-- Support for common text operations in languages with Latin script.
module Util.Text (
  capitalize,
  join_text,
  join_text2,
  join_spaced
) where

import Data.Char
import Data.List

-- Capitalize the first letter of a string.
capitalize :: String -> String
capitalize "" = ""
capitalize (c : cs) = (toUpper c : cs)

-- Concatenate a list of strings, filtering out the empty strings, and
-- insert the delimiter d between the strings.
join_text :: String -> [String] -> String
join_text d = concat . intersperse d . filter (not . null)

-- Concatenate a list of strings, filtering out the empty strings, and
-- insert the delimiter d between all strings except the last pair,
-- which is separated with the delimiter lastd.
join_text2 :: String -> String -> [String] -> String
join_text2 d lastd = concat . intersperse2 d lastd . filter (not . null)

join_spaced :: [String] -> String
join_spaced = join_text " "

-- Just like intersperse, but treat the last two elements of the
-- list specially: insert lastd instead of d between those.
intersperse2 :: a -> a -> [a] -> [a]
intersperse2 _ _ [] = []
intersperse2 _ _ [s] = [s]
intersperse2 _ lastd [s, s'] = [s, lastd, s']
intersperse2 d lastd (s : ss) = s : d : intersperse2 d lastd ss