add file storage: metadata schema, minio upload/download, content-type extension mapping

- add files_metadata and files_metadata_connections tables with CRUD helpers
- add FileMetadata type and Sha256Hash typedef; replace Media struct
- add minio upload, presigned download URL, and key generation
- fix bucket existence check to use FileStorageBucketName instead of hardcoded "main"
- fix files_metadata_connections table name and trailing comma in DDL
- fix column name original -> name in files_metadata schema
- add canonical MIME-to-extension map with .unk fallback
- add FileDownloadLinkTtl constant (24h)

packages/minio/minio.go

@@ -2,20 +2,47 @@ package minio
 
 import (
 	"context"
-	"go-socket/packages/globals"
 	"io"
+	"mime"
+	"net/url"
+
+	"go-socket/packages/globals"
 
 	"github.com/minio/minio-go/v7"
 	"github.com/minio/minio-go/v7/pkg/credentials"
 )
 
-var dbConn *minio.Client
+var minClient *minio.Client
+
+var canonicalExt = map[string]string{
+	"image/jpeg":      ".jpg",
+	"image/png":       ".png",
+	"image/gif":       ".gif",
+	"image/webp":      ".webp",
+	"video/mp4":       ".mp4",
+	"application/pdf": ".pdf",
+}
+
+func extensionFromContentType(ct string) string {
+	if ext, ok := canonicalExt[ct]; ok {
+		return ext
+	}
+	exts, err := mime.ExtensionsByType(ct)
+	if err != nil || len(exts) == 0 {
+		return ".unk"
+	}
+	return exts[0]
+}
+
+func getKey(hash string, contentType string) string {
+	return hash + extensionFromContentType(contentType)
+}
 
 func MinInit() {
 	ctx := context.Background()
 
 	var err error
-	dbConn, err = minio.New("localhost:9000", &minio.Options{
+	minClient, err = minio.New("localhost:9000", &minio.Options{
 		Creds:  credentials.NewStaticV4("root", "change_to_env", ""),
 		Secure: false,
 	}) // TODO change in production
@@ -23,22 +50,29 @@ func MinInit() {
 		panic(err)
 	}
 
-	exists, err := dbConn.BucketExists(ctx, "main")
+	exists, err := minClient.BucketExists(ctx, globals.FileStorageBucketName)
 	if err != nil {
 		panic(err)
 	}
 
 	if !exists {
-		err = dbConn.MakeBucket(ctx, globals.FileStorageBucketName, minio.MakeBucketOptions{})
+		err = minClient.MakeBucket(ctx, globals.FileStorageBucketName, minio.MakeBucketOptions{})
 		if err != nil {
 			return
 		}
 	}
-}
-
-func putFile(ctx context.Context, key string, reader io.Reader, size uint32, contentType string) error {
-	dbConn.PutObject(ctx, globals.FileStorageBucketName, key, reader, int64(size), minio.PutObjectOptions{
-		ContentType: contentType,
-	})
 
 }
+
+func upload(ctx context.Context, key string, body io.Reader, size int64, contentType string) error {
+	_, err := minClient.PutObject(ctx, globals.FileStorageBucketName, key, body, size,
+		minio.PutObjectOptions{
+			ContentType: contentType,
+		})
+	return err
+}
+
+func getDownloadUrl(ctx context.Context, key string) (*url.URL, error) {
+	u, err := minClient.PresignedGetObject(ctx, globals.FileStorageBucketName, key, globals.FileDownloadLinkTtl, nil)
+	return u, err
+}