Calculate Estimate Reading Time in Hakyll

[kutyel]

Still could not use this Haskell code:

readingTimeField :: String -> Snapshot -> Context String
readingTimeField key snapshot =
  field key calculate
 where
  calculate :: Item String -> Compiler String
  calculate item = do
    body <- loadSnapshotBody (itemIdentifier item) snapshot
    pure $ withTagList acc body
  acc ts = [TagText $ show $ time ts]
  -- M. Brysbaert, Journal of Memory and Language (2009) vol 109. DOI: 10.1016/j.jml.2019.104047
  time ts = foldr count 0 ts `div` 238
  count (TagText s) n = n + length (words s)
  count _ n = n

This generates a really weird error saying that the template depends on itself (Hakyll):

       >   [ERROR] Hakyll.Core.Runtime.pickAndChase: Dependency cycle detected: atom.xml depends on [(posts/2023-01-26-elm-to-haskell-part1.md,"content"),(posts/2023-02-23-elm-to-haskell-part2.md,"content"),(posts/2023-02-24-egghead-elm-ui-course.md,"content"),(posts/2023-03-01-elm-to-haskell-part3.md,"content")], index.html depends on [(posts/2023-01-26-elm-to-haskell-part1.md,"_final"),(posts/2023-02-23-elm-to-haskell-part2.md,"_final"),(posts/2023-02-24-egghead-elm-ui-course.md,"_final"),(posts/2023-03-01-elm-to-haskell-part3.md,"_final")], posts/2023-01-26-elm-to-haskell-part1.md depends on [(posts/2023-01-26-elm-to-haskell-part1.md,"content"),(templates/post.html,"_final")], posts/2023-02-23-elm-to-haskell-part2.md depends on [(posts/2023-02-23-elm-to-haskell-part2.md,"content"),(templates/post.html,"_final")], posts/2023-02-24-egghead-elm-ui-course.md depends on [(posts/2023-02-24-egghead-elm-ui-course.md,"content"),(templates/post.html,"_final")], posts/2023-03-01-elm-to-haskell-part3.md depends on [(posts/2023-03-01-elm-to-haskell-part3.md,"content"),(templates/post.html,"_final")], rss.xml depends on [(posts/2023-01-26-elm-to-haskell-part1.md,"content"),(posts/2023-02-23-elm-to-haskell-part2.md,"content"),(posts/2023-02-24-egghead-elm-ui-course.md,"content"),(posts/2023-03-01-elm-to-haskell-part3.md,"content")], sitemap.xml depends on [(posts/2023-01-26-elm-to-haskell-part1.md,"_final"),(posts/2023-02-23-elm-to-haskell-part2.md,"_final"),(posts/2023-02-24-egghead-elm-ui-course.md,"_final"),(posts/2023-03-01-elm-to-haskell-part3.md,"_final")]
       For full logs, run 'nix log /nix/store/2hamrx99pbhq4r7f28457xh28w4hxgkz-website.drv'.

Should investigate more but apparently the solution is not trivial 🤔

(cc: @rpearce @jaspervdj)

[rpearce]

I haven't had time to think about much recently. If I do this for myself, I'll circle back to helping you here.