import Foundation

struct WebsiteGeneratorConfiguration {

    let language: ContentLanguage

    let postsPerPage: Int

    let postFeedTitle: String

    let postFeedDescription: String

    let postFeedUrlPrefix: String
}

final class WebsiteGenerator {

    let language: ContentLanguage

    let content: Content

    let postsPerPage: Int

    let postFeedTitle: String

    let postFeedDescription: String

    let postFeedUrlPrefix: String

    init(content: Content, configuration: WebsiteGeneratorConfiguration) {
        self.content = content
        self.language = configuration.language
        self.postsPerPage = configuration.postsPerPage
        self.postFeedTitle = configuration.postFeedTitle
        self.postFeedDescription = configuration.postFeedDescription
        self.postFeedUrlPrefix = configuration.postFeedUrlPrefix
    }

    func generateWebsite() {
        createPostFeedPages()
    }

    private func createPostFeedPages() {
        let totalCount = content.posts.count
        guard totalCount > 0 else { return }

        let navBarData = createNavigationBarData()

        let numberOfPages = (totalCount + postsPerPage - 1) / postsPerPage // Round up
        for pageIndex in 1...numberOfPages {
            let startIndex = (pageIndex - 1) * postsPerPage
            let endIndex = min(pageIndex * postsPerPage, totalCount)
            let postsOnPage = content.posts[startIndex..<endIndex]
            createPostFeedPage(pageIndex, pageCount: numberOfPages, posts: postsOnPage, bar: navBarData)
        }
    }

    private func createNavigationBarData() -> NavigationBarData {
        let data = content.websiteData.localized(in: language)
        let navigationItems: [NavigationBarLink] = content.websiteData.navigationTags.map {
            let localized = $0.localized(in: language)
            return .init(text: localized.name, url: localized.urlComponent)
        }
        return NavigationBarData(
            navigationIconPath: "/assets/icons/ch.svg",
            iconDescription: data.iconDescription,
            navigationItems: navigationItems)
    }

    private func createPostFeedPage(_ pageIndex: Int, pageCount: Int, posts: ArraySlice<Post>, bar: NavigationBarData) {
        let posts = posts.map { $0.feedEntry(for: language) }

        let feed = PageInFeed(
            language: language,
            title: postFeedTitle,
            description: postFeedDescription,
            navigationBarData: bar,
            pageNumber: pageIndex,
            totalPages: pageCount,
            posts: posts)
        let fileContent = feed.content

        if pageIndex == 1 {
            save(fileContent, to: "\(postFeedUrlPrefix).html")
        } else {
            save(fileContent, to: "\(postFeedUrlPrefix)-\(pageIndex).html")
        }
    }

    private func save(_ content: String, to relativePath: String) {
        Content.accessFolderFromBookmark(key: Storage.outputPathBookmarkKey) { folder in
            let outputFile = folder.appendingPathComponent(relativePath, isDirectory: false)
            do {
                try content
                    .data(using: .utf8)!
                    .write(to: outputFile)
            } catch {
                print("Failed to save: \(error)")
            }
        }
    }
}