import Foundation

extension Section {

    static let defaultSectionOverviewItemCount = 6
    
    struct Metadata {

        let thumbnailStyle: ThumbnailStyle

        let sortByMostRecent: Bool

        let sortIndex: Int?

        let date: Date?

        let languages: [LocalizedMetadata]

        let sectionOverviewItemCount: Int
    }
}

extension Section.Metadata: Metadata {

    static let fileName = "section.json"

    static var initial: Section.Metadata {
        .init(thumbnailStyle: .large,
              sortByMostRecent: true,
              sortIndex: nil,
              date: nil,
              languages: [.initial],
              sectionOverviewItemCount: 6)
    }
}

extension Section.Metadata: LanguageContainer {

}

extension Section.Metadata: Codable {

    enum CodingKeys: CodingKey {
        case thumbnailStyle
        case sortByMostRecent
        case sortIndex
        case date
        case languages
        case sectionOverviewItemCount
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(thumbnailStyle, forKey: .thumbnailStyle)
        try container.encode(sortByMostRecent, forKey: .sortByMostRecent)
        try container.encodeIfPresent(sortIndex, forKey: .sortIndex)
        try container.encode(languages, forKey: .languages)
        if let date = date {
            let dateString = Page.metadataDateFormatter.string(from: date)
            try container.encode(dateString, forKey: .date)
        }
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        self.thumbnailStyle = try container.decode(ThumbnailStyle.self, forKey: .thumbnailStyle)
        self.sortByMostRecent = try container.decode(Bool.self, forKey: .sortByMostRecent)
        self.sortIndex = try container.decodeIfPresent(Int.self, forKey: .sortIndex)
        self.languages = try container.decode([Section.LocalizedMetadata].self, forKey: .languages)
        if let dateString = try container.decodeIfPresent(String.self, forKey: .date) {
            self.date = try Page.metadataDateFormatter.date(from: dateString)
                .unwrap(or: .invalidDateInPageMetadata(dateString))
        } else {
            self.date = nil
        }
        self.sectionOverviewItemCount = try container
            .decodeIfPresent(Int.self, forKey: .sectionOverviewItemCount) ?? Section.defaultSectionOverviewItemCount
    }
}