Slingshot PDK

Plug-in development kit

Slingshot Go PDK

Structure of a plugin

package main

import (
    slingshot "github.com/bots-garden/slingshot/go-pdk"
)

func helloHandler(argHandler []byte) []byte {
    input := string(argHandler)
    slingshot.Println("👋 hello world 🌍 " + string(input))

    return []byte("👋 Hello World 🌍")
}

//export callHandler
func callHandler() {
    slingshot.ExecHandler(helloHandler)
}

func main() {}

1. You must export a function (it will be called at the execution, here, it's callHandler).
2. slingshot.ExecHandler is an helper to execute the function (helloHandler). This helper will read the wasm shared memory to get the argument of the function (argHandler []byte).
3. Then the helper executes the function.
4. And finally write to the wasm shared memory to return the result of the function ([]byte("👋 Hello World 🌍")).

Build the Slingshot plugin

tinygo build -scheduler=none --no-debug \
    -o println.wasm \
    -target wasi main.go

Run the Slingshot plugin

./slingshot run --wasm=./println.wasm \
--handler=callHandler \
--input="🤓 I'm a geek"

Slingshot host functions

🚧 This is a work in progress

• slingshot.Print(text string)
• slingshot.Println(text string)
• slingshot.Log(text string)
• slingshot.MemorySet(key string, value string) (string, error)
• slingshot.MemoryGet(key string) (string, error)
• slingshot.InitRedisClient(redisClientId string, redisUri string) (string, error)
• slingshot.RedisSet(redisClientId string, key string, value string) (string, error)
• slingshot.RedisGet(redisClientId string, key string) (string, error)
• slingshot.RedisDel(redisClientId string, key string) (string, error)
• slingshot.RedisFilter(redisClientId string, key string) (string, error)
• slingshot.RedisPublish(redisClientId string, channel string, payload string) (string, error)
• slingshot.InitNatsConnection(natsConnectionId string, natsUrl string) (string, error)
• slingshot.NatsPublish(natsConnectionId string, subject string, data string) (string, error)
• slingshot.ReadFile(filePath string) (string, error)
• slingshot.WriteFile(filePath string, text string) error

Other examples

HTTP nano-service plug-in

package main

import (
    "strings"
    slingshot "github.com/bots-garden/slingshot/go-pdk"
    "github.com/valyala/fastjson"
)

var parser = fastjson.Parser{}

func helloHandler(http_request_data []byte) []byte {

    var text string
    var code string

    JSONData, err := parser.ParseBytes(http_request_data)
    if err != nil {
        text = "😡 Error: " + err.Error()
        code = "500"
    } else {
        text = "🩵 Hello " + string(JSONData.GetStringBytes("body"))
        code = "200"
    }

    headers := []string{
        `"Content-Type": "application/json; charset=utf-8"`,
        `"X-Slingshot-version": "0.0.0"`,
    }

    headersStr := strings.Join(headers, ",")

    response := `{"headers":{` + headersStr + `}, "textBody": "` + text + `", "statusCode": ` + code + `}`

    return []byte(response)

}

//export callHandler
func callHandler() {
    slingshot.ExecHandler(helloHandler)
}

func main() {}

Run:

./slingshot listen --wasm=./hello.wasm \
--handler=callHandler \
--http-port=7070

Redis subscriber plug-in

package main

import (
    slingshot "github.com/bots-garden/slingshot/go-pdk"
)

func messageHandler(input []byte) []byte {

    slingshot.Println("👋 message: " + string(input))
    return nil

}

//export callHandler
func callHandler() {
    slingshot.ExecHandler(messageHandler)
}

func main() {}

Run:

./slingshot redis subscribe \
    --wasm=./redissub.wasm \
    --handler=callHandler \
    --uri=${REDIS_URI} \
    --client-id=pubsubcli \
    --channel=news

Redis publisher plug-in

package main

import slingshot "github.com/bots-garden/slingshot/go-pdk"

func publishHandler(input []byte) []byte {

    redisURI := slingshot.GetEnv("REDIS_URI")
    idRedisClient, errInit := slingshot.InitRedisClient("pubsubcli", redisURI)
    if errInit != nil {
        slingshot.Println("😡 " + errInit.Error())
    } else {
        slingshot.Println("🙂 " + idRedisClient)
    }

    slingshot.RedisPublish("pubsubcli", "news", string(input))

    return nil
}

//export callHandler
func callHandler() {
    slingshot.ExecHandler(publishHandler)
}

func main() {}

Run:

./slingshot run --wasm=./redispub.wasm \
    --handler=callHandler \
    --input="I 💜 Wasm ✨"

Nats subscriber plug-in

package main

import slingshot "github.com/bots-garden/slingshot/go-pdk"

func messageHandler(input []byte) []byte {
    slingshot.Println("👋 NATS message: " + string(input))
    return nil
}

//export callHandler
func callHandler() {
    slingshot.ExecHandler(messageHandler)
}

func main() {}

Run:

./slingshot nats subscribe \
--wasm=./natssub.wasm \
--handler=callHandler \
--url=nats://0.0.0.0:4222 \
--connection-id=natsconn01 \
--subject=news

Nats publisher plug-in

package main

import (
    slingshot "github.com/bots-garden/slingshot/go-pdk"
)

func publishHandler(input []byte) []byte {

    natsURL := slingshot.GetEnv("NATS_URL")
    slingshot.Println("💜 NATS_URL: " + natsURL)
    idNatsConnection, errInit := slingshot.InitNatsConnection("natsconn01", natsURL)
    if errInit != nil {
        slingshot.Println("😡 " + errInit.Error())
    } else {
        slingshot.Println("🙂 " + idNatsConnection)
    }

    res, err := slingshot.NatsPublish("natsconn01", "news", string(input))

    if err != nil {
        slingshot.Println("😡 " + err.Error())
    } else {
        slingshot.Println("🙂 " + res)
    }
    return nil
}

//export callHandler
func callHandler() {
    slingshot.ExecHandler(publishHandler)
}

func main() {}

Run:

./slingshot run --wasm=./natspub.wasm \
    --handler=callHandler \
    --input="I 💜 Wasm ✨"

Read / Write a file

package main

import (
    slingshot "github.com/bots-garden/slingshot/go-pdk"
)

func helloHandler(argHandler []byte) []byte {

    content, err := slingshot.ReadFile("./hello.txt")
    if err != nil {
        slingshot.Log("😡 " + err.Error())
    }
    slingshot.Println(content)

    text := `
    <html>
      <h1>"Hello World!!!"</h1>
    </html>
    `

    errWrite := slingshot.WriteFile("./index.html", text)
    if errWrite != nil {
        slingshot.Log("😡 " + errWrite.Error())
    }

    return []byte("👋 Hello World 🌍")
}

//export callHandler
func callHandler() {
    slingshot.ExecHandler(helloHandler)
}

func main() {}

Run:

./slingshot run --wasm=./files.wasm \
    --handler=callHandler