From 9efb9402cd318520cc6e74150f7e67dbeb75c24e Mon Sep 17 00:00:00 2001
From: Ali Assar <150648843+Ali-Assar@users.noreply.github.com>
Date: Sat, 16 Mar 2024 17:58:44 +0330
Subject: [PATCH] Add Pagination (#50)

Here is the things I've done for pagination:

I edited the database query to support pagination
Then I saw home handler use GetPosts so i modified that handler in
app.go
and at the end I Changed SetupRoutes in app.go
---
 app/app.go                                   | 20 ++++++++++++++++++--
 database/database.go                         |  7 ++++---
 tests/app_tests/endpoint_tests/index_test.go |  6 +++---
 tests/mocks/mocks.go                         |  6 +++---
 4 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/app/app.go b/app/app.go
index c74adbf..fcd6858 100644
--- a/app/app.go
+++ b/app/app.go
@@ -3,6 +3,7 @@ package app
 import (
 	"bytes"
 	"net/http"
+	"strconv"
 	"time"
 
 	"github.com/gin-gonic/gin"
@@ -26,6 +27,9 @@ func SetupRoutes(app_settings common.AppSettings, database database.Database) *g
 	addCachableHandler(r, "GET", "/contact", contactHandler, &cache, app_settings, database)
 	addCachableHandler(r, "GET", "/post/:id", postHandler, &cache, app_settings, database)
 
+	// Add the pagination route as a cacheable endpoint
+	addCachableHandler(r, "GET", "/page/:num", homeHandler, &cache, app_settings, database)
+
 	// DO not cache as it needs to handlenew form values
 	r.POST("/contact-send", makeContactFormHandler())
 
@@ -81,7 +85,19 @@ func addCachableHandler(e *gin.Engine, method string, endpoint string, generator
 // / This function will act as the handler for
 // / the home page
 func homeHandler(c *gin.Context, settings common.AppSettings, db database.Database) ([]byte, error) {
-	posts, err := db.GetPosts()
+	pageNum := 0 // Default to page 0
+	if pageNumQuery := c.Param("num"); pageNumQuery != "" {
+		num, err := strconv.Atoi(pageNumQuery)
+		if err == nil && num > 0 {
+			pageNum = num
+		} else {
+			log.Error().Msgf("Invalid page number: %s", pageNumQuery)
+		}
+	}
+	limit := 10 // or whatever limit you want
+	offset := max((pageNum-1)*limit, 0)
+
+	posts, err := db.GetPosts(limit, offset)
 	if err != nil {
 		return nil, err
 	}
@@ -92,7 +108,7 @@ func homeHandler(c *gin.Context, settings common.AppSettings, db database.Databa
 
 	err = index_view.Render(c, html_buffer)
 	if err != nil {
-		log.Error().Msgf("could not render index: %v", err)
+		log.Error().Msgf("Could not render index: %v", err)
 		return []byte{}, err
 	}
 
diff --git a/database/database.go b/database/database.go
index 405316b..07e570f 100644
--- a/database/database.go
+++ b/database/database.go
@@ -11,7 +11,7 @@ import (
 )
 
 type Database interface {
-	GetPosts() ([]common.Post, error)
+	GetPosts(int, int) ([]common.Post, error)
 	GetPost(post_id int) (common.Post, error)
 	AddPost(title string, excerpt string, content string) (int, error)
 	ChangePost(id int, title string, excerpt string, content string) error
@@ -28,8 +28,9 @@ type SqlDatabase struct {
 
 // / This function gets all the posts from the current
 // / database connection.
-func (db SqlDatabase) GetPosts() (all_posts []common.Post, err error) {
-	rows, err := db.Connection.Query("SELECT title, excerpt, id FROM posts;")
+func (db SqlDatabase) GetPosts(limit int, offset int) (all_posts []common.Post, err error) {
+	query := "SELECT title, excerpt, id FROM posts LIMIT ? OFFSET ?;"
+	rows, err := db.Connection.Query(query, limit, offset)
 	if err != nil {
 		return make([]common.Post, 0), err
 	}
diff --git a/tests/app_tests/endpoint_tests/index_test.go b/tests/app_tests/endpoint_tests/index_test.go
index 79c73c4..d20583f 100644
--- a/tests/app_tests/endpoint_tests/index_test.go
+++ b/tests/app_tests/endpoint_tests/index_test.go
@@ -24,7 +24,7 @@ func TestIndexSuccess(t *testing.T) {
 	}
 
 	database_mock := mocks.DatabaseMock{
-		GetPostsHandler: func() ([]common.Post, error) {
+		GetPostsHandler: func(limit int, offset int) ([]common.Post, error) {
 			return []common.Post{
 				{
 					Title:   "TestPost",
@@ -38,7 +38,7 @@ func TestIndexSuccess(t *testing.T) {
 
 	r := app.SetupRoutes(app_settings, database_mock)
 	w := httptest.NewRecorder()
-	req, _ := http.NewRequest("GET", "/", nil)
+	req, _ := http.NewRequest("GET", "/page/0", nil)
 	r.ServeHTTP(w, req)
 
 	assert.Equal(t, http.StatusOK, w.Code)
@@ -57,7 +57,7 @@ func TestIndexFailToGetPosts(t *testing.T) {
 	}
 
 	database_mock := mocks.DatabaseMock{
-		GetPostsHandler: func() ([]common.Post, error) {
+		GetPostsHandler: func(limit int, offset int) ([]common.Post, error) {
 			return []common.Post{}, fmt.Errorf("invalid")
 		},
 	}
diff --git a/tests/mocks/mocks.go b/tests/mocks/mocks.go
index 2de05fb..8c04f07 100644
--- a/tests/mocks/mocks.go
+++ b/tests/mocks/mocks.go
@@ -8,11 +8,11 @@ import (
 
 type DatabaseMock struct {
 	GetPostHandler  func(int) (common.Post, error)
-	GetPostsHandler func() ([]common.Post, error)
+	GetPostsHandler func(int, int) ([]common.Post, error)
 }
 
-func (db DatabaseMock) GetPosts() ([]common.Post, error) {
-	return db.GetPostsHandler()
+func (db DatabaseMock) GetPosts(limit int, offset int) ([]common.Post, error) {
+	return db.GetPostsHandler(limit, offset)
 }
 
 func (db DatabaseMock) GetPost(post_id int) (common.Post, error) {