Improve Telegram integration

- Remove dependency on `go-telegram-bot-api`
- Add new options: optional topic ID, disable page preview, disable notifications
- Add new button to go to article

internal/integration/telegrambot/client.go

@@ -0,0 +1,174 @@
+// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package telegrambot // import "miniflux.app/v2/internal/integration/telegrambot"
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"time"
+
+	"miniflux.app/v2/internal/version"
+)
+
+const (
+	defaultClientTimeout = 10 * time.Second
+	telegramAPIEndpoint  = "https://api.telegram.org"
+
+	MarkdownFormatting   = "Markdown"
+	MarkdownV2Formatting = "MarkdownV2"
+	HTMLFormatting       = "HTML"
+)
+
+type Client struct {
+	botToken string
+	chatID   string
+}
+
+func NewClient(botToken, chatID string) *Client {
+	return &Client{
+		botToken: botToken,
+		chatID:   chatID,
+	}
+}
+
+// Specs: https://core.telegram.org/bots/api#getme
+func (c *Client) GetMe() (*User, error) {
+	endpointURL, err := url.JoinPath(telegramAPIEndpoint, "/bot"+c.botToken, "/getMe")
+	if err != nil {
+		return nil, fmt.Errorf("telegram: unable to join base URL and path: %w", err)
+	}
+
+	request, err := http.NewRequest(http.MethodGet, endpointURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("telegram: unable to create request: %v", err)
+	}
+
+	request.Header.Set("Accept", "application/json")
+	request.Header.Set("User-Agent", "Miniflux/"+version.Version)
+
+	httpClient := &http.Client{Timeout: defaultClientTimeout}
+	response, err := httpClient.Do(request)
+	if err != nil {
+		return nil, fmt.Errorf("telegram: unable to send request: %v", err)
+	}
+	defer response.Body.Close()
+
+	var userResponse UserResponse
+	if err := json.NewDecoder(response.Body).Decode(&userResponse); err != nil {
+		return nil, fmt.Errorf("telegram: unable to decode user response: %w", err)
+	}
+
+	if !userResponse.Ok {
+		return nil, fmt.Errorf("telegram: unable to send message: %s (error code is %d)", userResponse.Description, userResponse.ErrorCode)
+	}
+
+	return &userResponse.Result, nil
+}
+
+// Specs: https://core.telegram.org/bots/api#sendmessage
+func (c *Client) SendMessage(message *MessageRequest) (*Message, error) {
+	endpointURL, err := url.JoinPath(telegramAPIEndpoint, "/bot"+c.botToken, "/sendMessage")
+	if err != nil {
+		return nil, fmt.Errorf("telegram: unable to join base URL and path: %w", err)
+	}
+
+	requestBody, err := json.Marshal(message)
+	if err != nil {
+		return nil, fmt.Errorf("telegram: unable to encode request body: %v", err)
+	}
+
+	request, err := http.NewRequest(http.MethodPost, endpointURL, bytes.NewReader(requestBody))
+	if err != nil {
+		return nil, fmt.Errorf("telegram: unable to create request: %v", err)
+	}
+
+	request.Header.Set("Content-Type", "application/json")
+	request.Header.Set("Accept", "application/json")
+	request.Header.Set("User-Agent", "Miniflux/"+version.Version)
+
+	httpClient := &http.Client{Timeout: defaultClientTimeout}
+	response, err := httpClient.Do(request)
+	if err != nil {
+		return nil, fmt.Errorf("telegram: unable to send request: %v", err)
+	}
+	defer response.Body.Close()
+
+	var messageResponse MessageResponse
+	if err := json.NewDecoder(response.Body).Decode(&messageResponse); err != nil {
+		return nil, fmt.Errorf("telegram: unable to decode discovery response: %w", err)
+	}
+
+	if !messageResponse.Ok {
+		return nil, fmt.Errorf("telegram: unable to send message: %s (error code is %d)", messageResponse.Description, messageResponse.ErrorCode)
+	}
+
+	return &messageResponse.Result, nil
+}
+
+type InlineKeyboard struct {
+	InlineKeyboard []InlineKeyboardRow `json:"inline_keyboard"`
+}
+
+type InlineKeyboardRow []*InlineKeyboardButton
+
+type InlineKeyboardButton struct {
+	Text string `json:"text"`
+	URL  string `json:"url,omitempty"`
+}
+
+type User struct {
+	ID                      int64  `json:"id"`
+	IsBot                   bool   `json:"is_bot"`
+	FirstName               string `json:"first_name"`
+	LastName                string `json:"last_name"`
+	Username                string `json:"username"`
+	LanguageCode            string `json:"language_code"`
+	IsPremium               bool   `json:"is_premium"`
+	CanJoinGroups           bool   `json:"can_join_groups"`
+	CanReadAllGroupMessages bool   `json:"can_read_all_group_messages"`
+	SupportsInlineQueries   bool   `json:"supports_inline_queries"`
+}
+
+type Chat struct {
+	ID    int64  `json:"id"`
+	Type  string `json:"type"`
+	Title string `json:"title"`
+}
+
+type Message struct {
+	MessageID       int64 `json:"message_id"`
+	From            User  `json:"from"`
+	Chat            Chat  `json:"chat"`
+	MessageThreadID int64 `json:"message_thread_id"`
+	Date            int64 `json:"date"`
+}
+
+type BaseResponse struct {
+	Ok          bool   `json:"ok"`
+	ErrorCode   int    `json:"error_code"`
+	Description string `json:"description"`
+}
+
+type UserResponse struct {
+	BaseResponse
+	Result User `json:"result"`
+}
+
+type MessageRequest struct {
+	ChatID                string          `json:"chat_id"`
+	MessageThreadID       int64           `json:"message_thread_id,omitempty"`
+	Text                  string          `json:"text"`
+	ParseMode             string          `json:"parse_mode,omitempty"`
+	DisableWebPagePreview bool            `json:"disable_web_page_preview"`
+	DisableNotification   bool            `json:"disable_notification"`
+	ReplyMarkup           *InlineKeyboard `json:"reply_markup,omitempty"`
+}
+
+type MessageResponse struct {
+	BaseResponse
+	Result Message `json:"result"`
+}