// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

package v1alpha1

import (
	"context"
	"errors"
	"fmt"
	"io"
	"log"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/siderolabs/go-kmsg"
	"golang.org/x/sync/errgroup"

	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime"
	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime/logging"
	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime/v1alpha1/acpi"
	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime/v1alpha2"
	krnl "github.com/siderolabs/talos/pkg/kernel"
	"github.com/siderolabs/talos/pkg/machinery/api/common"
	"github.com/siderolabs/talos/pkg/machinery/api/machine"
	"github.com/siderolabs/talos/pkg/machinery/kernel"
)

// Controller represents the controller responsible for managing the execution
// of sequences.
type Controller struct {
	s  runtime.Sequencer
	r  *Runtime
	v2 *v1alpha2.Controller

	priorityLock *PriorityLock[runtime.Sequence]
}

// NewController intializes and returns a controller.
func NewController() (*Controller, error) {
	s, err := NewState()
	if err != nil {
		return nil, err
	}

	// TODO: this should be streaming capacity and probably some constant
	e := NewEvents(1000, 10)

	l := logging.NewCircularBufferLoggingManager(log.New(os.Stdout, "machined fallback logger: ", log.Flags()))

	ctlr := &Controller{
		r:            NewRuntime(s, e, l),
		s:            NewSequencer(),
		priorityLock: NewPriorityLock[runtime.Sequence](),
	}

	ctlr.v2, err = v1alpha2.NewController(ctlr.r)
	if err != nil {
		return nil, err
	}

	if err := ctlr.setupLogging(); err != nil {
		return nil, err
	}

	return ctlr, nil
}

func (c *Controller) setupLogging() error {
	machinedLog, err := c.r.Logging().ServiceLog("machined").Writer()
	if err != nil {
		return err
	}

	if c.r.State().Platform().Mode() == runtime.ModeContainer {
		// send all the logs to machinedLog as well, but skip /dev/kmsg logging
		log.SetOutput(io.MultiWriter(log.Writer(), machinedLog))
		log.SetPrefix("[talos] ")

		return nil
	}

	// disable ratelimiting for kmsg, otherwise logs might be not visible.
	// this should be set via kernel arg, but in case it's not set, try to force it.
	if err = krnl.WriteParam(&kernel.Param{
		Key:   "proc.sys.kernel.printk_devkmsg",
		Value: "on\n",
	}); err != nil {
		var serr syscall.Errno

		if !(errors.As(err, &serr) && serr == syscall.EINVAL) { // ignore EINVAL which is returned when kernel arg is set
			log.Printf("failed setting kernel.printk_devkmsg: %s, error ignored", err)
		}
	}

	if err = kmsg.SetupLogger(nil, "[talos]", machinedLog); err != nil {
		return fmt.Errorf("failed to setup logging: %w", err)
	}

	return nil
}

// Run executes all phases known to the controller in serial. `Controller`
// aborts immediately if any phase fails.
func (c *Controller) Run(ctx context.Context, seq runtime.Sequence, data any, setters ...runtime.LockOption) error {
	// We must ensure that the runtime is configured since all sequences depend
	// on the runtime.
	if c.r == nil {
		return runtime.ErrUndefinedRuntime
	}

	ctx, err := c.priorityLock.Lock(ctx, time.Minute, seq, setters...)
	if err != nil {
		if errors.Is(err, runtime.ErrLocked) {
			c.Runtime().Events().Publish(context.Background(), &machine.SequenceEvent{
				Sequence: seq.String(),
				Action:   machine.SequenceEvent_NOOP,
				Error: &common.Error{
					Code:    common.Code_LOCKED,
					Message: fmt.Sprintf("sequence not started: %s", runtime.ErrLocked.Error()),
				},
			})
		}

		return err
	}

	defer c.priorityLock.Unlock()

	phases, err := c.phases(seq, data)
	if err != nil {
		return err
	}

	err = c.run(ctx, seq, phases, data)
	if err != nil {
		code := common.Code_FATAL

		if errors.Is(err, context.Canceled) {
			code = common.Code_CANCELED
		}

		c.Runtime().Events().Publish(ctx, &machine.SequenceEvent{
			Sequence: seq.String(),
			Action:   machine.SequenceEvent_NOOP,
			Error: &common.Error{
				Code:    code,
				Message: fmt.Sprintf("sequence failed: %s", err.Error()),
			},
		})

		return err
	}

	return nil
}

// V1Alpha2 implements the controller interface.
func (c *Controller) V1Alpha2() runtime.V1Alpha2Controller {
	return c.v2
}

// Runtime implements the controller interface.
func (c *Controller) Runtime() runtime.Runtime {
	return c.r
}

// Sequencer implements the controller interface.
func (c *Controller) Sequencer() runtime.Sequencer {
	return c.s
}

// ListenForEvents starts the event listener. The listener will trigger a
// shutdown in response to a SIGTERM signal and ACPI button/power event.
func (c *Controller) ListenForEvents(ctx context.Context) error {
	sigs := make(chan os.Signal, 1)

	signal.Notify(sigs, syscall.SIGTERM)

	errCh := make(chan error, 2)

	go func() {
		<-sigs
		signal.Stop(sigs)

		log.Printf("shutdown via SIGTERM received")

		if err := c.Run(ctx, runtime.SequenceShutdown, &machine.ShutdownRequest{Force: true}, runtime.WithTakeover()); err != nil {
			if !runtime.IsRebootError(err) {
				log.Printf("shutdown failed: %v", err)
			}
		}

		errCh <- nil
	}()

	if c.r.State().Platform().Mode() == runtime.ModeContainer {
		return nil
	}

	go func() {
		if err := acpi.StartACPIListener(); err != nil {
			errCh <- err

			return
		}

		log.Printf("shutdown via ACPI received")

		if err := c.Run(ctx, runtime.SequenceShutdown, &machine.ShutdownRequest{Force: true}, runtime.WithTakeover()); err != nil {
			if !runtime.IsRebootError(err) {
				log.Printf("failed to run shutdown sequence: %s", err)
			}
		}

		errCh <- nil
	}()

	err := <-errCh

	return err
}

func (c *Controller) run(ctx context.Context, seq runtime.Sequence, phases []runtime.Phase, data any) error {
	c.Runtime().Events().Publish(ctx, &machine.SequenceEvent{
		Sequence: seq.String(),
		Action:   machine.SequenceEvent_START,
	})

	defer c.Runtime().Events().Publish(ctx, &machine.SequenceEvent{
		Sequence: seq.String(),
		Action:   machine.SequenceEvent_STOP,
	})

	start := time.Now()

	var (
		number int
		phase  runtime.Phase
		err    error
	)

	log.Printf("%s sequence: %d phase(s)", seq.String(), len(phases))

	defer func() {
		if err != nil {
			if !runtime.IsRebootError(err) {
				log.Printf("%s sequence: failed", seq.String())
			}
		} else {
			log.Printf("%s sequence: done: %s", seq.String(), time.Since(start))
		}
	}()

	for number, phase = range phases {
		if phase.CheckFunc != nil && !phase.CheckFunc() {
			continue
		}

		// Make the phase number human friendly.
		number++

		start := time.Now()

		progress := fmt.Sprintf("%d/%d", number, len(phases))

		log.Printf("phase %s (%s): %d tasks(s)", phase.Name, progress, len(phase.Tasks))

		if err = c.runPhase(ctx, phase, seq, data); err != nil {
			if !runtime.IsRebootError(err) {
				log.Printf("phase %s (%s): failed", phase.Name, progress)
			}

			return fmt.Errorf("error running phase %d in %s sequence: %w", number, seq.String(), err)
		}

		log.Printf("phase %s (%s): done, %s", phase.Name, progress, time.Since(start))

		select {
		case <-ctx.Done():
			return ctx.Err()
		default:
		}
	}

	return nil
}

func (c *Controller) runPhase(ctx context.Context, phase runtime.Phase, seq runtime.Sequence, data any) error {
	c.Runtime().Events().Publish(ctx, &machine.PhaseEvent{
		Phase:  phase.Name,
		Action: machine.PhaseEvent_START,
	})

	defer c.Runtime().Events().Publish(ctx, &machine.PhaseEvent{
		Phase:  phase.Name,
		Action: machine.PhaseEvent_STOP,
	})

	eg, ctx := errgroup.WithContext(ctx)

	for number, task := range phase.Tasks {
		// Make the task number human friendly.
		number++

		eg.Go(func() error {
			progress := fmt.Sprintf("%d/%d", number, len(phase.Tasks))

			if err := c.runTask(ctx, progress, task, seq, data); err != nil {
				return fmt.Errorf("task %s: failed, %w", progress, err)
			}

			return nil
		})
	}

	return eg.Wait()
}

func (c *Controller) runTask(ctx context.Context, progress string, f runtime.TaskSetupFunc, seq runtime.Sequence, data any) error {
	task, taskName := f(seq, data)
	if task == nil {
		return nil
	}

	start := time.Now()

	c.Runtime().Events().Publish(ctx, &machine.TaskEvent{
		Task:   taskName,
		Action: machine.TaskEvent_START,
	})

	var err error

	log.Printf("task %s (%s): starting", taskName, progress)

	defer func() {
		if err != nil {
			if !runtime.IsRebootError(err) {
				log.Printf("task %s (%s): failed: %s", taskName, progress, err)
			}
		} else {
			log.Printf("task %s (%s): done, %s", taskName, progress, time.Since(start))
		}
	}()

	defer c.Runtime().Events().Publish(ctx, &machine.TaskEvent{
		Task:   taskName,
		Action: machine.TaskEvent_STOP,
	})

	logger := log.New(log.Writer(), fmt.Sprintf("[talos] task %s (%s): ", taskName, progress), log.Flags())

	err = task(ctx, logger, c.r)

	return err
}

//nolint:gocyclo
func (c *Controller) phases(seq runtime.Sequence, data any) ([]runtime.Phase, error) {
	var phases []runtime.Phase

	switch seq {
	case runtime.SequenceBoot:
		phases = c.s.Boot(c.r)
	case runtime.SequenceInitialize:
		phases = c.s.Initialize(c.r)
	case runtime.SequenceInstall:
		phases = c.s.Install(c.r)
	case runtime.SequenceShutdown:
		in, ok := data.(*machine.ShutdownRequest)
		if !ok {
			return nil, runtime.ErrInvalidSequenceData
		}

		phases = c.s.Shutdown(c.r, in)
	case runtime.SequenceReboot:
		phases = c.s.Reboot(c.r)
	case runtime.SequenceUpgrade:
		in, ok := data.(*machine.UpgradeRequest)
		if !ok {
			return nil, runtime.ErrInvalidSequenceData
		}

		phases = c.s.Upgrade(c.r, in)
	case runtime.SequenceStageUpgrade:
		in, ok := data.(*machine.UpgradeRequest)
		if !ok {
			return nil, runtime.ErrInvalidSequenceData
		}

		phases = c.s.StageUpgrade(c.r, in)
	case runtime.SequenceMaintenanceUpgrade:
		in, ok := data.(*machine.UpgradeRequest)
		if !ok {
			return nil, runtime.ErrInvalidSequenceData
		}

		phases = c.s.MaintenanceUpgrade(c.r, in)
	case runtime.SequenceReset:
		in, ok := data.(runtime.ResetOptions)
		if !ok {
			return nil, runtime.ErrInvalidSequenceData
		}

		phases = c.s.Reset(c.r, in)
	case runtime.SequenceNoop:
	default:
		return nil, fmt.Errorf("sequence not implemented: %q", seq)
	}

	return phases, nil
}