121 lines
2.8 KiB
Ruby
121 lines
2.8 KiB
Ruby
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module Liquid
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# Container for liquid nodes which conveniently wraps decision making logic
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#
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# Example:
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#
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# c = Condition.new('1', '==', '1')
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# c.evaluate #=> true
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#
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class Condition #:nodoc:
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@@operators = {
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'==' => lambda { |cond, left, right| cond.send(:equal_variables, left, right) },
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'!=' => lambda { |cond, left, right| !cond.send(:equal_variables, left, right) },
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'<>' => lambda { |cond, left, right| !cond.send(:equal_variables, left, right) },
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'<' => :<,
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'>' => :>,
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'>=' => :>=,
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'<=' => :<=,
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'contains' => lambda { |cond, left, right| left.include?(right) },
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}
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def self.operators
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@@operators
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end
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attr_reader :attachment
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attr_accessor :left, :operator, :right
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def initialize(left = nil, operator = nil, right = nil)
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@left, @operator, @right = left, operator, right
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@child_relation = nil
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@child_condition = nil
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end
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def evaluate(context = Context.new)
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result = interpret_condition(left, right, operator, context)
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case @child_relation
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when :or
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result || @child_condition.evaluate(context)
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when :and
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result && @child_condition.evaluate(context)
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else
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result
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end
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end
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def or(condition)
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@child_relation, @child_condition = :or, condition
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end
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def and(condition)
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@child_relation, @child_condition = :and, condition
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end
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def attach(attachment)
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@attachment = attachment
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end
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def else?
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false
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end
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def inspect
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"#<Condition #{[@left, @operator, @right].compact.join(' ')}>"
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end
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private
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def equal_variables(left, right)
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if left.is_a?(Symbol)
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if right.respond_to?(left)
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return right.send(left.to_s)
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else
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return nil
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end
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end
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if right.is_a?(Symbol)
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if left.respond_to?(right)
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return left.send(right.to_s)
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else
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return nil
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end
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end
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left == right
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end
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def interpret_condition(left, right, op, context)
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# If the operator is empty this means that the decision statement is just
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# a single variable. We can just poll this variable from the context and
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# return this as the result.
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return context[left] if op == nil
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left, right = context[left], context[right]
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operation = self.class.operators[op] || raise(ArgumentError.new("Unknown operator #{op}"))
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if operation.respond_to?(:call)
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operation.call(self, left, right)
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elsif left.respond_to?(operation) and right.respond_to?(operation)
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left.send(operation, right)
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else
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nil
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end
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end
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end
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class ElseCondition < Condition
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def else?
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true
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end
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def evaluate(context)
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true
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end
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end
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end
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