import Foundation

struct SiteGenerator {

    let site: Site

    let templates: TemplateFactory

    private let files: FileProcessor

    private var outputFolder: URL {
        files.outputFolder
    }

    init(site: Site, files: FileProcessor) throws {
        self.site = site
        let templatesFolder = site.inputFolder.appendingPathComponent("templates")
        self.templates = try TemplateFactory(templateFolder: templatesFolder)
        self.files = files
    }

    func generate() throws {
        try site.metadata.languages.forEach { metadata in
            let language = metadata.languageIdentifier
            let template = try LocalizedSiteTemplate(
                factory: templates,
                language: language,
                site: site,
                files: files)

            
            // Generate sections
            let overviewGenerator = OverviewPageGenerator(factory: template, files: files)
            let pageGenerator = PageGenerator(factory: template, files: files)
            let backLinkText = try site.backLinkText(for: language)
            var elementsToProcess: [(element: SiteElement, backText: String?)] = site.elements.map { ($0, backLinkText) }
            while let (element, backText) = elementsToProcess.popLast() {
                if let section = element as? Section {
                    try overviewGenerator.generate(
                        section: section,
                        language: language,
                        backText: backText)
                    let elementBackText = try element.backLinkText(for: language)
                    let nestedElements = section.elements.map { ($0, elementBackText) }
                    elementsToProcess.append(contentsOf: nestedElements)
                }
                if let page = element as? Page {
                    #warning("Determine previous and next pages")
                    try pageGenerator.generate(
                        page: page,
                        language: language,
                        backText: backText ?? metadata.defaultBackLinkText,
                        nextPage: nil,
                        previousPage: nil)
                    for file in page.metadata.requiredFiles {
                        let relativePath = page.path + "/" + file
                        files.require(file: relativePath)
                    }
                }
            }

            let generator = IndexPageGenerator(factory: template)

            // Generate front page
            let relativeUrl = site.localizedPath(for: language)
            let indexPageUrl = outputFolder.appendingPathComponent(relativeUrl)
            let button = site.nextLanguage(for: language)
            try generator.generate(
                site: site,
                language: language,
                languageButton: button,
                sectionItemCount: 6,
                to: indexPageUrl)
        }
    }
}