package apply

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

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

// Defends novox/hq ADR 0117: a service that omits its state leaves the unit's lifecycle to the
// machine. The mesh reflects its triggers on a unit already running and does nothing else to it —
// never starts, stops, enables or disables it, and forgets it when undeclared.

// unitIn is a service manager whose one unit is active or not, recording what it is asked.
func unitIn(active bool, commands *[]string) Runner {
	return func(_ context.Context, name string, args ...string) (string, error) {
		line := name + " " + strings.Join(args, " ")
		*commands = append(*commands, line)
		switch {
		case strings.Contains(line, "is-enabled"):
			return "enabled", nil
		case strings.Contains(line, "show") && strings.Contains(line, "ActiveState"):
			if active {
				return "LoadState=loaded\nActiveState=active\nSubState=running", nil
			}
			return "LoadState=loaded\nActiveState=inactive\nSubState=dead", nil
		}
		return "", nil
	}
}

func statelessDecl(path, content, triggers string) string {
	return fmt.Sprintf(`{"declaration":1,"resources":[
	  {"id":"uplink.conf","type":"file","path":%q,"into":"block","content":%q},
	  {"id":"uplink.manager","type":"service","unit":"NetworkManager.service",%s}
	]}`, path, content, triggers)
}

// touched is whether any command would change the unit's lifecycle.
func touched(commands []string) []string {
	var changing []string
	for _, c := range commands {
		for _, verb := range []string{" start ", " stop ", " restart ", " enable ", " disable ", " reload "} {
			if strings.Contains(c+" ", verb) {
				changing = append(changing, c)
			}
		}
	}
	return changing
}

func TestAStatelessServiceRunningIsReloadedForItsTrigger(t *testing.T) {
	path := filepath.Join(t.TempDir(), "mesh.conf")
	var commands []string
	report, _, err := Apply(context.Background(), archHost(t),
		parse(t, statelessDecl(path, "[main]\ndns=none\n", `"reload-on":["uplink.conf"]`)),
		store.State{}, store.OriginDeclared, unitIn(true, &commands), nil, nil)
	if err != nil {
		t.Fatal(err)
	}
	joined := strings.Join(commands, "\n")
	if !strings.Contains(joined, "systemctl reload NetworkManager.service") {
		t.Errorf("the running manager was not reloaded; commands were %v", commands)
	}
	for _, c := range touched(commands) {
		if !strings.Contains(c, "reload") {
			t.Errorf("the manager's lifecycle was touched: %s", c)
		}
	}
	if o := outcomeOf(report, "uplink.manager"); o.Action != "updated" || !strings.Contains(o.Detail, "reloaded for uplink.conf") {
		t.Errorf("reported as %q: %s", o.Action, o.Detail)
	}
}

func TestAStatelessServiceNotRunningIsLeftSo(t *testing.T) {
	path := filepath.Join(t.TempDir(), "mesh.conf")
	for _, triggers := range []string{`"reload-on":["uplink.conf"]`, `"restart-on":["uplink.conf"]`} {
		var commands []string
		report, _, err := Apply(context.Background(), archHost(t),
			parse(t, statelessDecl(path, fmt.Sprintf("# %s\n", triggers), triggers)),
			store.State{}, store.OriginDeclared, unitIn(false, &commands), nil, nil)
		if err != nil {
			t.Fatal(err)
		}
		if changing := touched(commands); len(changing) > 0 {
			t.Errorf("%s: an inactive unit was acted on: %v", triggers, changing)
		}
		if o := outcomeOf(report, "uplink.manager"); o.Action != "unchanged" ||
			o.Detail != "not running; the change applies at its next start" {
			t.Errorf("%s: reported as %q: %s", triggers, o.Action, o.Detail)
		}
	}
}

func TestAStatelessServiceIsRestartedOnlyForItsRestartTrigger(t *testing.T) {
	path := filepath.Join(t.TempDir(), "mesh.conf")
	var commands []string
	d := parse(t, statelessDecl(path, "x\n", `"restart-on":["uplink.conf"]`))
	_, state, err := Apply(context.Background(), archHost(t), d, store.State{}, store.OriginDeclared,
		unitIn(true, &commands), nil, nil)
	if err != nil {
		t.Fatal(err)
	}
	if !strings.Contains(strings.Join(commands, "\n"), "stop NetworkManager.service") {
		t.Errorf("not restarted for its restart trigger; commands were %v", commands)
	}
	// Nothing it reflects changed: nothing is asked of the unit at all.
	commands = nil
	report, _, err := Apply(context.Background(), archHost(t), d, state, store.OriginDeclared,
		unitIn(true, &commands), nil, nil)
	if err != nil {
		t.Fatal(err)
	}
	if changing := touched(commands); len(changing) > 0 {
		t.Errorf("with nothing changed the unit was acted on: %v", changing)
	}
	if got := outcomeOf(report, "uplink.manager").Action; got != "unchanged" {
		t.Errorf("with nothing changed it was %q", got)
	}
}

func TestAStatelessServiceUndeclaredIsForgottenNotStopped(t *testing.T) {
	path := filepath.Join(t.TempDir(), "mesh.conf")
	var commands []string
	_, state, err := Apply(context.Background(), archHost(t),
		parse(t, statelessDecl(path, "x\n", `"reload-on":["uplink.conf"]`)),
		store.State{}, store.OriginDeclared, unitIn(true, &commands), nil, nil)
	if err != nil {
		t.Fatal(err)
	}
	if rec, _ := state.Find("uplink.manager"); !rec.Stateless {
		t.Fatal("the record does not say the service was stateless")
	}
	if steps := Plan(somethingElse(t), state, store.OriginDeclared); !hasStep(steps, "forget", "uplink.manager") {
		t.Errorf("the preview does not forget it: %v", steps)
	}
	commands = nil
	report, _, err := Apply(context.Background(), archHost(t), somethingElse(t), state, store.OriginDeclared,
		unitIn(true, &commands), nil, nil)
	if err != nil {
		t.Fatal(err)
	}
	if changing := touched(commands); len(changing) > 0 {
		t.Errorf("undeclaring acted on the unit: %v", changing)
	}
	o := outcomeOf(report, "uplink.manager")
	if o.Action != "forgotten" || o.Detail != "its state was never the mesh's" {
		t.Errorf("undeclaring was %q: %s", o.Action, o.Detail)
	}
}

func TestAStatelessServiceIsNeverHeldOnAnAdoptedNode(t *testing.T) {
	path := filepath.Join(t.TempDir(), "mesh.conf")
	resources := fmt.Sprintf(`{"id":"uplink.conf","type":"file","path":%q,"into":"block","content":"x\n"},
	  {"id":"uplink.manager","type":"service","unit":"NetworkManager.service","reload-on":["uplink.conf"]}`, path)
	d := adopted(t, `{"taken":[],"untaken":{"uplink":["uplink.conf","uplink.manager"]}}`, resources)
	for _, s := range Plan(d, store.State{}, store.OriginDeclared) {
		if s.ID == "uplink.manager" && (s.Verb == "hold" || s.Verb == "create" || strings.Contains(s.Why, "replaces")) {
			t.Errorf("the preview holds or replaces a stateless service: %+v", s)
		}
	}
	var commands []string
	report, state, err := ApplyKeeping(context.Background(), archHost(t), d, store.State{},
		store.OriginDeclared, unitIn(true, &commands), nil, nil, KeepIn(t.TempDir()))
	if err != nil {
		t.Fatal(err)
	}
	if got := outcomeOf(report, "uplink.manager").Action; got == "held" {
		t.Fatal("a stateless service was held, though it replaces nothing that was found")
	}
	if len(state.Held) != 0 {
		t.Errorf("something was held: %+v", state.Held)
	}
	for _, c := range touched(commands) {
		if !strings.Contains(c, "reload") {
			t.Errorf("the adopted node's manager lifecycle was touched: %s", c)
		}
	}
}

func hasStep(steps []Step, verb, id string) bool {
	for _, s := range steps {
		if s.Verb == verb && s.ID == id {
			return true
		}
	}
	return false
}