import Foundation

struct OverviewPageGenerator {

    private let factory: LocalizedSiteTemplate

    let outputFolder: URL

    init(factory: LocalizedSiteTemplate, imageProcessor: ImageProcessor) {
        self.factory = factory
        self.outputFolder = imageProcessor.outputFolder
    }

    func generate(
        section: Section,
        language: String,
        backText: String?) throws {
            let url = outputFolder.appendingPathComponent(section.localizedPath(for: language))

            let metadata = section.localized(for: language)

            var content = [OverviewPageTemplate.Key : String]()
            content[.head] = try makeHead(section: section, language: language)
            let languageButton = section.nextLanguage(for: language)
            content[.topBar] = factory.topBar.generate(
                section: section.sectionId,
                languageButton: languageButton)
            content[.sections] = try makeContent(section: section, language: language)
            content[.title] = metadata.title
            content[.subtitle] = metadata.subtitle
            content[.titleText] = metadata.description
            content[.footer] = SiteGenerator.pageFooter
            content[.backLink] = backText.unwrapped { factory.makeBackLink(text: $0, language: language) }
            try factory.overviewPage.generate(content, to: url)
    }

    private func makeContent(section: Section, language: String) throws -> String {
        if section.hasNestingElements {
            let sections = section.elements.compactMap { $0 as? Section }
            return try factory.overviewSection.generate(
                sections: sections,
                in: section,
                language: language,
                sectionItemCount: section.metadata.sectionOverviewItemCount)
        } else {
            return try factory.overviewSection.generate(section: section, language: language)
        }
    }

    private func makeHead(section: Section, language: String) throws -> String {
        let localized = section.localized(for: language)

        let image = section.linkPreviewImage(for: language)
        let info = PageHeadInfo(
            author: factory.author,
            linkPreviewTitle: localized.title,
            linkPreviewDescription: localized.linkPreviewDescription,
            linkPreviewImage: image,
            customHeadContent: try section.customHeadContent())
        return try factory.pageHead.generate(page: info)
    }
}