import Foundation

/// Emits vCard 3.0 for a click-wheel iPod.
///
/// Version 3.0 rather than 4.0 deliberately: the click-wheel address book was
/// written against 2.1/3.0 and does not recognise 4.0's `VERSION` or its
/// property forms. Nothing here emits `PHOTO`, `LOGO`, `SOUND` or `X-`
/// properties — the categories that made hand-exported files fail — because
/// they are simply never written rather than stripped afterwards.
public enum VCardWriter {
    /// Renders one contact as a complete, CRLF-terminated vCard.
    public static func makeVCard(for contact: IPodContact) -> String {
        var builder = ContentLineBuilder()

        builder.appendVerbatim("BEGIN", "VCARD")
        builder.appendVerbatim("VERSION", "3.0")

        // N is ordered family;given;middle;prefix;suffix and is required in 3.0.
        builder.appendStructured("N", components: [
            contact.familyName,
            contact.givenName,
            contact.middleName,
            contact.namePrefix,
            contact.nameSuffix,
        ])
        builder.append("FN", contact.displayName)

        if !contact.organization.isEmpty {
            builder.appendStructured("ORG", components: [contact.organization])
        }
        if !contact.jobTitle.isEmpty {
            builder.append("TITLE", contact.jobTitle)
        }

        for phone in contact.phoneNumbers where !phone.value.isEmpty {
            let type = phone.label.isEmpty ? "VOICE" : phone.label
            builder.append("TEL", parameters: [("TYPE", type)], value: phone.value)
        }

        for email in contact.emailAddresses where !email.value.isEmpty {
            let type = email.label.isEmpty ? "INTERNET" : "INTERNET,\(email.label)"
            builder.append("EMAIL", parameters: [("TYPE", type)], value: email.value)
        }

        for address in contact.postalAddresses {
            // ADR is po-box;extended;street;locality;region;postal-code;country.
            let components = [
                "", "",
                address.street,
                address.city,
                address.state,
                address.postalCode,
                address.country,
            ]
            guard components.contains(where: { !$0.isEmpty }) else { continue }
            let value = components.map(ContentLine.escapeText).joined(separator: ";")
            let name = address.label.isEmpty ? "ADR" : "ADR;TYPE=\(address.label)"
            builder.appendRawLine("\(name):\(value)")
        }

        if let birthday = contact.birthday, let formatted = formatBirthday(birthday) {
            builder.appendVerbatim("BDAY", formatted)
        }

        builder.appendVerbatim("END", "VCARD")

        return builder.render()
    }

    /// Formats a birthday as `YYYY-MM-DD`.
    ///
    /// Returns nil for year-less birthdays. Contacts.app allows them, but vCard
    /// 3.0 has no representation Apple doesn't express through an `X-` parameter
    /// (`X-APPLE-OMIT-YEAR`), and an invented year would show a wrong age on the
    /// device — so those birthdays are dropped instead.
    static func formatBirthday(_ components: DateComponents) -> String? {
        guard let year = components.year,
              let month = components.month,
              let day = components.day,
              year > 1
        else { return nil }

        return String(format: "%04d-%02d-%02d", year, month, day)
    }
}