From 52e986e644bfb6661aaf6e0a7d729dad95e18b8e Mon Sep 17 00:00:00 2001
From: Unlock Music Dev <dev@unlock-music.dev>
Date: Mon, 5 Dec 2022 00:06:38 +0800
Subject: [PATCH] feat(qmc): support .mflach on darwin

---
 algo/qmc/key_mmkv.go | 92 ++++++++++++++++++++++++++++++++++++++++++++
 algo/qmc/qmc.go      | 12 ++++--
 2 files changed, 101 insertions(+), 3 deletions(-)
 create mode 100644 algo/qmc/key_mmkv.go

diff --git a/algo/qmc/key_mmkv.go b/algo/qmc/key_mmkv.go
new file mode 100644
index 0000000..b7f89d8
--- /dev/null
+++ b/algo/qmc/key_mmkv.go
@@ -0,0 +1,92 @@
+package qmc
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+
+	"unlock-music.dev/mmkv"
+)
+
+var streamKeyVault mmkv.MMKV
+
+func readKeyFromMMKV(file string) ([]byte, error) {
+	if file == "" {
+		return nil, errors.New("file path is required while reading key from mmkv")
+	}
+
+	//goland:noinspection GoBoolExpressions
+	if runtime.GOOS != "darwin" {
+		return nil, errors.New("mmkv vault not supported on this platform")
+	}
+
+	if streamKeyVault == nil {
+		mmkvDir, err := getRelativeMMKVDir(file)
+		if err != nil {
+			mmkvDir, err = getDefaultMMKVDir()
+			if err != nil {
+				return nil, fmt.Errorf("mmkv key valut not found: %w", err)
+			}
+		}
+		mmkv.InitializeMMKV(mmkvDir)
+		streamKeyVault = mmkv.MMKVWithID("MMKVStreamEncryptId")
+	}
+
+	buf := streamKeyVault.GetBytes(file)
+	if len(buf) == 0 {
+		_, partName := filepath.Split(file)
+		keys := streamKeyVault.AllKeys()
+		for _, key := range keys {
+			if strings.HasSuffix(key, partName) {
+				buf = streamKeyVault.GetBytes(key)
+				break
+			}
+		}
+	}
+
+	if len(buf) == 0 {
+		return nil, errors.New("key not found in mmkv vault")
+	}
+
+	return deriveKey(buf)
+}
+
+func getRelativeMMKVDir(file string) (string, error) {
+	mmkvDir := filepath.Join(filepath.Dir(file), "../mmkv")
+	if _, err := os.Stat(mmkvDir); err != nil {
+		return "", fmt.Errorf("stat default mmkv dir: %w", err)
+	}
+
+	keyFile := filepath.Join(mmkvDir, "MMKVStreamEncryptId")
+	if _, err := os.Stat(keyFile); err != nil {
+		return "", fmt.Errorf("stat default mmkv file: %w", err)
+	}
+
+	return mmkvDir, nil
+}
+
+func getDefaultMMKVDir() (string, error) {
+	homeDir, err := os.UserHomeDir()
+	if err != nil {
+		return "", fmt.Errorf("get user home dir: %w", err)
+	}
+
+	mmkvDir := filepath.Join(
+		homeDir,
+		"Library/Containers/com.tencent.QQMusicMac/Data", // todo: make configurable
+		"Library/Application Support/QQMusicMac/mmkv",
+	)
+	if _, err := os.Stat(mmkvDir); err != nil {
+		return "", fmt.Errorf("stat default mmkv dir: %w", err)
+	}
+
+	keyFile := filepath.Join(mmkvDir, "MMKVStreamEncryptId")
+	if _, err := os.Stat(keyFile); err != nil {
+		return "", fmt.Errorf("stat default mmkv file: %w", err)
+	}
+
+	return mmkvDir, nil
+}
diff --git a/algo/qmc/qmc.go b/algo/qmc/qmc.go
index 96e56c7..987d01a 100644
--- a/algo/qmc/qmc.go
+++ b/algo/qmc/qmc.go
@@ -14,7 +14,8 @@ import (
 )
 
 type Decoder struct {
-	raw io.ReadSeeker // raw is the original file reader
+	raw    io.ReadSeeker // raw is the original file reader
+	params *common.DecoderParams
 
 	audio    io.Reader // audio is the encrypted audio data
 	audioLen int       // audioLen is the audio data length
@@ -39,7 +40,7 @@ func (d *Decoder) Read(p []byte) (int, error) {
 }
 
 func NewDecoder(p *common.DecoderParams) common.Decoder {
-	return &Decoder{raw: p.Reader}
+	return &Decoder{raw: p.Reader, params: p}
 }
 
 func (d *Decoder) Validate() error {
@@ -97,7 +98,12 @@ func (d *Decoder) validateDecode() error {
 	return nil
 }
 
-func (d *Decoder) searchKey() error {
+func (d *Decoder) searchKey() (err error) {
+	if d.params.Extension == ".mflach" {
+		d.decodedKey, err = readKeyFromMMKV(d.params.FilePath)
+		return err
+	}
+
 	fileSizeM4, err := d.raw.Seek(-4, io.SeekEnd)
 	if err != nil {
 		return err