YoutubeCommentStats.swift

import Foundation

func getData(_ urlString: String) -> Data? {
    guard let url = URL(string: urlString) else { return nil }
    return try? Data(contentsOf: url)
}

struct Result {
    var comments: Int
    var words: Int
    var characters: Int
    var nextPage: String?
    
    mutating func append(_ new: Result) {
        comments += new.comments
        words += new.words
        characters += new.characters
        nextPage = new.nextPage
    }
}

func parse(data: Data?) -> Result? {
    guard let data = data else { return nil }
    guard let root = try? JSONSerialization.jsonObject(with: data, options: []) as? [String: Any] else { return nil }
    let next = root["nextPageToken"] as? String
    guard let items = root["items"] as? [[String: Any]] else { return nil }
    let comments = items.compactMap { (dict) -> String? in
        guard let snippet = dict["snippet"] as? [String: Any] else { return nil }
        guard let topLevelComment = snippet["topLevelComment"] as? [String: Any] else { return nil }
        guard let snippet2 = topLevelComment["snippet"] as? [String: Any] else { return nil }
        return snippet2["textDisplay"] as? String
    }
    var words = 0
    var symbols = 0
    for comment in comments {
        words += comment.split(separator: " ").count
        symbols += comment.count
    }
    return Result(comments: comments.count, words: words, characters: symbols, nextPage: next)
}

func collect() -> Result? {
    let key = ""
    let maxResults = 100
    let textFormat = "plainText"
    let videoId = ""
    let part = "snippet"
    
    let url = "https://www.googleapis.com/youtube/v3/commentThreads" +
        "?key=\(key)" +
        "&textFormat=\(textFormat)" +
        "&maxResults=\(maxResults)" +
        "&videoId=\(videoId)" +
        "&part=\(part)"
    guard var result = parse(data: getData(url)) else { return nil }
    while result.nextPage != nil {
        guard let new = parse(data: getData(url + "&pageToken=\(result.nextPage!)")) else { break }
        result.append(new)
    }
    return result
}

print(collect())