package tasks

import (
    "fmt"

    "github.com/hibiken/asynq"
)

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

//----------------------------------------------
// 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 {
    payload := map[string]interface{}{"user_id": userID, "template_id": tmplID}
    return asynq.NewTask(TypeEmailDelivery, payload)
}

func NewImageResizeTask(src string) *asynq.Task {
    payload := map[string]interface{}{"src": src}
    return asynq.NewTask(TypeImageResize, payload)
}

//---------------------------------------------------------------
// 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 {
    userID, err := t.Payload.GetInt("user_id")
    if err != nil {
        return err
    }
    tmplID, err := t.Payload.GetString("template_id")
    if err != nil {
        return err
    }
    fmt.Printf("Send Email to User: user_id = %d, template_id = %s\n", userID, tmplID)
    // Email delivery code ...
    return nil
}

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

func (p *ImageProcessor) ProcessTask(ctx context.Context, t *asynq.Task) error {
    src, err := t.Payload.GetString("src")
    if err != nil {
        return err
    }
    fmt.Printf("Resize image: src = %s\n", src)
    // Image resizing code ...
    return nil
}

func NewImageProcessor() *ImageProcessor {
    // ... return an instance
}

package main

import (
    "fmt"
    "log"
    "time"

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

const redisAddr = "127.0.0.1:6379"

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

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

    t := tasks.NewEmailDeliveryTask(42, "some:template:id")
    res, err := c.Enqueue(t)
    if err != nil {
        log.Fatal("could not enqueue task: %v", err)
    }
    fmt.Printf("Enqueued Result: %+v\n", res)


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

    t = tasks.NewEmailDeliveryTask(42, "other:template:id")
    res, err = c.Enqueue(t, asynq.ProcessIn(24*time.Hour))
    if err != nil {
        log.Fatal("could not schedule task: %v", err)
    }
    fmt.Printf("Enqueued Result: %+v\n", res)


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

    c.SetDefaultOptions(tasks.TypeImageResize, asynq.MaxRetry(10), asynq.Timeout(3*time.Minute))

    t = tasks.NewImageResizeTask("some/blobstore/path")
    res, err = c.Enqueue(t)
    if err != nil {
        log.Fatal("could not enqueue task: %v", err)
    }
    fmt.Printf("Enqueued Result: %+v\n", res)

    // ---------------------------------------------------------------------------
    // Example 4: Pass options to tune task processing behavior at enqueue time.
    //            Options passed at enqueue time override default ones, if any.
    // ---------------------------------------------------------------------------

    t = tasks.NewImageResizeTask("some/blobstore/path")
    res, err = c.Enqueue(t, asynq.Queue("critical"), asynq.Timeout(30*time.Second))
    if err != nil {
        log.Fatal("could not enqueue task: %v", err)
    }
    fmt.Printf("Enqueued Result: %+v\n", res)
}

package main

import (
    "log"

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

const redisAddr = "127.0.0.1:6379"

func main() {
    r := asynq.RedisClientOpt{Addr: redisAddr}

    srv := asynq.NewServer(r, 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)
    }
}