Figuring out func as parameter

[marianvlad]

Hi,

After weeks of searching something similar I found this on Reddit and looks promising for my project but after hours of trying and checking the source code for examples, I was getting stuck...

This is a good example of what I want but I can't use func as parameters by default:
https://github.com/risor-io/risor/blob/main/examples/go/struct/main.go

package main

import (
    "fmt"
    "sync"
)

// Crawler represents a generic crawler
type Crawler struct {
    Response string
    Status   int
}

// CrawlerRegistry is responsible for registering and calling crawlers
type CrawlerRegistry struct {
    crawlers map[string]func(crawler *Crawler, query string)
    mutex    sync.RWMutex
}

// NewCrawlerRegistry creates a new instance of CrawlerRegistry
func NewCrawlerRegistry() *CrawlerRegistry {
    return &CrawlerRegistry{
        crawlers: make(map[string]func(crawler *Crawler, query string)),
    }
}

// Register registers a new crawler with the given name and callback function
func (cr *CrawlerRegistry) Register(name string, callback func(crawler *Crawler, query string)) {
    cr.mutex.Lock()
    defer cr.mutex.Unlock()
    cr.crawlers[name] = callback
}

// Call invokes the registered crawler with the given name and query
func (cr *CrawlerRegistry) Call(name string, query string) *Crawler {
    cr.mutex.RLock()
    defer cr.mutex.RUnlock()
    if callback, ok := cr.crawlers[name]; ok {
        crawler := &Crawler{}
        callback(crawler, query)
        return crawler
    }
    return nil
}

func main() {
    // Create a new crawler registry
    app := NewCrawlerRegistry()

    // Register a crawler for "google"
    app.Register("google", func(crawler *Crawler, query string) {
        // This is just an example, you can replace it with your actual crawler logic
        crawler.Response = fmt.Sprintf("Crawling data from Google for query: %s", query)
        crawler.Status = 200
    })

    // Call the registered crawler with query "animals"
    result := app.Call("google", "animals")

    // Print the response and status
    if result != nil {
        fmt.Printf("Response: %s\n", result.Response)
        fmt.Printf("Status: %d\n", result.Status)
    } else {
        fmt.Println("Crawler not found")
    }
}

crawler.Register("github", func (crawler, query) {
    // http request logic..
})

crawler.Call("github", "risor") // should be called from risor code and also golang

I tried different things like the code below, but everything failed. Firstly I tried with multiple return values in .Register() but I think the language doesn't supporting it.

name, errObj := object.AsString(args[0])
if errObj != nil {
	return errObj
}

fnRes, isFnRes := args[1].(*object.Function)
if !isFnRes {
	return object.NewError(errors.New("expected second arg to be a function"))
}

callFn, hasCallFn := object.GetCallFunc(ctx)
if !hasCallFn {
	return object.NewError(errors.New("no callFn found in context"))
}

[myzie]

Hi @marianvlad, I can definitely help with this. I'm going to be AFK for most of today but will follow up on this soon.

There are a few approaches that will work I think. One would be to wrap the CrawlerRegistry with a Risor Proxy. Second would be to make a new Risor object type that wraps CrawlerRegistry and/or Crawler that you can customize yourself. I suspect the second option will work the best for you.

It's fairly easy to implement the Risor object.Object interface to wrap new Go types.

Regarding passing around callable functions, the object.BuiltinFunction signature may be what we want to leverage.

I'll follow up soon though and share some concrete code.

[myzie]

@marianvlad - here is a gist that hopefully helps:

https://gist.github.com/myzie/601cf170f88b09efd2012ea322a80259

Let me know what you think.

[marianvlad]

I'm speechless ❤️. I think it took me years to achieve the same working code. Now, I have a deeper understanding of how Risor works and how to extend its functionality. Honestly, I purchased the books "Writing an Interpreter" and "Writing a Compiler" in 2019, and the bundle in 2020. I read "Writing an Interpreter" once, but my experience with Golang was limited, and I understood nothing. Today, I started reading "Writing an Interpreter" again. I'm on page 70 :)

This is great, and I think you could use it as an example in the risor code if you want. Thank you so much for your time!

[marianvlad]

https://gist.github.com/myzie/601cf170f88b09efd2012ea322a80259?permalink_comment_id=4925070#gistcomment-4925070