require_relative 'sub_lookup'

# Add support for Hiera-like interpolation expressions. The expressions may contain keys that uses dot-notation
# to further navigate into hashes and arrays
#
module Puppet::Pops
module Lookup
module Interpolation
  include SubLookup

  def interpolate(subject, lookup_invocation, allow_methods)
    case subject
    when String
      subject.index('%{').nil? ? subject : interpolate_string(subject, lookup_invocation, allow_methods)
    when Array
      subject.map { |element| interpolate(element, lookup_invocation, allow_methods) }
    when Hash
      Hash[subject.map { |k, v| [k, interpolate(v, lookup_invocation, allow_methods)] }]
    else
      subject
    end
  end

  private

  EMPTY_INTERPOLATIONS = {
    '' => true,
    '::' => true,
    '""' => true,
    "''" => true,
    '"::"' => true,
    "'::'" => true
  }.freeze

  # Matches a key that is quoted using a matching pair of either single or double quotes.
  QUOTED_KEY = /^(?:"([^"]+)"|'([^']+)')$/

  def interpolate_string(subject, lookup_invocation, allow_methods)
    lookup_invocation.with(:interpolate, subject) do
      subject.gsub(/%\{([^\}]*)\}/) do |match|
        expr = $1
        # Leading and trailing spaces inside an interpolation expression are insignificant
        expr.strip!
        value = nil
        unless EMPTY_INTERPOLATIONS[expr]
          method_key, key = get_method_and_data(expr, allow_methods)
          is_alias = method_key == 'alias'

          # Alias is only permitted if the entire string is equal to the interpolate expression
          raise Puppet::DataBinding::LookupError, "'alias' interpolation is only permitted if the expression is equal to the entire string" if is_alias && subject != match

          segments = split_key(key) { |problem| Puppet::DataBinding::LookupError.new("#{problem} in string: #{subject}") }
          root_key = segments.shift
          value = interpolate_method(method_key).call(root_key, lookup_invocation)
          value = sub_lookup(key, lookup_invocation, segments, value) unless segments.empty?
          value = lookup_invocation.check(key) { interpolate(value, lookup_invocation, allow_methods) }

          # break gsub and return value immediately if this was an alias substitution. The value might be something other than a String
          return value if is_alias
        end
        value.nil? ? '' : value
      end
    end
  end

  def interpolate_method(method_key)
    @@interpolate_methods ||= begin
      global_lookup = lambda { |key, lookup_invocation| Lookup.lookup(key, nil, '', true, nil, lookup_invocation) }
      scope_lookup = lambda do |key, lookup_invocation|
        lookup_invocation.with(:scope, nil) do
          ovr = lookup_invocation.override_values
          if ovr.include?(key)
            lookup_invocation.report_found_in_overrides(key, ovr[key])
          else
            scope = lookup_invocation.scope
            if scope.include?(key)
              lookup_invocation.report_found(key, scope[key])
            else
              defaults = lookup_invocation.default_values
              if defaults.include?(key)
                lookup_invocation.report_found_in_defaults(key, defaults[key])
              else
                nil
              end
            end
          end
        end
      end

      {
        'lookup' => global_lookup,
        'hiera' => global_lookup, # this is just an alias for 'lookup'
        'alias' => global_lookup, # same as 'lookup' but expression must be entire string and result is not subject to string substitution
        'scope' => scope_lookup,
        'literal' => lambda { |key, _| key }
      }.freeze
    end
    interpolate_method = @@interpolate_methods[method_key]
    raise Puppet::DataBinding::LookupError, "Unknown interpolation method '#{method_key}'" unless interpolate_method
    interpolate_method
  end

  def get_method_and_data(data, allow_methods)
    if match = data.match(/^(\w+)\((?:["]([^"]+)["]|[']([^']+)['])\)$/)
      raise Puppet::DataBinding::LookupError, 'Interpolation using method syntax is not allowed in this context' unless allow_methods
      key = match[1]
      data = match[2] || match[3] # double or single qouted
    else
      key = 'scope'
    end
    [key, data]
  end
end
end
end
