commit ab799e113d497df307c8b15f8b931922cf9344fe
Author: Sotirios Pupakis <sotirek@gmail.com>
Date:   Fri Sep 5 03:34:32 2025 +0200

    initial

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..56bdcdf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+downloads/*
\ No newline at end of file
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..b705b1b
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module gitea.tbdevent.eu/ilbinek/reforger_utils
+
+go 1.25.0
diff --git a/pakUtils.go b/pakUtils.go
new file mode 100644
index 0000000..c85b037
--- /dev/null
+++ b/pakUtils.go
@@ -0,0 +1,215 @@
+package reforger_utils
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io"
+)
+
+func readString(r io.Reader, expected string) error {
+	buf := make([]byte, 4)
+	if _, err := io.ReadFull(r, buf); err != nil {
+		return fmt.Errorf("failed to read identifier: %w", err)
+	}
+	if string(buf) != expected {
+		return fmt.Errorf("expected identifier '%s', but got '%s'", expected, string(buf))
+	}
+	return nil
+}
+
+func parseEntry(r *bytes.Reader) (PakEntry, error) {
+	var pakEntry PakEntry
+	if err := binary.Read(r, binary.LittleEndian, &pakEntry.Offset); err != nil {
+		return PakEntry{}, fmt.Errorf("failed to read file offset: %w", err)
+	}
+
+	if err := binary.Read(r, binary.LittleEndian, &pakEntry.Size); err != nil {
+		return PakEntry{}, fmt.Errorf("failed to read file size: %w", err)
+	}
+
+	if err := binary.Read(r, binary.LittleEndian, &pakEntry.OriginalSize); err != nil {
+		return PakEntry{}, fmt.Errorf("failed to read uncompressed size: %w", err)
+	}
+
+	r.Seek(4, io.SeekCurrent) // NULL
+
+	if err := binary.Read(r, binary.BigEndian, &pakEntry.CompressType); err != nil {
+		return PakEntry{}, fmt.Errorf("failed to read compression type: %w", err)
+	}
+
+	if err := binary.Read(r, binary.BigEndian, &pakEntry.UnknownData); err != nil {
+		return PakEntry{}, fmt.Errorf("failed to read unknown data: %w", err)
+	}
+
+	return pakEntry, nil
+}
+
+func parseEntries(r *bytes.Reader, dataBlockLength int64) ([]PakEntry, error) {
+	var entries []PakEntry
+	read := 0
+
+	for r.Len() > 0 {
+		// read byte to determine entry type
+		entryType, err := r.ReadByte()
+		if err != nil {
+			return nil, fmt.Errorf("failed to read entry type: %w", err)
+		}
+
+		nameLength, err := r.ReadByte()
+		if err != nil {
+			return nil, fmt.Errorf("failed to read name length: %w", err)
+		}
+
+		name := make([]byte, nameLength)
+		if _, err := io.ReadFull(r, name); err != nil {
+			return nil, fmt.Errorf("failed to read name: %w", err)
+		}
+
+		switch entryType {
+		case 0x00: // Directory
+			ent, size, err := parseDirectory(r, string(name), dataBlockLength)
+			if err != nil {
+				return nil, fmt.Errorf("failed to parse directory '%s': %w", string(name), err)
+			}
+			read += 1 + 1 + int(nameLength) + size
+			entries = append(entries, ent...)
+		case 0x01: // File
+			pakEntry, err := parseEntry(r)
+			if err != nil {
+				return nil, fmt.Errorf("failed to parse entry for file '%s': %w", string(name), err)
+			}
+
+			pakEntry.Name = string(name)
+
+			entries = append(entries, pakEntry)
+			read += 1 + 1 + int(nameLength) + 4 + 4 + 4 + 4 + 4 + 4 // entryType + nameLength + name + offset + size + originalSize + NULL + compressType + unknownData
+
+		default:
+			return nil, fmt.Errorf("unknown entry type: %d", entryType)
+		}
+	}
+
+	return entries, nil
+}
+
+func parseDirectory(r *bytes.Reader, path string, dataBlockOffset int64) ([]PakEntry, int, error) {
+	var entries []PakEntry
+	var totalSize int
+
+	// read the number of entries in the directory
+	var entryCount uint32
+	if err := binary.Read(r, binary.LittleEndian, &entryCount); err != nil {
+		return nil, 0, fmt.Errorf("failed to read entry count for directory '%s': %w", path, err)
+	}
+
+	totalSize += 4
+
+	for i := 0; i < int(entryCount); i++ {
+		// read byte to determine entry type
+		entryType, err := r.ReadByte()
+		if err != nil {
+			return nil, 0, fmt.Errorf("failed to read entry type: %w", err)
+		}
+
+		nameLength, err := r.ReadByte()
+		if err != nil {
+			return nil, 0, fmt.Errorf("failed to read name length: %w", err)
+		}
+
+		name := make([]byte, nameLength)
+		if _, err := io.ReadFull(r, name); err != nil {
+			return nil, 0, fmt.Errorf("failed to read name: %w", err)
+		}
+
+		totalSize += 1 + 1 + int(nameLength)
+
+		switch entryType {
+		case 0x00: // Directory
+			subEntries, size, err := parseDirectory(r, path+"/"+string(name), dataBlockOffset)
+			if err != nil {
+				return nil, 0, fmt.Errorf("failed to parse directory '%s': %w", path+"/"+string(name), err)
+			}
+			entries = append(entries, subEntries...)
+			totalSize += size
+		case 0x01: // File
+			pakEntry, err := parseEntry(r)
+			if err != nil {
+				return nil, 0, fmt.Errorf("failed to parse entry for file '%s': %w", path+"/"+string(name), err)
+			}
+			pakEntry.Name = path + "/" + string(name)
+			entries = append(entries, pakEntry)
+			totalSize += 4 + 4 + 4 + 4 + 4 + 4
+		}
+	}
+
+	return entries, totalSize, nil
+}
+
+func GetPakFileInfo(data []byte) ([]PakEntry, error) {
+	r := bytes.NewReader(data)
+
+	// Read FORM header
+	if err := readString(r, "FORM"); err != nil {
+		return nil, err
+	}
+	r.Seek(4, io.SeekCurrent) // Skip total file size
+
+	// Read PAC1 header
+	if err := readString(r, "PAC1"); err != nil {
+		return nil, err
+	}
+
+	var dataBlockOffset int64 = -1
+
+	// Find DATA and FILE chunks
+	for {
+		chunkIDBytes := make([]byte, 4)
+		_, err := io.ReadFull(r, chunkIDBytes)
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, fmt.Errorf("failed to read chunk ID: %w", err)
+		}
+		chunkID := string(chunkIDBytes)
+
+		var chunkSize uint32
+		if err := binary.Read(r, binary.BigEndian, &chunkSize); err != nil {
+			return nil, fmt.Errorf("failed to read chunk size for %s: %w", chunkID, err)
+		}
+
+		switch chunkID {
+		case "HEAD":
+			r.Seek(int64(chunkSize), io.SeekCurrent)
+		case "DATA":
+			// The file offsets are relative to the start of the data within this block.
+			// So we record the start position of the data block.
+			dataBlockOffset, err = r.Seek(0, io.SeekCurrent)
+			if err != nil {
+				return nil, fmt.Errorf("could not get DATA block offset: %w", err)
+			}
+			r.Seek(int64(chunkSize), io.SeekCurrent)
+		case "FILE":
+			if dataBlockOffset == -1 {
+				return nil, fmt.Errorf("FILE chunk found before DATA chunk")
+			}
+
+			// skip unknown data
+			r.Seek(6, io.SeekCurrent)
+
+			entries, err := parseEntries(r, dataBlockOffset)
+
+			if err != nil {
+				return nil, fmt.Errorf("failed to parse FILE entries: %w", err)
+			}
+
+			return entries, nil
+		default:
+			// Skip unknown chunks
+			r.Seek(int64(chunkSize), io.SeekCurrent)
+		}
+	}
+
+	return nil, fmt.Errorf("FILE chunk not found in archive")
+}
diff --git a/structs.go b/structs.go
new file mode 100644
index 0000000..9d4c505
--- /dev/null
+++ b/structs.go
@@ -0,0 +1,100 @@
+package reforger_utils
+
+import "time"
+
+type AssetsReply []struct {
+	ID                         int         `json:"id"`
+	Blocked                    bool        `json:"blocked"`
+	DeletedAt                  interface{} `json:"deletedAt"`
+	Private                    bool        `json:"private"`
+	GameVersion                string      `json:"gameVersion"`
+	PlatformCompatibility      string      `json:"platformCompatibility"`
+	PlatformCompatibilityValue int         `json:"platformCompatibilityValue"`
+	Accessible                 bool        `json:"accessible"`
+	Version                    string      `json:"version"`
+	TotalFileSize              int         `json:"totalFileSize"`
+	Deleted                    bool        `json:"deleted"`
+	AccessValue                int         `json:"accessValue"`
+	Files                      []struct {
+		Md5          string `json:"md5"`
+		Name         string `json:"name"`
+		Size         int    `json:"size"`
+		ContentType  string `json:"contentType"`
+		ManifestPath string `json:"manifestPath"`
+	} `json:"files"`
+	Asset struct {
+		ID             string      `json:"id"`
+		Meta           interface{} `json:"meta"`
+		Name           string      `json:"name"`
+		Type           string      `json:"type"`
+		Owned          bool        `json:"owned"`
+		Blocked        bool        `json:"blocked"`
+		Private        bool        `json:"private"`
+		Summary        string      `json:"summary"`
+		Unlisted       bool        `json:"unlisted"`
+		CreatedAt      time.Time   `json:"createdAt"`
+		UpdatedAt      time.Time   `json:"updatedAt"`
+		DependencyTree struct {
+			Access                     string      `json:"access"`
+			Blocked                    bool        `json:"blocked"`
+			Private                    bool        `json:"private"`
+			Unlisted                   bool        `json:"unlisted"`
+			DeletedAt                  interface{} `json:"deletedAt"`
+			AccessValue                int         `json:"accessValue"`
+			GameVersion                string      `json:"gameVersion"`
+			PlatformCompatibility      string      `json:"platformCompatibility"`
+			PlatformCompatibilityValue int         `json:"platformCompatibilityValue"`
+		} `json:"dependencyTree"`
+		CurrentVersionID     int    `json:"currentVersionId"`
+		CurrentVersionSize   int    `json:"currentVersionSize"`
+		CurrentVersionNumber string `json:"currentVersionNumber"`
+	} `json:"asset"`
+	Dependencies []interface{} `json:"dependencies"`
+}
+
+type Manifest struct {
+	Version   int    `json:"version"`
+	Size      int    `json:"size"`
+	Sha512    string `json:"sha512"`
+	Remainder struct {
+		Sha512  string `json:"sha512"`
+		Size    int    `json:"size"`
+		Offsets []int  `json:"offsets"`
+	} `json:"remainder"`
+	Fragments []struct {
+		Sha512  string `json:"sha512"`
+		Size    int    `json:"size"`
+		Offsets []int  `json:"offsets"`
+	} `json:"fragments"`
+}
+
+type RDBHeader struct {
+	Magic      [4]byte // "FORM"
+	Length     uint32
+	Tag        [4]byte // "RDBC"
+	Version    uint32
+	EntryCount uint32
+}
+
+type RDBEntry struct {
+	Path             string
+	Hash             [16]byte
+	CompressedSize   uint32
+	UncompressedSize uint32
+	Flags            uint32
+	Offset           uint64
+}
+
+type Frag struct {
+	Offset int
+	Size   int
+}
+
+type PakEntry struct {
+	Name         string
+	Offset       uint32
+	Size         uint32
+	OriginalSize uint32
+	CompressType uint32
+	UnknownData  uint32
+}
diff --git a/util.go b/util.go
new file mode 100644
index 0000000..7109c24
--- /dev/null
+++ b/util.go
@@ -0,0 +1,179 @@
+package reforger_utils
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"slices"
+	"strings"
+)
+
+var Debug = false
+
+func DoAssetsRequest(addonID, version string) AssetsReply {
+	url := "https://api-ar-workshop.bistudio.com/workshop-api/api/v3.0/s2s/assets/download-list"
+	body := `{"assets":{"` + addonID + `":"` + version + `"}}`
+	req, err := http.NewRequest("POST", url, strings.NewReader(body))
+	if err != nil {
+		panic(err)
+	}
+
+	req.Header.Add("x-client-id", "$edb1b7862bba5cade1f6e06bfdeac2c")
+	req.Header.Add("x-client-secret", "$8b415ea2aa11bd51f2f5b5a9dcb8476")
+	req.Header.Add("Content-Type", "application/json")
+	req.Header.Add("user-agent", "Arma Reforger/1.4.0.53 (Headless; Windows)")
+	req.Header.Add("content-length", fmt.Sprintf("%d", len(body)))
+
+	res, err := http.DefaultClient.Do(req)
+	if err != nil {
+		panic(err)
+	}
+	defer res.Body.Close()
+
+	if res.StatusCode != 200 {
+		// print entire body
+		body, _ := io.ReadAll(res.Body)
+		fmt.Println(string(body))
+		panic("bad status: " + res.Status)
+	}
+
+	// Process response
+	decoder := json.NewDecoder(res.Body)
+	var assetsReply AssetsReply
+	if err := decoder.Decode(&assetsReply); err != nil {
+		panic(err)
+	}
+
+	return assetsReply
+}
+
+func GetManifest(manifestUrl string) Manifest {
+	url := "https://ar-gcp-cdn.bistudio.com/manifest/" + manifestUrl
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		panic(err)
+	}
+
+	res, err := http.DefaultClient.Do(req)
+	if err != nil {
+		panic(err)
+	}
+	defer res.Body.Close()
+
+	if res.StatusCode != 200 {
+		panic("bad status: " + res.Status)
+	}
+
+	// Decode the JSON response
+	var manifest Manifest
+	if err := json.NewDecoder(res.Body).Decode(&manifest); err != nil {
+		panic(err)
+	}
+
+	return manifest
+}
+
+func Download(manifest Manifest, downloadDir string, filen string) []byte {
+
+	if Debug {
+		// create the directory if it doesn't exist
+		if err := os.MkdirAll(downloadDir + "/fragments/" + filen, os.ModePerm); err != nil {
+			panic(err)
+		}
+	}
+
+	// download remainder
+	downloaded := 0
+	remContent := make([]byte, 0)
+	currentRem := 0
+	if (manifest.Remainder.Size > 0) {
+		url := transformShaToURL(manifest.Remainder.Sha512, manifest.Remainder.Size)
+		content := getContent(url)
+		remContent = content
+		downloaded += len(content)
+		
+		if Debug {
+			// save remainder to file in the fragments/ directory, prefix with gap
+			if err := os.WriteFile(filepath.Join(downloadDir, "fragments", filen, fmt.Sprintf("%d.%s.%d.bytes", manifest.Remainder.Offsets[0], manifest.Remainder.Sha512, manifest.Remainder.Size)), remContent, os.ModePerm); err != nil {
+				panic(err)
+			}
+		}
+	}
+	
+	trackFrag := make([]Frag, 0)
+
+	// start downloading chunks
+	//currentOffset := 0
+	ret := make([]byte, manifest.Size)
+	for _, fragment := range manifest.Fragments {
+		url := transformShaToURL(fragment.Sha512, fragment.Size)
+		content := getContent(url)
+		downloaded += len(content) * len(fragment.Offsets)
+		for _, offset := range fragment.Offsets {
+			trackFrag = append(trackFrag, Frag{Offset: offset, Size: len(content)})
+			copy(ret[offset:offset+len(content)], content)
+		}
+
+		if Debug {
+			// save fragment to file in the fragments/ directory
+			if err := os.WriteFile(filepath.Join(downloadDir, "fragments", filen, fmt.Sprintf("%d.%s.%d.bytes", fragment.Offsets[0], fragment.Sha512, fragment.Size)), content, os.ModePerm); err != nil {
+				panic(err)
+			}
+		}
+		
+		percent := float32(downloaded) / float32(manifest.Size) * 100.0
+        fmt.Printf("\r\033[32mDownloaded\033[0m %d/%d (\033[36m%.2f%%\033[0m) of \033[33m%s\033[0m", downloaded, manifest.Size, percent, filen)
+	}
+
+	// sort trackFrag by Offset
+	slices.SortFunc(trackFrag, func(a, b Frag) int {
+		return a.Offset - b.Offset
+	})
+
+	// check for gaps in trackFrag and fill with remainder content
+	curPos := 0
+	for _, frag := range trackFrag {
+		if frag.Offset > curPos {
+			// gap detected
+			gapSize := frag.Offset - curPos
+			if currentRem + gapSize > len(remContent) {
+				panic("not enough remainder content to fill gap")
+			}
+			copy(ret[curPos:curPos+gapSize], remContent[currentRem:currentRem+gapSize])
+			remContent = remContent[gapSize:]
+		}
+		curPos = frag.Offset + frag.Size
+	}
+
+	// Append rest of remainder content
+	copy(ret[curPos:], remContent)
+	fmt.Println()
+
+	return ret
+}
+
+func getContent(url string) []byte {
+	resp, err := http.Get(url)
+	if err != nil {
+		panic(err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		panic("bad status: " + resp.Status)
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		panic(err)
+	}
+
+	return body
+}
+
+func transformShaToURL(sha512s string, size int) string {
+	return "https://ar-gcp-cdn.bistudio.com/fragment/" + sha512s[0:4] + "/" + sha512s[4:8] + "/" + sha512s[8:] + "/" + fmt.Sprintf("%d", size)
+}