Finds RSS feeds for bogs

feed_finder.fs

open System.IO
open FSharp.Data

let readLines filePath = File.ReadAllLines(filePath);;

let downloadWebAsync (links:seq<string>) =
    links
    |> Seq.map HtmlDocument.AsyncLoad
    
let castToOption (linkElements:seq<HtmlNode>) =
    linkElements 
    |> Seq.choose (fun x -> 
        x.TryGetAttribute("type") 
        |> Option.map (fun a -> x.Attribute("href").Value(), a.Value())
    ) 

let getLinkElements (doc:HtmlDocument) : seq<HtmlNode> =
    doc.Descendants["link"] 

let filterOnlyRss (_:string, t:string) =
    t.Equals("application/rss+xml", System.StringComparison.OrdinalIgnoreCase)

let filterNoComments (uri:string, _:string) =
    uri.ToLower().Contains("comments") = false

let getLinks = 
    readLines "urls.txt"
    |> Seq.filter (fun f -> f.StartsWith("//") = false)

let loadAll = 
    getLinks
    |> downloadWebAsync
    |> Async.Parallel
    |> Async.RunSynchronously
    |> Seq.map getLinkElements
    |> Seq.map castToOption
    |> Seq.map (Seq.filter (filterOnlyRss))
    |> Seq.map (Seq.filter (filterNoComments))
//    

[<EntryPoint>]
let main argv = 
    
    let all = loadAll
    all
        |> Seq.concat
        |> Seq.distinct
        |>  Seq.iter (fun (x,y) -> printfn "%s" x)

    0

thanks, that works perfectly. now i need to understand whats going on there :)

Krzysiek przerobił świetnie, ale dorzucę jeszcze swoje "muśnięcia":

#r "./packages/FSharp.Data/lib/net40/FSharp.Data.dll"
open System
open System.IO
open FSharp.Data

let readLines filePath = File.ReadAllLines(filePath)

let downloadWebAsync = HtmlDocument.AsyncLoad >> Async.Catch

let getLinkElements (doc:HtmlDocument) = doc.Descendants["link"]

let tryGetLinkInfo (link:HtmlNode) =
    let getHref() = link.Attribute("href").Value()
    link.TryGetAttribute("type") |> Option.map (fun t -> getHref(), t.Value())

let filterOnlyRss (_, t:string) =
    t.Equals("application/rss+xml", StringComparison.OrdinalIgnoreCase)

let filterNoComments (uri:string, _) = not (uri.ToLower().Contains("comments"))

let getLinks =
    readLines "h:/projekty/_robol/urls.txt"
    |> Seq.filter (fun f -> not (f.StartsWith("//")))

let loadAll () =
    getLinks
    |> Seq.map downloadWebAsync
    |> Async.Parallel
    |> Async.RunSynchronously

let findLinks =
    getLinkElements
    >> Seq.choose tryGetLinkInfo
    >> Seq.filter filterOnlyRss
    >> Seq.filter filterNoComments

let filterErrors = function
| Choice1Of2 d -> Some(d)
| Choice2Of2 e -> printfn "FAIELD WITH: %A" e; None

loadAll ()
|> Seq.choose filterErrors
|> Seq.collect findLinks
|> Seq.distinct
|> Seq.iter (fun (x, _) -> printfn "%s" x)