1 files changed, 83 insertions, 0 deletions
diff --git a/internal/helper/helper.go b/internal/helper/helper.go
new file mode 100644
index 00000000..378d9471
--- /dev/null
+++ b/internal/helper/helper.go
@@ -0,0 +1,83 @@
+// Package helper runs external helpers with optional sandboxing.
+package helper
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"time"
+
+	"hakurei.app/internal/helper/proc"
+)
+
+var WaitDelay = 2 * time.Second
+
+const (
+	// HakureiHelper is set to 1 when args fd is enabled and 0 otherwise.
+	HakureiHelper = "HAKUREI_HELPER"
+	// HakureiStatus is set to 1 when stat fd is enabled and 0 otherwise.
+	HakureiStatus = "HAKUREI_STATUS"
+)
+
+type Helper interface {
+	// Start starts the helper process.
+	Start() error
+	// Wait blocks until Helper exits.
+	Wait() error
+
+	fmt.Stringer
+}
+
+func newHelperFiles(
+	ctx context.Context,
+	wt io.WriterTo,
+	stat bool,
+	argF func(argsFd, statFd int) []string,
+	extraFiles []*os.File,
+) (hl *helperFiles, args []string) {
+	hl = new(helperFiles)
+	hl.ctx = ctx
+	hl.useArgsFd = wt != nil
+	hl.useStatFd = stat
+
+	hl.extraFiles = new(proc.ExtraFilesPre)
+	for _, f := range extraFiles {
+		_, v := hl.extraFiles.Append()
+		*v = f
+	}
+
+	argsFd := -1
+	if hl.useArgsFd {
+		f := proc.NewWriterTo(wt)
+		argsFd = int(proc.InitFile(f, hl.extraFiles))
+		hl.files = append(hl.files, f)
+	}
+
+	statFd := -1
+	if hl.useStatFd {
+		f := proc.NewStat(&hl.stat)
+		statFd = int(proc.InitFile(f, hl.extraFiles))
+		hl.files = append(hl.files, f)
+	}
+
+	args = argF(argsFd, statFd)
+	return
+}
+
+// helperFiles provides a generic wrapper around helper ipc.
+type helperFiles struct {
+	// whether argsFd is present
+	useArgsFd bool
+	// whether statFd is present
+	useStatFd bool
+
+	// closes statFd
+	stat io.Closer
+	// deferred extraFiles fulfillment
+	files []proc.File
+	// passed through to [proc.Fulfill] and [proc.InitFile]
+	extraFiles *proc.ExtraFilesPre
+
+	ctx context.Context
+}