From 4e82fbddc1d8582fe33f66fb759573f767dbd1f7 Mon Sep 17 00:00:00 2001
From: "Alexander \"Arav\" Andreev" <me@arav.su>
Date: Mon, 22 May 2023 23:05:52 +0400
Subject: [PATCH] Added functionality to delete unused categories from a DB.

---
 cmd/dwelling-home/main.go                     |  1 +
 internal/http/api_handlers.go                 |  9 +++++
 pkg/mindflow/database/sqlite/db.go            | 40 +++++++++++++++----
 .../sqlite/queries/categoryDeleteUnused.sql   |  6 +++
 pkg/mindflow/mindflow.go                      |  1 +
 5 files changed, 49 insertions(+), 8 deletions(-)
 create mode 100644 pkg/mindflow/database/sqlite/queries/categoryDeleteUnused.sql

diff --git a/cmd/dwelling-home/main.go b/cmd/dwelling-home/main.go
index 65f3c79..94fb664 100644
--- a/cmd/dwelling-home/main.go
+++ b/cmd/dwelling-home/main.go
@@ -105,6 +105,7 @@ func main() {
 	mindflowApi := http.NewMindflowApiHandlers(mindflowDB)
 
 	srv.POST("/api/mindflow", mindflowApi.New)
+	srv.DELETE("/api/mindflow/category", mindflowApi.DeleteUnusedCategories)
 	srv.PATCH("/api/mindflow/:id", mindflowApi.Edit)
 	srv.DELETE("/api/mindflow/:id", mindflowApi.Delete)
 
diff --git a/internal/http/api_handlers.go b/internal/http/api_handlers.go
index 75891b3..0300313 100644
--- a/internal/http/api_handlers.go
+++ b/internal/http/api_handlers.go
@@ -3,6 +3,7 @@ package http
 import (
 	"fmt"
 	"image/jpeg"
+	"log"
 	"net/http"
 	"strconv"
 	"strings"
@@ -252,6 +253,14 @@ func (h *MindflowApiHandlers) New(w http.ResponseWriter, r *http.Request) {
 	http.Redirect(w, r, "/mindflow/admin", http.StatusMovedPermanently)
 }
 
+func (h *MindflowApiHandlers) DeleteUnusedCategories(w http.ResponseWriter, r *http.Request) {
+	if err := h.db.DeleteUnusedCategories(); err != nil {
+		log.Println("Cannot delete unused categories:", err)
+		http.Error(w, "Cannot delete unused categories: "+err.Error(), http.StatusInternalServerError)
+		return
+	}
+}
+
 func (h *MindflowApiHandlers) Edit(w http.ResponseWriter, r *http.Request) {
 	var post *mindflow.Post
 	var err error
diff --git a/pkg/mindflow/database/sqlite/db.go b/pkg/mindflow/database/sqlite/db.go
index 61ae632..2398b6b 100644
--- a/pkg/mindflow/database/sqlite/db.go
+++ b/pkg/mindflow/database/sqlite/db.go
@@ -22,6 +22,8 @@ var (
 	queryCategoryNew string
 	//go:embed queries/categoryDelete.sql
 	queryCategoryDelete string
+	//go:embed queries/categoryDeleteUnused.sql
+	queryCategoryDeleteUnused string
 	//go:embed queries/postGetAll.sql
 	queryPostGetAll string
 	//go:embed queries/postNew.sql
@@ -33,14 +35,15 @@ var (
 )
 
 var (
-	stmtCategoryById   *sql.Stmt
-	stmtCategoryGetAll *sql.Stmt
-	stmtCategoryNew    *sql.Stmt
-	stmtCategoryDelete *sql.Stmt
-	stmtPostGetAll     *sql.Stmt
-	stmtPostNew        *sql.Stmt
-	stmtPostEdit       *sql.Stmt
-	stmtPostDelete     *sql.Stmt
+	stmtCategoryById         *sql.Stmt
+	stmtCategoryGetAll       *sql.Stmt
+	stmtCategoryNew          *sql.Stmt
+	stmtCategoryDelete       *sql.Stmt
+	stmtCategoryDeleteUnused *sql.Stmt
+	stmtPostGetAll           *sql.Stmt
+	stmtPostNew              *sql.Stmt
+	stmtPostEdit             *sql.Stmt
+	stmtPostDelete           *sql.Stmt
 )
 
 func initDBStatements(db *sql.DB) error {
@@ -71,6 +74,11 @@ func initDBStatements(db *sql.DB) error {
 		return errors.Wrap(err, "failed to prepare queryCategoryDelete")
 	}
 
+	stmtCategoryDeleteUnused, err = db.Prepare(queryCategoryDeleteUnused)
+	if err != nil {
+		return errors.Wrap(err, "failed to prepare queryCategoryDeleteUnused")
+	}
+
 	stmtPostGetAll, err = db.Prepare(queryPostGetAll)
 	if err != nil {
 		return errors.Wrap(err, "failed to prepare queryPostGetAll")
@@ -288,6 +296,22 @@ func (s *SQLiteMindflow) DeleteCategory(id int64) (err error) {
 	return nil
 }
 
+func (s *SQLiteMindflow) DeleteUnusedCategories() (err error) {
+	tx, err := s.db.Begin()
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+
+	if _, err = tx.Stmt(stmtCategoryDeleteUnused).Exec(); err != nil {
+		return err
+	}
+
+	tx.Commit()
+
+	return nil
+}
+
 func (s *SQLiteMindflow) Close() error {
 	stmtCategoryById.Close()
 	stmtCategoryGetAll.Close()
diff --git a/pkg/mindflow/database/sqlite/queries/categoryDeleteUnused.sql b/pkg/mindflow/database/sqlite/queries/categoryDeleteUnused.sql
new file mode 100644
index 0000000..6f1a3b5
--- /dev/null
+++ b/pkg/mindflow/database/sqlite/queries/categoryDeleteUnused.sql
@@ -0,0 +1,6 @@
+DELETE FROM `category`
+ WHERE `category`.`category_id` NOT IN (
+    SELECT `category_id`
+      FROM `post`
+     GROUP BY `post`.`category_id`
+    HAVING COUNT(`post`.`post_id`) > 0 );
\ No newline at end of file
diff --git a/pkg/mindflow/mindflow.go b/pkg/mindflow/mindflow.go
index 1dad008..5978438 100644
--- a/pkg/mindflow/mindflow.go
+++ b/pkg/mindflow/mindflow.go
@@ -43,5 +43,6 @@ type Mindflow interface {
 	Categories() ([]Category, error)
 	NewCategory(name string) (int64, error)
 	GetCategoryByID(id int64) (string, error)
+	DeleteUnusedCategories() error
 	Close() error
 }