Feature/smart change

README.md

@@ -20,6 +20,8 @@ Or install it yourself as:
 
 ## Usage
 
+### .parse
+
 Simple. Very similiar with `Date.parse`. Just:
 ```ruby
 ['invalid', 'monday', '01-01-2019'].each do |date|
@@ -36,6 +38,27 @@ If your date is valid, then will return your valid date.
 If your date is not valid, then will return your alternate.
 Simple, right?
 
+### .smart_change
+
+```ruby
+Dalt.smart_change('31-12-2019', month: 2)
+```
+
+```
+=> 29 February 2019
+```
+
+You can even use alternet in `.smart_change`
+
+```ruby
+Dalt.smart_change('31-12-2019', month: 2, alt: 'Alternate date')
+```
+
+```
+=> "Alternate date"
+```
+
+
 ## Contributing
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/whatdacode/dalt. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.

lib/dalt.rb

@@ -1,11 +1,16 @@
 require 'date'
 require 'dalt/error/without_alternate'
+require 'dalt/formatter'
 require 'dalt/parser'
 require 'dalt/version'
 
 # Dalt will use instance of Dalt::Parser
 module Dalt
-  def self.parse(text, alt: nil)
-    @date = Dalt::Parser.new(text, alt: alt).parse
+  def self.parse(date, alt: nil)
+    @date = Dalt::Parser.new(date.to_s, alt: alt).parse
+  end
+
+  def self.smart_change(date, options)
+    Dalt::Formatter.new(date.to_s, options).smart_change
   end
 end

lib/dalt/formatter.rb

@@ -0,0 +1,75 @@
+module Dalt
+  # This class will handle all of date formatting
+  class Formatter
+    def initialize(date, options = {})
+      @date = Date.parse(date.to_s)
+      @options = options
+    end
+
+    def smart_change
+      Parser.new(date_after_changed.to_s, alt: @options.fetch(:alt, smart_changing)).parse
+    end
+
+    private
+
+    def date_after_changed
+      return Date.civil year, month, -1 if end_of_month?
+
+      Date.new year, month, day
+    rescue ArgumentError
+      nil
+    end
+
+    def day
+      @day ||= @options.fetch(:day, @date.day)
+    end
+
+    def end_of_month
+      Date.civil year, month, -1
+    end
+
+    def end_of_month?
+      @date.month != @date.next_day.month
+    end
+
+    def month
+      @month ||= @options.fetch(:month, @date.month)
+    end
+
+    def month_changed?
+      @options.fetch(:month, false)
+    end
+
+    # Automatically assigned to max posibility of changes
+    # Note: Order matter
+    def smart_changing
+      return smart_month_changing if month_changed?
+
+      # means the only day will be change,
+      # so we can just return max posibility of day which is end of month
+      end_of_month
+    end
+
+    def smart_month_changing
+      # When month is out of range, we automatically assign it to max poisibility of month,
+      # which is december || 12
+      new_date = if month > 12
+                   Date.new year, 12
+                 else
+                   Date.new year, month
+                 end
+
+      new_end_of_month = Date.civil(new_date.year, new_date.month, -1)
+
+      # its double check for day. If after we changed the day and day is out of range,
+      # then we automatically assign it to max posibility of day which is end of month
+      return new_end_of_month if new_end_of_month.day < day
+
+      Date.new new_date.year, new_date.month, day
+    end
+
+    def year
+      @year ||= @options.fetch(:year, @date.year)
+    end
+  end
+end

spec/dalt/formatter_spec.rb

@@ -0,0 +1,81 @@
+RSpec.describe Dalt::Formatter do
+  describe '#smart_change' do
+    let(:changer) { described_class.new(date, options) }
+
+    context 'changing the month' do
+      let(:date) { Date.parse('31-01-2019') }
+
+      context 'change end of the month' do
+        let(:options) { { month: 2 } }
+        it 'returns end of the month of selected month' do
+          expect(changer.smart_change).to eql Date.parse('28-02-2019')
+        end
+      end
+
+      context 'out of range month' do
+        context 'have alternate options' do
+          let(:options) { { month: 13, alt: 'Alternate date' } }
+          it 'returns alternate' do
+            expect(changer.smart_change).to eql 'Alternate date'
+          end
+        end
+
+        context 'have no alternate options' do
+          let(:options) { { month: 13 } }
+
+          it 'return max month' do
+            expect(changer.smart_change).to eq Date.parse('31-12-2019')
+          end
+        end
+      end
+    end
+
+    context 'changing the day' do
+      let(:date) { Date.parse('01-02-2019') }
+
+      context 'day is out of range' do
+        context 'have alternate options' do
+          let(:options) { { day: 31, alt: 'Alternate date' } }
+          it 'returns alternate' do
+            expect(changer.smart_change).to eql 'Alternate date'
+          end
+        end
+
+        context 'have no alternate options' do
+          let(:options) { { day: 31 } }
+
+          it 'return last date on that month' do
+            expect(changer.smart_change).to eq Date.parse('28-02-2019')
+          end
+        end
+      end
+
+      context 'day is in range' do
+        let(:options) { { day: 20, alt: 'Alternate date' } }
+        it 'returns the new date' do
+          expect(changer.smart_change).to eq Date.parse('20-02-2019')
+        end
+      end
+    end
+
+    context 'change both day and month' do
+      let(:date) { Date.parse('01-02-2019') }
+
+      context 'both is out of range' do
+        context 'have alternate' do
+          let(:options) { { day: 32, month: 13, year: 2020, alt: 'Alternate date' } }
+          it 'return the alternate' do
+            expect(changer.smart_change).to eq 'Alternate date'
+          end
+        end
+
+        context 'have no alternate' do
+          let(:options) { { day: 32, month: 13, year: 2020 } }
+          it 'return max posibility of day and month' do
+            expect(changer.smart_change).to eq Date.parse('31-12-2020')
+          end
+        end
+      end
+    end
+  end
+end

spec/dalt_spec.rb

@@ -1,11 +1,31 @@
 RSpec.describe Dalt do
-  it 'return date if valid' do
-    parse = described_class.parse('monday', alt: 'Hello')
-    expect(parse).to eq(Date.parse('monday'))
+  describe '.parse' do
+    it 'return date if valid' do
+      parse = described_class.parse('monday', alt: 'Hello')
+      expect(parse).to eq(Date.parse('monday'))
+    end
+
+    it 'return alternate if invalid' do
+      parse = described_class.parse('invalid', alt: 'Hello')
+      expect(parse).to eq('Hello')
+    end
   end
 
-  it 'return alternate if invalid' do
-    parse = described_class.parse('invalid', alt: 'Hello')
-    expect(parse).to eq('Hello')
+  describe '.smart_change' do
+    it 'returns date if no alternate' do
+      format = described_class.smart_change('31-01-2012', day: 32, month: 31, year: 2020)
+
+      expect(format).to eq Date.parse '31-12-2020'
+    end
+
+    it 'returns alternet if alternate exist' do
+      format = described_class.smart_change('31-01-2012',
+                                            day: 32,
+                                            month: 31,
+                                            year: 2020,
+                                            alt: 'Alternate date')
+
+      expect(format).to eq 'Alternate date'
+    end
   end
 end