Module: Pago::Serde

Defined in:
lib/pago/serde.rb

Overview

JSON conversion helpers shared by every generated model and service.

Class Method Summary collapse

Class Method Details

.array(value) ⇒ Object

Map a JSON array through the given block, preserving nil.



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# File 'lib/pago/serde.rb', line 26

def array(value)
  return nil if value.nil?
  return value unless value.is_a?(Array)

  value.map { |item| yield(item) }
end

.best_variant(data, variants) ⇒ Class?

Returns the variant whose declared keys best match the payload.

Returns:

  • (Class, nil) —

    the variant whose declared keys best match the payload.



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# File 'lib/pago/serde.rb', line 110

def best_variant(data, variants)
  keys = data.keys.map(&:to_s)
  best = nil
  best_score = -1
  variants.each do |variant|
    next unless variant.respond_to?(:json_keys) && variant.respond_to?(:required_json_keys)
    next unless (variant.required_json_keys - keys).empty?

    score = (variant.json_keys.values & keys).size
    if score > best_score
      best = variant
      best_score = score
    end
  end
  best
end

.candidates(data, variants, seen = []) ⇒ Array<Class>

A tagged union whose tag the payload carries but this release does not know contributes nothing: the payload states it is a variant we cannot name, so scoring it against the variants we do know would mislabel it.

Returns:

  • (Array<Class>) —

    the concrete models a payload could be resolved to.



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# File 'lib/pago/serde.rb', line 83

def candidates(data, variants, seen = [])
  variants.flat_map do |variant|
    if union_module?(variant)
      next [] if seen.include?(variant)

      nested = dispatch_variant(data, variant)
      next candidates(data, [nested], seen + [variant]) if nested
      next [] if tagged?(data, variant)

      candidates(data, variant.variants, seen + [variant])
    elsif variant.respond_to?(:json_keys)
      [variant]
    else
      []
    end
  end
end

.dispatch_variant(data, union_module) ⇒ Class, ...

Returns the variant a nested union's discriminator selects.

Returns:

  • (Class, Module, nil) —

    the variant a nested union's discriminator selects.



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# File 'lib/pago/serde.rb', line 134

def dispatch_variant(data, union_module)
  return nil unless union_module.const_defined?(:DISCRIMINATOR, false)

  discriminator = union_module.const_get(:DISCRIMINATOR)
  mapping = union_module.mapping
  return nil if discriminator.nil? || mapping.nil?

  mapping[data[discriminator]]
end

.dump(value) ⇒ Object

Recursively convert models, arrays and hashes into JSON-ready values.



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# File 'lib/pago/serde.rb', line 42

def dump(value)
  case value
  when ::Pago::Model then value.to_json_hash
  when Array then value.map { |item| dump(item) }
  when Hash
    value.each_with_object({}) do |(key, item), result|
      result[key.is_a?(Symbol) ? key.to_s : key] = dump(item)
    end
  when Symbol then value.to_s
  else value
  end
end

.map(value) ⇒ Object

Map the values of a JSON object through the given block, preserving nil.



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# File 'lib/pago/serde.rb', line 34

def map(value)
  return nil if value.nil?
  return value unless value.is_a?(Hash)

  value.each_with_object({}) { |(key, item), result| result[key] = yield(item) }
end

.object(data) ⇒ Hash?

Returns the value when it is a JSON object, nil otherwise.

Returns:

  • (Hash, nil) —

    the value when it is a JSON object, nil otherwise.



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# File 'lib/pago/serde.rb', line 19

def object(data)
  return nil if data.nil?

  data.is_a?(Hash) ? data : nil
end

.path(template, params = {}) ⇒ Object

Interpolate {name} placeholders of a path template.



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# File 'lib/pago/serde.rb', line 145

def path(template, params = {})
  template.gsub(/\{(\w+)\}/) do
    name = Regexp.last_match(1)
    value = params[name]
    raise ::Pago::Error, "Missing value for path parameter #{name.inspect}" if value.nil?

    ::URI.encode_www_form_component(scalar(value)).gsub("+", "%20")
  end
end

.query(params = {}) ⇒ Object

Flatten query parameters into [name, value] pairs.

Nil values are dropped, arrays repeat the parameter and hashes are encoded as name[key]=value, matching the deep-object style used by the API.



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# File 'lib/pago/serde.rb', line 159

def query(params = {})
  pairs = []
  params.each do |name, value|
    next if value.nil?

    case value
    when Hash
      value.each do |key, nested|
        pairs << ["#{name}[#{key}]", scalar(nested)] unless nested.nil?
      end
    when Array
      value.each { |item| pairs << [name.to_s, scalar(item)] unless item.nil? }
    else
      pairs << [name.to_s, scalar(value)]
    end
  end
  pairs
end

.scalar(value) ⇒ String

Returns the query string representation of a scalar value.

Returns:

  • (String) —

    the query string representation of a scalar value.



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# File 'lib/pago/serde.rb', line 179

def scalar(value)
  case value
  when Time then value.utc.strftime("%Y-%m-%dT%H:%M:%SZ")
  else value.to_s
  end
end

.tagged?(data, union_module) ⇒ Boolean

Returns whether the payload carries this union's discriminator.

Returns:

  • (Boolean) —

    whether the payload carries this union's discriminator.



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# File 'lib/pago/serde.rb', line 102

def tagged?(data, union_module)
  return false unless union_module.const_defined?(:DISCRIMINATOR, false)

  discriminator = union_module.const_get(:DISCRIMINATOR)
  !discriminator.nil? && !union_module.mapping.nil? && data.key?(discriminator)
end

.union(data, discriminator: nil, mapping: nil, variants: []) ⇒ Object

Resolve a union payload to one of its variants.

A discriminated union dispatches on its discriminator property. Otherwise the candidate models are scored against the payload: a candidate is eligible only when every key its schema requires is present, and the one matching the most keys wins. A union whose variants are themselves unions contributes the variant its own discriminator selects, falling back to all of them. When nothing matches, the raw payload is returned untouched rather than raising, so a variant added server side never breaks a client.



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# File 'lib/pago/serde.rb', line 64

def union(data, discriminator: nil, mapping: nil, variants: [])
  return nil if data.nil?
  return data unless data.is_a?(Hash)

  if discriminator && mapping
    variant = mapping[data[discriminator]]
    return variant.from_json(data) if variant.respond_to?(:from_json)
    return data if data.key?(discriminator)
  end

  variant = best_variant(data, candidates(data, variants))
  variant ? variant.from_json(data) : data
end

.union_module?(variant) ⇒ Boolean

Returns whether the variant is a generated union factory module.

Returns:

  • (Boolean) —

    whether the variant is a generated union factory module.



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# File 'lib/pago/serde.rb', line 128

def union_module?(variant)
  variant.is_a?(Module) && !variant.is_a?(Class) &&
    variant.respond_to?(:variants) && variant.respond_to?(:mapping)
end