user-management/app/Main.hs

module Main where

import UserManager
import Control.Exception
import Text.Printf
import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as B
import qualified Data.Map as Map

-- Main entry point of the program
main :: IO ()
main = do
    putStrLn "Welcome to User Management Console!"  -- display a message to the user
    initializeDB  -- initialize the database
    mainMenu       -- start the main menu

-- Main menu of the program
mainMenu :: IO ()
mainMenu = do
    putStrLn "1. Add User"         -- display the options to the user
    putStrLn "2. List Users"
    putStrLn "3. Find User"
    putStrLn "4. Delete User"
    putStrLn "5. (DEBUG) Generate and Add Users"
    putStrLn "6. Exit"
    putStrLn "Choose an option: "  -- ask the user to choose an option
    option <- getLine
    case option of
        "1" -> addUserHandler  -- handle the option chosen by the user
        "2" -> maplistUsersHandler
        "3" -> findUserHandler
        "4" -> deleteUserHandler
        "5" -> do
            putStrLn "Enter the number of users to generate and add: "
            numUsers <- readLn :: IO Int
            generateAndAddUsers numUsers
            putStrLn $ "Generated and added " ++ show numUsers ++ " users"
            mainMenu
        "6" -> putStrLn "Exiting..."  -- exit the program
        _   -> putStrLn "Invalid option" >> mainMenu


formatUser :: User -> ByteString
formatUser user = B.pack $ printf "Name: %s Email: %s Password: %s" (userName user) (userEmail user) (userPassword user)

-- Handle the addition of a user
addUserHandler :: IO ()
addUserHandler = do
    putStrLn "Enter user name: "  -- ask the user for a name
    name <- getLine
    putStrLn "Enter user email: "  -- ask the user for an email
    email <- getLine
    putStrLn "Enter user password: "  -- ask the user for a password
    password <- getLine
    addUser name email password `catch` handler  -- add the user to the database, handling any errors
    mainMenu

-- Handle the listing of all users
listUsersHandler :: IO ()
listUsersHandler = do
    putStrLn ""
    users <- listUsers  -- get the list of all users from the database
    let numberedUsers :: [(Int, User)]
        numberedUsers = zipWith (\n user -> (n, user)) [1..] users  -- add numbering to the users
        formattedUsers = map (\(n, user) -> printf "%3d. %-15s %-20s %s" n (userName user) (userEmail user) (userPassword user)) numberedUsers  -- format each user as a table row
        tableHeader = "No. Name                 Email                  Password"  -- create the table header
    putStrLn tableHeader  -- print the table header
    putStrLn $ replicate (length tableHeader) '-'  -- print a line of dashes under the header
    mapM_ putStrLn formattedUsers  -- print each user as a table row
    putStrLn ""
    mainMenu

-- Handle the listing of all users using Data.Map
maplistUsersHandler :: IO ()
maplistUsersHandler = do
    putStrLn ""
    users <- listUsers  -- get the list of all users from the database
    let userMap = Map.fromList $ map (\user -> (userName user, user)) users  -- create a map with user names as keys
        numberedUsers :: [(Int, (UserName, User))]
        numberedUsers = zipWith (\n (name, user) -> (n, (name, user))) [1..] (Map.toList userMap)  -- add numbering to the users
        formattedUsers = map (\(n, (name, user)) -> printf "%3d. %-15s %-20s %s" n name (userEmail user) (userPassword user)) numberedUsers  -- format each user as a table row
        tableHeader = "No. Name                 Email                  Password"  -- create the table header
    putStrLn tableHeader  -- print the table header
    putStrLn $ replicate (length tableHeader) '-'  -- print a line of dashes under the header
    mapM_ putStrLn formattedUsers  -- print each user as a table row
    putStrLn ""
    mainMenu

-- Handle the finding of a user
findUserHandler :: IO ()
findUserHandler = do
    putStrLn "Enter user name or email to find: "  -- ask the user for a name or email to search for
    searchTerm <- getLine
    users <- findUsers searchTerm  -- search the database for users matching the search term
    case users of
        [] -> putStrLn "User not found"
        _  -> mapM_ (putStrLn . B.unpack . formatUser) users  -- print the users to the console using the formatted string
    mainMenu

-- Handle the deletion of a user
deleteUserHandler :: IO ()
deleteUserHandler = do
    putStrLn "Enter user name to delete: "  -- ask the user for a name to delete
    name <- getLine
    deleteUser name `catch` handler  -- delete the user from the database, handling any errors
    mainMenu

-- Handle any exceptions that are thrown by the program
handler :: SomeException -> IO ()
handler ex = putStrLn $ "An error occurred: " ++ show ex