import Foundation
import Ink

struct PageGenerator {

    struct NavigationLink {

        let link: String

        let text: String
    }

    private let factory: LocalizedSiteTemplate

    init(factory: LocalizedSiteTemplate) {
        self.factory = factory
    }

    func generate(page: Element, language: String, nextPage: NavigationLink?, previousPage: NavigationLink?) {
        guard !page.isExternalPage else {
            return
        }
        guard page.state != .draft else {
            return
        }
        let path = page.fullPageUrl(for: language)
        let inputContentPath = page.path + "/\(language).md"
        let metadata = page.localized(for: language)
        let nextLanguage = page.nextLanguage(for: language)
        let pageContent = makeContent(page: page, language: language, path: inputContentPath)
        let pageIncludesCode = pageContent?.includesCode ?? false
        
        var content = [PageTemplate.Key : String]()
        content[.head] = factory.pageHead.generate(page: page, language: language, includesCode: pageIncludesCode)
        let sectionUrl = page.sectionUrl(for: language)
        content[.topBar] = factory.topBar.generate(sectionUrl: sectionUrl, languageButton: nextLanguage)
        content[.contentClass] = "content"

        if !page.useCustomHeader {
            content[.header] = makeHeader(page: page, metadata: metadata, language: language)
        }
        content[.content] = pageContent?.content ?? factory.placeholder
        content[.previousPageLinkText] = previousPage.unwrapped { factory.factory.html.makePrevText($0.text) }
        content[.previousPageUrl] = previousPage?.link
        content[.nextPageLinkText] = nextPage.unwrapped { factory.factory.html.makeNextText($0.text) }
        content[.nextPageUrl] = nextPage?.link
        content[.footer] = page.customFooterContent()

        if pageIncludesCode {
            let highlightCode = factory.factory.html.codeHighlightFooter()
            content[.footer] = (content[.footer].unwrapped { $0 + "\n" } ?? "") + highlightCode
        }

        let url = files.urlInOutputFolder(path)
        guard factory.page.generate(content, to: url) else {
            return
        }
        log.add(info: "Generated \(pageContent == nil ? "empty page " : "")\(path)", source: page.path)
    }

    private func makeContent(page: Element, language: String, path: String) -> (content: String, includesCode: Bool)? {
        guard let content = files.contentOfOptionalFile(atPath: path, source: page.path) else {
            return nil
        }
        return PageContentGenerator(factory: factory.factory)
            .generate(page: page, language: language, content: content)
    }

    private func makeHeader(page: Element, metadata: Element.LocalizedMetadata, language: String) -> String {
        let content = factory.makeHeaderContent(page: page, metadata: metadata, language: language)
        return factory.factory.leftHeader.generate(content)
    }

}