package ingest

import (
	"strings"
	"testing"
)

// The decoder guards the one path in this zone that DESTROYS a user's file: intake reads a manifest
// with no chapters in it as "the engine cut the source and there is no book in it", and removes the
// upload. So a document that is not a manifest must not be able to arrive as an EMPTY manifest —
// `{}`, `null` and a document of fields this build has never heard of all decode into the same zeros
// otherwise. Found by the seam lens of the dofix review.
//
// The check is on the PRESENCE of the version and never on its value: pinning the value would make
// every engine release a platform release, which is the reason it was left ungated in the first
// place.
//
// Mutation caught: dropping the manifest_version check from DecodeManifest.
func TestADocumentThatIsNotAManifestIsNotAnEmptyManifest(t *testing.T) {
	for _, body := range []string{
		`{}`,
		`null`,
		`{"error":"the book is locked"}`,
		`{"chapters":[],"units":[]}`,
		`{"manifest_version":""}`,
	} {
		if _, err := DecodeManifest([]byte(body)); err == nil {
			t.Errorf("%s decoded as a manifest", body)
		} else if !strings.Contains(err.Error(), "manifest") {
			t.Errorf("%s: %v", body, err)
		}
	}
	// A manifest of a version this build has never seen is still a manifest: what it identifies as is
	// recorded, not judged.
	m, err := DecodeManifest([]byte(`{"manifest_version":"tm-manifest-v9","chapters_total":2283,"units_total":4402}`))
	if err != nil {
		t.Fatalf("a manifest of a later version was refused: %v", err)
	}
	if m.ChaptersTotal != 2283 || m.Version != "tm-manifest-v9" {
		t.Fatalf("manifest = %+v", m)
	}
	// And a genuinely empty book decodes, because that is a real answer with a real consequence.
	if _, err := DecodeManifest([]byte(`{"manifest_version":"tm-manifest-v2","chapters_total":0}`)); err != nil {
		t.Fatalf("an empty book was refused: %v", err)
	}
}