require 'spec_helper'

shared_examples 'a generically generated function' do
  it 'returns a function class' do
    expect(function.class.superclass).to eq(described_class)
  end

  it 'returns a class whose instance responds to the variables' do
    variables.each do |variable|
      expect(function).to respond_to(variable)
    end
  end

  it 'returns a function that uses the block to process to_tex' do
    expect(function.to_tex).to eq('x^{y}')
  end

  it 'returns a function that uses the block to process to_gnu' do
    expect(function.to_gnu).to eq('x**(y)')
  end

  it 'returns a function thtat knows how to calculate' do
    expect(function.calculate(x: 2, y: 3)).to eq(8)
  end
end

describe Danica::Function do
  let(:variables) { %i(x y) }
  let(:function_class) do
    described_class.build(*variables) do
      Danica::Operator::Power.new(x, y)
    end
  end

  describe '.build' do
    let(:function) do
      function_class.new
    end

    it_behaves_like 'a generically generated function'

    context 'when no block is given' do
      let(:function_class) do
        described_class.build(*variables)
      end

      it 'returns a function class' do
        expect(function_class.superclass).to eq(described_class)
      end
    end

    context 'when creating a class using build' do
      let(:function_class) { Danica::Hyperbole }

      it 'has the defined variables on class definition' do
        expect(function_class.variables_names).to eq([:x])
      end

      it 'has the defined variables' do
        expect(function.variables_hash).to eq(x: Danica::Wrapper::Variable.new(name: :x))
      end

      context 'when calling to_tex' do
        it 'build function from block' do
          expect(function.to_tex).to eq('x^{2}')
        end
      end

      context 'when calling to_gnu' do
        it 'build function from block' do
          expect(function.to_gnu).to eq('x**(2)')
        end
      end
    end

    context 'when using a class that inherits from another class' do
      let(:function_class) { Danica::SaddleHyperbole }

      it 'has the defined variables on class definition' do
        expect(function_class.variables_names).to eq([:x, :y])
      end

      it 'has the defined variables' do
        expect(function.variables_hash).to eq(
          x: Danica::Wrapper::Variable.new(name: :x),
          y: Danica::Wrapper::Variable.new(name: :y)
        )
      end

      context 'when calling to_tex' do
        it 'build function from block' do
          expect(function.to_tex).to eq('x^{2} -y^{2}')
        end
      end

      context 'when calling to_gnu' do
        it 'build function from block' do
          expect(function.to_gnu).to eq('x**(2) -y**(2)')
        end
      end
    end
  end

  describe '.create' do
    let(:function) do
      described_class.create(*variables) do
        Danica::Operator::Power.new(x, y)
      end
    end
    it_behaves_like 'a generically generated function'
  end

  describe '#describe_tex' do
    context 'when function has a name' do
      let(:function) do
        function_class.new(name: :f)
      end

      it 'returns the full function description' do
        expect(function.describe_tex).to eq('f(x, y) = x^{y}')
      end
    end

    context 'when a variable is set as a constant' do
      let(:function) do
        function_class.new(name: :f, x: Danica::PI)
      end

      it 'ignores the constant in the definition' do
        expect(function.describe_tex).to eq('f(y) = \pi^{y}')
      end

      context 'from a hash' do
        let(:function) do
          function_class.new(name: :f, x: { latex: '\pi', gnu: 'pi', value: 3.14 })
        end

        it 'ignores the constant in the definition' do
          expect(function.describe_tex).to eq('f(y) = \pi^{y}')
        end
      end
    end

    context 'when a variable is a number' do
      let(:function) do
        function_class.new(name: :f, x: 2)
      end

      it 'sohws the variable as number' do
        expect(function.describe_tex).to eq('f(2, y) = 2^{y}')
      end
    end

    context 'when a variable has value' do
      let(:function) do
        function_class.new(name: :f, x: 2)
      end

      it 'sohws the variable as number' do
        expect(function.describe_tex).to eq('f(2, y) = 2^{y}')
      end
    end
  end

  describe '#describe_gnu' do
    context 'when function has a name' do
      let(:function) do
        function_class.new(name: :f)
      end

      it 'returns the full function description' do
        expect(function.describe_gnu).to eq('f(x, y) = x**(y)')
      end
    end

    context 'when a variable is set as a constant' do
      let(:function) do
        function_class.new(name: :f, x: Danica::PI)
      end

      it 'ignores the constant in the definition' do
        expect(function.describe_gnu).to eq('f(y) = pi**(y)')
      end

      context 'from a hash' do
        let(:function) do
          function_class.new(name: :f, x: { latex: '\pi', gnu: 'pi', value: 3.14 })
        end

        it 'ignores the constant in the definition' do
          expect(function.describe_gnu).to eq('f(y) = pi**(y)')
        end
      end
    end

    context 'when a variable has value' do
      let(:function) do
        function_class.new(name: :f, x: { name: :x, value: 2 })
      end

      it 'sohws the variable as number' do
        expect(function.describe_gnu).to eq('f(2, y) = 2**(y)')
      end
    end

    context 'when a variable is a number' do
      let(:function) do
        function_class.new(name: :f, x: 2)
      end

      it 'sohws the variable as number' do
        expect(function.describe_gnu).to eq('f(2, y) = 2**(y)')
      end
    end
  end

  describe 'spatial' do
    let(:variables) do
      {
        time: :t,
        acceleration: 'a',
        initial_space: { name: :S0, latex: 'S_0' },
        initial_velocity: { name: :V0, latex: 'V_0' }
      }
    end

    subject { described_class::Spatial.new(variables) }
    it_behaves_like 'an object that respond to basic_methods'

    describe '#to_tex' do
      context 'when creating the spatial operator for constantly accelerated movement' do
        let(:expected) { 'S_0 + V_0 \cdot t + \frac{a \cdot t^{2}}{2}'  }

        it 'return the latex format CAM' do
          expect(subject.to_tex).to eq(expected)
        end
      end
    end

    describe '#to_gnu' do
      context 'when creating the spatial operator for constantly accelerated movement' do
        let(:expected) { 'S0 + V0 * t + (a * t**(2))/(2)'  }

        it 'return the latex format CAM' do
          expect(subject.to_gnu).to eq(expected)
        end
      end
    end

    describe '#variables_hash' do
      let(:expected) do
        {
          time: Danica::Wrapper::Variable.new(name: :t),
          acceleration: Danica::Wrapper::Variable.new(name: 'a'),
          initial_space: Danica::Wrapper::Variable.new( name: :S0, latex: 'S_0' ),
          initial_velocity: Danica::Wrapper::Variable.new( name: :V0, latex: 'V_0' )
        }
      end

      context 'when variables are already wrapped with Danica::Wrapper::Variable' do
        let(:variables) { expected }
        it 'returns a hash with the variabels' do
          expect(subject.variables_hash).to eq(expected)
        end
      end

      context 'when variables have been defined with string name' do
        before do
          variables.change_keys!(&:to_s)
        end

        it 'returns a hash with the variabels' do
          expect(subject.variables_hash).to eq(expected)
        end
      end

      context 'when variables are not wrapped yet' do
        it 'returns a hash with the variabels' do
          expect(subject.variables_hash).to eq(expected)
        end
      end

      context 'when changing a variable' do
        before do
          subject.time = :x
          expected[:time] = Danica::Wrapper::Variable.new(name: :x)
        end

        it do
          expect(subject.variables_hash).to eq(expected)
        end
      end

      context 'when initializing with array' do
        context 'as hash' do
          let(:variables) { [ :t, 'a', {name: :S0, latex: 'S_0'}, { name: :V0, latex: 'V_0' } ] }
          subject { described_class::Spatial.new(variables) }

          it 'returns a hash with the variabels' do
            expect(subject.variables_hash).to eq(expected)
          end
        end
      end

      context 'when initializing with sequence' do
        context 'as hash' do
          let(:variables) { [ :t, 'a', {name: :S0, latex: 'S_0'}, { name: :V0, latex: 'V_0' } ] }
          subject { described_class::Spatial.new(*variables, {}) }

          it 'returns a hash with the variabels' do
            expect(subject.variables_hash).to eq(expected)
          end
        end
      end

      context 'when initializing with variables array' do
        context 'as hash' do
          let(:variables) { [ :t, 'a', {name: :S0, latex: 'S_0'}, { name: :V0, latex: 'V_0' } ] }
          subject { described_class::Spatial.new(variables: variables) }

          it 'returns a hash with the variabels' do
            expect(subject.variables_hash).to eq(expected)
          end
        end
      end
    end

    describe '#variables' do
      context 'when initialized with an array of variables' do
        subject { described_class::Spatial.new(variables: variables.values) }
        let(:expected) { variables.values.map { |v| subject.send(:wrap_value, v)} }
        it do
          expect(subject.variables.compact).to eq(expected)
        end
      end

      context 'when not initializing all variables' do
        subject { described_class::Spatial.new }
        let(:time) { Danica::Wrapper::Variable.new(name: :t) }

        context 'when initialized with an empty variable set' do
          it do
            expect(subject.variables.compact).not_to be_empty
          end
        end

        context 'when changing a variable' do
          before do
            subject.time = time
          end

          it 'returns the list of variables merged default and new variables' do
            expect(subject.variables.compact).to eq([
              time,
              Danica::Wrapper::Variable.new(name: :acceleration),
              Danica::Wrapper::Variable.new(name: :initial_space),
              Danica::Wrapper::Variable.new(name: :initial_velocity)
            ])
          end
        end

        context 'when initializing with a variable set' do
          let(:names) { [ :t, :a, :s0, :v0 ] }
          subject { described_class::Spatial.new *names }

          it 'returns the variables given oin initialization' do
            expect(subject.variables.map(&:name)).to eq(names)
          end

          context 'when initializing variables with a hash out of order' do
            let(:variables) do
              {
                initial_velocity: :v0,
                initial_space: :s0,
                acceleration: :a,
                time: :t
              }
            end
            subject { described_class::Spatial.new variables }

            it 'returns the variables given on initialization' do
              expect(subject.variables.map(&:name)).to eq(names)
            end
          end
        end
      end
    end

    describe '#calculate' do
      context 'when all variables have value' do
        let(:time_value) { 2 }
        let(:time) { time_value }
        let(:acceleration) { 3 }
        let(:initial_space) { 1 }
        let(:initial_velocity) { 1 }
        subject { described_class::Spatial.new(time, acceleration, initial_space, initial_velocity) }
        let(:expected) { initial_space + initial_velocity * time_value + acceleration * (time_value ** 2) / 2.0 }

        it 'retuirns the calculated value' do
          expect(subject.calculate).to eq(expected)
        end

        context 'when not all variables have value' do
          let(:time) { :t }

          it do
            expect { subject.calculate }.to raise_error(Danica::Exception::NotDefined)
          end

          context 'but calling calculate with a value for the variables' do
            it 'calculate using the given value' do
              expect(subject.calculate(time_value)).to eq(expected)
            end

            it 'does not change the values of then valued variables' do
              expect do
                subject.calculate(time_value)
              end.not_to change(subject.time, :valued?)
            end
          end

          context 'when calling with a hash for the values' do
            it 'calculate using the given value' do
              expect(subject.calculate(time: time_value)).to eq(expected)
            end

            it 'does not change the values of then valued variables' do
              expect do
                subject.calculate(time: time_value)
              end.not_to change(subject.time, :valued?)
            end
          end
        end
      end
    end
  end

  describe 'baskara' do
    context 'when using the default value for variables' do
      subject { described_class::Baskara.new }
      it_behaves_like 'an object that respond to basic_methods'

      describe '#to_tex' do
        let(:expected) { '\frac{-b \pm \sqrt{b^{2} -4 \cdot a \cdot c}}{2 \cdot a}'  }

        it 'return the latex format CAM' do
          expect(subject.to_tex).to eq(expected)
        end
      end

      describe '#to_gnu' do
        let(:expected) { '(-b + sqrt(b**(2) -4 * a * c))/(2 * a)'  }

        it 'return the gnu format CAM' do
          expect(subject.to_gnu).to eq(expected)
        end
      end
    end
  end
end