package tasks

import (
    "context"
    "encoding/json"
    "fmt"
    "log"
    "time"
    "github.com/hibiken/asynq"
)

// A list of task types.
const (
    TypeEmailDelivery   = "email:deliver"
    TypeImageResize     = "image:resize"
)

type EmailDeliveryPayload struct {
    UserID     int
    TemplateID string
}

type ImageResizePayload struct {
    SourceURL string
}

//----------------------------------------------
// Write a function NewXXXTask to create a task.
// A task consists of a type and a payload.
//----------------------------------------------

func NewEmailDeliveryTask(userID int, tmplID string) (*asynq.Task, error) {
    payload, err := json.Marshal(EmailDeliveryPayload{UserID: userID, TemplateID: tmplID})
    if err != nil {
        return nil, err
    }
    return asynq.NewTask(TypeEmailDelivery, payload), nil
}

func NewImageResizeTask(src string) (*asynq.Task, error) {
    payload, err := json.Marshal(ImageResizePayload{SourceURL: src})
    if err != nil {
        return nil, err
    }
    // task options can be passed to NewTask, which can be overridden at enqueue time.
    return asynq.NewTask(TypeImageResize, payload, asynq.MaxRetry(5), asynq.Timeout(20 * time.Minute)), nil
}

//---------------------------------------------------------------
// Write a function HandleXXXTask to handle the input task.
// Note that it satisfies the asynq.HandlerFunc interface.
//
// Handler doesn't need to be a function. You can define a type
// that satisfies asynq.Handler interface. See examples below.
//---------------------------------------------------------------

func HandleEmailDeliveryTask(ctx context.Context, t *asynq.Task) error {
    var p EmailDeliveryPayload
    if err := json.Unmarshal(t.Payload(), &p); err != nil {
        return fmt.Errorf("json.Unmarshal failed: %v: %w", err, asynq.SkipRetry)
    }
    log.Printf("Sending Email to User: user_id=%d, template_id=%s", p.UserID, p.TemplateID)
    // Email delivery code ...
    return nil
}

// ImageProcessor implements asynq.Handler interface.
type ImageProcessor struct {
    // ... fields for struct
}

func (processor *ImageProcessor) ProcessTask(ctx context.Context, t *asynq.Task) error {
    var p ImageResizePayload
    if err := json.Unmarshal(t.Payload(), &p); err != nil {
        return fmt.Errorf("json.Unmarshal failed: %v: %w", err, asynq.SkipRetry)
    }
    log.Printf("Resizing image: src=%s", p.SourceURL)
    // Image resizing code ...
    return nil
}

func NewImageProcessor() *ImageProcessor {
	return &ImageProcessor{}
}

package main

import (
    "log"
    "time"

    "github.com/hibiken/asynq"
    "your/app/package/tasks"
)

const redisAddr = "127.0.0.1:6379"

func main() {
    client := asynq.NewClient(asynq.RedisClientOpt{Addr: redisAddr})
    defer client.Close()

    // ------------------------------------------------------
    // Example 1: Enqueue task to be processed immediately.
    //            Use (*Client).Enqueue method.
    // ------------------------------------------------------

    task, err := tasks.NewEmailDeliveryTask(42, "some:template:id")
    if err != nil {
        log.Fatalf("could not create task: %v", err)
    }
    info, err := client.Enqueue(task)
    if err != nil {
        log.Fatalf("could not enqueue task: %v", err)
    }
    log.Printf("enqueued task: id=%s queue=%s", info.ID, info.Queue)


    // ------------------------------------------------------------
    // Example 2: Schedule task to be processed in the future.
    //            Use ProcessIn or ProcessAt option.
    // ------------------------------------------------------------

    info, err = client.Enqueue(task, asynq.ProcessIn(24*time.Hour))
    if err != nil {
        log.Fatalf("could not schedule task: %v", err)
    }
    log.Printf("enqueued task: id=%s queue=%s", info.ID, info.Queue)


    // ----------------------------------------------------------------------------
    // Example 3: Set other options to tune task processing behavior.
    //            Options include MaxRetry, Queue, Timeout, Deadline, Unique etc.
    // ----------------------------------------------------------------------------

    task, err = tasks.NewImageResizeTask("https://example.com/myassets/image.jpg")
    if err != nil {
        log.Fatalf("could not create task: %v", err)
    }
    info, err = client.Enqueue(task, asynq.MaxRetry(10), asynq.Timeout(3 * time.Minute))
    if err != nil {
        log.Fatalf("could not enqueue task: %v", err)
    }
    log.Printf("enqueued task: id=%s queue=%s", info.ID, info.Queue)
}

package main

import (
    "log"

    "github.com/hibiken/asynq"
    "your/app/package/tasks"
)

const redisAddr = "127.0.0.1:6379"

func main() {
    srv := asynq.NewServer(
        asynq.RedisClientOpt{Addr: redisAddr},
        asynq.Config{
            // Specify how many concurrent workers to use
            Concurrency: 10,
            // Optionally specify multiple queues with different priority.
            Queues: map[string]int{
                "critical": 6,
                "default":  3,
                "low":      1,
            },
            // See the godoc for other configuration options
        },
    )

    // mux maps a type to a handler
    mux := asynq.NewServeMux()
    mux.HandleFunc(tasks.TypeEmailDelivery, tasks.HandleEmailDeliveryTask)
    mux.Handle(tasks.TypeImageResize, tasks.NewImageProcessor())
    // ...register other handlers...

    if err := srv.Run(mux); err != nil {
        log.Fatalf("could not run server: %v", err)
    }
}