feat(media): download and decrypt media

internal/deezer/media.go

@@ -1,5 +1,13 @@
 package deezer
 
+import (
+	"fmt"
+	"net/http"
+	"os"
+
+	"github.com/mathismqn/godeez/internal/crypto"
+)
+
 type Media struct {
 	Errors []MediaError `json:"errors"`
 	Data   []struct {
@@ -25,3 +33,67 @@ type Source struct {
 	URL      string `json:"url"`
 	Provider string `json:"provider"`
 }
+
+const ChunkSize = 2048
+
+func (m *Media) Download(filename, songID string) error {
+	url := m.Data[0].Media[0].Sources[0].URL
+
+	resp, err := http.Get(url)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("unexpected status code: %d", resp.StatusCode)
+	}
+
+	file, err := os.Create(filename)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	key := crypto.GetBlowfishKey(songID)
+	buffer := make([]byte, ChunkSize)
+
+	for chunk := 0; ; chunk++ {
+		totalRead := 0
+		for totalRead < ChunkSize {
+			n, err := resp.Body.Read(buffer[totalRead:])
+			if err != nil {
+				if err.Error() == "EOF" {
+					break
+				}
+				return err
+			}
+
+			if n > 0 {
+				totalRead += n
+			}
+		}
+
+		if totalRead == 0 {
+			break
+		}
+
+		if chunk%3 == 0 && totalRead == ChunkSize {
+			buffer, err = crypto.DecryptBlowfish(buffer, key)
+			if err != nil {
+				return err
+			}
+		}
+
+		_, err = file.Write(buffer[:totalRead])
+		if err != nil {
+			return err
+		}
+
+		if totalRead < ChunkSize {
+			break
+		}
+	}
+
+	return nil
+}