package apply

import (
	"context"
	"os"
	"path/filepath"
	"strings"
	"testing"

	"github.com/novox/mesh-host/internal/declaration"
	"github.com/novox/mesh-host/internal/store"
)

func aProcess() *declaration.Process {
	return &declaration.Process{
		ID: "server", Type: declaration.TypeProcess, Name: "greeter",
		Source: "https://store.invalid/greeter/daemon",
		Digest: "sha256:" + strings.Repeat("a", 64),
		Run:    []string{"node", "index.js"},
		Env:    map[string]string{"MESH_NODE": "anchor", "A_FIRST": "1"},
	}
}

// The unit the mesh writes says what it runs, where, and that it comes back.
func TestTheUnitRunsWhatTheDaemonSaid(t *testing.T) {
	unit := unitFor(aProcess())
	for _, want := range []string{
		"ExecStart=node index.js",
		"WorkingDirectory=/var/lib/mesh/daemons/greeter",
		"Restart=always",
		"WantedBy=multi-user.target",
	} {
		if !strings.Contains(unit, want) {
			t.Fatalf("the unit does not say %q:\n%s", want, unit)
		}
	}
}

// **Generated whole and saying so.** Every managed file on a machine carries this, because an edit
// that survives until the next declaration and then vanishes is worse than one that is refused.
func TestTheUnitSaysItIsTheMeshs(t *testing.T) {
	unit := unitFor(aProcess())
	if !strings.HasPrefix(unit, "#") || !strings.Contains(unit, "Do not edit") {
		t.Fatalf("the unit does not say it is generated:\n%s", unit)
	}
}

// **Deterministic, because the unit is half the daemon's identity.** Environment held in a map
// would be written in Go's iteration order, so every apply would see a different unit and call an
// unchanged daemon changed — restarting it on every declaration for ever.
func TestTheUnitIsTheSameEveryTime(t *testing.T) {
	first := unitFor(aProcess())
	for i := 0; i < 20; i++ {
		if again := unitFor(aProcess()); again != first {
			t.Fatalf("two renderings of one daemon differ:\n%s\n---\n%s", first, again)
		}
	}
	// And sorted, so the order is a decision rather than luck.
	if strings.Index(first, "A_FIRST") > strings.Index(first, "MESH_NODE") {
		t.Fatalf("environment is not in a stable order:\n%s", first)
	}
}

// **Two daemons from one bundle differing only in their command are different daemons.** Tracking
// the digest alone would call the second one unchanged and leave the first one running.
func TestAProcesssIdentityIncludesHowItIsRun(t *testing.T) {
	one := aProcess()
	two := aProcess()
	two.Run = []string{"node", "other.js"}
	if unitFor(one) == unitFor(two) {
		t.Fatal("two daemons with different commands render one unit, so a change would be missed")
	}
}

// A process that runs as somebody says so, and one that does not says nothing — rather than naming
// root explicitly, which would be a claim the mesh does not need to make.
func TestAProcessRunsAsWhoItSaid(t *testing.T) {
	as := aProcess()
	as.User = "greeter"
	if !strings.Contains(unitFor(as), "User=greeter") {
		t.Fatalf("the unit does not run as the user it named:\n%s", unitFor(as))
	}
	if strings.Contains(unitFor(aProcess()), "User=") {
		t.Fatalf("a process that named no user had one written for it:\n%s", unitFor(aProcess()))
	}
}

// **Three modes, one kind.** A scheduled process is a timer plus a unit that finishes, not a unit
// that stays up — and the difference has to be in what is written, or a schedule becomes a second
// copy running continuously between fires.
func TestAScheduledProcessRunsOnItsCadenceRatherThanContinuously(t *testing.T) {
	every := aProcess()
	every.Schedule = "0 3 * * *"

	unit := unitFor(every)
	if strings.Contains(unit, "Restart=always") {
		t.Fatalf("a scheduled process is restarted whenever it exits, so it never stops:\n%s", unit)
	}
	if !strings.Contains(unit, "Type=oneshot") {
		t.Fatalf("a scheduled process is not a step that finishes:\n%s", unit)
	}

	timer := timerFor(every)
	if !strings.Contains(timer, "OnCalendar=") {
		t.Fatalf("a scheduled process has no cadence:\n%s", timer)
	}
	// A fire missed while the machine was off happens when it returns, rather than being skipped —
	// the difference between a machine that was down and a schedule that quietly stopped.
	if !strings.Contains(timer, "Persistent=true") {
		t.Fatalf("a missed fire is skipped silently:\n%s", timer)
	}
}

// Five-field cron becomes what a timer reads, rather than the host waking to decide.
func TestACronBecomesATimersCalendar(t *testing.T) {
	for cron, want := range map[string]string{
		"0 3 * * *":   "*-*-* 3:0:00",
		"30 4 1 * *":  "*-*-1 4:30:00",
		"0 0 * * mon": "mon *-*-* 0:0:00",
	} {
		if got := calendarFor(cron); got != want {
			t.Fatalf("%q became %q rather than %q", cron, got, want)
		}
	}
}

// And the long-running mode is unchanged by any of it: it stays up and comes back.
func TestAProcessThatStaysUpIsStillRestartedWhenItExits(t *testing.T) {
	unit := unitFor(aProcess())
	if !strings.Contains(unit, "Restart=always") {
		t.Fatalf("a process that should stay up is not restarted when it exits:\n%s", unit)
	}
	if strings.Contains(unit, "Type=oneshot") {
		t.Fatalf("a process that should stay up is declared a step:\n%s", unit)
	}
}

// **A unit file reinterprets a value in three ways nothing else does**, and a module's environment
// routinely contains all three — a generated password is arbitrary bytes.
func TestAnEnvironmentValueMeansWhatTheDeclarationSaid(t *testing.T) {
	// A percent begins a specifier: %H is the hostname. A password containing one would be
	// silently replaced, failing as an authentication error nobody can explain from the
	// declaration.
	percent := aProcess()
	percent.Env = map[string]string{"PASSWORD": "a%Hb"}
	if !strings.Contains(unitFor(percent), "%%H") {
		t.Fatalf("a percent was left as a systemd specifier:\n%s", unitFor(percent))
	}

	// Whitespace separates assignments: unquoted, K=a b sets K to "a" and reads "b" as another.
	spaced := aProcess()
	spaced.Env = map[string]string{"GREETING": "hello there"}
	if !strings.Contains(unitFor(spaced), `"GREETING=hello there"`) {
		t.Fatalf("a value with a space was not quoted:\n%s", unitFor(spaced))
	}

	// A quote would end the quoting early, and what follows would be read as unit syntax.
	quoted := aProcess()
	quoted.Env = map[string]string{"TOKEN": `a"b`}
	line := ""
	for _, l := range strings.Split(unitFor(quoted), "\n") {
		if strings.HasPrefix(l, "Environment=") {
			line = l
		}
	}
	if !strings.Contains(line, `\"`) {
		t.Fatalf("a quote was not escaped, so the value ends early: %s", line)
	}
}

func TestAnUndeclaredProcessIsRemovedWithItsUnitAndBundle(t *testing.T) {
	// novox/hq ADR 0118: a process's unit and bundle are the host's own, so they go with the
	// declaration. Before, there was no way to remove a process at all, and one left undeclared
	// failed every apply on its node.
	units, bundles := t.TempDir(), t.TempDir()
	wasUnits, wasBundles := unitDir, daemonRoot
	unitDir, daemonRoot = units, bundles
	t.Cleanup(func() { unitDir, daemonRoot = wasUnits, wasBundles })

	for _, f := range []string{"mesh-job.service", "mesh-job.timer"} {
		if err := os.WriteFile(filepath.Join(units, f), []byte("[Unit]\n"), 0o644); err != nil {
			t.Fatal(err)
		}
	}
	if err := os.MkdirAll(filepath.Join(bundles, "mesh-job", "bin"), 0o755); err != nil {
		t.Fatal(err)
	}
	var commands []string
	run := func(ctx context.Context, name string, args ...string) (string, error) {
		commands = append(commands, strings.Join(args, " "))
		return "", nil
	}
	known := store.State{Resources: []store.Applied{{ID: "p", Type: "process", Target: "mesh-job"}}}
	d := parse(t, `{"declaration":1,"resources":[
	  {"id":"f","type":"file","path":"`+filepath.Join(t.TempDir(), "a")+`","content":"a\n"}
	]}`)
	report, after, err := Apply(context.Background(), archHost(t), d, known, store.OriginCarried, run, nil, nil)
	if err != nil {
		t.Fatalf("an undeclared process failed the apply: %v", err)
	}
	joined := strings.Join(commands, "; ")
	timer, service := strings.Index(joined, "disable --now mesh-job.timer"), strings.Index(joined, "disable --now mesh-job.service")
	if timer < 0 || service < 0 || timer > service {
		t.Errorf("the timer and the unit were not stopped, timer first: %s", joined)
	}
	if !strings.Contains(joined, "daemon-reload") {
		t.Errorf("the service manager was not told its units changed: %s", joined)
	}
	for _, gone := range []string{filepath.Join(units, "mesh-job.service"), filepath.Join(units, "mesh-job.timer"), filepath.Join(bundles, "mesh-job")} {
		if _, err := os.Stat(gone); !os.IsNotExist(err) {
			t.Errorf("%s is still there", gone)
		}
	}
	if o := outcomeOf(report, "p"); o.Action != "removed" {
		t.Errorf("outcome %+v, want removed", o)
	}
	if _, still := after.Find("p"); still {
		t.Error("the host still believes it owns the process")
	}

	// Again, with everything already gone: forgotten, not an error.
	_, _, err = Apply(context.Background(), archHost(t), d, known, store.OriginCarried, run, nil, nil)
	if err != nil {
		t.Errorf("removing a process that is already gone failed: %v", err)
	}
}

func TestAProcessRecordedUnderAPathlikeNameIsRefusedNotRemoved(t *testing.T) {
	// filepath.Join(daemonRoot, "..") is the mesh's own directory, and removal deletes what that
	// names, whole. A record is what some host wrote, perhaps under looser rules than today's, so
	// the removal holds the name to the declaration's rule again (novox/hq ADR 0118).
	root := t.TempDir()
	bundles := filepath.Join(root, "daemons")
	wasUnits, wasBundles := unitDir, daemonRoot
	unitDir, daemonRoot = t.TempDir(), bundles
	t.Cleanup(func() { unitDir, daemonRoot = wasUnits, wasBundles })
	precious := filepath.Join(root, "state.json")
	if err := os.MkdirAll(filepath.Join(bundles, "other"), 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(precious, []byte("{}"), 0o600); err != nil {
		t.Fatal(err)
	}
	for _, name := range []string{"..", ".", "", "-x"} {
		known := store.State{Resources: []store.Applied{{ID: "p", Type: "process", Target: name}}}
		d := parse(t, `{"declaration":1,"resources":[
		  {"id":"f","type":"file","path":"`+filepath.Join(t.TempDir(), "a")+`","content":"a\n"}
		]}`)
		if _, _, err := Apply(context.Background(), archHost(t), d, known, store.OriginCarried, noServices, nil, nil); err == nil {
			t.Errorf("a process recorded as %q was removed by name", name)
		}
		for _, still := range []string{precious, filepath.Join(bundles, "other")} {
			if _, err := os.Stat(still); err != nil {
				t.Fatalf("removing a process recorded as %q took %s with it", name, still)
			}
		}
	}
}