import Foundation

enum InputValidator {
    private static let mastodonCharacterLimit = 500
    private static let maxImages = 4
    private static let maxImageBytes = 15 * 1024 * 1024

    static func validatePost(text: String, images: [ImageAttachment], accounts: [Account]) throws {
        let trimmed = text.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmed.isEmpty else {
            throw PostingError(message: "Post cannot be empty.")
        }

        guard !accounts.isEmpty else {
            throw PostingError(message: "Select at least one account.")
        }

        guard images.count <= maxImages else {
            throw PostingError(message: "You can attach up to \(maxImages) images.")
        }

        for image in images {
            guard !image.data.isEmpty else {
                throw PostingError(message: "One of the selected images is empty or unreadable.")
            }
            guard image.data.count <= maxImageBytes else {
                throw PostingError(message: "Image \(image.filename) is too large. Max size is 15 MB.")
            }
        }

        if accounts.contains(where: { $0.serviceType == .mastodon }) && text.count > mastodonCharacterLimit {
            throw PostingError(
                message: "Mastodon posts are limited to \(mastodonCharacterLimit) characters."
            )
        }
    }
}