GoBlog/notifications.go

package main

import (
	"database/sql"
	"fmt"
	"log"
	"net/http"
	"reflect"
	"strconv"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/vcraescu/go-paginator"
)

const notificationsPath = "/notifications"

type notification struct {
	ID   int
	Time int64
	Text string
}

func sendNotification(text string) {
	n := &notification{
		Time: time.Now().Unix(),
		Text: text,
	}
	if err := saveNotification(n); err != nil {
		log.Println("Failed to save notification:", err.Error())
	}
	if an := appConfig.Notifications; an != nil {
		if tg := an.Telegram; tg != nil && tg.Enabled {
			err := sendTelegramMessage(n.Text, "", tg.BotToken, tg.ChatID)
			if err != nil {
				log.Println("Failed to send Telegram notification:", err.Error())
			}
		}
	}
}

func saveNotification(n *notification) error {
	if _, err := appDbExec("insert into notifications (time, text) values (@time, @text)", sql.Named("time", n.Time), sql.Named("text", n.Text)); err != nil {
		return err
	}
	return nil
}

type notificationsRequestConfig struct {
	offset, limit int
}

func buildNotificationsQuery(config *notificationsRequestConfig) (query string, args []interface{}) {
	args = []interface{}{}
	query = "select id, time, text from notifications order by id desc"
	if config.limit != 0 || config.offset != 0 {
		query += " limit @limit offset @offset"
		args = append(args, sql.Named("limit", config.limit), sql.Named("offset", config.offset))
	}
	return
}

func getNotifications(config *notificationsRequestConfig) ([]*notification, error) {
	notifications := []*notification{}
	query, args := buildNotificationsQuery(config)
	rows, err := appDbQuery(query, args...)
	if err != nil {
		return nil, err
	}
	for rows.Next() {
		n := &notification{}
		err = rows.Scan(&n.ID, &n.Time, &n.Text)
		if err != nil {
			return nil, err
		}
		notifications = append(notifications, n)
	}
	return notifications, nil
}

func countNotifications(config *notificationsRequestConfig) (count int, err error) {
	query, params := buildNotificationsQuery(config)
	query = "select count(*) from (" + query + ")"
	row, err := appDbQueryRow(query, params...)
	if err != nil {
		return
	}
	err = row.Scan(&count)
	return
}

type notificationsPaginationAdapter struct {
	config *notificationsRequestConfig
	nums   int64
}

func (p *notificationsPaginationAdapter) Nums() (int64, error) {
	if p.nums == 0 {
		nums, _ := countNotifications(p.config)
		p.nums = int64(nums)
	}
	return p.nums, nil
}

func (p *notificationsPaginationAdapter) Slice(offset, length int, data interface{}) error {
	modifiedConfig := *p.config
	modifiedConfig.offset = offset
	modifiedConfig.limit = length

	notifications, err := getNotifications(&modifiedConfig)
	reflect.ValueOf(data).Elem().Set(reflect.ValueOf(&notifications).Elem())
	return err
}

func notificationsAdmin(w http.ResponseWriter, r *http.Request) {
	// Adapter
	pageNoString := chi.URLParam(r, "page")
	pageNo, _ := strconv.Atoi(pageNoString)
	p := paginator.New(&notificationsPaginationAdapter{config: &notificationsRequestConfig{}}, 10)
	p.SetPage(pageNo)
	var notifications []*notification
	err := p.Results(&notifications)
	if err != nil {
		serveError(w, r, err.Error(), http.StatusInternalServerError)
		return
	}
	// Navigation
	var hasPrev, hasNext bool
	var prevPage, nextPage int
	var prevPath, nextPath string
	hasPrev, _ = p.HasPrev()
	if hasPrev {
		prevPage, _ = p.PrevPage()
	} else {
		prevPage, _ = p.Page()
	}
	if prevPage < 2 {
		prevPath = notificationsPath
	} else {
		prevPath = fmt.Sprintf("%s/page/%d", notificationsPath, prevPage)
	}
	hasNext, _ = p.HasNext()
	if hasNext {
		nextPage, _ = p.NextPage()
	} else {
		nextPage, _ = p.Page()
	}
	nextPath = fmt.Sprintf("%s/page/%d", notificationsPath, nextPage)
	// Render
	render(w, r, templateNotificationsAdmin, &renderData{
		Data: map[string]interface{}{
			"Notifications": notifications,
			"HasPrev":       hasPrev,
			"HasNext":       hasNext,
			"Prev":          slashIfEmpty(prevPath),
			"Next":          slashIfEmpty(nextPath),
		},
	})
}