package appconfig

import (
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"os"
	"testing"
)

// TestRenderHeldBeforeAnswersTheHashBeforeTheWrite (moves Plan 5 Task 9a,
// fix round 1, I1): the caller learns the sha256 of the exact bytes the
// render is about to place, before anything is written, so it can journal
// its ownership first; the write that follows places those bytes; a refusal
// from the callback writes nothing and sends no ack.
func TestRenderHeldBeforeAnswersTheHashBeforeTheWrite(t *testing.T) {
	ctx, s, reg, dd, privB64, _ := execKit(t)
	priv, err := ParsePrivateKey(privB64, "test")
	if err != nil {
		t.Fatal(err)
	}
	heldFixture(t, ctx, s)
	rt := landingRow()
	if err := reg.Upsert(rt); err != nil {
		t.Fatal(err)
	}
	path := ConfigEnvPath(dd, rt)

	refused := errors.New("the journal refused")
	if _, err := RenderHeldBefore(ctx, s, priv, dd, rt, heldOp, heldBox, func(string) error { return refused }); !errors.Is(err, refused) {
		t.Fatalf("a refusing callback: %v", err)
	}
	if _, err := os.Stat(path); !os.IsNotExist(err) {
		t.Fatalf("a refused render wrote the file: %v", err)
	}
	if _, _, err := s.Get(ctx, ConfigAckKey(heldBox, heldHost)); err == nil {
		t.Fatal("a refused render wrote the ack")
	}

	var told string
	got, err := RenderHeldBefore(ctx, s, priv, dd, rt, heldOp, heldBox, func(sha string) error {
		if _, err := os.Stat(path); !os.IsNotExist(err) {
			t.Errorf("the file was there before the callback: %v", err)
		}
		told = sha
		return nil
	})
	if err != nil {
		t.Fatal(err)
	}
	body, err := os.ReadFile(path)
	if err != nil {
		t.Fatal(err)
	}
	sum := sha256.Sum256(body)
	if want := hex.EncodeToString(sum[:]); told != want || got.SHA256 != want {
		t.Fatalf("callback %q, render %q, file %q", told, got.SHA256, want)
	}
	if a := readAck(t, ctx, s); a.FileSHA256 != told {
		t.Fatalf("ack %q, callback %q", a.FileSHA256, told)
	}
}