package main

// The module's shape (novox/hq issue 746): the setting's default is what the kernel boots with, so
// assigning the module changes nothing until a machine sets another value; the script is written into the
// module's own state and run by a sandboxed oneshot unit that is reloaded (applied again) when the script,
// and so the setting, changes and restarted only when the unit does; and the script itself sets, verifies,
// gives back and refuses as it says.

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

func TestTheDefaultChangesNothingAndTheUnitFollowsTheSetting(t *testing.T) {
	m := manifest(t)
	s := m.Settings["transparent-huge-pages"]
	if s["kind"] != "preference" || s["default"] != "always" || s["why"] == "" {
		t.Fatalf("the setting: %v", s)
	}
	var ids []string
	for _, r := range m.Resources {
		ids = append(ids, r["id"].(string))
	}
	if strings.Join(ids, " ") != "state huge-pages unit apply" {
		t.Fatalf("order: %v", ids)
	}
	script := m.resource(t, "huge-pages")
	// The script runs as root, so the setting it is written from is set at the terminal alone (issue 339).
	if script["path"] != "${dir:state}/huge-pages" || script["mode"] != "0755" || script["trusted"] != true ||
		!strings.Contains(script["content"].(string), "want='${setting:transparent-huge-pages}'") {
		t.Fatalf("the script: %v", script["path"])
	}
	unit := m.resource(t, "unit")["content"].(string)
	for _, line := range []string{"Type=oneshot", "RemainAfterExit=yes", "ExecStart=${dir:state}/huge-pages apply",
		"ExecReload=${dir:state}/huge-pages apply", "ExecStop=${dir:state}/huge-pages restore", "WantedBy=sysinit.target",
		"DefaultDependencies=no", "ProtectSystem=strict", "ReadWritePaths=${dir:state}", "ProtectHome=yes", "PrivateNetwork=yes",
		"NoNewPrivileges=yes"} {
		if !strings.Contains(unit, line+"\n") {
			t.Errorf("the unit lacks %q", line)
		}
	}
	apply := m.resource(t, "apply")
	if apply["unit"] != "mesh-kernel-huge-pages.service" || apply["state"] != "running" || apply["boot"] != "enabled" {
		t.Fatalf("apply: %v", apply)
	}
	// A new value reloads (apply again); only a new unit restarts, whose stop would pass back through the
	// mode the machine was found with.
	if on := apply["restart-on"].([]any); len(on) != 1 || on[0] != "unit" {
		t.Fatalf("restart-on: %v", on)
	}
	if on := apply["reload-on"].([]any); len(on) != 1 || on[0] != "huge-pages" {
		t.Fatalf("reload-on: %v", on)
	}
	if h := apply["health"].(map[string]any); h["kind"] != "unit" {
		t.Fatalf("health: %v", h)
	}
}

// bed is the script as the mesh writes it for one value of the setting, a stand-in transparent_hugepage
// directory, the module's state, and a PATH whose journalctl records that it was asked to rotate.
type bed struct {
	script, sys, state, rotated, path, bin string
}

func newBed(t *testing.T, want, found string) bed {
	return newBedIn(t, t.TempDir(), want, found)
}

// newBedIn writes the script for want into dir; a second bed in the same dir shares the machine and the
// state, as a reload with a new value does.
func newBedIn(t *testing.T, dir, want, found string) bed {
	t.Helper()
	b := bed{script: filepath.Join(dir, "huge-pages"), sys: filepath.Join(dir, "thp"), state: filepath.Join(dir, "state"),
		rotated: filepath.Join(dir, "rotated")}
	content := manifest(t).resource(t, "huge-pages")["content"].(string)
	content = strings.ReplaceAll(content, "${setting:transparent-huge-pages}", want)
	content = strings.ReplaceAll(content, "${dir:state}", b.state)
	if strings.Contains(content, "${") {
		t.Fatalf("a substitution the test does not make is left in the script")
	}
	bin := filepath.Join(dir, "bin")
	for _, d := range []string{b.sys, b.state, bin} {
		if err := os.MkdirAll(d, 0o755); err != nil {
			t.Fatal(err)
		}
	}
	write(t, b.script, content, 0o755)
	if found != "" {
		write(t, filepath.Join(b.sys, "enabled"), found, 0o644)
	}
	write(t, filepath.Join(bin, "journalctl"), "#!/bin/sh\necho \"$@\" >>"+b.rotated+"\n", 0o755)
	b.bin = bin
	b.booted(t, "running")
	b.path = bin + string(os.PathListSeparator) + os.Getenv("PATH")
	return b
}

// booted makes the service manager say state for is-system-running.
func (b bed) booted(t *testing.T, state string) {
	t.Helper()
	write(t, filepath.Join(b.bin, "systemctl"), "#!/bin/sh\n[ \"$1\" = is-system-running ] && echo "+state+"\n", 0o755)
}

func write(t *testing.T, p, content string, mode os.FileMode) {
	t.Helper()
	if err := os.WriteFile(p, []byte(content), mode); err != nil {
		t.Fatal(err)
	}
}

func (b bed) run(t *testing.T, verb string) (string, error) {
	t.Helper()
	cmd := exec.Command("sh", b.script, verb, b.sys, b.state)
	cmd.Env = append(os.Environ(), "PATH="+b.path)
	out, err := cmd.CombinedOutput()
	return string(out), err
}

func (b bed) file(t *testing.T, p string) string {
	t.Helper()
	raw, err := os.ReadFile(p)
	if err != nil {
		return ""
	}
	return string(raw)
}

func TestApplySetsTheModeRotatesTheJournalOnceAndRestoreGivesBackWhatWasFound(t *testing.T) {
	// novox's file on 2026-10-14, read through node-reads.
	b := newBed(t, "madvise", "[always] madvise never\n")
	out, err := b.run(t, "apply")
	if err != nil || !strings.Contains(out, "always -> madvise") {
		t.Fatalf("apply: %v %s", err, out)
	}
	if got := b.file(t, filepath.Join(b.sys, "enabled")); got != "madvise\n" {
		t.Fatalf("written: %q", got)
	}
	if got := b.file(t, filepath.Join(b.state, "found")); got != "always\n" {
		t.Fatalf("found: %q", got)
	}
	if got := b.file(t, b.rotated); got != "--rotate\n" {
		t.Fatalf("rotation: %q", got)
	}
	// Applied again (a restart with the same value): nothing written, nothing rotated, found kept.
	if out, err := b.run(t, "apply"); err != nil || !strings.Contains(out, "madvise, as set") {
		t.Fatalf("again: %v %s", err, out)
	}
	if got := b.file(t, b.rotated); got != "--rotate\n" {
		t.Fatalf("rotated again: %q", got)
	}
	if out, err := b.run(t, "restore"); err != nil || !strings.Contains(out, "back to always") {
		t.Fatalf("restore: %v %s", err, out)
	}
	if got := b.file(t, filepath.Join(b.sys, "enabled")); got != "always\n" {
		t.Fatalf("restored: %q", got)
	}
	// Nothing of the module is kept once it is stopped.
	if _, err := os.Stat(filepath.Join(b.state, "found")); !os.IsNotExist(err) {
		t.Fatalf("found kept after restore: %v", err)
	}
}

func TestAReloadWithANewValueGoesStraightThereAndNeverRewritesFound(t *testing.T) {
	dir := t.TempDir()
	b := newBedIn(t, dir, "madvise", "[always] madvise never\n")
	if out, err := b.run(t, "apply"); err != nil {
		t.Fatalf("apply: %v %s", err, out)
	}
	// The setting changes to never: the mesh rewrites the script and reloads the unit, which applies again.
	n := newBedIn(t, dir, "never", "")
	out, err := n.run(t, "apply")
	if err != nil || !strings.Contains(out, "madvise -> never") {
		t.Fatalf("reload: %v %s", err, out)
	}
	if got := n.file(t, filepath.Join(n.state, "found")); got != "always\n" {
		t.Fatalf("found rewritten by a reload: %q", got)
	}
}

func TestNoRotationWhileTheMachineIsStarting(t *testing.T) {
	for _, state := range []string{"initializing", "starting"} {
		b := newBed(t, "madvise", "[always] madvise never\n")
		b.booted(t, state)
		out, err := b.run(t, "apply")
		if err != nil || !strings.Contains(out, "still starting") {
			t.Fatalf("%s: %v %s", state, err, out)
		}
		if got := b.file(t, filepath.Join(b.sys, "enabled")); got != "madvise\n" {
			t.Fatalf("%s: not set: %q", state, got)
		}
		if got := b.file(t, b.rotated); got != "" {
			t.Fatalf("%s: rotated at boot: %q", state, got)
		}
	}
}

func TestAlwaysIsSetWithoutRotating(t *testing.T) {
	b := newBed(t, "always", "always [madvise] never\n")
	if out, err := b.run(t, "apply"); err != nil || !strings.Contains(out, "madvise -> always") {
		t.Fatalf("apply: %v %s", err, out)
	}
	if got := b.file(t, b.rotated); got != "" {
		t.Fatalf("rotated for always: %q", got)
	}
}

func TestAValueTheKernelDoesNotTakeIsRefusedBeforeAnythingIsWritten(t *testing.T) {
	b := newBed(t, "sometimes", "[always] madvise never\n")
	out, err := b.run(t, "apply")
	if err == nil || !strings.Contains(out, "takes always, madvise or never") {
		t.Fatalf("accepted: %v %s", err, out)
	}
	if got := b.file(t, filepath.Join(b.sys, "enabled")); got != "[always] madvise never\n" {
		t.Fatalf("written anyway: %q", got)
	}
}

func TestAWriteThatDoesNotTakeFailsTheUnit(t *testing.T) {
	if os.Getuid() == 0 {
		t.Skip("root writes a read-only file")
	}
	b := newBed(t, "madvise", "[always] madvise never\n")
	if err := os.Chmod(filepath.Join(b.sys, "enabled"), 0o444); err != nil {
		t.Fatal(err)
	}
	if out, err := b.run(t, "apply"); err == nil {
		t.Fatalf("a refused write passed: %s", out)
	}
}

func TestAKernelWithoutHugePagesIsSaid(t *testing.T) {
	b := newBed(t, "madvise", "")
	if out, err := b.run(t, "apply"); err == nil || !strings.Contains(out, "built without transparent huge pages") {
		t.Fatalf("%v %s", err, out)
	}
}