// Copyright (c) 2026 Storm Dragon
// SPDX-License-Identifier: GPL-3.0-or-later

package tentacle

import (
	"context"
	"encoding/json"
	"errors"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"syscall"
	"testing"
	"time"
)

func supervisor_program(t testing.TB) []string {
	t.Helper()
	executable, err := os.Executable()
	if err != nil {
		t.Fatal(err)
	}
	return []string{executable, "-test.run=^TestSupervisorHelper$", "--", "supervisor"}
}

func supervised_manager(t testing.TB) *Manager {
	t.Helper()
	manager, err := NewSupervisedManager(supervisor_program(t), "auto")
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() {
		ctx, cancel := context.WithTimeout(context.Background(), 7*time.Second)
		defer cancel()
		if err := manager.Shutdown(ctx); err != nil {
			t.Error(err)
		}
		if manager.Stats() != (Stats{}) {
			t.Error(manager.Stats())
		}
	})
	return manager
}

func supervised_descendant(t testing.TB, session *Session) int {
	t.Helper()
	result, err := session.Invoke(context.Background(), "echo", nil)
	if err != nil {
		t.Fatal(err)
	}
	value := wait_result(t, result)
	var pid int
	if value.Err != nil || json.Unmarshal(value.Value, &pid) != nil || pid <= 1 {
		t.Fatalf("descendant: %+v", value)
	}
	return pid
}

func wait_supervised_reap(t *testing.T, pid int) {
	t.Helper()
	deadline := time.NewTimer(6 * time.Second)
	defer deadline.Stop()
	ticker := time.NewTicker(time.Millisecond)
	defer ticker.Stop()
	for {
		if _, err := os.Stat("/proc/" + strconv.Itoa(pid)); os.IsNotExist(err) || errors.Is(err, syscall.ESRCH) {
			return
		}
		select {
		case <-deadline.C:
			t.Fatalf("supervisor did not reap descendant %d", pid)
		case <-ticker.C:
		}
	}
}

func TestSupervisorHelper(t *testing.T) {
	if os.Args[len(os.Args)-1] == "supervisor" {
		if err := RunSupervisor(context.Background()); err != nil {
			os.Exit(1)
		}
		os.Exit(0)
	}
	if len(os.Args) < 3 || os.Args[len(os.Args)-2] != "supervisor-owner" {
		return
	}
	marker := os.Args[len(os.Args)-1]
	manager, err := NewSupervisedManager(supervisor_program(t), "auto")
	if err != nil {
		t.Fatal(err)
	}
	session := start_active(t, manager, "sample", "spawn-chain")
	pid := supervised_descendant(t, session)
	if err := os.WriteFile(marker, []byte(strconv.Itoa(pid)), 0600); err != nil {
		t.Fatal(err)
	}
	// Abrupt reader death: no Disable, Shutdown, deferred cleanup or signals.
	os.Exit(0)
}

func TestSupervisionWithoutInitToolsCleansDetachedDescendants(t *testing.T) {
	t.Setenv("PATH", "")
	t.Setenv("CTHULHU_TENTACLE_CGROUP_PARENT", "")
	for _, mode := range []string{"spawn", "spawn-detached", "spawn-chain"} {
		t.Run(mode, func(t *testing.T) {
			manager := supervised_manager(t)
			first := start_active(t, manager, "first", mode)
			second := start_active(t, manager, "second", "spawn-detached")
			pid := supervised_descendant(t, first)
			other := supervised_descendant(t, second)
			first.Disable()
			wait_signal(t, first.Done())
			if state, err := first.Status(); state != Stopped || err != nil {
				t.Fatalf("disable: %s %v", state, err)
			}
			wait_supervised_reap(t, pid)
			if _, err := os.Stat("/proc/" + strconv.Itoa(other)); err != nil {
				t.Fatal("another session was terminated", err)
			}
			second.Disable()
			wait_signal(t, second.Done())
			wait_supervised_reap(t, other)
		})
	}
}

func TestSupervisionCleansDescendantsAfterReaderDeath(t *testing.T) {
	t.Setenv("PATH", "")
	t.Setenv("CTHULHU_TENTACLE_CGROUP_PARENT", "")
	executable, _ := os.Executable()
	marker := filepath.Join(t.TempDir(), "descendant")
	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
	defer cancel()
	command := exec.CommandContext(ctx, executable, "-test.run=^TestSupervisorHelper$", "--", "supervisor-owner", marker)
	if output, err := command.CombinedOutput(); err != nil {
		t.Fatalf("owner: %v %s", err, output)
	}
	data, err := os.ReadFile(marker)
	if err != nil {
		t.Fatal(err)
	}
	pid, err := strconv.Atoi(string(data))
	if err != nil || pid <= 1 {
		t.Fatal("invalid descendant marker")
	}
	wait_supervised_reap(t, pid)
}

func TestSupervisionReapsExitedDescendantWhileSessionActive(t *testing.T) {
	t.Setenv("CTHULHU_TENTACLE_CGROUP_PARENT", "")
	manager := supervised_manager(t)
	session := start_active(t, manager, "sample", "spawn-chain")
	pid := supervised_descendant(t, session)
	if err := syscall.Kill(pid, syscall.SIGKILL); err != nil {
		t.Fatal(err)
	}
	wait_supervised_reap(t, pid)
	if state, err := session.Status(); state != Active || err != nil {
		t.Fatalf("descendant exit retired the live session: %s %v", state, err)
	}
	// A status flag alone does not prove the main child's protocol still works.
	_ = supervised_descendant(t, session)
}

func TestSupervisionMissingProgramReleasesCapacity(t *testing.T) {
	t.Setenv("CTHULHU_TENTACLE_CGROUP_PARENT", "")
	manager := supervised_manager(t)
	spec := Spec{ID: "sample", Program: []string{filepath.Join(t.TempDir(), "missing")}}
	session, err := manager.Start(context.Background(), spec)
	if err != nil {
		t.Fatal(err)
	}
	wait_signal(t, session.Done())
	if state, failure := session.Status(); state != Failed || failure == nil {
		t.Fatal(state, failure)
	}
	healthy := start_active(t, manager, "sample", "echo")
	healthy.Disable()
	wait_signal(t, healthy.Done())
}

func TestSupervisionRejectsInvalidExplicitCgroupParent(t *testing.T) {
	for _, parent := range []string{"relative", t.TempDir()} {
		if _, err := NewSupervisedManager(supervisor_program(t), parent); !errors.Is(err, ErrContainment) {
			t.Fatalf("silently ignored explicit parent %q: %v", parent, err)
		}
	}
	t.Setenv("CTHULHU_TENTACLE_CGROUP_PARENT", t.TempDir())
	if _, err := NewSupervisedManager(supervisor_program(t), "auto"); !errors.Is(err, ErrContainment) {
		t.Fatalf("silently ignored configured parent: %v", err)
	}
}

func TestSupervisionCancelledStartupReleasesCapacity(t *testing.T) {
	t.Setenv("CTHULHU_TENTACLE_CGROUP_PARENT", "")
	manager := supervised_manager(t)
	session, err := manager.Start(context.Background(), child_spec(t, "sample", "hang-start"))
	if err != nil {
		t.Fatal(err)
	}
	wait_control(t, func() bool {
		session.mutex.Lock()
		defer session.mutex.Unlock()
		return len(session.pending) > 0
	})
	session.Disable()
	wait_signal(t, session.Done())
	if state, err := session.Status(); state != Stopped || err != nil {
		t.Fatal(state, err)
	}
	healthy := start_active(t, manager, "sample", "echo")
	healthy.Disable()
	wait_signal(t, healthy.Done())
}

func TestSupervisionDetectsChildExitAfterActivation(t *testing.T) {
	t.Setenv("CTHULHU_TENTACLE_CGROUP_PARENT", "")
	manager := supervised_manager(t)
	session := start_active(t, manager, "sample", "exit-active")
	wait_signal(t, session.Done())
	if state, err := session.Status(); state != Failed || !errors.Is(err, ErrExited) {
		t.Fatal(state, err)
	}
}