main.go

// Copyright (c) 2013-2014 José Carlos Nieto, https://menteslibres.net/xiam
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

// The rest package helps you creating HTTP clients for APIs with Go.

package rest

import (
	"bytes"
	"compress/gzip"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"mime/multipart"
	"net/http"
	"net/http/cookiejar"
	"net/url"
	"os"
	"path"
	"reflect"
	"strconv"
	"strings"
	"time"
)

const debugEnv = `REST_DEBUG`

const (
	debugLevelSilence = iota
	debugLevelVerbose
)

var debugLevel = debugLevelSilence

var DefaultTimeout = 5 * time.Second
var DefaultContentType = "application/x-www-form-urlencoded; charset=UTF-8"

var (
	ioReadCloserType = reflect.TypeOf((*io.ReadCloser)(nil)).Elem()
	bytesBufferType  = reflect.TypeOf((**bytes.Buffer)(nil)).Elem()
	restResponseType = reflect.TypeOf((*Response)(nil)).Elem()
)

// Response can be used as a response value, useful when you need to work with
// headers, status codes and such.
type Response struct {
	Status        string
	StatusCode    int
	Proto         string
	ProtoMajor    int
	ProtoMinor    int
	ContentLength int64
	http.Header
	Body []byte
}

// File can be used to represent a file that you'll later upload within a
// multipart request.
type File struct {
	Name string
	io.Reader
}

type FileMap map[string][]File

// MultipartMessage struct for multipart requests, you can't generate a
// MultipartMessage directly, use rest.NewMultipartMessage() instead.
type MultipartMessage struct {
	contentType string
	buf         io.Reader
}

// Client is useful in case you need to communicate with an API and you'd like
// to use the same prefix for all of your requests or in scenarios where it
// would be handy to keep a session cookie.
type Client struct {
	// These headers will be added in every request.
	Header http.Header
	// String to be added at the begining of every URL in Get(), Post(), Put()
	// and Delete() methods.
	Prefix string
	// Jar to store cookies.
	CookieJar *cookiejar.Jar
	// Timeout for request
	Timeout time.Duration
}

// DefaulClient is the default client used on top level functions like
// rest.Get(), rest.Post(), rest.Delete() and rest.Put().
var DefaultClient = new(Client)

func debugLevelEnabled(level int) bool {
	if level <= debugLevel {
		return true
	}
	return false
}

func init() {
	// If the enviroment variable REST_DEBUG is present, we enable verbose
	// logging.
	debugSetting := os.Getenv(debugEnv)
	debugLevel, _ = strconv.Atoi(debugSetting)
}

// New creates a new client, in all following GET, POST, PUT and DELETE
// requests given paths will be prefixed with the given client's prefix value.
func New(prefix string) (*Client, error) {
	var err error

	if _, err = url.Parse(prefix); err != nil {
		return nil, fmt.Errorf(ErrInvalidPrefix.Error(), err.Error())
	}

	self := new(Client)
	self.Prefix = strings.TrimRight(prefix, "/") + "/"
	self.Header = http.Header{}
	self.Timeout = DefaultTimeout

	if self.CookieJar, err = cookiejar.New(nil); err != nil {
		return nil, err
	}

	return self, nil
}

// Taken from net/http
func basicAuth(username, password string) string {
	auth := username + ":" + password
	return base64.StdEncoding.EncodeToString([]byte(auth))
}

// Sets the request's basic authorization header to be used in all requests.
func (self *Client) SetBasicAuth(username string, password string) {
	self.Header.Set("Authorization", "Basic "+basicAuth(username, password))
}

func (self *Client) newMultipartRequest(dst interface{}, method string, addr *url.URL, body *MultipartMessage) error {
	var res *http.Response
	var req *http.Request

	var err error

	if body == nil {
		return ErrCouldNotCreateMultipart
	}

	if req, err = http.NewRequest(method, addr.String(), body.buf); err != nil {
		return err
	}

	req.Header.Set("Content-Type", body.contentType)

	if res, err = self.do(req); err != nil {
		return err
	}

	if err = self.handleResponse(dst, res); err != nil {
		return err
	}

	return nil
}

func (self *Client) newRequest(dst interface{}, method string, addr *url.URL, body *strings.Reader) error {
	var res *http.Response
	var req *http.Request

	var err error

	if body == nil {
		if req, err = http.NewRequest(method, addr.String(), nil); err != nil {
			return err
		}
	} else {
		if req, err = http.NewRequest(method, addr.String(), body); err != nil {
			return err
		}
	}

	switch method {
	case "POST", "PUT":
		if req.Header.Get("Content-Type") == "" {
			req.Header.Set("Content-Type", DefaultContentType)
		}
	}

	if res, err = self.do(req); err != nil {
		return err
	}

	if err = self.handleResponse(dst, res); err != nil {
		return err
	}

	return nil
}

// Put performs a HTTP PUT request and, when complete, attempts to convert the
// response body into the datatype given by dst (a pointer to a struct, map or
// []byte array).
func (self *Client) Put(dst interface{}, path string, data url.Values) error {
	var addr *url.URL
	var err error
	var body *strings.Reader

	if addr, err = url.Parse(self.Prefix + strings.TrimLeft(path, "/")); err != nil {
		return err
	}

	if data != nil {
		body = strings.NewReader(data.Encode())
	}

	return self.newRequest(dst, "PUT", addr, body)
}

// Delete performs a HTTP DELETE request and, when complete, attempts to
// convert the response body into the datatype given by dst (a pointer to a
// struct, map or []byte array).
func (self *Client) Delete(dst interface{}, path string, data url.Values) error {
	var addr *url.URL
	var err error
	var body *strings.Reader

	if addr, err = url.Parse(self.Prefix + strings.TrimLeft(path, "/")); err != nil {
		return err
	}

	if data != nil {
		body = strings.NewReader(data.Encode())
	}

	return self.newRequest(dst, "DELETE", addr, body)
}

// PutMultipart performs a HTTP PUT multipart request and, when complete,
// attempts to convert the response body into the datatype given by dst (a
// pointer to a struct, map or []byte array).
func (self *Client) PutMultipart(dst interface{}, uri string, data *MultipartMessage) error {
	var addr *url.URL
	var err error

	if addr, err = url.Parse(self.Prefix + strings.TrimLeft(uri, "/")); err != nil {
		return err
	}

	return self.newMultipartRequest(dst, "PUT", addr, data)
}

// PostMultipart performs a HTTP POST multipart request and, when complete,
// attempts to convert the response body into the datatype given by dst (a
// pointer to a struct, map or []byte array).
func (self *Client) PostMultipart(dst interface{}, uri string, data *MultipartMessage) error {
	var addr *url.URL
	var err error

	if addr, err = url.Parse(self.Prefix + strings.TrimLeft(uri, "/")); err != nil {
		return err
	}

	return self.newMultipartRequest(dst, "POST", addr, data)
}

// PutRaw performs a HTTP PUT request with a custom body and, when complete,
// attempts to convert the response body into the datatype given by dst (a
// pointer to a struct, map or []byte array).
func (self *Client) PutRaw(dst interface{}, path string, body []byte) error {
	var addr *url.URL
	var err error
	var bodyReader *strings.Reader

	if addr, err = url.Parse(self.Prefix + strings.TrimLeft(path, "/")); err != nil {
		return err
	}

	if body != nil {
		bodyReader = strings.NewReader(string(body))
	}

	return self.newRequest(dst, "PUT", addr, bodyReader)
}

// PostRaw performs a HTTP POST request with a custom body and, when complete,
// attempts to convert the response body into the datatype given by dst (a
// pointer to a struct, map or []byte array).
func (self *Client) PostRaw(dst interface{}, path string, body []byte) error {
	var addr *url.URL
	var err error
	var bodyReader *strings.Reader

	if addr, err = url.Parse(self.Prefix + strings.TrimLeft(path, "/")); err != nil {
		return err
	}

	if body != nil {
		bodyReader = strings.NewReader(string(body))
	}

	return self.newRequest(dst, "POST", addr, bodyReader)
}

// Post performs a HTTP POST request and, when complete, attempts to convert
// the response body into the datatype given by dst (a pointer to a struct, map
// or []byte array).
func (self *Client) Post(dst interface{}, path string, data url.Values) error {
	var addr *url.URL
	var err error
	var body *strings.Reader

	if addr, err = url.Parse(self.Prefix + strings.TrimLeft(path, "/")); err != nil {
		return err
	}

	if data != nil {
		body = strings.NewReader(data.Encode())
	}

	return self.newRequest(dst, "POST", addr, body)
}

// Get performs a HTTP GET request and, when complete, attempts to convert the
// response body into the datatype given by dst (a pointer to a struct, map or
// []byte array).
func (self *Client) Get(dst interface{}, path string, data url.Values) error {
	var addr *url.URL
	var err error

	if addr, err = url.Parse(self.Prefix + strings.TrimLeft(path, "/")); err != nil {
		return err
	}

	if data != nil {
		if addr.RawQuery == "" {
			addr.RawQuery = data.Encode()
		} else {
			addr.RawQuery = addr.RawQuery + "&" + data.Encode()
		}
	}

	return self.newRequest(dst, "GET", addr, nil)
}

// NewMultipartMessage creates a *MultipartMessage based on the given parameters.
// This is useful for PostMultipart() and PutMultipart().
func NewMultipartMessage(params url.Values, filemap FileMap) (*MultipartMessage, error) {

	dst := bytes.NewBuffer(nil)

	body := multipart.NewWriter(dst)

	if filemap != nil {
		for key, files := range filemap {

			for _, file := range files {

				writer, err := body.CreateFormFile(key, path.Base(file.Name))

				if err != nil {
					return nil, err
				}

				if _, err = io.Copy(writer, file.Reader); err != nil {
					return nil, err
				}
			}
		}
	}

	if params != nil {
		for key := range params {
			for _, value := range params[key] {
				body.WriteField(key, value)
			}
		}
	}

	body.Close()

	return &MultipartMessage{body.FormDataContentType(), dst}, nil
}

// Returns the body of the request as a io.ReadCloser
func (self *Client) body(res *http.Response) (io.ReadCloser, error) {
	var body io.ReadCloser
	var err error

	if res.Header.Get("Content-Encoding") == "gzip" {
		if body, err = gzip.NewReader(res.Body); err != nil {
			return nil, err
		}
	} else {
		body = res.Body
	}

	return body, nil
}

func fromBytes(dst reflect.Value, buf []byte) error {
	var err error

	switch dst.Kind() {
	case reflect.String:
		// string
		dst.Set(reflect.ValueOf(string(buf)))
		return nil
	case reflect.Slice:
		switch dst.Type().Elem().Kind() {
		// []byte
		case reflect.Uint8:
			dst.Set(reflect.ValueOf(buf))
			return nil
		// []interface{}
		case reflect.Interface:
			t := []interface{}{}
			err = json.Unmarshal(buf, &t)

			if err == nil {
				dst.Set(reflect.ValueOf(t))
				return nil
			}
		}
	case reflect.Map:
		switch dst.Type().Elem().Kind() {
		case reflect.Interface:
			// map[string] interface{}
			m := map[string]interface{}{}

			err = json.Unmarshal(buf, &m)

			if err == nil {
				dst.Set(reflect.ValueOf(m))
				return nil
			}
		}
	}

	if err != nil {
		return err
	}

	return fmt.Errorf(ErrCouldNotConvert.Error(), reflect.TypeOf(buf), dst.Type())
}

func (self *Client) handleResponse(dst interface{}, res *http.Response) error {

	body, err := self.body(res)

	if err != nil {
		return err
	}

	if dst == nil {
		return nil
	}
	rv := reflect.ValueOf(dst)

	if rv.Kind() != reflect.Ptr || rv.IsNil() {
		return ErrDestinationNotAPointer
	}

	t := res.Header.Get("Content-Type")

	switch rv.Elem().Type() {
	case restResponseType:
		var err error

		r := Response{}

		r.Body, err = ioutil.ReadAll(body)

		if debugLevelEnabled(debugLevelVerbose) {
			log.Printf("Body:\n%s\n", string(r.Body))
		}

		if err != nil {
			return err
		}

		r.Header = res.Header
		r.Status = res.Status
		r.StatusCode = res.StatusCode
		r.Proto = res.Proto
		r.ProtoMajor = res.ProtoMajor
		r.ProtoMinor = res.ProtoMinor
		r.ContentLength = res.ContentLength

		rv.Elem().Set(reflect.ValueOf(r))
	case ioReadCloserType:
		rv.Elem().Set(reflect.ValueOf(body))
	case bytesBufferType:
		buf, err := ioutil.ReadAll(body)

		if debugLevelEnabled(debugLevelVerbose) {
			log.Printf("Body:\n%s\n", string(buf))
		}

		if err != nil {
			return err
		}

		dst := bytes.NewBuffer(buf)

		rv.Elem().Set(reflect.ValueOf(dst))
	default:
		buf, err := ioutil.ReadAll(body)

		if debugLevelEnabled(debugLevelVerbose) {
			log.Printf("Body:\n%s\n", string(buf))
		}

		if err != nil {
			return err
		}

		if strings.HasPrefix(t, "application/json") == true {
			if rv.Elem().Kind() == reflect.Struct || rv.Elem().Kind() == reflect.Map {
				err = json.Unmarshal(buf, dst)
				return err
			}
		}

		err = fromBytes(rv.Elem(), buf)

		if err != nil {
			return err
		}
	}

	return nil
}

func (self *Client) do(req *http.Request) (*http.Response, error) {
	client := new(http.Client)

	// Adding cookie jar
	if self.CookieJar != nil {
		client.Jar = self.CookieJar
	}

	// Copying headers
	for k := range self.Header {
		req.Header.Set(k, self.Header.Get(k))
	}

	if req.Body == nil {
		req.Header.Del("Content-Type")
		req.Header.Del("Content-Length")
	}

	client.Timeout = self.Timeout

	res, err := client.Do(req)

	if debugLevelEnabled(debugLevelVerbose) {

		log.Printf("Fetching %v\n", req.URL.String())

		log.Printf("> %s %s", req.Method, req.Proto)
		for k := range req.Header {
			for kk := range req.Header[k] {
				log.Printf("> %s: %s", k, req.Header[k][kk])
			}
		}

		log.Printf("< %s %s", res.Proto, res.Status)
		for k := range res.Header {
			for kk := range res.Header[k] {
				log.Printf("< %s: %s", k, res.Header[k][kk])
			}
		}

		log.Printf("\n")
	}

	return res, err
}

// Get performs a HTTP GET request using the default client and, when complete,
// attempts to convert the response body into the datatype given by dst (a
// pointer to a struct, map or []byte array).
func Get(dest interface{}, uri string, data url.Values) error {
	return DefaultClient.Get(dest, uri, data)
}

// Post performs a HTTP POST request using the default client and, when
// complete, attempts to convert the response body into the datatype given by
// dst (a pointer to a struct, map or []byte array).
func Post(dest interface{}, uri string, data url.Values) error {
	return DefaultClient.Post(dest, uri, data)
}

// Put performs a HTTP PUT request using the default client and, when complete,
// attempts to convert the response body into the datatype given by dst (a
// pointer to a struct, map or []byte array).
func Put(dest interface{}, uri string, data url.Values) error {
	return DefaultClient.Put(dest, uri, data)
}

// Delete performs a HTTP DELETE request using the default client and, when
// complete, attempts to convert the response body into the datatype given by
// dst (a pointer to a struct, map or []byte array).
func Delete(dest interface{}, uri string, data url.Values) error {
	return DefaultClient.Delete(dest, uri, data)
}

// PostMultipart performs a HTTP POST multipart request using the default
// client and, when complete, attempts to convert the response body into the
// datatype given by dst (a pointer to a struct, map or []byte array).
func PostMultipart(dest interface{}, uri string, data *MultipartMessage) error {
	return DefaultClient.PostMultipart(dest, uri, data)
}

// PutMultipart performs a HTTP PUT multipart request using the default client
// and, when complete, attempts to convert the response body into the datatype
// given by dst (a pointer to a struct, map or []byte array).
func PutMultipart(dest interface{}, uri string, data *MultipartMessage) error {
	return DefaultClient.PutMultipart(dest, uri, data)
}