From 33b5b73ab283d0465c26789b0f08c1bd1aece196 Mon Sep 17 00:00:00 2001
From: qowevisa <qowevisa@gmail.com>
Date: Thu, 31 Oct 2024 11:07:34 +0200
Subject: [PATCH] Add generic CRUD interface for UserIdentifiable entities

---
 handlers/user_scope_CRUD.go | 171 ++++++++++++++++++++++++++++++++++++
 1 file changed, 171 insertions(+)
 create mode 100644 handlers/user_scope_CRUD.go

diff --git a/handlers/user_scope_CRUD.go b/handlers/user_scope_CRUD.go
new file mode 100644
index 0000000..174f10a
--- /dev/null
+++ b/handlers/user_scope_CRUD.go
@@ -0,0 +1,171 @@
+package handlers
+
+import (
+	"fmt"
+
+	"git.qowevisa.me/Qowevisa/gonuts/db"
+	"git.qowevisa.me/Qowevisa/gonuts/types"
+	"github.com/gin-gonic/gin"
+)
+
+// GetHandler returns a generic handler for retrieving an entity by ID.
+func GetHandler[T db.UserIdentifiable, R any](transform func(inp T) R) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		userID, err := GetUserID(c)
+		if err != nil {
+			c.JSON(500, types.ErrorResponse{Message: err.Error()})
+			return
+		}
+
+		id, err := ParseID(c)
+		if err != nil {
+			c.JSON(400, types.ErrorResponse{Message: "Invalid request"})
+			return
+		}
+
+		dbc := db.Connect()
+		// NOTE: DO NOT fuck with this
+		// only by pure luck with GORM First function we don't have SEGFAULT
+		var entity T
+		if err := dbc.First(&entity, id).Error; err != nil {
+			c.JSON(400, types.ErrorResponse{Message: err.Error()})
+			return
+		}
+
+		if entity.GetID() == 0 {
+			c.JSON(401, types.ErrorResponse{Message: fmt.Sprintf("Entity with %d id was not found", id)})
+			return
+		}
+		if entity.GetUserID() != userID {
+			c.JSON(403, types.ErrorResponse{Message: fmt.Sprintf("This entity is not yours")})
+			return
+		}
+
+		ret := transform(entity)
+
+		c.JSON(200, ret)
+	}
+}
+
+// CreateHandler returns a generic handler for creating an entity.
+func CreateHandler[T db.UserIdentifiable, R any](entity T, applyChanges func(src R, dst T)) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		userID, err := GetUserID(c)
+		if err != nil {
+			c.JSON(500, types.ErrorResponse{Message: err.Error()})
+			return
+		}
+
+		var updates R
+		if err := c.ShouldBindJSON(&updates); err != nil {
+			c.JSON(400, types.ErrorResponse{Message: "Invalid request"})
+			return
+		}
+
+		applyChanges(updates, entity)
+		entity.SetUserID(userID)
+		dbc := db.Connect()
+		if err := dbc.Create(entity).Error; err != nil {
+			c.JSON(500, types.ErrorResponse{Message: err.Error()})
+			return
+		}
+
+		c.JSON(200, types.Message{Message: fmt.Sprintf("Entity created with ID %d", entity.GetID())})
+	}
+}
+
+// UpdateHandler returns a generic handler for updating an entity.
+func UpdateHandler[T db.UserIdentifiable, R any](
+	// Filter used to apply only needed changes from srt to dst before updating dst
+	filter func(src R, dst T),
+	// Transform used to output only needed fields from inp to response
+	transform func(inp T) R) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		userID, err := GetUserID(c)
+		if err != nil {
+			c.JSON(500, types.ErrorResponse{Message: err.Error()})
+			return
+		}
+
+		id, err := ParseID(c)
+		if err != nil {
+			c.JSON(400, types.ErrorResponse{Message: "Invalid request"})
+			return
+		}
+
+		dbc := db.Connect()
+		// NOTE: DO NOT fuck with this
+		// only by pure luck with GORM First function we don't have SEGFAULT
+		var entity T
+		if err := dbc.First(&entity, id).Error; err != nil {
+			c.JSON(400, types.ErrorResponse{Message: err.Error()})
+			return
+		}
+
+		if entity.GetID() == 0 {
+			c.JSON(401, types.ErrorResponse{Message: fmt.Sprintf("Entity with %d id was not found", id)})
+			return
+		}
+		if entity.GetUserID() != userID {
+			c.JSON(403, types.ErrorResponse{Message: fmt.Sprintf("This entity is not yours")})
+			return
+		}
+
+		var updates R
+		if err := c.ShouldBindJSON(&updates); err != nil {
+			c.JSON(400, types.ErrorResponse{Message: "Invalid request"})
+			return
+		}
+
+		filter(updates, entity)
+		if err := dbc.Save(&entity).Error; err != nil {
+			c.JSON(500, types.ErrorResponse{Message: err.Error()})
+			return
+		}
+
+		ret := transform(entity)
+		c.JSON(200, ret)
+	}
+}
+
+// DeleteHandler returns a generic handler for deleting an entity by ID.
+func DeleteHandler[T db.UserIdentifiable]() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		userID, err := GetUserID(c)
+		if err != nil {
+			c.JSON(500, types.ErrorResponse{Message: err.Error()})
+			return
+		}
+
+		id, err := ParseID(c)
+		if err != nil {
+			c.JSON(400, types.ErrorResponse{Message: "Invalid request"})
+			return
+		}
+
+		dbc := db.Connect()
+		// NOTE: DO NOT fuck with this
+		// only by pure luck with GORM First function we don't have SEGFAULT
+		var entity T
+		if err := dbc.First(&entity, id).Error; err != nil {
+			c.JSON(400, types.ErrorResponse{Message: err.Error()})
+			return
+		}
+
+		if entity.GetID() == 0 {
+			c.JSON(401, types.ErrorResponse{Message: fmt.Sprintf("Entity with %d id was not found", id)})
+			return
+		}
+		if entity.GetUserID() != userID {
+			c.JSON(403, types.ErrorResponse{Message: fmt.Sprintf("This entity is not yours")})
+			return
+		}
+
+		if err := dbc.Delete(entity).Error; err != nil {
+			c.JSON(500, types.ErrorResponse{Message: err.Error()})
+			return
+		}
+
+		c.JSON(200, types.Message{Message: fmt.Sprintf("Entity with ID %d deleted", entity.GetID())})
+	}
+}