import Foundation

extension Page {

    struct Metadata {

        let date: Date

        let endDate: Date?

        let author: String?

        let isDraft: Bool

        let sortIndex: Int?

        let languages: [LocalizedMetadata]

        #warning("Add hideFromOverview property")

        let requiredFiles: [String]

        #warning("Add files for which errors are ignored when missing")
    }
}

extension Page.Metadata: Metadata {

    static let fileName = "page.json"

    static var initial: Page.Metadata {
        .init(
            date: .now,
            endDate: .now,
            author: nil,
            isDraft: true,
            sortIndex: 0,
            languages: [.initial],
            requiredFiles: [])
    }
}

extension Page.Metadata: LanguageContainer {

}

extension Page.Metadata: Codable {

    enum CodingKeys: CodingKey {
        case date
        case endDate
        case author
        case isDraft
        case sortIndex
        case languages
        case requiredFiles
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        let dateString = Page.metadataDateFormatter.string(from: date)
        try container.encode(dateString, forKey: .date)
        if let date = endDate {
            let endDateString = Page.metadataDateFormatter.string(from: date)
            try container.encode(endDateString, forKey: .endDate)
        }
        try container.encodeIfPresent(author, forKey: .author)
        try container.encode(isDraft, forKey: .isDraft)
        try container.encodeIfPresent(sortIndex, forKey: .sortIndex)
        try container.encode(languages, forKey: .languages)
        if !requiredFiles.isEmpty {
            try container.encode(requiredFiles, forKey: .requiredFiles)
        }
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        let dateString = try container.decode(String.self, forKey: .date)
        self.date = try Page.metadataDateFormatter.date(from: dateString)
            .unwrap(or: .invalidDateInPageMetadata(dateString))
        self.author = try container.decodeIfPresent(String.self, forKey: .author)
        self.languages = try container.decode([Page.LocalizedMetadata].self, forKey: .languages)
        self.isDraft = try container.decodeIfPresent(Bool.self, forKey: .isDraft) ?? false
        self.sortIndex = try container.decodeIfPresent(Int.self, forKey: .sortIndex)
        if let endDateString = try container.decodeIfPresent(String.self, forKey: .endDate) {
            self.endDate = try Page.metadataDateFormatter.date(from: endDateString)
                .unwrap(or: .invalidDateInPageMetadata(endDateString))
        } else {
            self.endDate = nil
        }
        self.requiredFiles = try container.decodeIfPresent([String].self, forKey: .requiredFiles) ?? []
    }
}