Implement pack importing/exporting for downloaded Curseforge packs

Abstract out hash implementations
Implement file saving/downloading

curseforge/packinterop/zip.go

@@ -0,0 +1,57 @@
+package packinterop
+
+import (
+	"archive/zip"
+	"errors"
+)
+
+type zipReaderFile struct {
+	NameInternal string
+	*zip.File
+}
+
+func (f zipReaderFile) Name() string {
+	return f.NameInternal
+}
+
+type zipPackSource struct {
+	MetaFile       *zip.File
+	Reader         *zip.Reader
+	cachedFileList []ImportPackFile
+}
+
+func (s zipPackSource) GetFile(path string) (ImportPackFile, error) {
+	if s.cachedFileList == nil {
+		s.cachedFileList = make([]ImportPackFile, len(s.Reader.File))
+		for i, v := range s.Reader.File {
+			s.cachedFileList[i] = zipReaderFile{v.Name, v}
+		}
+	}
+	for _, v := range s.cachedFileList {
+		if v.Name() == path {
+			return v, nil
+		}
+	}
+	return zipReaderFile{}, errors.New("file not found in zip")
+}
+
+func (s zipPackSource) GetFileList() ([]ImportPackFile, error) {
+	if s.cachedFileList == nil {
+		s.cachedFileList = make([]ImportPackFile, len(s.Reader.File))
+		for i, v := range s.Reader.File {
+			s.cachedFileList[i] = zipReaderFile{v.Name, v}
+		}
+	}
+	return s.cachedFileList, nil
+}
+
+func (s zipPackSource) GetPackFile() ImportPackFile {
+	return zipReaderFile{s.MetaFile.Name, s.MetaFile}
+}
+
+func GetZipPackSource(metaFile *zip.File, reader *zip.Reader) ImportPackSource {
+	return zipPackSource{
+		MetaFile: metaFile,
+		Reader:   reader,
+	}
+}