From 1f258ea17e6f83a5b4a03bdc0594cc329010d710 Mon Sep 17 00:00:00 2001
From: mikestefanello <mike.stefanello@gmail.com>
Date: Fri, 3 Dec 2021 07:20:01 -0500
Subject: [PATCH] Added pager.

---
 controllers/page.go |  7 ++++++
 pager/pager.go      | 56 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+)
 create mode 100644 pager/pager.go

diff --git a/controllers/page.go b/controllers/page.go
index e2631d1..b438583 100644
--- a/controllers/page.go
+++ b/controllers/page.go
@@ -5,10 +5,15 @@ import (
 	"net/http"
 
 	"goweb/msg"
+	"goweb/pager"
 
 	"github.com/labstack/echo/v4"
 )
 
+const (
+	DefaultItemsPerPage = 20
+)
+
 type Page struct {
 	AppName    string
 	Title      string
@@ -25,6 +30,7 @@ type Page struct {
 		Description string
 		Keywords    []string
 	}
+	Pager pager.Pager
 }
 
 func NewPage(c echo.Context) Page {
@@ -33,6 +39,7 @@ func NewPage(c echo.Context) Page {
 		Reverse:    c.Echo().Reverse,
 		Path:       c.Request().URL.Path,
 		StatusCode: http.StatusOK,
+		Pager:      pager.NewPager(c, DefaultItemsPerPage),
 	}
 
 	p.IsHome = p.Path == "/"
diff --git a/pager/pager.go b/pager/pager.go
new file mode 100644
index 0000000..d9b87ef
--- /dev/null
+++ b/pager/pager.go
@@ -0,0 +1,56 @@
+package pager
+
+import (
+	"math"
+	"strconv"
+
+	"github.com/labstack/echo/v4"
+)
+
+type Pager struct {
+	Items        int
+	Page         int
+	ItemsPerPage int
+	Pages        int
+}
+
+func NewPager(c echo.Context, itemsPerPage int) Pager {
+	p := Pager{
+		ItemsPerPage: itemsPerPage,
+		Page:         1,
+	}
+
+	if page := c.QueryParam("page"); page != "" {
+		if pageInt, err := strconv.Atoi(page); err != nil {
+			if pageInt > 0 {
+				p.Page = pageInt
+			}
+		}
+	}
+
+	return p
+}
+
+func (p *Pager) SetItems(items int) {
+	p.Items = items
+	p.Pages = int(math.Ceil(float64(items) / float64(p.ItemsPerPage)))
+
+	if p.Page > p.Pages {
+		p.Page = p.Pages
+	}
+}
+
+func (p *Pager) IsBeginning() bool {
+	return p.Page == 1
+}
+
+func (p *Pager) IsEnd() bool {
+	return p.Page >= p.Pages
+}
+
+func (p *Pager) GetOffset() int {
+	if p.Page == 0 {
+		p.Page = 1
+	}
+	return (p.Page - 1) * p.ItemsPerPage
+}