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package main
import (
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"crypto/sha256"
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"encoding/json"
"fmt"
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"io"
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"io/fs"
"log"
"net/http"
"os"
"strings"
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"sync"
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)
// Information for a LineageOS ROM available for download
type LineageOSROM struct {
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Datetime int ` json:"datetime" ` // Unix timestamp - i.e. 1685907926
Filename string ` json:"filename" ` // .zip filename - i.e. lineage-20.0-20230604-UNOFFICIAL-sunfish.zip
ID string ` json:"id" ` // A unique identifier such as a SHA256 hash of the .zip - i.e. 603bfc02e403e5fd1bf9ed74383f1d6c9ec7fb228d03c4b37753033d79488e93
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Romtype string ` json:"romtype" ` // i.e. NIGHTLY or UNOFFICIAL
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Size int ` json:"size" ` // size of .zip file in bytes
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URL string ` json:"url" ` // Accessible URL where client could download the .zip file
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Version string ` json:"version" ` // LineageOS version - i.e. 20.0
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}
// The HTTP response JSON should be a JSON array of lineageOSROMS available for download
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type HTTPResponseJSON struct {
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Response [ ] LineageOSROM ` json:"response" `
}
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// Caches data about available ROMs in memory so we don't need to reference the filesystem for each request
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type ROMCache struct {
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ROMs [ ] LineageOSROM ` json:"roms" `
Cached map [ string ] bool ` json:"-" ` // to quickly lookup if a file is already cached
sync . Mutex ` json:"-" ` // We have multiple goroutines that may be accessing this data simultaneously, so we much lock / unlock it to prevent race conditions
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}
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const (
romDirectory = "public" // directory where ROMs are available for download
buildOutDirectory = "out" // directory from build system containing artifacts which we can move to romDirectory
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cacheFile = "public/romcache.json"
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)
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var ( // evil global variable
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romCache ROMCache
)
func init ( ) {
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// intialize and load ROMCache from file - so we don't have to rehash all the big files again
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romCache = ROMCache { }
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romCache . Cached = make ( map [ string ] bool )
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romCacheJson , err := os . ReadFile ( cacheFile )
if err != nil {
if err != os . ErrNotExist { // don't care if it doesn't exist, just skip it
log . Printf ( "failed to read romCache file : %v" , err )
}
} else { // if opening the file's successful, then load the contents
err = json . Unmarshal ( romCacheJson , & romCache )
if err != nil {
log . Printf ( "failed to unmarshal romCacheJson to romCache struct: %v" , err )
}
}
for _ , rom := range romCache . ROMs {
romCache . Cached [ rom . ID ] = true
log . Printf ( "loaded cached file: %s" , rom . Filename )
}
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// Check if any new build artifacts and preload the romCache
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moveBuildArtifacts ( )
go updateROMCache ( )
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}
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// HTTP Server
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func main ( ) {
//Public static files
http . Handle ( "/public/" , http . StripPrefix ( "/public/" , http . FileServer ( http . Dir ( "public" ) ) ) )
// ROM list
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http . HandleFunc ( "/" , lineageOSROMListHandler )
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log . Print ( "Service listening on :8080" )
log . Fatal ( http . ListenAndServe ( ":8080" , nil ) )
}
// Reads the ROM files on the filesystem and populates a slice of linageOSROMs
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func updateROMCache ( ) {
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log . Printf ( "updating ROM cache" )
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f , err := os . Open ( romDirectory )
if err != nil {
log . Printf ( "failed to open ROM directory: %v" , err )
return
}
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defer f . Close ( )
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files , err := f . ReadDir ( 0 )
if err != nil {
log . Printf ( "failed to read files in directory: %v" , err )
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return
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}
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for i , v := range files {
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isLineageROM , splitName := isLineageROMZip ( v )
if ! isLineageROM {
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continue
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}
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// skip already cached files
romCache . Lock ( )
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if _ , ok := romCache . Cached [ v . Name ( ) ] ; ok {
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romCache . Unlock ( )
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continue
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}
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romCache . Unlock ( )
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go func ( v fs . DirEntry ) {
fInfo , err := v . Info ( )
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if err != nil {
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log . Printf ( "failed to get file info '%s': %v" , v . Name ( ) , err )
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return
}
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fileHash , err := hashFile ( fmt . Sprintf ( "%s/%s" , romDirectory , v . Name ( ) ) )
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if err != nil {
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log . Printf ( "ingore zip file '%s', failed to get sha256 hash: %v" , v . Name ( ) , err )
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return
}
lineageOSROM := LineageOSROM {
Datetime : int ( fInfo . ModTime ( ) . Unix ( ) ) ,
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Filename : v . Name ( ) ,
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ID : fileHash ,
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Romtype : splitName [ 3 ] , // UNOFFICIAL
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Size : int ( fInfo . Size ( ) ) ,
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URL : fmt . Sprintf ( "https://lineageos-ota.deadbeef.codes/public/%s" , v . Name ( ) ) ,
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Version : splitName [ 1 ] ,
}
romCache . Lock ( )
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if _ , ok := romCache . Cached [ v . Name ( ) ] ; ok { // it's possible another goroutine was already working to cache the file, so we check at the end
romCache . Unlock ( )
return
}
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romCache . ROMs = append ( romCache . ROMs , lineageOSROM )
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romCache . Cached [ v . Name ( ) ] = true
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romCache . Unlock ( )
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} ( files [ i ] )
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}
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// save file to disk for next startup so we don't have to rehash all the files again
romCache . Lock ( )
romCacheJson , err := json . Marshal ( romCache )
romCache . Unlock ( )
if err != nil {
log . Printf ( "failed to marshal romCache to json: %v" , err )
return
}
err = os . WriteFile ( cacheFile , romCacheJson , 0644 )
if err != nil {
log . Printf ( "failed to write '%s' file: %v" , cacheFile , err )
log . Printf ( "attempting to remove '%s' to ensure integrity during next program startup..." , cacheFile )
err = os . Remove ( cacheFile )
if err != nil {
log . Printf ( "failed to remove file '%s': %v" , cacheFile , err )
}
return
}
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}
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// returns true if new builds were moved
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func moveBuildArtifacts ( ) bool {
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f , err := os . Open ( buildOutDirectory )
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if err != nil {
log . Printf ( "failed to open ROM directory: %v" , err )
return false
}
defer f . Close ( )
files , err := f . ReadDir ( 0 )
if err != nil {
log . Printf ( "failed to read files in directory: %v" , err )
return false
}
var newROMs bool
for _ , v := range files {
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if isLineageROM , _ := isLineageROMZip ( v ) ; ! isLineageROM { // skip files that aren't LineageOS ROMs
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continue
}
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newROMs = true
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log . Printf ( "new build found - moving file %s" , v . Name ( ) )
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romCache . Lock ( ) // lock to prevent multiple concurrent goroutines moving the same file
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err := moveBuildFile ( fmt . Sprintf ( "%s/%s" , buildOutDirectory , v . Name ( ) ) , fmt . Sprintf ( "%s/%s" , romDirectory , v . Name ( ) ) )
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romCache . Unlock ( )
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if err != nil {
log . Printf ( "failed to move file '%s' from out to rom directory: %v" , v . Name ( ) , err )
continue
}
}
return newROMs
}
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// false if a file is not a LineageOS ROM .zip file
// no formal validation is performed - only file naming convention is checked
// also returns a lineage ROM's filename sliced and delimited by -'s
// Example filename: lineage-20.0-20230604-UNOFFICIAL-sunfish.zip
func isLineageROMZip ( v fs . DirEntry ) ( bool , [ ] string ) {
// skip directories, non .zip files and files that don't begin with lineage-
if v . Type ( ) . IsDir ( ) || ! strings . HasSuffix ( v . Name ( ) , ".zip" ) || ! strings . HasPrefix ( v . Name ( ) , "lineage-" ) {
return false , nil
}
splitName := strings . Split ( v . Name ( ) , "-" )
// expect 5 dashes
return len ( splitName ) == 5 , splitName
}
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// http - GET /
// Writes JSON response for the updater app to know what versions are available to download
func lineageOSROMListHandler ( w http . ResponseWriter , r * http . Request ) {
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go func ( ) {
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newBuilds := moveBuildArtifacts ( )
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if newBuilds {
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updateROMCache ( )
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}
} ( )
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romCache . Lock ( )
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httpResponseJSON := & HTTPResponseJSON { Response : romCache . ROMs }
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romCache . Unlock ( )
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b , err := json . Marshal ( httpResponseJSON )
if err != nil {
w . WriteHeader ( http . StatusInternalServerError )
log . Printf ( "failed to marshal lineageOSROMs to json: %v" , err )
return
}
w . Write ( b )
}
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// Returns a sha256 hash of a file located at the path provided
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func hashFile ( filename string ) ( string , error ) {
f , err := os . Open ( filename )
if err != nil {
return "" , fmt . Errorf ( "failed to open file '%s': %v: " , filename , err )
}
defer f . Close ( )
h := sha256 . New ( )
if _ , err := io . Copy ( h , f ) ; err != nil {
return "" , fmt . Errorf ( "failed to copy data from file to hash function: %v" , err )
}
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return fmt . Sprintf ( "%x" , h . Sum ( nil ) ) , nil
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}
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// A custom "move file" function because in docker container the mounted folders are different overlay filesystems
// Instead of os.Rename, we must copy and delete
func moveBuildFile ( src , dst string ) error {
sourceFileStat , err := os . Stat ( src )
if err != nil {
return err
}
if ! sourceFileStat . Mode ( ) . IsRegular ( ) {
return fmt . Errorf ( "%s is not a regular file" , src )
}
source , err := os . Open ( src )
if err != nil {
return err
}
defer source . Close ( )
destination , err := os . Create ( dst )
if err != nil {
return err
}
defer destination . Close ( )
_ , err = io . Copy ( destination , source )
if err != nil {
return fmt . Errorf ( "failed to copy file: %v" , err )
}
err = os . Remove ( src )
if err != nil {
return fmt . Errorf ( "failed to delete source file after copy: %v" , err )
}
return nil
}