package upgrade

import (
	"os"
	"os/exec"
	"path/filepath"
	"reflect"
	"strings"
	"testing"
	"time"
)

// The launcher's record, read as the launcher writes it: the launcher itself writes it here, so the
// two cannot drift (novox/hq to-be 45 §8).
func TestTheLaunchersRecordIsReadAsTheLauncherWritesIt(t *testing.T) {
	state := t.TempDir()
	libexec := t.TempDir()
	versions := filepath.Join(libexec, VersionsDirName)
	base := time.Now().Add(-2 * time.Hour)
	for i, v := range []string{"1.0", "2.0"} {
		binary := deliver(t, versions, v, base.Add(time.Duration(i)*time.Hour))
		// Each fails, so the one run iteration ends.
		if err := os.WriteFile(binary, []byte("#!/bin/sh\nexit 1\n"), 0o755); err != nil {
			t.Fatal(err)
		}
	}
	if err := os.WriteFile(filepath.Join(state, KnownGoodName), []byte("1.0\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(state, AttemptsName), []byte("3\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	launch := exec.Command("sh", "../../packaging/nox-mesh-host-launch")
	launch.Env = append(os.Environ(), "MESH_HOST_STATE_DIR="+state, "MESH_HOST_LIBEXEC="+libexec,
		"MESH_HOST_BIN=/nonexistent", "MESH_HOST_RUN_ONCE=1", "MESH_HOST_BACKOFF=0")
	_ = launch.Run()
	verdicts, err := ReadRolledBack(RolledBackPath(filepath.Join(state, "state.json")))
	if err != nil {
		t.Fatal(err)
	}
	if len(verdicts) == 0 {
		t.Fatal("the launcher rolled back and nothing was read from its record")
	}
	v := verdicts[0]
	if v.From != "2.0" || v.To != "1.0" || v.Outcome != "rolled-back" || !strings.Contains(v.Why, "failed 3 times") ||
		time.Since(v.At) > time.Minute {
		t.Fatalf("the record reads as %+v", v)
	}
}

// A version the launcher rolled back is never what this host stands aside for: it would be refused,
// and the host would stand aside after every apply for ever.
func TestTheHostNeverStandsAsideForARolledBackVersion(t *testing.T) {
	dir := t.TempDir()
	base := time.Now().Add(-2 * time.Hour)
	deliver(t, dir, "1.0", base)
	deliver(t, dir, "2.0", base.Add(time.Hour))
	if _, waiting, err := Successor(dir, "1.0", "2.0"); err != nil || waiting {
		t.Fatalf("standing aside for a rolled-back version (%v, %v)", waiting, err)
	}
	deliver(t, dir, "3.0", base.Add(90*time.Minute))
	if next, waiting, err := Successor(dir, "1.0", "2.0"); err != nil || !waiting || next.Version != "3.0" {
		t.Fatalf("a newer version after a rollback is not stood aside for: %+v %v %v", next, waiting, err)
	}
}

// Nothing newer than the running version is retired: a successor waiting, or one rolled back that the
// mesh still declares — either would only be delivered again.
func TestRetireNeverRemovesANewerVersion(t *testing.T) {
	dir := t.TempDir()
	base := time.Now().Add(-4 * time.Hour)
	for i, v := range []string{"one", "two", "three", "four"} {
		deliver(t, dir, v, base.Add(time.Duration(i)*time.Hour))
	}
	removed, err := Retire(dir, "two")
	if err != nil {
		t.Fatal(err)
	}
	if len(removed) != 0 {
		t.Fatalf("retired %v while running two: one is its predecessor, three and four are newer", removed)
	}
}

// Proved: known-good, the counter cleared, older versions retired, and the launcher's verdicts ended —
// unless this is the version a rollback went back to, about which they still stand.
func TestProvingAHostEndsTheLaunchersVerdictsOnlyWhenItIsNewer(t *testing.T) {
	state := filepath.Join(t.TempDir(), "state.json")
	dir := t.TempDir()
	base := time.Now().Add(-4 * time.Hour)
	for i, v := range []string{"0.9", "1.0", "2.0", "3.0"} {
		deliver(t, dir, v, base.Add(time.Duration(i)*time.Hour))
	}
	record := "2.0\t1.0\t1759744800\trolled-back\tit failed 3 times in a row\n"
	if err := os.WriteFile(RolledBackPath(state), []byte(record), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(AttemptsPath(state), []byte("2\n"), 0o644); err != nil {
		t.Fatal(err)
	}

	// The version gone back to reports: it is known-good, and the rollback still stands.
	if _, err := Proved(state, dir, "1.0"); err != nil {
		t.Fatal(err)
	}
	if v, _ := ReadRolledBack(RolledBackPath(state)); len(v) != 1 {
		t.Fatal("proving the version a rollback went back to ended the rollback")
	}
	if got, _ := ReadKnownGood(KnownGoodPath(state)); got != "1.0" {
		t.Fatalf("known-good is %q", got)
	}
	if raw, _ := os.ReadFile(AttemptsPath(state)); strings.TrimSpace(string(raw)) != "0" {
		t.Fatalf("the start counter was not cleared: %q", raw)
	}

	// A newer one reports: the rollback ends, and what is older than its predecessor goes.
	retired, err := Proved(state, dir, "3.0")
	if err != nil {
		t.Fatal(err)
	}
	if v, _ := ReadRolledBack(RolledBackPath(state)); len(v) != 0 {
		t.Fatalf("a newer host proved itself and the old rollback still stands: %+v", v)
	}
	if !reflect.DeepEqual(retired, []string{"0.9", "1.0"}) {
		t.Fatalf("retired %v, want 0.9 and 1.0 — 2.0 is 3.0's predecessor", retired)
	}
}

// A line the launcher's record cannot be read by is named, never guessed at.
func TestAnUnreadableRecordLineIsNamed(t *testing.T) {
	path := filepath.Join(t.TempDir(), RolledBackName)
	if err := os.WriteFile(path, []byte("2.0\t1.0\t1759744800\trolled-back\twhy\ngarbage\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	verdicts, err := ReadRolledBack(path)
	if len(verdicts) != 1 || err == nil || !strings.Contains(err.Error(), "line(s) 2") {
		t.Fatalf("read %+v, %v", verdicts, err)
	}
}