internal/outcome: rename run from main

The "main.go" name is quite confusing as this is often only present in main packages.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/outcome/run.go

@@ -0,0 +1,45 @@
+package outcome
+
+import (
+	"context"
+	"log"
+	"time"
+	_ "unsafe" // for go:linkname
+
+	"hakurei.app/hst"
+	"hakurei.app/message"
+)
+
+// IsPollDescriptor reports whether fd is the descriptor being used by the poller.
+//
+// Made available here to determine and reject impossible fd.
+//
+//go:linkname IsPollDescriptor internal/poll.IsPollDescriptor
+func IsPollDescriptor(fd uintptr) bool
+
+// Main runs an app according to [hst.Config] and terminates. Main does not return.
+func Main(ctx context.Context, msg message.Msg, config *hst.Config, fd int) {
+	// avoids runtime internals or standard streams
+	if fd >= 0 {
+		if IsPollDescriptor(uintptr(fd)) || fd < 3 {
+			log.Fatalf("invalid identifier fd %d", fd)
+		}
+	}
+
+	var id hst.ID
+	if err := hst.NewInstanceID(&id); err != nil {
+		log.Fatal(err.Error())
+	}
+
+	k := outcome{syscallDispatcher: direct{msg}}
+
+	finaliseTime := time.Now()
+	if err := k.finalise(ctx, msg, &id, config); err != nil {
+		printMessageError(msg.GetLogger().Fatalln, "cannot seal app:", err)
+		panic("unreachable")
+	}
+	msg.Verbosef("finalise took %.2f ms", float64(time.Since(finaliseTime).Nanoseconds())/1e6)
+
+	k.main(msg, fd)
+	panic("unreachable")
+}