lab3

#r "/home/thefacetakt/Downloads/fsdata/fsharp-FSharp.Data-46c2766/bin/FSharp.Data.dll"
open FSharp.Data

let implode x = List.fold (fun str x -> str + x.ToString()) "" x

let explode (s:string) =
    [for c in s -> c]

let wikipedia = "https://en.wikipedia.org"


let languagesUls = HtmlDocument.Load("https://en.wikipedia.org/wiki/List_of_programming_languages").Descendants ["ul"] |> Seq.skip 4 |> Seq.take 26

let languages = (languagesUls
    |> Seq.map (fun x -> x.Descendants ["a"])
    |> Seq.map ( Seq.choose ( fun x -> x.TryGetAttribute("href")  |> Option.map (fun a -> x.InnerText(), a.Value())))) |> Seq.concat

let parseYear s =
    let rec parseYear' = function
        |[] -> []
        |a::b::c::d::xs when (List.filter System.Char.IsDigit [a; b; c; d])
                         |> List.length
                         |> (=) 4 -> [a; b; c; d]
        |x::xs -> parseYear' xs
    s |> explode |> parseYear' |> implode |> int


let firstAppeared = "First" + (char 160).ToString() + "appeared"

let takeFirst = function
    |x when (Seq.length x > 0) -> Some(Seq.nth 0 x)
    |_ -> None

let processLanguage (name, link) = async {
    let! page = HtmlDocument.AsyncLoad(wikipedia + link)

    return (name, page.Descendants["table"]
                 |> Seq.choose (fun x -> x.TryGetAttribute("class") |> Option.map (fun y -> if y.Value() = "infobox vevent" then Some(x) else None))
                 |> Seq.map (Option.map (fun table ->
                     table.Descendants ["tr"]
                     |> Seq.filter (fun x -> x.Descendants ["th"]
                                             |> Seq.exists (fun y -> y.InnerText() = firstAppeared))))
                 |> Seq.choose (fun x -> x)
                 |> Seq.concat
                 |> Seq.map (fun x -> x.Descendants ["td"]
                                      |> takeFirst
                                      |> Option.map (fun x-> parseYear (x.InnerText())))
                 |> Seq.choose (fun x -> x)
                 |> takeFirst)
}

let res = languages
            |> Seq.map processLanguage
            |> Async.Parallel
            |> Async.RunSynchronously
            |> Array.toList
            |> List.choose (fun x ->
                                match x with
                                | (a, Some y) -> Some(y, a)
                                | _ -> None)