Download free PragPub issues from 2009.07 to 2013.07

download_pragpub.hs

import Text.Printf
import System.Process

-- Downloads free PragPub issues from 2009.07 to 2013.07 from https://pragprog.com/magazines
-- relies on 'wget' command for downloading
-- run `processAll` to download

-- constants
savePath = "/Users/Dapeng/Downloads/PragPub/"

startYear = 2009
startMonth = 6
allIssues = [1..49]
allFormats = ["pdf", "epub", "mobi"]

-- functions
processAll :: IO ()
processAll =
  let
    everything = [(num, fmt) | num <- allIssues, fmt <- allFormats]
  in
    sequence_ . map (\issue -> process issue >>= putStrLn) $ everything

process :: (Integer, String) -> IO String
process = download . parse

parse :: (Integer, String) -> (Integer, String, String)
parse (num, fmt) =
  (num, fmt, toLongName num fmt)

toLongName :: Integer -> String -> String
toLongName num fmt =
  printf "PragPub - %s.%s" (toYearMonth num) fmt

toYearMonth :: Integer -> String
toYearMonth num =
  let
    d = (startMonth + num) `div` 12
    r = (startMonth + num) `mod` 12
    (year, month) =
      case r of
        0 -> (startYear + d, 12)
        _ -> (startYear + d, r)
  in
    show year ++ "." ++ printf "%02d" month

download :: (Integer, String, String) -> IO String
download (num, fmt, name) =
  let
    url = printf "https://pragprog.com/magazines/download/%d.%s" num fmt :: String
    path = savePath ++ name
  in
    readProcess "wget" [url, "-O", path] ""