feat(swagger-object) : Improve object creation

Add creation of Swagger::Object by some object instance

(Related to #18)

Author: MathiusD

spec/swagger/object_spec.cr

@@ -1,4 +1,10 @@
 require "../spec_helper"
+struct Project
+  property id, name, description, vcs, open_source
+
+  def initialize(@id : Int32, @name : String, @vcs : String, @open_source : Bool, @description : String? = nil)
+  end
+end
 
 describe Swagger::Object do
   describe "#new" do
@@ -41,5 +47,24 @@ describe Swagger::Object do
       raw.properties.should be_nil
       raw.items.should eq("Comment")
     end
+
+    it "should generate schema of object from object instance" do
+      raw = Swagger::Object.create_from_instance(
+        Project.new(1, "swagger", "git", true, "Swagger contains a OpenAPI / Swagger universal documentation generator and HTTP server handler.")
+      )
+      raw.name.should eq "Project"
+      raw.type.should eq "object"
+      raw.properties.should eq [
+        Swagger::Property.new("id", "integer", "int32", example: 1, required: true),
+        Swagger::Property.new("name", example: "swagger", required: true),
+        Swagger::Property.new("vcs", example: "git", required: true),
+        Swagger::Property.new("open_source", "boolean", example: true, required: true),
+        Swagger::Property.new(
+          "description",
+          example: "Swagger contains a OpenAPI / Swagger universal documentation generator and HTTP server handler.",
+          required: false
+        ),
+      ]
+    end
   end
 end

src/swagger/object.cr

@@ -21,5 +21,32 @@ module Swagger
     def initialize(@name : String, @type : String, @properties : Array(Property)? = nil,
                    @items : (self | String)? = nil)
     end
+
+    def self.create_from_instance(reflecting instance : T, custom_name : String? = nil) forall T
+      {% begin %}
+        properties = [] of Property
+        {% for ivar in T.instance.instance_vars %}
+          {{ iname = ivar.name.stringify }}
+          swagger_data_type = Utils::SwaggerDataType.create_from_class({{ ivar.type }})
+          {{ irequired = !ivar.type.union? }}
+          value = {% if T.class? || T.struct? %} instance.{{ ivar.name }} {% else %} {{ ivar.default_value.stringify }} {% end %}
+          properties << Property.new(
+            {{ iname }},
+            swagger_data_type.type,
+            format: swagger_data_type.format,
+            {% if ivar.type <= String || ivar.type <= Int32 ||
+                  ivar.type <= Int64 || ivar.type <= Float64 ||
+                  ivar.type <= Bool %}
+              example: value,
+            {% else %}
+              example: value.to_s,
+            {% end %}
+            required: {{ irequired }}
+          )
+        {% end %}
+
+        self.new(custom_name ? custom_name.as(String) : instance.class.name, "object", properties)
+      {% end %}
+    end
   end
 end

src/swagger/utils.cr

@@ -0,0 +1,48 @@
+module Utils
+  struct SwaggerDataType
+    property type : String
+    property format : String?
+
+    def initialize(@type : String, @format : String?)
+    end
+
+    def self.create_from_class(type : T.class) forall T
+      {% begin %}
+        {% if T.union? %}
+          return self.create_from_class({{ T.union_types.find { |var| var != Nil } }})
+        {% else %}
+          # Cf https://swagger.io/specification/#data-types
+          {% if T <= String || T <= Nil %}
+            swagger_type = "string"
+            swagger_format = nil
+          {% elsif T <= Int %}
+            swagger_type = "integer"
+            {% if T <= Int32 %}
+              swagger_format = "int32"
+            {% elsif T <= Int64 %}
+              swagger_format = "int64"
+            {% else %}
+              swagger_format = nil
+            {% end %}
+          {% elsif T <= Number %}
+            swagger_type = "number"
+            {% if T <= Float32 %}
+              swagger_format = "float"
+            {% elsif T <= Float64 %}
+              swagger_format = "double"
+            {% else %}
+              swagger_format = nil
+            {% end %}
+          {% elsif T <= Bool %}
+            swagger_type = "boolean"
+            swagger_format = nil
+          {% else %}
+            swagger_type = {{ T.stringify }}
+            swagger_format = nil
+          {% end %}
+          return self.new(swagger_type, swagger_format)
+        {% end %}
+      {% end %}
+    end
+  end
+end