package runner

import (
	"context"
	logger "courgette/internal/logging"
	workflow "courgette/internal/workflow"
	"errors"
	"fmt"
	"sync"
)

type Runner struct {
	Labels map[string]string
	Driver ContainerDriver
	Runs   int
	// Deferred tasks, in order their were scheduled.
	deferred *DeferredTaskManager
}

func NewRunner(driver ContainerDriver, labels map[string]string) Runner {
	return Runner{
		Driver:   driver,
		Labels:   labels,
		deferred: NewDeferredTaskManager(),
	}
}

// Executes a workflow using the runner.
//
// This is the high-level call that will set up the container
// that the jobs will be executed in, run the jobs's steps and
// tear down the container once no longer useful.
func (r *Runner) RunWorkflow(workflow workflow.Workflow) TaskTracker {
	logger.Info("Executing workflow: %s", workflow.SourcePath)
	rootTracker := NewTaskTracker(nil)

	workflowContext := context.WithValue(context.Background(), "workflow", workflow)

	for _, group := range workflow.GetJobsAsGroups() {
		var groupWait sync.WaitGroup

		for _, job := range group {
			groupWait.Add(1)

			jobContext := context.WithValue(workflowContext, "currentJob", job)

			runJob := func(context context.Context) {
				defer groupWait.Done()
				jobTracker := NewTaskTracker(rootTracker).SetStatus("started")

				runnerImage, defined := r.Labels[job.RunsOn]

				if !defined {
					jobTracker.SetStatus("failed").SetError(fmt.Errorf("Unknown runner image label: %s", job.RunsOn))
					return
				}

				containerName := fmt.Sprintf("runner-%s", jobTracker.TaskId)

				logger.Info("Using image %s (label: %s)", runnerImage, job.RunsOn)

				if pullError := r.Driver.Pull(runnerImage); pullError != nil {
					jobTracker.SetStatus("failed").SetError(pullError)
					return
				}

				if runError := r.RunJobInContainer(runnerImage, containerName, context); runError != nil {
					jobTracker.SetStatus("failed").SetError(runError)
					return
				}

				jobTracker.SetStatus("success")
				r.deferred.RunDeferredTasksInScope(fmt.Sprintf("job-%s", containerName))
			}

			go runJob(jobContext)
		}

		groupWait.Wait()
	}

	r.deferred.RunAllDeferredTasks()

	return *rootTracker
}

// Executes a command within the given container.
//
// If the command raises an error while in the container or fails to run
// the command at all, an error is returned, otherwise nil.
func (r *Runner) RunCommandInContainer(containerId string, command string) error {
	result := r.Driver.Exec(containerId, command)

	if result.Error != nil {
		return result.Error
	}

	if result.ExitCode != 0 {
		return errors.New(fmt.Sprintf("Command returned a non-zero exit code (%d).", result.ExitCode))
	}

	return nil
}

// Executes a job within a container.
//
// The container is started before the job steps are run and cleaned up after.
func (r *Runner) RunJobInContainer(imageUri string, containerId string, jobContext context.Context) error {
	r.Driver.Start(imageUri, containerId)

	r.deferred.Queue(fmt.Sprintf("job-%s", containerId), func() {
		logger.Info("Started cleaning up %s", containerId)
		r.Driver.Stop(containerId)
	})

	job := jobContext.Value("currentJob").(workflow.Job)

	logger.Info("Started %s", containerId)
	for stepIndex, step := range job.Steps {
		logger.Info("Run: %s", step.Run)
		logger.Info("Using working directory %s", jobContext.Value("workflow").(workflow.Workflow).GetWorkingDirectory(job.Name, stepIndex))
		var stepError error

		if step.Run != "" {
			stepError = r.RunCommandInContainer(containerId, step.Run)
		}

		if stepError != nil {
			return stepError
		}
	}

	return nil
}