first_var = 1
#global
$var
#class
@@var
#instance
@var
#local
var
#block 
var

#exp
4 ** 2

x += 2

# return integer 3
10/3

# Fixnum or Bignum
123.class
x = 1234 ** 3
x.class

#method
-200.abs
200.next

12345.67.class
#method
123.34.round
123.34.floor
123.34.ceil
123.34.to_i  

"hello"
'world'
"hello" + ' ' + "world"
"hello"*5
"1" * 5
'I\'m escaped.'
"I'm good"
#tab
"\t"
#return
"\n"

# quote variable with double quote
# ruby evaluation
a = "hi"
puts "I want to say #{a}."
puts "1 + 1 = #{1+1}"

#method
"hi".reverse
"hi".capitalize
"hi".downcase
"hi".upcase
"hi".length
"hi".reverse.upcase

data_set = []
data_set = ["a",1,"2"]
data_set[0] = "d"
data_set[2] = nil
#append
data_set << "e"
#clear
data_set.clear
data_set = []

array = [1,2,3,4,5]
array2 = [1,"2.0",3.0,[1,2],"dog"]
puts array.inspect
array2.to_s
array.join(", ")
x = "1,2,3,4,5"
y = x.split(",")
y.reverse
array.sort
#unique
array.uniq
array.uniq! #will replace the original
array.delete_at(2) # delete the position
array.delete(4) # delete the value
array.push(4)
array.pop
array.shift
array.unshift(1)

array + array2

person = { 'first' => 'Kevin', 'last' => 'Jordan'}
person['first']
person.index('Kevin')
person.keys
person.values
person.length
person.clear
person['gender'] = 'male'

:test

#not
!
#and
&&
#or
||

true
false

#method
x.nil?
2.between?(1,4)
[].empty?
a.include?(2)
hash.has_key?('a')
hash.has_value?(2)

#range
# inclusive, include the last
1..10
# exclusive, exclude the last
1...10

x.begin
x.end
x.first
x.last

alpha = 'a'..'m'
[*alpha]

TEST = 100

if boolean
    ...
elsif boolean
    ...
else    
    ...
end

# or 
puts "sth" if name == "a"

unless boolean
    ...
end
# or
if !boolean
    ...
end
# case
case
when boolean
    ...
when boolean
    ...
else
    ...
end
# or
case test_value
when value
    ...
when value
    ...
else
    ...
end

# ternary operator
boolean ? code1 : code2

loop do
    ...
end

while boolean
    ...
end  


until boolean
    ...
end

puts x += 2 while x < 100

5.times do
    puts 'hello'
end

1.upto(5) {puts "hello"}

(1..5).each {puts "hello"}

1.upto(5) do |i|
    puts "hello" + i.to_s
end

for i in something
    ...
end

array.each {|num| puts num * 2}

#return a single object
(1..10).find {|i| i==5 }
(1..10).detect {|i| i==5 }

#find all
(1..10).find_all {|i| i%3 == 0}
(1..10).select {|i| i%3 == 0}
#return a single boolean
(1..10).any? {|i| i%3 == 0}
(1..10).all? {|i| i%3 == 0}
#delete if
[*1..10].delete_if {|i| i%3 == 0}

hash1.merge(hash2)
hash1.merge(hash2) {|key,old,new| new*5}
hash1.merge(hash2) {|key,old,new| old < new? old:new}

array.collect{|i| i+1}

#compare with spaceship operator
1 <=> 2

array.sort {|v1,v2| v1 <=> v2}

(1..10).inject {|memo,n| memo+n if n != 3}

def some_name(args="default")
    ...
    # return the last value or
    return 1+1
end

# load methods file
ruby methods.rb
require "methods.rb"

8+2
8.+(2)

class SomeName
    ...
    def some_method
        ...
    end
end

# use

animal = Animal.new
animal.method1

class Animal
    def noise=noise
        @noise = noise
    end
    
    def noise
        @noise
    end
end

a1 = Animal.new
a1.noise = "Hoo!"
puts a1.noise

attr_reader :name
attr_writer :name
# use both reader and writer
attr_accessor :name, :age

# equal to

def name
    @name
end

def name =(value)
    @name = value
end

def initialize(name, legs =4)
    @name = name
    @legs = leg
end

# will always be executed

a1 = Animal.new("a")

Animal.new

def self.method_name

end

def self.create_with_attributes(noise,color)
    animal = Animal.new(noise)
    #or 
    animal = self.new(noise)
    animal.color = color
    return animal
end

class Animal
    @@species = ['cat','dog']
    @@total = 0
    @@current = []
    
    def self.current
        @@current
    end
    
    def self.current= (array=[])
        @@current = array
    end
    
    def initialize()
        ...
        @@total += 1
        @@current << self
    end
end

class Cow < Animal
    def new_method
    end
end

class Array
    def to_s
        self.join(',')
    end
end

class Cow < Animal
    def new_method
        
        super
        return 'xx'
    end
end

module Romantic
    class Date
        ...
    end
end
# self defined Date class
dinner = Rommantic::Date.new
# ruby internal Date class
dinner.date = Date.new

module info
    ...
end


class Student
    include info
end

# load module, use path, load every times
load 'info.rb'
# require module, like load but only load once
require 'info.rb'

class ToDoList
    include Enumerable
    attr_accessor :items
    
    def initialize
        @items = []
    end
# told enumerable which variable to use    
    def each
        @ items.each {|item| yield item}
    end
end

# chomp remove the escaping ending charactor
input = gets "hello.\r\n".chomp
# or 
input = gets.chomp

File.join('path1','path2','name')

# absolute path
File.expand_path(__FILE__)
File.dirname(__FILE__)
# back up to parent dir
File.join('current`,`..`,`file`)  
# get ex file
"ex\ file" 
# get ex\ file
'ex\ file` 

# create new file object, name, mode
file = File.new('some.txt','w')
file.close

File.open('file1.txt','r') do |file|
    # read and will automatically be closed
end

file = File.new('file1.txt','w')
# has a line return
file.puts "abc"
# no return
file.print "eff"
file.write "an"
# append
file << "mno"
file.close

file = File.new('file1.txt','r')
file.gets
file.gets.chomp
file.close

File.open('file1.txt','r') do |file|
    while line = file.gets
        puts "** " + line.chomp.reverse + " **"
    end
end
# or each line
File.open('file1.txt','r') do |file|
    file.each_line {|line| puts line.upcase}
end

file = File.new('file1.txt','r+')
# return the position of pointer
file.pos
file.read(3)
file.pos
# get from the pointer to the return
file.gets
file.pos = 13
# end of the file?
file.eof?
# move the pointer to 0
file.rewind
# no. of gets
file.lineno

while line = file.gets
    puts "Line #{file.lineno}: #{line}"
end

File.rename('old.txt','newname.txt')

File.delete('file.txt')

# copy
require 'fileutils'
FileUtils.copy('old.txt','new.txt')

File.exist?(file)
File.directory?(file)
File.readable?(file)
File.writable?(file)
File.executable?(file)
# size in bytes
File.size(file)
File.dirname(file)
File.expand_path(file)
File.basename(path)
# extension
File.extname(file)
# modify, access, status change
File.mtime, .atime, .ctime

#instance method
myfile = File.new("file")
myfile.stat
myfile.stat.size
myfile.stat.readable?

Dir.pwd
Dir.chdir("..")

Dir.entries('.').each do |entry|
    print entry + ": "
    if File.file?(entry) && File.readable?(entry)
        File.open(entry, 'r') do |file|
            puts file.gets
        end
    else
        puts
    end
end

Dir.foreach('.') {|entry| puts entry}

Dir.mkdir('temp')
Dir.delete('temp')
# use FileUtils to remove dir with inside contents

APP_ROOT = File.dirname(__FILE__)
# load files
$:.unshift( File.join(APP_ROOT,'lib') )
require 'guide'

guide = Guide.new('restaurants.txt')
guide.launch!

require 'Restaurant'
class Guide
    class Config
        @@actions =['list','find','add','quit']
        def self.action; @@actions; end
    end
    
    def initialize(path=nil)
        Restaurant.filepath = path
        if Restaurant.file_usable?
            puts "Found restaurant file."
        elsif Restaurant.create_file
            puts "Create restaurant file."
        else
            puts "Exiting. \n\n"
            exit!
        end
    end
    
    def launch!
    introduction
    until result == :quit
        action, args = get_action
        result = do_action(action, args)
    end
    conclusion
    end
    
    def get_action
        action = nil
        until Guide::Config.actions.include?(action)
            puts "Actions: " + Guide::Config.actions.join(", ") if action
            print ">"
            user_response = gets.chomp
            args = user_response.downcase.strip.split(" ")
            action = args.shift
        end
        return action, args
    end
    
    def do_action(action,args=[])
        case action 
        when 'list'
            list(args)
        when 'find'
            keyword = args.shift
            find(keyword)  
        when 'add'
            add
        when 'quit'
            return :quit
        else
            puts "\nI don't understand that.\n"
        end
    end
    def list(args=[])
        sort_order = args.shift || "name"
        sort_order = "name" unless ['name','cuisine','price'].include?(sort_order)
        
        puts "\nListing restaurants\n\n".upcase
        restaurants = Restaurant.saved_restaurants
        restaurants.sort! do |r1,r2|
            case sort_order
            when 'name'
                r1.name.downcase <=> r2.name.downcase
            when 'cuisine'
                r1.cuisine <=> r2.cuisine.downcase 
            when 'price'
                r1.price.to_i <=> r2.price.to_i
            end
        end
        restaurants.each do |rest|
            puts rest.name + "  |  " + rest.cuisine + "  |  " + "  |  " rest.price
    end
    
    def add
        puts "\nAdd a restaurant\n".upcase
        
        restaurant = Restaurant.build_with_questions
        if restaurant.save
            puts "\nRestaurant Added\n\n"
        else 
            puts "\nSave Error: not added\n\n"
    end
    
    def find(keyword ="")
        output_action_header("Find a restaurant")
        if keyword
            restaurants = Restaurant.saved_restaurants
            found = restaurants.select do |rest|
                rest.name.downcase.include?(keyword.downcase)  ||
                rest.cuisine.downcase.include?(keyword.downcase) ||
                rest.price.to_i <= keyword.to_i
            end
            output_restaurant_table(found)
            #search
        else
            puts "Find using a key phrase"
        end
        
    end
    
    def introduction
        puts "welcome"
    end
    
    def conclusion
        puts "goodbye"
    end
end

class Restaurant

    @@filepath = nil
    def self.filepath=(path=nil)
        @@filepath = File.join(APP_ROOT,path)
    end
    
    attr_accessor :name, :cuisine, :price
    
    
    def self.file_exist?
        if @@filepath && File.exists?(@@filepath)
            return true
        else
            return false
        end
    end
    
    def self.file_usable?
        return false unless @@filepath
        return false unless File.exists?(@@filepath)
        return false unless File.readable?(@@filepath)
        return false unless File.writable?(@@filepath)
        return true
    end

    def sef.create_file
        File.open(@@filepath, 'w') unless file_exists?
        return file_usable?
    end
    
    def self.saved_restaurants
        restaurants = []
        if file_usable?
            file = File.new(@@filepath,'r')
            file.each_line do |line|
                restaurants << Restaurant.new.import_line(line.chomp)
            end
            file.close
        end
        return restaurants
    end
    
    def self.build_with_questions
        args = {}
        print "Restaurant name: "
        args[:name] = gets.chomp.strip
        
        print "Restaurant cuisine: "
        args[:cuisine] = gets.chomp.strip
        
        print "Restaurant price: "
        args[:price] = gets.chomp.strip
        
        restaurant = self.new(args)
    end
        
    def initialize(args={})
        @name = args[:name]         || ""
        @cuisine = args[:cuisine]   || ""
        @price = args[:price]       || ""
    end
    
    def import_line(line)
        line_array = line.split("\t")
        @name, @cuisine, @price = line_array
        return self
    end
    def save
        return false unless Restaurant.file_usable?
        File.open(@@filepath, 'a') do |file|
            file.puts "#{[@name,@cuisine,@price].join("\t")}\n"
end