gateway.go

package gateway

import (
	"net/http"
	"strings"

	"github.com/iris-contrib/gateway/gateway"

	"github.com/aws/aws-lambda-go/lambda"
	"github.com/kataras/iris/v12"
	"github.com/kataras/iris/v12/core/router"
)

// Options holds the gateway options. All fields are optional.
type Options struct {
	// When not empty then a URL parameter of that key will be used to route the requests,
	// changes the default Iris Router behavior based on the Request's URI's Path, e.g. "path".
	//
	// This is extremely useful when the deployment allows only one request path to be ran
	// under a particular lambda function.
	//
	// Defaults to empty.
	URLPathParameter string
	// When not empty then a URL parameter of that key will be used
	// to route the requests based on the given method.
	//
	// Defaults to empty.
	URLMethodParameter string
}

// New returns a pair of iris Runner and Configurator
// to convert the http application to a lambda function
// using the Apex Gateway. That allows Iris-powered web application
// to be deployed and ran on host services like Netlify and Amazon AWS.
//
// Usage:
// app := iris.New()
// [...routes]
// runner, configurator := gateway.New(gateway.Options{URLPathParameter: "path"})
// app.Run(runner, configurator)
//
// Get the original API Gateway Request object through:
// req, ok := gateway.GetRequest(ctx.Request().Context())
func New(opts Options) (iris.Runner, iris.Configurator) {
	runner := func(app *iris.Application) error {
		g := gateway.NewGateway(app)
		lambda.StartHandler(g)
		return nil
	}

	configurator := func(app *iris.Application) {
		if opts.URLPathParameter != "" || opts.URLMethodParameter != "" {
			wrapper := makeWrapper(opts.URLPathParameter, opts.URLMethodParameter)
			app.WrapRouter(wrapper)
		}
	}

	return runner, configurator
}

func makeWrapper(pathKey, methodKey string) router.WrapperFunc {
	return func(w http.ResponseWriter, r *http.Request, router http.HandlerFunc) {
		req, _ := gateway.GetRequest(r.Context())

		if pathKey != "" {
			path := req.QueryStringParameters["path"]
			if len(path) > 0 {
				if path[0] != '/' {
					path = "/" + path
				}
				r.URL.Path = path
				r.URL.RawPath = path
				r.RequestURI = path
			}
		}

		if methodKey != "" {
			method := req.QueryStringParameters["method"]
			if len(method) > 0 {
				method = strings.ToUpper(method)
				r.Method = method
			}
		}

		router(w, r)
	}
}