package job

import (
	"context"
	"errors"
	"log"
	"time"

	"haixun-backend/internal/library/clock"
	"haixun-backend/internal/model/job/domain/entity"
	"haixun-backend/internal/model/job/domain/enum"
	domusecase "haixun-backend/internal/model/job/domain/usecase"
	"haixun-backend/internal/model/job/resume"
)

type Runner struct {
	workerID   string
	workerType string
	jobs       domusecase.UseCase
	handlers   map[string]StepHandler
}

type StepContext struct {
	JobID     string
	WorkerID  string
	Run       *entity.Run
	Template  *entity.Template
	Step      entity.TemplateStep
	Heartbeat func(ctx context.Context) error
}

type StepHandler func(ctx context.Context, step StepContext) error

func NewRunner(workerID, workerType string, jobs domusecase.UseCase) *Runner {
	return &Runner{
		workerID:   workerID,
		workerType: workerType,
		jobs:       jobs,
		handlers:   map[string]StepHandler{},
	}
}

func (r *Runner) RegisterStepHandler(stepID string, handler StepHandler) {
	if stepID == "" || handler == nil {
		return
	}
	r.handlers[stepID] = handler
}

func (r *Runner) Start(ctx context.Context) {
	log.Printf("job worker started: id=%s type=%s", r.workerID, r.workerType)
	for {
		select {
		case <-ctx.Done():
			log.Printf("job worker stopped: id=%s", r.workerID)
			return
		default:
			run, err := r.jobs.ClaimNext(ctx, domusecase.ClaimNextRequest{
				WorkerType: r.workerType,
				WorkerID:   r.workerID,
			})
			if err != nil {
				log.Printf("job worker claim error: %v", err)
				time.Sleep(time.Second)
				continue
			}
			if run == nil {
				continue
			}
			r.execute(ctx, run)
		}
	}
}

func (r *Runner) execute(ctx context.Context, run *entity.Run) {
	jobID := run.ID.Hex()
	template, err := r.jobs.GetTemplate(ctx, run.TemplateType)
	if err != nil {
		_, _ = r.jobs.FailRun(ctx, domusecase.FailRunRequest{JobID: jobID, WorkerID: r.workerID, Error: err.Error()})
		return
	}

	steps := make([]entity.StepProgress, len(run.Progress.Steps))
	copy(steps, run.Progress.Steps)
	totalSteps := len(template.Steps)
	if totalSteps == 0 {
		totalSteps = 1
	}
	completedBefore := resume.CountSucceededSteps(steps)

	for _, step := range template.Steps {
		existing := resume.StepProgressByID(steps, step.ID)
		if existing != nil && resume.ShouldSkipStep(existing.Status) {
			continue
		}

		if cancelled, _ := r.jobs.IsCancelRequested(ctx, jobID); cancelled {
			_, _ = r.jobs.AcknowledgeCancel(ctx, domusecase.AcknowledgeCancelRequest{
				JobID:    jobID,
				WorkerID: r.workerID,
			})
			return
		}

		now := clock.NowUnixNano()
		for i := range steps {
			if steps[i].ID == step.ID {
				steps[i].Status = enum.StepStatusRunning
				steps[i].StartedAt = &now
				steps[i].Message = "running"
			}
		}
		percentage := (completedBefore * 100) / totalSteps
		_, _ = r.jobs.UpdateProgress(ctx, domusecase.UpdateProgressRequest{
			JobID:      jobID,
			WorkerID:   r.workerID,
			Phase:      step.ID,
			Summary:    "running step " + step.ID,
			Percentage: percentage,
			Steps:      steps,
		})

		if err := r.runStep(ctx, run, template, step); err != nil {
			if err == errJobCancelled {
				_, _ = r.jobs.AcknowledgeCancel(ctx, domusecase.AcknowledgeCancelRequest{
					JobID:    jobID,
					WorkerID: r.workerID,
				})
				return
			}
			for i := range steps {
				if steps[i].ID == step.ID {
					steps[i].Status = enum.StepStatusFailed
					ended := clock.NowUnixNano()
					steps[i].EndedAt = &ended
					steps[i].Message = err.Error()
				}
			}
			_, _ = r.jobs.UpdateProgress(ctx, domusecase.UpdateProgressRequest{
				JobID: jobID, WorkerID: r.workerID, Phase: step.ID, Summary: "step failed", Steps: steps,
			})
			_, _ = r.jobs.FailRun(ctx, domusecase.FailRunRequest{
				JobID: jobID, WorkerID: r.workerID, Error: err.Error(), Phase: step.ID,
			})
			return
		}

		ended := clock.NowUnixNano()
		for i := range steps {
			if steps[i].ID == step.ID {
				steps[i].Status = enum.StepStatusSucceeded
				steps[i].EndedAt = &ended
				steps[i].Message = "done"
			}
		}
		completedBefore++
		percentage = (completedBefore * 100) / totalSteps
		_, _ = r.jobs.UpdateProgress(ctx, domusecase.UpdateProgressRequest{
			JobID:      jobID,
			WorkerID:   r.workerID,
			Phase:      step.ID,
			Summary:    "completed step " + step.ID,
			Percentage: percentage,
			Steps:      steps,
		})
	}

	_, _ = r.jobs.CompleteRun(ctx, domusecase.CompleteRunRequest{
		JobID:    jobID,
		WorkerID: r.workerID,
		Result: map[string]any{
			"message": "demo long task completed",
			"steps":   len(template.Steps),
		},
	})
}

var errJobCancelled = errors.New("job cancelled")

func (r *Runner) runStep(ctx context.Context, run *entity.Run, template *entity.Template, step entity.TemplateStep) error {
	jobID := run.ID.Hex()
	if handler := r.handlers[step.ID]; handler != nil {
		return handler(ctx, StepContext{
			JobID:    jobID,
			WorkerID: r.workerID,
			Run:      run,
			Template: template,
			Step:     step,
			Heartbeat: func(ctx context.Context) error {
				return r.jobs.RefreshRunLock(ctx, jobID, r.workerID, 300)
			},
		})
	}
	ticks := 10
	sleepEach := 500 * time.Millisecond
	if step.ID == "execute" {
		ticks = 20
	}

	for i := 0; i < ticks; i++ {
		select {
		case <-ctx.Done():
			return ctx.Err()
		default:
		}

		if err := r.jobs.RefreshRunLock(ctx, jobID, r.workerID, 300); err != nil {
			return err
		}
		cancelled, err := r.jobs.IsCancelRequested(ctx, jobID)
		if err != nil {
			return err
		}
		if cancelled {
			return errJobCancelled
		}

		time.Sleep(sleepEach)
	}
	return nil
}