import Foundation
import Ink

struct PageGenerator {

    struct NavigationLink {

        let link: String

        let text: String
    }

    private let factory: LocalizedSiteTemplate

    private let files: FileProcessor

    init(factory: LocalizedSiteTemplate, files: FileProcessor) {
        self.factory = factory
        self.files = files
    }

    func generate(page: Page, language: String, backText: String, nextPage: NavigationLink?, previousPage: NavigationLink?) throws {
        guard !page.isExternalPage else {
            return
        }
        guard !page.metadata.isDraft else {
            return
        }
        let path = page.fullPageUrl(for: language)
        let inputContentUrl = page.inputFolder.appendingPathComponent("\(language).md")
        #warning("Make prev and next navigation relative")
        let metadata = page.localized(for: language)
        let nextLanguage = page.nextLanguage(for: language)
        var content = [PageTemplate.Key : String]()
        content[.head] = try makeHead(page: page, language: language)
        content[.topBar] = factory.topBar.generate(section: page.sectionId, languageButton: nextLanguage)
        content[.contentClass] = "content"
        if !page.metadata.useCustomHeader {
            content[.header] = makeHeader(page: page.metadata, metadata: metadata, language: language, backText: backText)
        }
        content[.content] = try makeContent(page: page, language: language, url: inputContentUrl)
        content[.previousPageLinkText] = previousPage.unwrapped { factory.makePrevText($0.text) }
        content[.previousPageUrl] = previousPage?.link
        content[.nextPageLinkText] = nextPage.unwrapped { factory.makeNextText($0.text) }
        content[.nextPageUrl] = nextPage?.link
        content[.footer] = try page.customFooterContent()

        let url = files.outputFolder.appendingPathComponent(path)
        try factory.page.generate(content, to: url)
    }

    private func makeContent(page: Page, language: String, url: URL) throws -> String {
        guard url.exists else {
            print("Generated empty page \(page.path)")
            return factory.placeholder
        }
        print("Generated page \(page.path)")
        return try PageContentGenerator(factory: factory.factory, files: files)
            .generate(page: page, language: language, at: url)
    }

    private func makeHead(page: Page, language: String) throws -> String {
        let metadata = page.localized(for: language)
        let info = PageHeadInfo(
            author: page.metadata.author ?? factory.author,
            linkPreviewTitle: metadata.linkPreviewTitle,
            linkPreviewDescription: metadata.linkPreviewDescription,
            linkPreviewImage: page.linkPreviewImage(for: language),
            customHeadContent: try page.customHeadContent())
        return try factory.pageHead.generate(page: info)
    }

    private func makeHeader(page: Page.Metadata, metadata: Page.LocalizedMetadata, language: String, backText: String) -> String {
        var content = [HeaderKey : String]()
        content[.backLink] = factory.makeBackLink(text: backText, language: language)
        content[.title] = metadata.title
        content[.subtitle] = metadata.subtitle
        content[.date] = factory.makeDateString(start: page.date, end: page.endDate)
        return factory.factory.leftHeader.generate(content)
    }
}