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|
module Guff
class Template
getter :string
def initialize(@string : String)
@tokens = scan(@string)
@has_keys = @tokens.select { |t| t.type == :key }.size > 0
end
def run(args : Nil) : String
raise_missing if @has_keys
# return literal string
@string
end
def run(
args = {} of String => String : Hash(String, String)
) : String
if @has_keys
# check template args
raise_missing if args.size == 0
# build result
String.build do |r|
@tokens.each do |t|
r << t.get(args)
end
end
else
# no keys, return literal string
@string
end
end
private def raise_missing
raise "missing template args: %s" % [@tokens.select { |t|
t.type == :key
}.map { |t|
t.value
}.sort.join(", ")]
end
SCAN_RE = %r{
# match key
(?:%\{(?<key>[^\}]+)\})
|
# match literal value
(?<val>[^%]+)
|
# match literal percent
(?<pct>%)
}mx
private def scan(s : String)
r = [] of TemplateToken
s.scan(SCAN_RE) do |md|
if md["key"]?
r << TemplateToken.new(:key, md["key"].strip)
elsif md["val"]?
r << TemplateToken.new(:val, md["val"])
elsif md["pct"]?
r << TemplateToken.new(:val, "%")
else
# never reached
raise "unknown match: #{md}"
end
end
# return result
r
end
end
end
|
