(site: Element) throws {
        site.requiredFiles.forEach(files.require)
        site.externalFiles.forEach(files.exclude)
        try site.languages.forEach {
            try generate(site: site, metadata: $0)
        }
    }

    private func generate(site: Element, metadata: Element.LocalizedMetadata) throws {
        let language = metadata.language
        let template = try LocalizedSiteTemplate(
            factory: templates,
            language: language,
            site: site)

        // Generate sections
        let overviewGenerator = OverviewPageGenerator(factory: template)
        let pageGenerator = PageGenerator(factory: template)
        
        var elementsToProcess: [Element] = [site]
        while let element = elementsToProcess.popLast() {
            // Move recursively down to all pages
            elementsToProcess.append(contentsOf: element.elements)

            element.requiredFiles.forEach(files.require)
            element.externalFiles.forEach(files.exclude)

            if !element.elements.isEmpty {
                overviewGenerator.generate(section: element, language: language)
            } else {
                #warning("Determine previous and next pages (with relative links)")
                pageGenerator.generate(
                    page: element,
                    language: language,
                    nextPage: nil,
                    previousPage: nil)
            }
        }
    }
}