package worker

import (
	"context"
	"fmt"
	"log/slog"
	"strings"
	"time"

	"moku-backend/internal/jobs"
)

type JobStore interface {
	ClaimNext(ctx context.Context) (*jobs.Job, error)
	MarkSucceeded(ctx context.Context, jobID string) error
	MarkFailed(ctx context.Context, jobID, failure string) error
}

type Handler func(ctx context.Context, job jobs.Job) error

type Runner struct {
	store        JobStore
	logger       *slog.Logger
	pollInterval time.Duration
	handlers     map[string]Handler
}

func NewRunner(store JobStore, logger *slog.Logger, pollInterval time.Duration) *Runner {
	interval := pollInterval
	if interval <= 0 {
		interval = time.Second
	}

	return &Runner{
		store:        store,
		logger:       logger,
		pollInterval: interval,
		handlers:     make(map[string]Handler),
	}
}

func (runner *Runner) Register(kind string, handler Handler) {
	runner.handlers[strings.TrimSpace(kind)] = handler
}

func (runner *Runner) Run(ctx context.Context) error {
	for {
		select {
		case <-ctx.Done():
			return nil
		default:
		}

		job, err := runner.store.ClaimNext(ctx)
		if err != nil {
			if ctx.Err() != nil {
				return nil
			}

			return err
		}

		if job == nil {
			if err := waitForNextPoll(ctx, runner.pollInterval); err != nil {
				return nil
			}

			continue
		}

		handler, ok := runner.handlers[job.Kind]
		if !ok {
			failure := fmt.Sprintf("no handler registered for job kind %q", job.Kind)
			if err := runner.store.MarkFailed(ctx, job.ID, failure); err != nil {
				return err
			}

			runner.logger.Error("worker job failed", "jobID", job.ID, "kind", job.Kind, "error", failure)
			continue
		}

		if err := handler(ctx, *job); err != nil {
			if ctx.Err() != nil {
				return nil
			}

			failure := strings.TrimSpace(err.Error())
			if failure == "" {
				failure = "job handler returned an empty error"
			}

			if markErr := runner.store.MarkFailed(ctx, job.ID, failure); markErr != nil {
				return markErr
			}

			runner.logger.Error("worker job failed", "jobID", job.ID, "kind", job.Kind, "error", failure)
			continue
		}

		if err := runner.store.MarkSucceeded(ctx, job.ID); err != nil {
			return err
		}

		runner.logger.Info("worker job succeeded", "jobID", job.ID, "kind", job.Kind)
	}
}

func waitForNextPoll(ctx context.Context, interval time.Duration) error {
	timer := time.NewTimer(interval)
	defer timer.Stop()

	select {
	case <-ctx.Done():
		return ctx.Err()
	case <-timer.C:
		return nil
	}
}