# This script is modified by Jason Bryer (jason@bryer.org) from Huidong Tian's 
# original script. The blog post describing the method is here:
# http://withr.me/authentication-of-shiny-server-application-using-a-simple-method/ 
# The original R script is located here: https://gist.github.com/withr/9001831
#
# This script adds two new features: 1. Render a logout button, and 2. provide
# the ability for visitors to create a new account.
#
# Within your server.R file, be sure to use:
# 
# source('Login.R', local=TRUE)
#
# To use this file, you can add uiOutput('uiLogin'), uiOutput('uiNewAccount'),
# and uiOutput('uiLogout') anywhere in your shiny application. If you wish to
# have part of you application available only to authenticated users, you can
# checked to see if they are logged in with the USER$Logged field (this is a
# logical). Additional, USER$Username and USER$Group will give the username
# and password of the logged in user, respectively.

# This is the file that contains a data.frame PASSWORD used for authentication.
users.file <- 'users.rda'
default.group <- 'user' # The value for Group when creating new accounts

if(!file.exists(users.file)) {
	# Create initial, empty file, otherwise errors will occur below
	PASSWORD <- data.frame(Username = character(),
						   Password = character(),
						   Group = character(),
						   Email = character(),
						   stringsAsFactors = FALSE)
	save(PASSWORD, file=users.file)
}

USER <- reactiveValues(Logged = FALSE, 
					   Unique = format(Sys.time(), '%Y%m%d%H%M%S'),
					   Username = NA,
					   Email = NA,
					   Group = NA)

# Password input textbox
passwdInput <- function(inputId, label, value) {
	tagList(
		tags$label(label),
		tags$input(id=inputId, type="password", value=value, class='form-control')
	)
}

# Returns a panel for logging in. 
output$uiLogin <- renderUI({
	wellPanel(
		uiOutput('pass'),
		div(textInput(paste0("username", USER$Unique), 
					  "Username: ", value='')),
		div(passwdInput(paste0("password", USER$Unique), 
						"Password: ", value='')),
		br(), 
		actionButton("Login", "Login")
	)
})

# Provides a UI for creating an account
output$uiNewAccount <- renderUI({
	wellPanel(
		uiOutput('newuser'),
		div(textInput(paste0("newusername", USER$Unique), 
					  "Username: ", value='')),
		div(passwdInput(paste0("newpassword1", USER$Unique), 
						"Password: ", value='')),
		div(passwdInput(paste0("newpassword2", USER$Unique), 
						"Confirm Password: ", value='')),
		div(textInput(paste0('newemail', USER$Unique), 
					  "Email Address: ", value='')),
		br(),
		actionButton("CreateUser", "Create Account")
	)
})

# UI for a logout button
output$uiLogout <- renderUI({
	actionButton('logoutButton', 'Logout')
})

# Log the user out
observeEvent(input$logoutButton, {
	if(!is.null(input$logoutButton) & input$logoutButton == 1) {
		USER$Logged <- FALSE
		USER$Username <- USER$Group <- NA
		USER$Unique <- format(Sys.time(), '%Y%m%d%H%M%S')
		USER$Email <- NA
	}
})

# Add a new user
output$newuser <- renderText({
	text <- ''
	if(USER$Logged == FALSE) {
		if(!is.null(input$CreateUser)) {
			if(input$CreateUser > 0) {
				newusername <- input[[paste0('newusername', USER$Unique)]]
				newpassword1 <- input[[paste0('newpassword1', USER$Unique)]]
				newpassword2 <- input[[paste0('newpassword2', USER$Unique)]]
				newemail <- input[[paste0('newemail', USER$Unique)]]
				
				load(users.file)
				
				# Validate input fields
				if(is.null(newusername) |
				   is.null(newpassword1) |
				   is.null(newpassword2) |
				   is.null(newemail)) {
					text <- 'Please enter all fields'
				} else if(nchar(newusername) < 5 | 
						  nchar(newpassword1) < 5) {
					text <- 'Please enter username and password with at least 5 characters'
				} else if(newpassword1 != newpassword2) {
					text <- 'Passwords do not match'
				} else if(is.null(newemail) |
				   nchar(newemail) < 5 |
				   grep(".+@.+", newemail) < 1) {
					text <- 'Invalid email address'
				} else if(tolower(newusername) %in% PASSWORD$Username) {
					text <- 'Username already exists'
				} else { # Add the user
					newuser <- data.frame(
						Username = newusername,
						Password = newpassword1,
						Group = 'user',
						Email = newemail
					)
					for(i in names(PASSWORD)[(!names(PASSWORD) %in% names(newuser))]) {
						newuser[,i] <- NA # Make sure the data.frames line up
					}
					PASSWORD <- rbind(PASSWORD, newuser[,names(PASSWORD)])
					save(PASSWORD, file=users.file)
					USER$Logged <- TRUE
					USER$Username <- newusername
					USER$Group <- default.group
					USER$Email <- newemail
				}
			}
		}
	}
	text
})

# Log the user in
output$pass <- renderText({
	if(USER$Logged == FALSE) {
		if(!is.null(input$Login)) {
			if(input$Login > 0) {
				load(users.file)
				Username <- isolate(input[[paste0('username', USER$Unique)]])
				Password <- isolate(input[[paste0('password', USER$Unique)]])
				Id.username <- which(PASSWORD$Username == tolower(Username))
				if(!is.null(Id.username) & length(Id.username) == 1 & 
					Password == PASSWORD[Id.username,]$Password) 
				{
					USER$Logged <- TRUE
					USER$Username <- Username
					USER$Group <- PASSWORD[Id.username,]$Group
					USER$Email <- PASSWORD[Id.username,]$Email
				} else  {
					"Username or password failed!"
				}
			} 
		}
	}
})