import Foundation

final class FeedPageGenerator {

    let content: Content

    init(content: Content) {
        self.content = content
    }

    func navigationBar(in language: ContentLanguage) -> [NavigationBar.Link] {
        content.settings.navigationItems.map {
            .init(text: $0.title(in: language),
                               url: $0.absoluteUrl(in: language))
        }
    }

    var swiperIncludes: [HeaderElement] {
        var result = [HeaderElement]()
        if let swiperCss = content.settings.posts.swiperCssFile {
            result.append(.css(swiperCss))
        } else {
            #warning("Add warning message")
        }
        if let swiperJs = content.settings.posts.swiperJsFile {
            result.append(.js(file: swiperJs, defer: true))
        } else {
            #warning("Add warning message")
        }
        return result
    }

    var defaultHeaders: [HeaderElement] {
        if let header = content.settings.posts.defaultCssFile {
            return [.css(header)]
        } else {
            #warning("Add warning message")
            return []
        }
    }

    func generatePage(language: ContentLanguage,
                      posts: [FeedEntryData],
                      title: String,
                      description: String,
                      showTitle: Bool,
                      pageNumber: Int,
                      totalPages: Int) -> String {
        var headers = defaultHeaders
        var footer = ""
        if posts.contains(where: { $0.images.count > 1 }) {
            headers += swiperIncludes
            footer = swiperInitScript(posts: posts)
        }

        let page = GenericPage(
            language: language,
            title: title,
            description: description,
            links: navigationBar(in: language),
            headers: headers,
            additionalFooter: footer) { content in
                if showTitle {
                    content += "<h1>\(title)</h1>"
                }
                for post in posts {
                    content += FeedEntry(data: post).content
                }
                if totalPages > 1 {
                    content += PostFeedPageNavigation(currentPage: pageNumber, numberOfPages: totalPages, language: language).content
                }

            }
        return page.content
    }

    func swiperInitScript(posts: [FeedEntryData]) -> String {
        var result = "<script>"
        for post in posts {
            guard post.images.count > 1 else {
                continue
            }
            result += ImageGallery.swiperInit(id: post.entryId)
        }
        result += "</script>"
        return result

    }
}