initial commit - working code

new file:   .gitignore
	new file:   .idea/.gitignore
	new file:   .idea/Steamworks-Collection-Downloader.iml
	new file:   .idea/modules.xml
	new file:   .idea/vcs.xml
	new file:   downloader/downloadable.go
	new file:   downloader/downloader.go
	new file:   go.mod
	new file:   go.sum
	new file:   main.go
	new file:   manifest/entry.go
	new file:   manifest/manifest.go
	new file:   webapi/publishedFileDetailsResponse.go

manifest/entry.go

@@ -0,0 +1,19 @@
+package manifest
+
+type Entry struct {
+	ID                  string
+	TimeCreated         string
+	TimeUpdated         string
+	HContentFile        string
+	HContentFileSize    string
+	HContentPreview     string
+	HContentPreviewSize string
+}
+
+func (w Entry) FileNamePrefixed(prefix string) string {
+	return prefix + w.ID + ".vpk"
+}
+
+func (w Entry) PreviewFileNamePrefixed(prefix string) string {
+	return prefix + w.ID + ".jpg"
+}

manifest/manifest.go

@@ -0,0 +1,77 @@
+package manifest
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"os"
+)
+
+type Manifest struct {
+	filename string
+	prefix   string
+
+	Entries map[string]*Entry
+
+	*os.File
+}
+
+func (m *Manifest) Open(filename string, prefix string) (err error) {
+	filename = prefix + filename
+	m.File, err = os.OpenFile(filename, os.O_CREATE|os.O_RDWR, 0664)
+	if err != nil {
+		return err
+	}
+
+	buffer, err := ioutil.ReadAll(m)
+	if err != nil {
+		return err
+	}
+
+	err = m.Parse(buffer)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (m *Manifest) Parse(manifest []byte) error {
+	m.Entries = make(map[string]*Entry)
+
+	if len(manifest) == 0 {
+		return nil
+	}
+
+	err := json.Unmarshal(manifest, &m.Entries)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (m *Manifest) AddEntry(entry *Entry) error {
+	m.Entries[entry.ID] = entry
+
+	_, err := m.Seek(0, 0)
+	if err != nil {
+		return err
+	}
+
+	err = m.Truncate(0)
+	if err != nil {
+		return err
+	}
+
+	b, err := json.Marshal(m.Entries)
+	if err != nil {
+		return err
+	}
+
+	_, err = m.Write(b)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}