From 5311dee4b19fd60eab0ea5efd5a09f96a5219627 Mon Sep 17 00:00:00 2001
From: Vidhu Kant Sharma <vidhukant@vidhukant.com>
Date: Sat, 25 Nov 2023 20:04:12 +0530
Subject: first commit

---
 maltoken.go | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 maltoken.go

(limited to 'maltoken.go')

diff --git a/maltoken.go b/maltoken.go
new file mode 100644
index 0000000..d73ea79
--- /dev/null
+++ b/maltoken.go
@@ -0,0 +1,110 @@
+/*
+maltoken - A go package for the MyAnimeList OAuth mechanism
+Copyright © 2023 Vidhu Kant Sharma <vidhukant@vidhukant.com>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package maltoken
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"html"
+	"math/rand"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
+var SuccessHTML = "<p>Success! You may close this tab now.</p>"
+var BadRequestHTML = "<p>Invalid request.</p>"
+var ErrHTML = "<p>MyAnimeList responded with an error: %s</p>"
+
+func codeChallenge() string {
+	rand.Seed(time.Now().UnixNano())
+	b := make([]rune, 128)
+	for i := range b {
+		b[i] = letterRunes[rand.Intn(len(letterRunes))]
+	}
+	return string(b)
+}
+
+func GetChallengeLink(clientId string) (string, string) {
+	challenge := codeChallenge()
+	return challenge, "https://myanimelist.net/v1/oauth2/authorize?response_type=code&client_id=" + clientId + "&code_challenge=" + challenge
+}
+
+func Listen(clientId, verifier string, port int) (map[string]interface{}, error) {
+	var res map[string]interface{}
+	var e error
+
+	mux := http.NewServeMux()
+	server := &http.Server{
+		Addr: fmt.Sprintf(":%d", port),
+		Handler: mux,
+	}
+
+	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		code, codeExists := r.URL.Query()["code"]
+		if !codeExists {
+			fmt.Fprintf(w, BadRequestHTML)
+			return
+		}
+
+		resp, err := http.PostForm("https://myanimelist.net/v1/oauth2/token", url.Values {
+			"client_id": {clientId},
+			"code_verifier": {verifier},
+			"grant_type": {"authorization_code"},
+			"code": {code[0]},
+		})
+		if err != nil {
+			// error while making post request
+			e = err
+			go server.Shutdown(context.Background())
+			return
+		}
+
+		json.NewDecoder(resp.Body).Decode(&res)
+
+		if res["error"] != nil {
+			// MyAnimeList returned error
+			errMsg := fmt.Sprintf("%v (%v)", res["message"], res["error"])
+			e = errors.New(errMsg)
+
+			if strings.Contains(ErrHTML, "%s") {
+				fmt.Fprintf(w, ErrHTML, html.EscapeString(errMsg))
+			} else {
+				fmt.Fprintf(w, ErrHTML)
+			}
+
+			go server.Shutdown(context.Background())
+			return
+		}
+
+		fmt.Fprintf(w, SuccessHTML)
+		go server.Shutdown(context.Background())
+	})
+
+	err := server.ListenAndServe()
+	if err != nil && err != http.ErrServerClosed {
+		e = err
+	}
+
+	return res, e
+}
-- 
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