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require "../spec_helper.cr"
include Parcom
# Adapted from: https://bodil.lol/parser-combinators/
struct Attribute
getter name, value
def initialize(@name : String, @value : String)
end
def to_s(io : IO)
io << @name << "=" << @value
end
end
struct Element
getter name, attributes, children
def initialize(@name : String, @attributes : Array(Attribute), @children : Array(Element))
end
def to_s(io : IO)
io << String.build do |str|
str << "<" << @name << " " << @attributes.join(" ")
if @children.empty?
str << "/>"
else
str << ">"
@children.each { |c| str << c }
str << "</" << @name << ">"
end
end
end
end
def match_literal(s : String) : Parser(Char, String)
Parser(Char, Char).token_sequence(s.chars).map(&.join)
end
def letter
Parser(Char, Char).satisfy(&.letter?)
end
def alphanum_dash
Parser(Char, Char).satisfy { |c| c == '-' || c.alphanumeric? }
end
def identifier
(letter + alphanum_dash.many).map do |c, cs|
cs.unshift(c).join
end
end
def equal
Parser.token('=')
end
def quote
Parser.token('"')
end
def string_body
Parser(Char, Char).satisfy(&.!=('"')).many.map(&.join)
end
def string_literal
quote >> string_body << quote
end
def ws_char
Parser(Char, Char).satisfy(&.whitespace?)
end
def within_ws(p)
ws_char.many >> p << ws_char.many
end
def attr_pair
(identifier + (equal >> string_literal)).map do |name, value|
Attribute.new(name, value)
end
end
def attributes
(ws_char.some >> attr_pair).many
end
def element_start
match_literal("<") >> (identifier + attributes)
end
def single_element
(element_start << match_literal("/>")).map do |name, attributes|
Element.new(name, attributes, [] of Element)
end
end
def open_element
(element_start << match_literal(">")).map do |name, attributes|
Element.new(name, attributes, [] of Element)
end
end
def element
within_ws(single_element | parent_element)
end
def close_element(name : String)
match_literal("</") >> match_literal(name) << match_literal(">")
end
def parent_element : Parser(Char, Element)
open_element.and_then do |base_element|
(element.many << close_element(base_element.name)).map do |elems|
Element.new(
base_element.name,
base_element.attributes,
elems
)
end.as(Parser(Char, Element))
end
end
# Adapted from: https://bodil.lol/parser-combinators/
describe "markup language similar to XML" do
expected_value = Element.new(
"top",
[Attribute.new("label", "Top")],
[
Element.new(
"semi-bottom",
[Attribute.new("label", "Bottom")],
[] of Element
),
Element.new(
"middle",
[] of Attribute,
[
Element.new(
"bottom",
[Attribute.new("label", "another bottom")],
[] of Element
)
],
)
]
)
xml = "
<top label=\"Top\">
<semi-bottom label=\"Bottom\"/>
<middle>
<bottom label=\"another bottom\"/>
</middle>
</top>"
result = element.parse(Tokens.from_string(xml))
result.value.should eq(expected_value)
end
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