import Foundation
import Ink

struct LocalizedSiteTemplate {

    let author: String

    let factory: TemplateFactory

    let topBar: PrefilledTopBarTemplate

    // MARK: Site Elements

    var backNavigation: BackNavigationTemplate {
        factory.backNavigation
    }

    let pageHead: PageHeadGenerator

    let overviewSection: OverviewSectionGenerator

    private let fullDateFormatter: DateFormatter

    private let month: DateFormatter

    private let day: DateFormatter

    var language: String {
        topBar.language
    }

    // MARK: Pages

    var page: PageTemplate {
        factory.page
    }

    init(factory: TemplateFactory, language: String, site: Element) throws {
        self.author = site.author
        self.factory = factory

        let df = DateFormatter()
        df.dateStyle = .long
        df.timeStyle = .none
        df.locale = Locale(identifier: language)
        self.fullDateFormatter = df

        let df2 = DateFormatter()
        df2.dateFormat = "MMMM"
        df2.locale = Locale(identifier: language)
        self.month = df2

        let df3 = DateFormatter()
        df3.dateFormat = "dd"
        df3.locale = Locale(identifier: language)
        self.day = df3

        let sections = site.sortedItems.map {
            PrefilledTopBarTemplate.SectionInfo(
                name: $0.title(for: language),
                url: "\($0.path)/\(language).html")
        }

        self.topBar = try .init(
            factory: factory,
            language: language,
            sections: sections,
            topBarWebsiteTitle: site.topBarTitle)
        self.pageHead = PageHeadGenerator(
            factory: factory)
        self.overviewSection = OverviewSectionGenerator(
            factory: factory)
    }

    // MARK: Content

    func makePlaceholder(metadata: Element.LocalizedMetadata) -> String {
        factory.placeholder.generate([
            .title: metadata.placeholderTitle,
            .text: metadata.placeholderText])
    }

    func makeBackLink(text: String, language: String) -> String {
        let content: [BackNavigationTemplate.Key : String] = [
            .text: text,
            .url: "../\(language).html"
        ]
        return backNavigation.generate(content)
    }

    func makeDateString(start: Date?, end: Date?) -> String {
        guard let start = start else {
            return ""
        }
        guard let end = end else {
            return fullDateFormatter.string(from: start)
        }

        switch language {
        case "de":
            return makeGermanDateString(start: start, end: end)
        case "en":
            fallthrough
        default:
            return makeEnglishDateString(start: start, end: end)
        }
    }

    private func makeGermanDateString(start: Date, end: Date) -> String {
        guard Calendar.current.isDate(start, equalTo: end, toGranularity: .year) else {
            return "\(fullDateFormatter.string(from: start)) - \(fullDateFormatter.string(from: end))"
        }

        let startDay = day.string(from: start)
        guard Calendar.current.isDate(start, equalTo: end, toGranularity: .month) else {
            let startMonth = month.string(from: start)
            return "\(startDay). \(startMonth) - \(fullDateFormatter.string(from: end))"
        }
        return "\(startDay). - \(fullDateFormatter.string(from: end))"
    }

    private func makeEnglishDateString(start: Date, end: Date) -> String {
        guard Calendar.current.isDate(start, equalTo: end, toGranularity: .year) else {
            return "\(fullDateFormatter.string(from: start)) - \(fullDateFormatter.string(from: end))"
        }

        guard Calendar.current.isDate(start, equalTo: end, toGranularity: .month) else {
            let startDay = day.string(from: start)
            let startMonth = month.string(from: start)
            return "\(startMonth) \(startDay) - \(fullDateFormatter.string(from: end))"
        }
        return fullDateFormatter.string(from: start)
            .insert(" - \(day.string(from: end))", beforeLast: ",")
    }

    func makeHeaderContent(page: Element, metadata: Element.LocalizedMetadata, language: String) -> [HeaderKey : String] {
        let backText = page.backLinkText(for: language)

        var content = [HeaderKey : String]()
        if let backText = backText.nonEmpty {
            content[.backLink] = makeBackLink(text: backText, language: language)
        }
        if let suffix = metadata.titleSuffix {
            content[.title] = factory.html.make(title: metadata.title, suffix: suffix)
        } else {
            content[.title] = metadata.title
        }
        content[.subtitle] = metadata.subtitle
        content[.date] = makeDateString(start: page.date, end: page.endDate)
        return content
    }
}