From fcd6477ec35d7aff7cdb9367490e19aa44c1017a Mon Sep 17 00:00:00 2001
From: Maximilian <max@mpatterson.xyz>
Date: Mon, 13 Feb 2023 23:41:45 -0600
Subject: [PATCH] Migration implementation, auto migrate when starting program

---
 database/migrate.go  | 105 +++++++++++++++++++++++++++++++++++++++++++
 main.go              |  10 ++++-
 models/migrations.go |  21 +++++++++
 3 files changed, 135 insertions(+), 1 deletion(-)
 create mode 100644 database/migrate.go
 create mode 100644 models/migrations.go

diff --git a/database/migrate.go b/database/migrate.go
new file mode 100644
index 0000000..489fe49
--- /dev/null
+++ b/database/migrate.go
@@ -0,0 +1,105 @@
+package database
+
+import (
+	"GoWeb/app"
+	"errors"
+	"fmt"
+	"github.com/lib/pq"
+	"log"
+	"reflect"
+)
+
+// Migrate given a dummy object of any type, it will create a table with the same name as the type and create columns with the same name as the fields of the object
+func Migrate(app *app.App, anyStruct interface{}) error {
+	valueOfStruct := reflect.ValueOf(anyStruct)
+	typeOfStruct := valueOfStruct.Type()
+
+	tableName := typeOfStruct.Name()
+	err := createTable(app, tableName)
+	if err != nil {
+		return err
+	}
+
+	for i := 0; i < valueOfStruct.NumField(); i++ {
+		fieldType := typeOfStruct.Field(i)
+		fieldName := fieldType.Name
+		if fieldName != "Id" && fieldName != "id" {
+			err := createColumn(app, tableName, fieldName, fieldType.Type.Name())
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+// createTable creates a table with the given name if it doesn't exist, it is assumed that id will be the primary key
+func createTable(app *app.App, tableName string) error {
+	sanitizedTableQuery := fmt.Sprintf("CREATE TABLE IF NOT EXISTS \"%s\" (\"Id\" serial primary key)", tableName)
+
+	_, err := app.Db.Query(sanitizedTableQuery)
+	if err != nil {
+		log.Println("Error creating table: " + tableName)
+		return err
+	}
+
+	log.Println("Table created successfully (or already exists): " + tableName)
+	return nil
+}
+
+// createColumn creates a column with the given name and type if it doesn't exist
+func createColumn(app *app.App, tableName, columnName, columnType string) error {
+	postgresType, err := getPostgresType(columnType)
+	if err != nil {
+		log.Println("Error creating column: " + columnName + " in table: " + tableName + " with type: " + postgresType)
+		return err
+	}
+
+	sanitizedTableName := pq.QuoteIdentifier(tableName)
+	query := fmt.Sprintf("ALTER TABLE %s ADD COLUMN IF NOT EXISTS \"%s\" %s", sanitizedTableName, columnName, postgresType)
+
+	_, err = app.Db.Query(query)
+	if err != nil {
+		log.Println("Error creating column: " + columnName + " in table: " + tableName + " with type: " + postgresType)
+		return err
+	}
+
+	log.Println("Column created successfully (or already exists):", columnName)
+
+	return nil
+}
+
+// Given a type in Go, return the corresponding type in Postgres
+func getPostgresType(goType string) (string, error) {
+	switch goType {
+	case "int":
+	case "int32":
+	case "uint":
+	case "uint32":
+		return "integer", nil
+	case "int64":
+	case "uint64":
+		return "bigint", nil
+	case "int16":
+	case "int8":
+	case "uint16":
+	case "uint8":
+	case "byte":
+		return "smallint", nil
+	case "string":
+		return "text", nil
+	case "float64":
+		return "double precision", nil
+	case "bool":
+		return "boolean", nil
+	case "time.Time":
+		return "timestamp", nil
+	case "[]byte":
+		return "bytea", nil
+	default:
+		return "text", nil
+	}
+
+	return "", errors.New("Unknown type: " + goType)
+}
diff --git a/main.go b/main.go
index 9b91ef6..5ea320c 100644
--- a/main.go
+++ b/main.go
@@ -4,6 +4,7 @@ import (
 	"GoWeb/app"
 	"GoWeb/config"
 	"GoWeb/database"
+	"GoWeb/models"
 	"GoWeb/routes"
 	"embed"
 	"log"
@@ -37,8 +38,15 @@ func main() {
 	file, err := os.OpenFile("logs/"+time.Now().Format("2006-01-02")+".log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
 	log.SetOutput(file)
 
-	// Connect to database
+	// Connect to database and run migrations
 	appLoaded.Db = database.ConnectDB(&appLoaded)
+	if appLoaded.Config.Db.AutoMigrate {
+		err = models.RunAllMigrations(&appLoaded)
+		if err != nil {
+			log.Println(err)
+			return
+		}
+	}
 
 	// Define Routes
 	routes.GetRoutes(&appLoaded)
diff --git a/models/migrations.go b/models/migrations.go
new file mode 100644
index 0000000..c76fce4
--- /dev/null
+++ b/models/migrations.go
@@ -0,0 +1,21 @@
+package models
+
+import (
+	"GoWeb/app"
+	"GoWeb/database"
+)
+
+// RunAllMigrations defines the structs that should be represented in the database
+func RunAllMigrations(app *app.App) error {
+	// Declare new dummy user for reflection
+	user := User{
+		Id:        1, // Id is handled automatically, but it is added here to show it will be skipped during column creation
+		Username:  "migrate",
+		Password:  "migrate",
+		AuthToken: "migrate",
+		CreatedAt: "2021-01-01 00:00:00",
+		UpdatedAt: "2021-01-01 00:00:00",
+	}
+
+	return database.Migrate(app, user)
+}