Implement pack importing/exporting for downloaded Curseforge packs

Abstract out hash implementations
Implement file saving/downloading

curseforge/packinterop/translation.go

@@ -0,0 +1,119 @@
+package packinterop
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"github.com/comp500/packwiz/core"
+	"io"
+	"io/ioutil"
+	"os"
+)
+
+func ReadMetadata(s ImportPackSource) ImportPackMetadata {
+	var packImport ImportPackMetadata
+	metaFile := s.GetPackFile()
+	rdr, err := metaFile.Open()
+	if err != nil {
+		fmt.Printf("Error reading file: %s\n", err)
+		os.Exit(1)
+	}
+
+	// Read the whole file (as we are going to parse it multiple times)
+	fileData, err := ioutil.ReadAll(rdr)
+	if err != nil {
+		fmt.Printf("Error reading file: %s\n", err)
+		os.Exit(1)
+	}
+
+	// Determine what format the file is
+	var jsonFile map[string]interface{}
+	err = json.Unmarshal(fileData, &jsonFile)
+	if err != nil {
+		fmt.Printf("Error parsing JSON: %s\n", err)
+		os.Exit(1)
+	}
+
+	isManifest := false
+	if v, ok := jsonFile["manifestType"]; ok {
+		isManifest = v.(string) == "minecraftModpack"
+	}
+	if isManifest {
+		packMeta := cursePackMeta{importSrc: s}
+		err = json.Unmarshal(fileData, &packMeta)
+		if err != nil {
+			fmt.Printf("Error parsing JSON: %s\n", err)
+			os.Exit(1)
+		}
+		packImport = packMeta
+	} else {
+		// Replace FileNameOnDisk with fileNameOnDisk
+		fileData = bytes.ReplaceAll(fileData, []byte("FileNameOnDisk"), []byte("fileNameOnDisk"))
+		packMeta := twitchInstalledPackMeta{importSrc: s}
+		err = json.Unmarshal(fileData, &packMeta)
+		if err != nil {
+			fmt.Printf("Error parsing JSON: %s\n", err)
+			os.Exit(1)
+		}
+		packImport = packMeta
+	}
+
+	return packImport
+}
+
+// AddonFileReference is a pair of Project ID and File ID to reference a single file on CurseForge
+type AddonFileReference struct {
+	ProjectID int
+	FileID    int
+}
+
+func WriteManifestFromPack(pack core.Pack, fileRefs []AddonFileReference, out io.Writer) error {
+	// TODO: should Required be false sometimes?
+	files := make([]struct {
+		ProjectID int  `json:"projectID"`
+		FileID    int  `json:"fileID"`
+		Required  bool `json:"required"`
+	}, len(fileRefs))
+	for i, fr := range fileRefs {
+		files[i] = struct {
+			ProjectID int  `json:"projectID"`
+			FileID    int  `json:"fileID"`
+			Required  bool `json:"required"`
+		}{ProjectID: fr.ProjectID, FileID: fr.FileID, Required: true}
+	}
+
+	modLoaders := make([]modLoaderDef, 0, 1)
+	forgeVersion, ok := pack.Versions["forge"]
+	if ok {
+		modLoaders = append(modLoaders, modLoaderDef{
+			ID:      "forge-" + forgeVersion,
+			Primary: true,
+		})
+	}
+
+	manifest := cursePackMeta{
+		Minecraft: struct {
+			Version    string         `json:"version"`
+			ModLoaders []modLoaderDef `json:"modLoaders"`
+		}{
+			Version:    pack.Versions["minecraft"],
+			ModLoaders: modLoaders,
+		},
+		ManifestType:    "minecraftModpack",
+		ManifestVersion: 1,
+		NameInternal:    pack.Name,
+		Version:         "", // TODO: store or take this?
+		Author:          "", // TODO: store or take this?
+		ProjectID:       0,  // TODO: store or take this?
+		Files:           files,
+		Overrides:       "overrides",
+	}
+
+	w := json.NewEncoder(out)
+	w.SetIndent("", "  ") // Match CF export
+	err := w.Encode(manifest)
+	if err != nil {
+		return err
+	}
+	return nil
+}