app_for_reddit/Reddit App/Utilities/RedditSubmitURLBuilder.swift

import Foundation

enum RedditSubmitURLBuilder {
    static func isSubmitPage(_ url: URL) -> Bool {
        guard let host = url.host?.lowercased(), host.contains("reddit.com") else { return false }
        return url.path.range(of: #"/r/[^/]+/submit"#, options: .regularExpression) != nil
    }

    static func submitURL(for draft: PostDraft) throws -> URL {
        try PostDraftValidator.validateForExport(draft)

        let subreddit = PostDraftValidator.normalizedSubreddit(draft.subreddit)
        var components = URLComponents()
        components.scheme = "https"
        components.host = "www.reddit.com"
        components.path = "/r/\(subreddit)/submit"

        var queryItems = [
            URLQueryItem(name: "title", value: draft.title.trimmingCharacters(in: .whitespaces)),
        ]

        switch draft.postType {
        case .text:
            queryItems.append(URLQueryItem(name: "selftext", value: "true"))
            let body = draft.body.trimmingCharacters(in: .whitespaces)
            if !body.isEmpty {
                queryItems.append(URLQueryItem(name: "text", value: body))
            }
        case .link:
            queryItems.append(
                URLQueryItem(name: "url", value: draft.linkURL.trimmingCharacters(in: .whitespaces))
            )
        case .image, .video:
            queryItems.append(URLQueryItem(name: "selftext", value: "true"))
            let body = draft.body.trimmingCharacters(in: .whitespaces)
            if !body.isEmpty {
                queryItems.append(URLQueryItem(name: "text", value: body))
            }
        case .poll:
            let body = draft.body.trimmingCharacters(in: .whitespaces)
            if !body.isEmpty {
                queryItems.append(URLQueryItem(name: "text", value: body))
            }
        }

        components.queryItems = queryItems

        guard let url = components.url else {
            throw PostDraftValidationError.invalidSubreddit
        }
        return url
    }
}