OpenAPI

Nova's OpenAPI support automatically generates and serves an OpenAPI 3.0 specification for your routes, plus an embedded Swagger UI. It provides:

• Automatic Spec Generation: Reflects Go structs, route definitions, parameters, request bodies, and responses into a valid OpenAPI 3.0 document.
• Component Schemas: Deduplicates and reuses schema definitions for structs, arrays, maps, and basic types.
• Path & Operation Mapping: Converts your router’s methods (Get, Post, etc.) into OpenAPI paths with OperationObject.
• Parameter Inference: Generates path, query, header, and cookie parameters, including required flags and examples.
• Request & Response Bodies: Maps RequestBody and Responses options to JSON media types and schemas.
• Servers Configuration: Embeds one or more server definitions (URLs) into the spec.
• Spec Endpoint: Serves the JSON spec at a configurable path (e.g. /openapi.json).
• Swagger UI: Embeds Swagger UI assets under a prefix (e.g. /docs), complete with static asset handling.

Table of Contents

1. Getting Started
2. Core Concepts
• OpenAPIConfig
• RouteOptions and ResponseOption
• Schema Generation
3. Registering and Serving the Spec
4. Serving Swagger UI
5. Full Example

Getting Started

To enable OpenAPI support in your Nova-powered app:

1. Import Nova’s router and OpenAPI helpers:

import "github.com/xlc-dev/nova/nova"

1. Define your routes with RouteOptions (including tags, summary, parameters, request/response schemas).
2. Call:

router.ServeOpenAPISpec("/openapi.json", nova.OpenAPIConfig{
 Title:       "My Nova API",
 Version:     "1.0.0",
 Description: "This is a sample API built with Nova.",
 Servers:     []nova.Server{{URL: fmt.Sprintf("http://%s:%d", host, port)}},
})
router.ServeSwaggerUI("/docs")

1. Start your server as usual: nova.Serve(ctx, router).

Core Concepts

OpenAPIConfig

Holds top‐level metadata for the spec:

type OpenAPIConfig struct {
  Title       string    // API title (required)
  Version     string    // Spec version (required)
  Description string    // Optional description
  Servers     []Server  // List of servers (URL + optional description)
}

RouteOptions and ResponseOption

Attach OpenAPI metadata when registering routes:

type RouteOptions struct {
  Tags        []string            // Operation tags (grouping)
  Summary     string              // Short summary
  Description string              // Detailed description
  OperationID string              // Unique operation ID
  Deprecated  bool                // Mark as deprecated
  RequestBody interface{}         // Request schema
  Responses   map[int]ResponseOption
  Parameters  []ParameterOption
}

type ResponseOption struct {
  Description string      // Response description
  Body        interface{} // Schema
}

• Responses: map HTTP status codes to ResponseOption.
• Parameters: define additional in:path|query|header|cookie parameters.

Schema Generation

Nova inspects Go types via reflection to build JSON Schemas:

• Structs:
• Generates components.schemas entries.
• Honors json:"...", description:"...", example:"..." tags.
• Marks fields non‐nullable or required unless omitempty.
• Primitives: maps Go kinds to type/format (e.g., time.Time → string + date‐time).
• Arrays & Slices:type: array + items.
• Maps:type: object + additionalProperties.
• References: reuses named schemas when the same struct type appears multiple times.

Registering and Serving the Spec

// After defining routes on your `router`:
router.ServeOpenAPISpec("/openapi.json", nova.OpenAPIConfig{
  Title:       "My API",
  Version:     "2.0.0",
  Description: "Auto‐generated OpenAPI spec",
  Servers: []nova.Server{
    {URL: "https://api.example.com"},
  },
})

• Endpoint: performs a GET /openapi.json, returning JSON with Content-Type: application/json.
• Internal: calls GenerateOpenAPISpec(router, config) under the hood.

Serving Swagger UI

Nova embeds the official Swagger UI and serves it statically:

router.ServeSwaggerUI("/docs")

• Access:
• GET /docs → redirects to /docs/ and serves index.html.
• GET /docs/{file} → serves CSS, JS, and favicon from embedded assets.
• Customization: To point the UI at your spec URL, pass query parameters to the /docs/index.html link (e.g. ?url=/openapi.json).

Full Example

package main

import (
	"fmt"
	"log"
	"net/http"
	"os"
	"strconv"
	"time"

	"github.com/xlc-dev/nova/nova"
)

func main() {
	cli, err := nova.NewCLI(&nova.CLI{
		Name:        "item-api",
		Version:     "1.0.0",
		Description: "A simple item API with OpenAPI & Swagger UI",
		GlobalFlags: []nova.Flag{},
		Action: func(ctx *nova.Context) error {
			router := nova.NewRouter()

			type Item struct {
				ID        int       `json:"id" description:"Item ID"`
				Name      string    `json:"name" example:"Widget"`
				CreatedAt time.Time `json:"createdAt" description:"Creation timestamp"`
			}

			router.Get("/items/{id}", func(w http.ResponseWriter, r *http.Request) {
				idStr := router.URLParam(r, "id")
				id, _ := strconv.Atoi(idStr)
				w.Header().Set("Content-Type", "application/json")
				fmt.Fprintf(w,
					`{"id":%d,"name":"Item%d","createdAt":"%q"}`,
					id, id, time.Now().Format(time.RFC3339),
				)
			}, &nova.RouteOptions{
				Tags:    []string{"Items"},
				Summary: "Retrieve an item by ID",
				Parameters: []nova.ParameterOption{{
					Name:        "id",
					In:          "path",
					Description: "ID of the item to retrieve",
					Schema:      int(0),
				}},
				Responses: map[int]nova.ResponseOption{
					200: {Description: "Success", Body: &Item{}},
					404: {Description: "Not found"},
				},
			})

			router.ServeOpenAPISpec("/openapi.json", nova.OpenAPIConfig{
				Title:       "Item API",
				Version:     "1.0.0",
				Description: "API for managing items",
				Servers: []nova.Server{
					{URL: fmt.Sprintf("http://%s:%d", "localhost", 8080)},
				},
			})

			router.ServeSwaggerUI("/docs")

			return nova.Serve(ctx, router)
		},
	})
	if err != nil {
		log.Fatalf("failed to initialize CLI: %v", err)
	}
	if err := cli.Run(os.Args); err != nil {
		log.Fatalf("runtime error: %v", err)
	}
}