{-# LANGUAGE NoImplicitPrelude     #-}
{-# LANGUAGE DeriveGeneric         #-}
{-# LANGUAGE OverloadedStrings     #-}
{-# LANGUAGE ScopedTypeVariables   #-}
{-# LANGUAGE Strict                #-}

--
-- Copyright (C) 2019, Maxim Lihachev, <envrm@yandex.ru>
--
-- This program is free software: you can redistribute it and/or modify it
-- under the terms of the GNU General Public License as published by the Free
-- Software Foundation, version 3.
--
-- This program is distributed in the hope that it will be useful, but WITHOUT
-- ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-- FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
-- more details.
--
-- You should have received a copy of the GNU General Public License along with
-- this program. If not, see <https://www.gnu.org/licenses/>.
--

--
-- | Список наиболее востребованных навыков с сайта hh.ru
--
module Main (main) where

import Relude                      ((+), (-), (.), (++), ($), (=<<),
                                   Int, String, Generic, Text, Show, IO,
                                   show, return, quot, replicate, flip, compare,
                                   on, snd, putStrLn, mapM_)

import Options.Applicative         ((<$>), (<*>), (<**>), info, execParser, helper,
                                    header, fullDesc, option, auto, long, short,
                                    argument, metavar, showDefault, value, help, some, str)

import Control.Lens                ((^.))
import Data.Semigroup              ((<>))
import Data.List.Unique            (count)
import Data.Aeson                  (FromJSON)
import Text.Printf                 (printf)
import Foreign.Marshal.Unsafe      (unsafeLocalState)
import Control.Parallel.Strategies (parMap, rdeepseq)
import Network.Wreq                (get, asJSON, responseBody)

import qualified Data.List as L
import qualified Data.Text as T

-- ------------------------------------------------------------------------------------

data Settings = Settings{ totalPages  :: Int
                        , topSkills   :: Int
                        , searchQuery :: [String] }

data Pages = Pages { pages  :: Int , found  :: Int } deriving (Generic)

newtype Vacancies = Vacancies { items      :: [Vacancy] } deriving (Generic)
newtype Vacancy   = Vacancy   { id         :: String    } deriving (Generic)
newtype Skills    = Skills    { key_skills :: [Skill]   } deriving (Generic)
newtype Skill     = Skill     { name       :: Text      } deriving (Generic)

type RatedSkill = (Text, Int)

instance FromJSON Pages
instance FromJSON Vacancies
instance FromJSON Vacancy
instance FromJSON Skills
instance FromJSON Skill

-- ------------------------------------------------------------------------------------

-- | Адрес HH API
hhAPI :: String
hhAPI = "https://api.hh.ru/vacancies"

-- | Запрос к странице hh.ru: https://api.hh.ru/vacancies?text=<query>&page=<number>
hhPage :: (FromJSON b, Show a) => String -> a -> IO b
hhPage query page = do
    r <- asJSON =<< get (hhAPI ++ "?text='" ++ query ++ "'&page=" ++ show page)
    return $ r ^. responseBody

-- | Список вакансий
getVacancies :: String -> Int -> [Vacancy]
getVacancies query n = items $ unsafeLocalState $ hhPage query n

-- | Список навыков
getSkills :: String -> IO [Text]
getSkills vacancy = do
    r <- asJSON =<< get (hhAPI ++ "/" ++ vacancy)
    return $ L.map name $ key_skills (r ^. responseBody)

--
-- | Список навыков из всех вакансий со страницы hh.ru
--
-- * Навыки, перечисленные через запятую, разделяются на отдельные слова.
-- * Все навыки приводятся в нижнем регистре.
--
--  [
--    "Linux",
--    "Terraform, Packer",
--    "Ansible"
--  ]
--
--  =>
--
--  [ "linux", "terraform", "packer", "ansible" ]
--
collectSkillsFromPage :: [Vacancy] -> [Text]
collectSkillsFromPage vids = L.concatMap unify allSkills
    where allSkills = L.concatMap (unsafeLocalState . getSkills . Main.id) vids
          unify skills = L.map (T.toLower . T.strip) $ T.splitOn "," skills

--  
-- | Вывод полосы визуализации количества вхождений навыка
--  
-- >>> bar 1 ("Linux", 167)
-- "1. [▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒                                  ] 167: linux"
--
bar :: Int -> RatedSkill -> String
bar i (s, n) = printf "%3d. [%-50s ] %3d: %s" i (replicate x '▒') n s
    where x = quot n 10 + 1 -- Отображение как минимум 1 деления шкалы

-- | Список уникальных навыков, отсортированых по количеству вхождений
sorted :: [Text] -> [RatedSkill]
sorted = L.sortBy (flip compare `on` snd) . count

-- | N наиболее востребованных навыков
top :: Int -> [Text] -> [RatedSkill]
top n l = L.take n $ sorted l

-- | Поиск навыков по конкретному запросу
getTopSkills :: Settings -> IO ()
getTopSkills (Settings getPages showLines searchQuery) =
  let query = L.unwords searchQuery in
    do p <- hhPage query 0

       putStrLn $ printf "# По запросу '%s' найдено вакансий: %d\n" query (found p)

       let pagesCount = L.minimum [pages p, getPages - 1] in
           mapM_ (\(n, l) -> putStrLn $ bar n l)
                  $ L.zip [1..]
                    $ top showLines
                      $ L.concat
                        $ parMap rdeepseq (collectSkillsFromPage . getVacancies query) [0..pagesCount]

-- ------------------------------------------------------------------------------------

main :: IO ()
main = getTopSkills =<< execParser opts
  where
    opts = info (args <**> helper)
      (fullDesc <> header "hhskills - поиск наиболее востребованных навыков по вакансиям hh.ru.")

    args = Settings <$> option auto (long "pages" <> short 'p' <> metavar "PAGES"
                                   <> showDefault <> value 10  <> help "Количество страниц для анализа")
                    <*> option auto (long "top"   <> short 't' <> metavar "TOP"
                                   <> showDefault <> value 20  <> help "Количество выводимых навыков")
                    <*> some (argument str (metavar "QUERY..."))