package api_impl

// SPDX-License-Identifier: GPL-3.0-or-later

import (
	"context"
	"errors"
	"fmt"
	"net/http"

	"github.com/gertd/go-pluralize"
	"github.com/labstack/echo/v4"
	"github.com/rs/zerolog"

	"git.blender.org/flamenco/internal/manager/persistence"
	"git.blender.org/flamenco/internal/uuid"
	"git.blender.org/flamenco/pkg/api"
)

func (f *Flamenco) TaskUpdate(e echo.Context, taskID string) error {
	logger := requestLogger(e)
	worker := requestWorkerOrPanic(e)

	if !uuid.IsValid(taskID) {
		logger.Debug().Msg("invalid task ID received")
		return sendAPIError(e, http.StatusBadRequest, "task ID not valid")
	}
	logger = logger.With().Str("taskID", taskID).Logger()

	// Fetch the task, to see if this worker is even allowed to send us updates.
	ctx := e.Request().Context()
	dbTask, err := f.persist.FetchTask(ctx, taskID)
	if err != nil {
		logger.Warn().Err(err).Msg("cannot fetch task")
		if errors.Is(err, persistence.ErrTaskNotFound) {
			return sendAPIError(e, http.StatusNotFound, "task %+v not found", taskID)
		}
		return sendAPIError(e, http.StatusInternalServerError, "error fetching task")
	}
	if dbTask == nil {
		panic("task could not be fetched, but database gave no error either")
	}

	// Decode the request body.
	var taskUpdate api.TaskUpdate
	if err := e.Bind(&taskUpdate); err != nil {
		logger.Warn().Err(err).Msg("bad request received")
		return sendAPIError(e, http.StatusBadRequest, "invalid format")
	}
	if dbTask.WorkerID == nil {
		logger.Warn().
			Msg("worker trying to update task that's not assigned to any worker")
		return sendAPIError(e, http.StatusConflict, "task %+v is not assigned to any worker, so also not to you", taskID)
	}
	if *dbTask.WorkerID != worker.ID {
		logger.Warn().Msg("worker trying to update task that's assigned to another worker")
		return sendAPIError(e, http.StatusConflict, "task %+v is not assigned to you", taskID)
	}

	// Status 'soft-failed' should never be sent by a Worker. Distinguishing
	// between soft and hard failures is up to the Manager.
	// Workers should always just send 'failed' instead.
	if taskUpdate.TaskStatus != nil && *taskUpdate.TaskStatus == api.TaskStatusSoftFailed {
		logger.Warn().Str("status", string(*taskUpdate.TaskStatus)).
			Msg("worker trying to update task to not-allowed status")
		return sendAPIError(e, http.StatusBadRequest,
			"task status %s not allowed to be sent by Worker", *taskUpdate.TaskStatus)
	}

	bgCtx, bgCtxCancel := bgContext()
	defer bgCtxCancel()

	taskUpdateErr := f.doTaskUpdate(bgCtx, logger, worker, dbTask, taskUpdate)
	workerUpdateErr := f.workerPingedTask(logger, dbTask)
	workerSeenErr := f.workerSeen(logger, worker)

	if taskUpdateErr != nil {
		return sendAPIError(e, http.StatusInternalServerError, "unable to handle task update: %v", taskUpdateErr)
	}
	if workerUpdateErr != nil {
		return sendAPIError(e, http.StatusInternalServerError, "unable to handle worker update: %v", workerUpdateErr)
	}
	if workerSeenErr != nil {
		return sendAPIError(e, http.StatusInternalServerError, "unable to handle worker 'last seen' update: %v", workerSeenErr)
	}

	return e.NoContent(http.StatusNoContent)
}

// doTaskUpdate actually updates the task and its log file.
func (f *Flamenco) doTaskUpdate(
	ctx context.Context,
	logger zerolog.Logger,
	w *persistence.Worker,
	dbTask *persistence.Task,
	update api.TaskUpdate,
) error {
	if dbTask.Job == nil {
		logger.Panic().Msg("dbTask.Job is nil, unable to continue")
	}

	var dbErrActivity error

	if update.Activity != nil {
		dbTask.Activity = *update.Activity
		// The state machine will also save the task, including its activity, but
		// relying on that here would create strong cohesion.
		dbErrActivity = f.persist.SaveTaskActivity(ctx, dbTask)
	}

	// Write the log first, because that's likely to contain the cause of the task
	// state change. Any subsequent task logs, for example generated by the
	// Manager in response to a status change, should be logged after that.
	if update.Log != nil {
		// Errors writing the log to disk are already logged by logStorage, and can be safely ignored here.
		_ = f.logStorage.Write(logger, dbTask.Job.UUID, dbTask.UUID, *update.Log)
	}

	if update.TaskStatus == nil {
		return dbErrActivity
	}

	oldTaskStatus := dbTask.Status
	var err error
	if *update.TaskStatus == api.TaskStatusFailed {
		// Failure is more complex than just going to the failed state.
		err = f.onTaskFailed(ctx, logger, w, dbTask, update)
	} else {
		// Just go to the given state.
		err = f.stateMachine.TaskStatusChange(ctx, dbTask, *update.TaskStatus)
	}

	if err != nil {
		logger.Error().Err(err).
			Str("newTaskStatus", string(*update.TaskStatus)).
			Str("oldTaskStatus", string(oldTaskStatus)).
			Msg("error changing task status")
		return fmt.Errorf("changing status of task %s to %q: %w",
			dbTask.UUID, *update.TaskStatus, err)
	}

	return nil
}

// onTaskFailed decides whether a task is soft- or hard-failed. Note that this
// means that the task may NOT go to the status mentioned in the `update`
// parameter, but go to `soft-failed` instead.
func (f *Flamenco) onTaskFailed(
	ctx context.Context,
	logger zerolog.Logger,
	worker *persistence.Worker,
	task *persistence.Task,
	update api.TaskUpdate,
) error {
	// Sanity check.
	if update.TaskStatus == nil || *update.TaskStatus != api.TaskStatusFailed {
		panic("onTaskFailed should only be called with a task update that indicates task failure")
	}

	// Bookkeeping of failure.
	numFailed, err := f.persist.AddWorkerToTaskFailedList(ctx, task, worker)
	if err != nil {
		return fmt.Errorf("adding worker to failure list of task: %w", err)
	}

	logger = logger.With().Str("taskType", task.Type).Logger()
	wasBlacklisted, shoudlFailJob, err := f.maybeBlocklistWorker(ctx, logger, worker, task)
	if err != nil {
		return fmt.Errorf("block-listing worker: %w", err)
	}
	if shoudlFailJob {
		// There are no more workers left to finish the job.
		return f.failJobAfterCatastroficTaskFailure(ctx, logger, worker, task)
	}
	if wasBlacklisted {
		// Requeue all tasks of this job & task type that were hard-failed before by this worker.
		reason := fmt.Sprintf("worker %s was blocked from tasks of type %q", worker.Name, task.Type)
		err := f.stateMachine.RequeueFailedTasksOfWorkerOfJob(ctx, worker, task.Job, reason)
		if err != nil {
			return err
		}
	}

	// Determine whether this is soft or hard failure.
	threshold := f.config.Get().TaskFailAfterSoftFailCount
	logger = logger.With().
		Int("failedByWorkerCount", numFailed).
		Int("threshold", threshold).
		Logger()
	if numFailed < threshold {
		return f.softFailTask(ctx, logger, worker, task, numFailed)
	}
	return f.hardFailTask(ctx, logger, worker, task, numFailed)
}

// maybeBlocklistWorker potentially block-lists the Worker, and checks whether
// there are any workers left to run tasks of this type.
//
// Returns whether the worker was blacklisted, and whether the entire job should
// be failed (in case this was the last worker that could have worked on this
// task).
func (f *Flamenco) maybeBlocklistWorker(
	ctx context.Context,
	logger zerolog.Logger,
	worker *persistence.Worker,
	task *persistence.Task,
) (wasBlacklisted, shouldFailJob bool, err error) {
	numFailures, err := f.persist.CountTaskFailuresOfWorker(ctx, task.Job, worker, task.Type)
	if err != nil {
		return false, false, fmt.Errorf("counting failures of worker on job %q, task type %q: %w", task.Job.UUID, task.Type, err)
	}
	// The received task update hasn't been persisted in the database yet,
	// so we should count that too.
	numFailures++

	threshold := f.config.Get().BlocklistThreshold
	if numFailures < threshold {
		logger.Info().
			Int("numFailedTasks", numFailures).
			Int("threshold", threshold).
			Msg("not enough failed tasks to blocklist worker")
		return false, false, nil
	}

	// Blocklist the Worker.
	if err := f.blocklistWorker(ctx, logger, worker, task); err != nil {
		return true, false, err
	}

	// Return hard-failure if there are no workers left for this task type.
	numWorkers, err := f.numWorkersCapableOfRunningTask(ctx, task)
	return true, numWorkers == 0, err
}

func (f *Flamenco) blocklistWorker(
	ctx context.Context,
	logger zerolog.Logger,
	worker *persistence.Worker,
	task *persistence.Task,
) error {
	logger.Warn().
		Str("job", task.Job.UUID).
		Msg("block-listing worker")
	err := f.persist.AddWorkerToJobBlocklist(ctx, task.Job, worker, task.Type)
	if err != nil {
		return fmt.Errorf("adding worker to block list: %w", err)
	}
	return nil
}

func (f *Flamenco) numWorkersCapableOfRunningTask(ctx context.Context, task *persistence.Task) (int, error) {
	// See which workers are left to run tasks of this type, on this job,
	workersLeft, err := f.persist.WorkersLeftToRun(ctx, task.Job, task.Type)
	if err != nil {
		return 0, fmt.Errorf("fetching workers available to run tasks of type %q on job %q: %w",
			task.Job.UUID, task.Type, err)
	}

	// Remove (from the list of available workers) those who failed this task before.
	failers, err := f.persist.FetchTaskFailureList(ctx, task)
	if err != nil {
		return 0, fmt.Errorf("fetching failure list of task %q: %w", task.UUID, err)
	}
	for _, failure := range failers {
		delete(workersLeft, failure.UUID)
	}

	return len(workersLeft), nil
}

// failJobAfterCatastroficTaskFailure fails the entire job.
// This function is meant to be called when a task is failed, causing a block of
// the worker, and leaving no workers any more to do tasks of this type.
func (f *Flamenco) failJobAfterCatastroficTaskFailure(
	ctx context.Context,
	logger zerolog.Logger,
	worker *persistence.Worker,
	task *persistence.Task,
) error {
	taskLog := fmt.Sprintf(
		"Task failed by worker %s, Manager will fail the entire job as there are no more workers left for tasks of type %q.",
		worker.Identifier(), task.Type,
	)
	if err := f.logStorage.WriteTimestamped(logger, task.Job.UUID, task.UUID, taskLog); err != nil {
		logger.Error().Err(err).Msg("error writing failure notice to task log")
	}

	if err := f.stateMachine.TaskStatusChange(ctx, task, api.TaskStatusFailed); err != nil {
		logger.Error().
			Err(err).
			Str("newStatus", string(api.TaskStatusFailed)).
			Msg("error changing task status")
	}

	newJobStatus := api.JobStatusFailed
	logger.Info().
		Str("job", task.Job.UUID).
		Str("newJobStatus", string(newJobStatus)).
		Msg("no more workers left to run tasks of this type, failing the entire job")
	reason := fmt.Sprintf("no more workers left to run tasks of type %q", task.Type)
	return f.stateMachine.JobStatusChange(ctx, task.Job, newJobStatus, reason)
}

func (f *Flamenco) hardFailTask(
	ctx context.Context,
	logger zerolog.Logger,
	worker *persistence.Worker,
	task *persistence.Task,
	numFailed int,
) error {
	// Add the failure to the task log.
	pluralizer := pluralize.NewClient()
	taskLog := fmt.Sprintf(
		"Task failed by %s, Manager will mark it as hard failure",
		pluralizer.Pluralize("worker", numFailed, true),
	)
	if err := f.logStorage.WriteTimestamped(logger, task.Job.UUID, task.UUID, taskLog); err != nil {
		logger.Error().Err(err).Msg("error writing failure notice to task log")
	}

	// Mark the task as failed.
	logger.Info().Str("newTaskStatus", string(api.TaskStatusFailed)).
		Msg("too many workers failed this task, hard-failing it")
	return f.stateMachine.TaskStatusChange(ctx, task, api.TaskStatusFailed)
}

func (f *Flamenco) softFailTask(
	ctx context.Context,
	logger zerolog.Logger,
	worker *persistence.Worker,
	task *persistence.Task,
	numFailed int,
) error {
	threshold := f.config.Get().TaskFailAfterSoftFailCount
	failsToThreshold := threshold - numFailed

	// Add the failure to the task log.
	pluralizer := pluralize.NewClient()
	taskLog := fmt.Sprintf(
		"Task failed by %s, Manager will mark it as soft failure. %d more %s will cause hard failure.",
		pluralizer.Pluralize("worker", numFailed, true),
		failsToThreshold,
		pluralizer.Pluralize("failure", failsToThreshold, false),
	)
	if err := f.logStorage.WriteTimestamped(logger, task.Job.UUID, task.UUID, taskLog); err != nil {
		logger.Error().Err(err).Msg("error writing failure notice to task log")
	}

	// Mark the task as soft-failed.
	logger.Info().Str("newTaskStatus", string(api.TaskStatusSoftFailed)).
		Msg("worker failed this task, soft-failing to give another worker a try")
	return f.stateMachine.TaskStatusChange(ctx, task, api.TaskStatusSoftFailed)
}