// 2018 Rackspace, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"): you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.

// Package raxmiddleware provides various middleware functions for use with gin
package raxmiddleware

import (
	"fmt"
	"os"
	"runtime"

	"github.com/gin-gonic/gin"
	"github.com/gofrs/uuid"
)

// CtxUUID defines the key to store in the gin.Context
const CtxUUID = "X-Request-Id"

// Boiler method serves as the method to read and set request and response headers as per current standards.
// Some of the response headers defined here are either set by best practices, or recommended as-per the
// Rackspace Engineering Handbook:
//   See: https://pages.github.rackspace.com/engineering/handbook/guides/api-design.html
//   Note: The www-authenticate header will be set in the specific authentication middleware.
func Boiler() gin.HandlerFunc {
	return func(c *gin.Context) {
		// Set the Server response header with the information about software, GO version and
		// application version, used by the origin server to handle the request.
		c.Header("Server", fmt.Sprintf("%s %s/%s", runtime.Version(), os.Getenv("APP"), os.Getenv("API_VER")))
		c.Header("X-Host", os.Getenv("VM"))

		if c.GetHeader("X-Request-Id") != "" {
			if id, err := uuid.FromString(c.GetHeader("X-Request-Id")); err == nil {
				c.Set(CtxUUID, id)
				c.Header("X-Request-Id", id.String())
				return
			}
		}
		id, _ := uuid.NewV4()
		c.Set(CtxUUID, id)
		c.Header("X-Request-Id", id.String())
	}
}