http: implement a simplified HTTP client

1 files changed, 206 insertions, 0 deletions

diff --git a/lib/http/client.go b/lib/http/client.go
new file mode 100644
index 00000000..b027ef5f
--- /dev/null
+++ b/lib/http/client.go
@@ -0,0 +1,206 @@
+// Copyright 2020, Shulhan <m.shulhan@gmail.com>. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"mime/multipart"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+//
+// Client is a wrapper for standard http.Client with simplified
+// functionalities.
+//
+type Client struct {
+	*http.Client
+	serverURL string
+}
+
+//
+// NewClient create and initialize new Client connection using serverURL to
+// minimize repetition.
+// The serverURL is any path that is static and will never changes during
+// request to server.
+//
+func NewClient(serverURL string) (client *Client) {
+	client = &Client{
+		serverURL: serverURL,
+		Client: &http.Client{
+			Transport: &http.Transport{
+				Proxy: http.ProxyFromEnvironment,
+				DialContext: (&net.Dialer{
+					Timeout:   30 * time.Second,
+					KeepAlive: 30 * time.Second,
+					DualStack: true,
+				}).DialContext,
+				ForceAttemptHTTP2:     true,
+				MaxIdleConns:          100,
+				IdleConnTimeout:       90 * time.Second,
+				TLSHandshakeTimeout:   10 * time.Second,
+				ExpectContinueTimeout: 1 * time.Second,
+			},
+		},
+	}
+
+	return client
+}
+
+//
+// Get send the GET request to server using path and params as query
+// parameters.
+// On success, it will return the response body.
+//
+func (client *Client) Get(path string, params url.Values) (
+	resBody []byte, err error,
+) {
+	if params != nil {
+		path += "?" + params.Encode()
+	}
+
+	httpRes, err := client.Client.Get(client.serverURL + path)
+	if err != nil {
+		return nil, fmt.Errorf("http: Get: %w", err)
+	}
+
+	resBody, err = ioutil.ReadAll(httpRes.Body)
+	if err != nil {
+		return nil, fmt.Errorf("http: Get: %w", err)
+	}
+
+	err = httpRes.Body.Close()
+	if err != nil {
+		return nil, fmt.Errorf("http: Get: %w", err)
+	}
+
+	return resBody, nil
+}
+
+//
+// PostForm send the POST request to path using
+// "application/x-www-form-urlencoded".
+//
+func (client *Client) PostForm(path string, params url.Values) (
+	resBody []byte, err error,
+) {
+	body := strings.NewReader(params.Encode())
+
+	url := client.serverURL + path
+	httpRes, err := client.Client.Post(url, ContentTypeForm, body)
+	if err != nil {
+		return nil, fmt.Errorf("Post: %w", err)
+	}
+
+	resBody, err = ioutil.ReadAll(httpRes.Body)
+	if err != nil {
+		return nil, fmt.Errorf("Post: %w", err)
+	}
+
+	err = httpRes.Body.Close()
+	if err != nil {
+		return nil, fmt.Errorf("Post: %w", err)
+	}
+
+	return resBody, nil
+}
+
+//
+// PostFormData send the POST request to path with all parameters is send
+// using "multipart/form-data".
+//
+func (client *Client) PostFormData(path string, params map[string][]byte) (
+	resBody []byte, err error,
+) {
+	url := client.serverURL + path
+
+	contentType, body, err := generateFormData(params)
+	if err != nil {
+		return nil, fmt.Errorf("http: PostFormData: %w", err)
+	}
+
+	httpRes, err := client.Client.Post(url, contentType,
+		strings.NewReader(body))
+	if err != nil {
+		return nil, fmt.Errorf("http: PostFormData: %w", err)
+	}
+
+	resBody, err = ioutil.ReadAll(httpRes.Body)
+	if err != nil {
+		return nil, fmt.Errorf("http: PostFormData: %w", err)
+	}
+
+	err = httpRes.Body.Close()
+	if err != nil {
+		return nil, fmt.Errorf("http: PostFormData: %w", err)
+	}
+
+	return resBody, nil
+}
+
+//
+// PostJSON send the POST request with content type set to "application/json"
+// and params encoded automatically to JSON.
+//
+func (client *Client) PostJSON(path string, params interface{}) (
+	resBody []byte, err error,
+) {
+	paramsJSON, err := json.Marshal(params)
+	if err != nil {
+		return nil, fmt.Errorf("PostJSON: %w", err)
+	}
+
+	url := client.serverURL + path
+
+	httpRes, err := client.Client.Post(url, ContentTypeJSON,
+		bytes.NewReader(paramsJSON))
+	if err != nil {
+		return nil, fmt.Errorf("PostJSON: %w", err)
+	}
+
+	resBody, err = ioutil.ReadAll(httpRes.Body)
+	if err != nil {
+		return nil, fmt.Errorf("PostJSON: %w", err)
+	}
+
+	err = httpRes.Body.Close()
+	if err != nil {
+		return nil, fmt.Errorf("PostJSON: %w", err)
+	}
+
+	return resBody, nil
+}
+
+func generateFormData(params map[string][]byte) (
+	contentType, body string, err error,
+) {
+	sb := new(strings.Builder)
+	w := multipart.NewWriter(sb)
+	for k, v := range params {
+		part, err := w.CreateFormField(k)
+		if err != nil {
+			return "", "", err
+		}
+		_, err = part.Write(v)
+		if err != nil {
+			return "", "", err
+		}
+	}
+
+	err = w.Close()
+	if err != nil {
+		return "", "", err
+	}
+
+	contentType = w.FormDataContentType()
+
+	return contentType, sb.String(), nil
+}