91 lines
2.0 KiB
Ruby
91 lines
2.0 KiB
Ruby
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module Liquid
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class Parser
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def initialize(input)
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l = Lexer.new(input)
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@tokens = l.tokenize
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@p = 0 # pointer to current location
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end
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def jump(point)
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@p = point
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end
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def consume(type = nil)
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token = @tokens[@p]
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if type && token[0] != type
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raise SyntaxError, "Expected #{type} but found #{@tokens[@p].first}"
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end
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@p += 1
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token[1]
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end
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# Only consumes the token if it matches the type
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# Returns the token's contents if it was consumed
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# or false otherwise.
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def consume?(type)
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token = @tokens[@p]
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return false unless token && token[0] == type
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@p += 1
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token[1]
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end
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# Like consume? Except for an :id token of a certain name
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def id?(str)
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token = @tokens[@p]
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return false unless token && token[0] == :id
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return false unless token[1] == str
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@p += 1
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token[1]
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end
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def look(type, ahead = 0)
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tok = @tokens[@p + ahead]
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return false unless tok
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tok[0] == type
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end
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def expression
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token = @tokens[@p]
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if token[0] == :id
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variable_signature
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elsif [:string, :number].include? token[0]
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consume
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elsif token.first == :open_round
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consume
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first = expression
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consume(:dotdot)
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last = expression
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consume(:close_round)
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"(#{first}..#{last})"
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else
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raise SyntaxError, "#{token} is not a valid expression"
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end
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end
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def argument
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str = ""
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# might be a keyword argument (identifier: expression)
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if look(:id) && look(:colon, 1)
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str << consume << consume << ' '.freeze
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end
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str << expression
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str
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end
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def variable_signature
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str = consume(:id)
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while look(:open_square)
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str << consume
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str << expression
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str << consume(:close_square)
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end
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if look(:dot)
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str << consume
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str << variable_signature
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end
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str
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end
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end
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end
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