apex/up

package proxy

import (
    "encoding/base64"
    "encoding/json"
    "net/http"
    "net/url"
    "strconv"
    "strings"

    "github.com/pkg/errors"
)

// NewRequest returns a new http.Request from the given Lambda event.
func NewRequest(e *Input) (*http.Request, error) {
    // path
    u, err := url.Parse(e.Path)
    if err != nil {
        return nil, errors.Wrap(err, "parsing path")
    }

    // querystring
    q := u.Query()
    for k, v := range e.QueryStringParameters {
        q.Set(k, v)
    }
    u.RawQuery = q.Encode()

    // base64 encoded body
    body := e.Body
    if e.IsBase64Encoded {
        b, err := base64.StdEncoding.DecodeString(body)
        if err != nil {
            return nil, errors.Wrap(err, "decoding base64 body")
        }
        body = string(b)
    }

    // new request
    req, err := http.NewRequest(e.HTTPMethod, u.String(), strings.NewReader(body))
    if err != nil {
        return nil, errors.Wrap(err, "creating request")
    }

    // remote addr
    req.RemoteAddr = e.RequestContext.Identity.SourceIP

    // header fields
    for k, v := range e.Headers {
        req.Header.Set(k, v)
    }

    // content-length
    if req.Header.Get("Content-Length") == "" && body != "" {
        req.Header.Set("Content-Length", strconv.Itoa(len(body)))
    }

    // custom fields
    b, _ := json.Marshal(e.RequestContext)
    req.Header.Set("X-Context", string(b))
    req.Header.Set("X-Request-Id", e.RequestContext.RequestID)
    req.Header.Set("X-Stage", e.RequestContext.Stage)

    // host
    req.URL.Host = req.Header.Get("Host")
    req.Host = req.URL.Host

    return req, nil
}