package main

import (
	"encoding/json"
	"fmt"
	"io/fs"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"
)

// Information for a LineageOS ROM available for download
type LineageOSROM struct {
	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
	Romtype          string `json:"romtype"`  // i.e. NIGHTLY or UNOFFICIAL
	Size             int    `json:"size"`     // size of .zip file in bytes
	URL              string `json:"url"`      // Accessible URL where client could download the .zip file
	Version          string `json:"version"`  // LineageOS version - i.e. 20.0
	// v2 API fields
	SHA1             string `json:"sha1,omitempty"`
	SHA256           string `json:"sha256,omitempty"`
	Date             string `json:"date,omitempty"`
	OSPatchLevel     string `json:"os_patch_level,omitempty"`
	OSSDKLevel       int    `json:"os_sdk_level,omitempty"`
	OTAPropertyFiles string `json:"ota_property_files,omitempty"`
}

// Structs for v2 API responses
type V2BuildResponse struct {
	Date     string        `json:"date"`
	Datetime int64         `json:"datetime"`
	Files    []V2BuildFile `json:"files"`
	Type     string        `json:"type"`
	Version  string        `json:"version"`
}

type V2BuildFile struct {
	Date             string `json:"date,omitempty"`
	Datetime         int64  `json:"datetime,omitempty"`
	Filename         string `json:"filename"`
	Filepath         string `json:"filepath"`
	OSPatchLevel     string `json:"os_patch_level,omitempty"`
	OSSDKLevel       int    `json:"os_sdk_level,omitempty"`
	OTAPropertyFiles string `json:"ota_property_files,omitempty"`
	SHA1             string `json:"sha1"`
	SHA256           string `json:"sha256"`
	Size             int64  `json:"size"`
	Type             string `json:"type,omitempty"`
	URL              string `json:"url"`
}

// The HTTP response JSON should be a JSON array of lineageOSROMS available for download
type HTTPResponseJSON struct {
	Response []LineageOSROM `json:"response"`
}

// Caches data about available ROMs in memory so we don't need to reference the filesystem for each request
type ROMCache struct {
	ROMs         []LineageOSROM  `json:"roms"`
	Cached       map[string]bool `json:"-"` // to quickly lookup if a file is already cached
	sync.RWMutex `json:"-"`      // We have multiple goroutines that may be accessing this data simultaneously, so we must lock / unlock it to prevent race conditions
}

const (
	romDirectory      = "public"               // directory where ROMs are available for download
	buildOutDirectory = "out"                  // directory from build system containing artifacts which we can move to romDirectory
	cacheFile         = "public/romcache.json" // persistence between server restarts so we don't have to rehash all the ROM files each time the program starts
)

var ( // evil global variables
	romCache ROMCache
	baseURL  string
)

func init() {
	// intialize and load ROMCache from file - so we don't have to rehash all the big files again
	romCache = ROMCache{}
	baseURL = os.Getenv("baseurl")
	if len(baseURL) < 1 {
		log.Fatalf("required environment variable 'baseurl' is not set.")
	}

	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)
		}
	}

	romCache.Cached = make(map[string]bool)

	var validROMs []LineageOSROM
	for _, rom := range romCache.ROMs {
		// A ROM is valid for v2 if it has SHA1 and Date fields populated
		if rom.SHA1 != "" && rom.Date != "" {
			romCache.Cached[rom.Filename] = true
			validROMs = append(validROMs, rom)
			log.Printf("loaded cached file: %s", rom.Filename)
		} else {
			log.Printf("cache entry for %s is missing v2 metadata, will re-process", rom.Filename)
		}
	}
	romCache.ROMs = validROMs

	// Check if any new build artifacts and load any new files into the romCache
	moveBuildArtifacts()
	go updateROMCache()
}

// HTTP Server
func main() {

	//Public static files
	http.Handle("/public/", http.StripPrefix("/public/", http.FileServer(http.Dir("public"))))

	// ROM list (legacy / catch-all)
	http.HandleFunc("/", lineageOSROMListHandler)

	// V2 ROM list and device info
	http.HandleFunc("/api/v2/devices/", lineageOSROMListHandlerV2)

	log.Print("Service listening on :8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
}

// Reads the ROM files on the filesystem recursively and populates a slice of lineageOSROMs
func updateROMCache() {

	log.Printf("updating ROM cache")

	type fileInfoPath struct {
		path      string
		info      fs.DirEntry
		splitName []string
	}

	var romFiles []fileInfoPath

	err := filepath.WalkDir(romDirectory, func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if d.IsDir() {
			return nil
		}
		isLineageROM, splitName := parseROMFileName(d)
		if isLineageROM {
			romFiles = append(romFiles, fileInfoPath{
				path:      path,
				info:      d,
				splitName: splitName,
			})
		}
		return nil
	})

	if err != nil {
		log.Printf("failed to walk ROM directory: %v", err)
		return
	}

	wg := sync.WaitGroup{}

	for i := range romFiles {
		v := romFiles[i]

		// skip already cached files
		romCache.RLock()
		if _, ok := romCache.Cached[v.info.Name()]; ok {
			romCache.RUnlock()
			continue
		}
		romCache.RUnlock()

		wg.Add(1)
		go func(file fileInfoPath) {
			defer wg.Done()
			fInfo, err := file.info.Info()
			if err != nil {
				log.Printf("failed to get file info '%s': %v", file.info.Name(), err)
				return
			}

			sha1Val, sha256Val, err := hashFileSha1AndSha256(file.path)
			if err != nil {
				log.Printf("ignore zip file '%s', failed to calculate hashes: %v", file.info.Name(), err)
				return
			}

			// Read ZIP metadata
			meta, err := readZipMetadata(file.path)
			if err != nil {
				log.Printf("failed to read metadata inside zip '%s': %v", file.info.Name(), err)
			}

			// Determine timestamp
			timestamp := int(fInfo.ModTime().Unix())
			if meta.Timestamp > 0 {
				timestamp = meta.Timestamp
			}

			// Format build date as YYYY-MM-DD
			buildDate := time.Unix(int64(timestamp), 0).UTC().Format("2006-01-02")

			// Calculate URL relative path from public directory
			relPath, err := filepath.Rel(romDirectory, file.path)
			if err != nil {
				log.Printf("failed to calculate relative path for '%s': %v", file.path, err)
				relPath = file.info.Name()
			}
			relPathSlash := filepath.ToSlash(relPath)

			lineageOSROM := LineageOSROM{
				Datetime:         timestamp,
				Filename:         file.info.Name(),
				ID:               sha256Val, // Keep ID as SHA256 for backward compatibility
				Romtype:          file.splitName[3],
				Size:             int(fInfo.Size()),
				URL:              fmt.Sprintf("%s/public/%s", baseURL, relPathSlash),
				Version:          file.splitName[1],
				SHA1:             sha1Val,
				SHA256:           sha256Val,
				Date:             buildDate,
				OSPatchLevel:     meta.PatchLevel,
				OSSDKLevel:       meta.SDKLevel,
				OTAPropertyFiles: meta.OTAPropertyFiles,
			}

			romCache.Lock()
			if _, ok := romCache.Cached[file.info.Name()]; ok { // it's possible another goroutine was already working to cache the file, so we check at the end
				romCache.Unlock()
				return
			}
			romCache.ROMs = append(romCache.ROMs, lineageOSROM)
			romCache.Cached[file.info.Name()] = true
			romCache.Unlock()

		}(v)
	}

	// save file to disk for next startup so we don't have to rehash all the files again
	wg.Wait()
	romCache.RLock()
	romCacheJson, err := json.Marshal(romCache)
	romCache.RUnlock()
	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
	}
}

// http - GET /
// The LineageOS updater app needs a JSON array of type LineageOSROM
// Marshals romCache.ROMs to JSON to serve as the response body
func lineageOSROMListHandler(w http.ResponseWriter, r *http.Request) {
	checkNewBuilds()

	romCache.RLock()
	httpResponseJSON := &HTTPResponseJSON{Response: romCache.ROMs}
	romCache.RUnlock()

	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)
}

func checkNewBuilds() {
	go func() { // Also checks for new builds
		newBuilds := moveBuildArtifacts()
		if newBuilds {
			updateROMCache()
		}
	}()
}

func lineageOSROMListHandlerV2(w http.ResponseWriter, r *http.Request) {
	checkNewBuilds()

	// Path: /api/v2/devices/{device}/builds
	// or: /api/v2/devices/{device}
	parts := strings.Split(strings.Trim(r.URL.Path, "/"), "/")
	if len(parts) < 4 {
		http.Error(w, "Bad Request", http.StatusBadRequest)
		return
	}

	device := parts[3]
	isBuildsRequest := len(parts) >= 5 && parts[4] == "builds"

	if isBuildsRequest {
		romCache.RLock()
		defer romCache.RUnlock()

		var builds []V2BuildResponse

		for _, rom := range romCache.ROMs {
			filenameParts := strings.Split(strings.TrimSuffix(rom.Filename, ".zip"), "-")
			romDevice := ""
			if len(filenameParts) > 0 {
				romDevice = filenameParts[len(filenameParts)-1]
			}

			if romDevice != device {
				continue
			}

			relPath := rom.Filename
			if strings.Contains(rom.URL, "/public/") {
				parts := strings.SplitN(rom.URL, "/public/", 2)
				if len(parts) == 2 {
					relPath = parts[1]
				}
			}

			file := V2BuildFile{
				Date:             rom.Date,
				Datetime:         int64(rom.Datetime),
				Filename:         rom.Filename,
				Filepath:         "/public/" + relPath,
				OSPatchLevel:     rom.OSPatchLevel,
				OSSDKLevel:       rom.OSSDKLevel,
				OTAPropertyFiles: rom.OTAPropertyFiles,
				SHA1:             rom.SHA1,
				SHA256:           rom.SHA256,
				Size:             int64(rom.Size),
				Type:             strings.ToLower(rom.Romtype),
				URL:              rom.URL,
			}

			build := V2BuildResponse{
				Date:     rom.Date,
				Datetime: int64(rom.Datetime),
				Files:    []V2BuildFile{file},
				Type:     strings.ToLower(rom.Romtype),
				Version:  rom.Version,
			}

			builds = append(builds, build)
		}

		if builds == nil {
			builds = []V2BuildResponse{}
		}

		b, err := json.Marshal(builds)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			log.Printf("failed to marshal v2 builds to json: %v", err)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		w.Write(b)
	} else {
		romCache.RLock()
		defer romCache.RUnlock()

		versionsSet := make(map[string]bool)
		for _, rom := range romCache.ROMs {
			filenameParts := strings.Split(strings.TrimSuffix(rom.Filename, ".zip"), "-")
			romDevice := ""
			if len(filenameParts) > 0 {
				romDevice = filenameParts[len(filenameParts)-1]
			}
			if romDevice == device {
				versionsSet[rom.Version] = true
			}
		}

		var versions []string
		for v := range versionsSet {
			versions = append(versions, v)
		}
		if versions == nil {
			versions = []string{}
		}

		deviceInfo := map[string]interface{}{
			"name":         device,
			"model":        device,
			"oem":          "LineageOS",
			"info_url":     fmt.Sprintf("https://wiki.lineageos.org/devices/%s/", device),
			"versions":     versions,
			"dependencies": []string{},
		}

		b, err := json.Marshal(deviceInfo)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			log.Printf("failed to marshal v2 device info to json: %v", err)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		w.Write(b)
	}
}