task_manager.rb

require 'sinatra'
require 'sinatra/content_for'
require 'tilt/erubis'

require_relative 'database_persistence'

configure do
  enable :sessions
  set :session_secret, 'secret'  # This is used by Sinatra to encrypt session information and to enable state to persist between program restarts.
  set :erb, :escape_html => true # escape potentially unsafe user input
end

configure(:development) do   # loads the referenced files when working in developement environment
  require 'sinatra/reloader'  
  also_reload "./database_persistence.rb" 
end 

# This will execute before any pattern is matched with a route.
before do
  @storage = DatabasePersistance.new(logger)
end

get '/' do
  redirect '/lists'
end

# View all lists
get '/lists' do
  @lists = @storage.all_lists
  erb :lists, layout: :layout
end

# Render the `new list` form
get '/list/new' do
  erb :new_list
end

# Create a new list 
post '/lists' do
  list_name     = params[:list_name].strip
  error_message = validate(list_name) { @storage.all_lists.any? { |list| list[:name] == list_name } }

  if error_message
    session[:error] = error_message
    erb :new_list
  else
    @storage.create_new_list(list_name)
    session[:success] = 'The list has been created.'
    redirect '/lists'
  end
end

# View a single todo list
get '/lists/:id' do |id|
  @list_id = id.to_i  
  @list    = load_list(@list_id) # retruns a hash if a list exists otherwise redirects
  @todos   = @storage.find_todos_for_list(@list_id)

  erb :list
end

# Edit an existing todo list
get '/lists/:id/edit' do |id|
  @list_id = id.to_i
  @list    = load_list(@list_id)

  erb :edit_list
end

# update an existing todo list
post '/lists/:id' do |id|
  list_name     = params[:list_name].strip
  @list_id      = id.to_i
  @list         = load_list(@list_id)
  error_message = validate(list_name) { @storage.all_lists.any? { |list| list[:name] == list_name } }

  if error_message
    session[:error] = error_message
    erb :edit_list
  else
    @storage.update_list_name(@list_id, list_name)
    session[:success] = 'The list has been updated.'
    redirect "/lists/#{@list_id}"
  end
end

# Delete a todo list
post '/lists/:id/delete' do |id|
  list_id = id.to_i

  @storage.delete_list(list_id)

  session[:success] = "The list has been deleted."
  
  if env["HTTP_X_REQUESTED_WITH"] == "XMLHttpRequest"
    "/lists"
  else
    redirect "/lists"
  end
end

# add a new todo task to a list
post "/lists/:id/todos" do |id|
  list_id       = id.to_i
  todo_name     = params[:todo].strip
  @list         = load_list(list_id)
  @todos        = @storage.find_todos_for_list(list_id)
  error_message = validate(todo_name) { @todos.any? { |todo| todo[:name] == todo_name } }

  if error_message
    session[:error] = error_message
    erb :list
  else
    @storage.create_new_todo(list_id, todo_name)
    session[:success] = 'Todo item has been added.'
    redirect "/lists/#{list_id}"
  end
end

# Delete a Todo from a list
post "/lists/:list_id/todos/:todo_id/delete" do |list_id, todo_id|
  list_id = list_id.to_i
  todo_id  = todo_id.to_i 

  @storage.delete_todo_from_list(list_id, todo_id)
  session[:success] = "Todo item has been deleted." 


  if env["HTTP_X_REQUESTED_WITH"] == "XMLHttpRequest"
    "/lists/#{list_id}"
  else
    redirect "/lists/#{list_id}"
  end
end 

# Update the status of a todo
post "/lists/:list_id/todos/:todo_id" do |list_id, todo_id|
  list_id      = list_id.to_i
  list         = load_list(list_id)
  todo_id      = todo_id.to_i
  is_completed = params[:completed] == "true"

  @storage.update_todo_status(list_id, todo_id, is_completed)

  session[:success] = "Todo item has been updated."
  redirect "/lists/#{list_id}"
end

# Mark all todos as complete for a list
post "/lists/:list_id/complete_all" do |list_id|
  list_id = list_id.to_i
  list    = load_list(list_id)

  @storage.mark_all_todos_as_completed(list_id)

  session[:success] = "All todos have been completed."

  redirect "/lists/#{list_id}"
end

not_found do
  redirect "/"
end

# returns a list if it exists, otherwise redirects to "/lists" and displays flash error message
def load_list(id) 
  list = @storage.find_list(id)
  return list if list

  session[:error] = "The specified list was not found"
  redirect '/lists' 
end

# returns a String message if the user input is invalid otherwise returns nil if the name is valid.
def validate(user_input)
  unless user_input.size.between?(1, 100)
    return "Entry name must be between 1 and 100 characters"
  end

  invalid = yield   # yielding to the block for validation, the block will return a boolean, either true or false. 

  "Entry name must be unique." if invalid
end

after do # closing databse connection
  @storage.disconnect
end

helpers do
  def list_complete?(list)
    list[:todos_count] > 0 && list[:remaining_todos_count] == 0
  end

  def list_class(list)
    "complete" if list_complete?(list)
  end

  # takes an array of hashes and reorders them while keeping record of their origianl index.
  # it then yields each sorted hash with its original index to the explicit block
  # this feature is intended exculsievly for the `lists` view template.
   def sort_lists(lists, &block)
    sorted_list = sort(lists) {|list| list_complete?(list) ? 1 : 0 }
    sorted_list.each(&block)
  end

  def sort_todos(todos, &block)
    sorted_list = sort(todos) { |todo| todo[:completed] ? 1 : 0 }
    sorted_list.each(&block)
  end

# this method expects an implicit block to be passed as an argument when it is invoked.
  def sort(list)
    list.sort_by {|item| yield(item) }
  end

=begin
# Important Notes regarding Line 31 & Line 36
  - Ruby doesn't provide any built-in mechanism for comparing boolean values(`true` and `false`). 
  - I took advantage of the way `Enumerable#sort_by` works in order to sort boolean values based on integer values which do implement comparison(<=>) in their class.
  - `Enumerable#sort_by` works in 3 steps:
      1. It yields each element of the caller collection to the block, and caches the return value of the block at each iteration temporarily.
      2. sorts all of the block's cached returned values from step 1, which correspond to elements in the calling collection
      3. returns a new sorted collection object(e.i Array), within which elements are sorted based on the sorted return values of th block from step # 2.

  - The above works if the values returned by the block at each initial iteration(step #1) implement a comparison method and are of the same class
  - The above could possibly be overidden with custom classes/objects)
# Example: 
  - suppose at step # 1, you invoke a custom method within the block. if the method returns `nil`,`false`, `true` or raises an `exception`` for any of the passed in elements, 
   `Enumrable#sort_by` will not work and an exception will be raised.
=end
end