ChatGPT and creating a asynchronous Lua webpage with Lighttpd

Posted by vonnagy on Dec 25 2022

I always was interested how to use Lua asynchronously – I found documentation at OpenResty a bit cumbersome. This was a conversation I had with ChatGPT, that eventually brought about an interesting, albeit untested result.

Me: Using Lighttd, how can one write a simple “hello world” web page?

ChatGPT: To write a simple “Hello World” web page using Lighttpd, you will need to do the following:

Install Lighttpd on your web server. You can find instructions for installing Lighttpd on different platforms on the Lighttpd website (https://www.lighttpd.net/).
Create a new file in the root directory of your web server (e.g., /var/www/html/index.html) and add the following code to it:


<html>
  <head>
    <title>Hello World</title>
  </head>
  <body>
    <h1>Hello World</h1>
  </body>
</html>

Save the file and start the Lighttpd server. On most systems, you can start the Lighttpd server by running the following command:


sudo service lighttpd start

Open a web browser and navigate to the URL of your web server (e.g., http://localhost/). You should see the “Hello World” message displayed on the page.

This is a very basic example of how to create a “Hello World” web page using Lighttpd. You can use additional HTML tags and CSS styles to customize the appearance and layout of the page as needed.

I hope this helps! If you have any further questions or need more information, please don’t hesitate to ask.

Me: Thank you. Using the same example from above, could you generate a “hello world” using lua?

ChatGPT: Certainly! To write a simple “Hello World” web page using Lua and Lighttpd, you will need to do the following:

Install Lighttpd on your web server and configure it to support Lua scripts. You can do this by installing the mod_magnet module and adding the following lines to your Lighttpd configuration file (usually located at /etc/lighttpd/lighttpd.conf):


server.modules += ( "mod_magnet" )
magnet.attract-physical-path-to = ( "/usr/local/lib/liblua.so" )

Create a new file in the root directory of your web server (e.g., /var/www/html/index.html) and add the following code to it:


<html>
  <head>
    <title>Hello World</title>
  </head>
  <body>
    <?
      function say_hello()
        return "<h1>Hello World</h1>"
      end
    ?>
  </body>
</html>

Save the file and start the Lighttpd server. On most systems, you can start the Lighttpd server by running the following command:


sudo service lighttpd start

Open a web browser and navigate to the URL of your web server (e.g., http://localhost/). You should see the “Hello World” message displayed on the page.

This is a very basic example of how to create a “Hello World” web page using Lua and Lighttpd. You can use additional Lua functions and HTML tags to customize the appearance and behavior of the page as needed.

I hope this helps! If you have any further questions or need more information, please don’t hesitate to ask.

Me: Thank you! Can you further the example above by creating an entire webpage in Lua?

ChatGPT: Certainly! Here is an example of how you can create an entire web page using Lua and Lighttpd:


-- define the say_hello function
function say_hello()
  return "<h1>Hello World</h1>"
end

-- define the page content
function page_content()
  return [[
    <html>
      <head>
        <title>Hello World</title>
      </head>
      <body>
        ]] .. say_hello() .. [[
      </body>
    </html>
  ]]
end

-- set the Content-Type header
request.set_header("Content-Type", "text/html")

-- write the page content to the response
request.write(page_content())

To use this code with Lighttpd, you will need to configure Lighttpd to support Lua scripts using the mod_magnet module, as described in my previous response. You can then save the code above in a file in the root directory of your web server (e.g., /var/www/html/index.html) and access it via a web browser to see the “Hello World” message displayed on the page.

This is a very basic example of how to create a web page using Lua and Lighttpd. You can use additional Lua functions and HTML tags to customize the appearance and behavior of the page as needed.

I hope this helps! If you have any further questions or need more information, please don’t hesitate to ask.

Me: neat! Is there any speed difference the first example you posted where lua is written between HTML tags and the last example where the entire page is in LUA?

ChatGPT: There may be some differences in the speed at which the two examples you mentioned are processed by the web server and displayed in a web browser. However, the specific performance characteristics of each example will depend on a number of factors, including the complexity of the code, the capabilities of the web server and the client device, and the network conditions.

In general, using Lua to generate the entire content of a web page may be faster than using a mix of HTML and Lua, because it allows the web server to process the entire page in a single pass and send the completed page to the client in a single HTTP response. This can reduce the overhead associated with multiple server-client interactions and potentially improve the overall performance of the page.

On the other hand, using a mix of HTML and Lua may be more convenient in some cases, because it allows you to mix static and dynamic content in the same page and take advantage of the features and capabilities of HTML for formatting and layout.

Ultimately, the choice between using a mix of HTML and Lua and using Lua to generate the entire content of a web page will depend on your specific needs and requirements. You may need to consider the trade-offs between performance and convenience, as well as other factors such as maintainability and scalability, when deciding which approach to use.

Me: Neat, thank you. Using Lua and lighthttd, could you give an example of a simple asyncronous request: could you call 3 remote json files remote asyncronously? What would be the simplest solution for this?

Sure! Here is an example of how you can use Lua and Lighttpd to make asynchronous HTTP requests to retrieve JSON data from three remote servers and process the responses as they arrive:


-- define a function to make an HTTP GET request
function http_get(url)
  local response = {}
  http.request{
    url = url,
    sink = ltn12.sink.table(response),
    create = function()
      return nil, {
        method = "GET",
        headers = {
          ["User-Agent"] = "My HTTP Client"
        }
      }
    end,
    onredirect = function(headers)
      -- handle redirects
    end,
    onerror = function(error_message)
      -- handle errors
    end
  }
  return response
end

-- define a function to parse a JSON response
function parse_json(response)
  local json = require "dkjson"
  return json.decode(response[1])
end

-- define an array of URLs to fetch
local urls = {
  "http://example.com/data1.json",
  "http://example.com/data2.json",
  "http://example.com/data3.json"
}

-- make an asynchronous HTTP GET request to each URL
for _, url in ipairs(urls) do
  http.async.http.request{
    url = url,
    sink = ltn12.sink.chain(ltn12.sink.table(response), parse_json),
    create = function()
      return nil, {
        method = "GET",
        headers = {
          ["User-Agent"] = "My HTTP Client"
        }
      }
    end,
    onredirect = function(headers)
      -- handle redirects
    end,
    onerror = function(error_message)
      -- handle errors
    end,
    onsuccess = function(response)
      -- process the JSON response
    end
  }
end

ChatGPT: This code uses the async.http module from the LuaSocket library to make asynchronous HTTP requests to the specified URLs. The requests are processed in parallel, and the responses are passed through a JSON parser and processed as they arrive.

I hope this helps! If you have any further questions or need more information, please don’t hesitate to ask.

Me: Thank you! Using the same example, could you print a table with the fields firstname and lastname for each row, concatenate with a “nbsp;” between first and last name?

Certainly! Here is an example of how you can use the code from my previous response to retrieve JSON data from three remote servers, parse the responses, and print the “firstname” and “lastname” fields for each row, concatenated with a non-breaking space character between them:


-- define a function to make an HTTP GET request
function http_get(url)
  local response = {}
  http.request{
    url = url,
    sink = ltn12.sink.table(response),
    create = function()
      return nil, {
        method = "GET",
        headers = {
          ["User-Agent"] = "My HTTP Client"
        }
      }
    end,
    onredirect = function(headers)
      -- handle redirects
    end,
    onerror = function(error_message)
      -- handle errors
    end
  }
  return response
end

-- define a function to parse a JSON response
function parse_json(response)
  local json = require "dkjson"
  return json.decode(response[1])
end

-- define an array of URLs to fetch
local urls = {
  "http://example.com/data1.json",
  "http://example.com/data2.json",
  "http://example.com/data3.json"
}

-- make an asynchronous HTTP GET request to each URL
for _, url in ipairs(urls) do
  http.async.http.request{
    url = url,
    sink = ltn12.sink.chain(ltn12.sink.table(response), parse_json),
    create = function()
      return nil, {
        method = "GET",
        headers = {
          ["User-Agent"] = "My HTTP Client"
        }
      }
    end,
    onredirect = function(headers)
      -- handle redirects
    end,
    onerror = function(error_message)
      -- handle errors
    end,
    onsuccess = function(response)
      -- process the JSON response
      for _, row in ipairs(response) do
        print(row.firstname .. "&nbsp;" .. row.lastname)
      end

Me: In the above example, is the result printed in an html table?

ChatGPT: No, the code in my previous response does not create an HTML table. It simply prints the “firstname” and “lastname” fields for each row in the JSON data, concatenated with a non-breaking space character, to the console.

If you want to display the data in an HTML table, you will need to modify the code to generate the appropriate HTML tags. For example, you could use the following code to generate an HTML table with two columns, “First Name” and “Last Name”, and a row for each item in the JSON data:


-- define a function to make an HTTP GET request
function http_get(url)
  local response = {}
  http.request{
    url = url,
    sink = ltn12.sink.table(response),
    create = function()
      return nil, {
        method = "GET",
        headers = {
          ["User-Agent"] = "My HTTP Client"
        }
      }
    end,
    onredirect = function(headers)
      -- handle redirects
    end,
    onerror = function(error_message)
      -- handle errors
    end
  }
  return response
end

-- define a function to parse a JSON response
function parse_json(response)
  local json = require "dkjson"
  return json.decode(response[1])
end

-- define an array of URLs to fetch
local urls = {
  "http://example.com/data1.json",
  "http://example.com/data2.json",
  "http://example.com/data3.json"
}

-- make an asynchronous HTTP GET request to each URL
for _, url in ipairs(urls) do
  http.async.http.request{
    url = url,
    sink = ltn12.sink.chain(ltn12.sink.table(response), parse_json),
    create = function()
      return nil, {
        method = "GET",
        headers = {
          ["User-Agent"] = "My HTTP Client"
        }
      }
    end,
    onredirect = function(headers)
      -- handle redirects
    end,
    onerror = function(error_message)
      -- handle errors
    end,
    onsuccess = function(response)
      -- process the JSON response
      print("<table>")
      print("<tr><th>First Name</th><th>Last Name</th></tr>")
      for _, row in ipairs(response) do
        print("<tr><td>" .. row.firstname .. "</td><td>" .. row.lastname .. "</td></tr>")
      end
      print("</table>")
    end
  }
end

This code generates an HTML table with a header row and a row for each item in the JSON data, and prints it to the console. You can modify the code as needed to customize the appearance and behavior of the table, and to integrate it with your web application.

I hope this helps!

Me: brilliant. i’ve learned more from you than I have from tutorial websites! Could you explain this line of code? local json = require “dkjson”

ChatGPT: Certainly! The line of code local json = require “dkjson” is used to load the “dkjson” module, which is a third-party Lua library that provides functions for encoding and decoding JSON data.

The require function is a built-in function in Lua that loads and executes a module, and returns the value returned by the module’s code. In this case, the “dkjson” module returns a table containing functions for encoding and decoding JSON data.

Here is an example of how you could use the “dkjson” module to encode a Lua table as a JSON string:


local json = require "dkjson"

local data = {
  firstname = "John",
  lastname = "Doe",
  age = 30
}

local json_string = json.encode(data)
print(json_string)

This code would output the following JSON string to the console:


{"age":30,"firstname":"John","lastname":"Doe"}

And here is an example of how you could use the “dkjson” module to decode a JSON string into a Lua table:


local json = require "dkjson"

local json_string = '{"age":30,"firstname":"John","lastname":"Doe"}'
local data = json.decode(json_string)

print(data.firstname .. " " .. data.lastname)

This code would output the following string to the console:


John Doe

I hope this helps to clarify how the “dkjson” module is used in Lua! If you have any further questions or need more information, please don’t hesitate to ask.

Me: hi could you comment each line of the function http_get(url) for clarity?

ChatGPT: Certainly! Here is a commented version of the http_get function:


-- define a function to make an HTTP GET request
function http_get(url)
  -- create a table to store the response
  local response = {}

  -- make an HTTP GET request to the specified URL
  http.request{
    url = url,                   -- the URL to request
    sink = ltn12.sink.table(response),  -- the sink to store the response data
    create = function()
      -- create the request object
      return nil, {
        method = "GET",            -- specify the HTTP method as GET
        headers = {
          ["User-Agent"] = "My HTTP Client"  -- set the User-Agent header
        }
      }
    end,
    onredirect = function(headers)
      -- handle redirects
    end,
    onerror = function(error_message)
      -- handle errors
    end
  }

  -- return the response data
  return response
end

This function makes an HTTP GET request to the specified URL and stores the response data in a table. It returns the table when the request is complete.

The http.request function is a built-in function in the “socket” library that makes an HTTP request to a specified URL and returns the response data. It takes a table as an argument that specifies the request parameters, such as the URL, the request method, the headers, and the sink to store the response data.

The sink parameter is set to ltn12.sink.table(response), which uses the “ltn12” library to store the response data in the response table. The create parameter is a function that returns the request object, which specifies the request method and headers. The onredirect and onerror parameters are functions that handle redirects and errors, respectively.

I hope this helps to clarify how the http_get function works! If you have any further questions or need more information, please don’t hesitate to ask.

Me: In your above response is ‘sink’ a reserved word? Is just the name for a variable? Could you explain why used the word sink?

ChatGPT: In the context of the http.request function in the “socket” library, “sink” is a term used to refer to a function or object that receives and processes the response data from an HTTP request. It is not a reserved word in Lua, but rather a convention used to describe the function or object that receives the response data.

The “ltn12” library, which stands for Lua Transfer Protocol, provides a set of functions and objects that can be used as sinks to process response data from HTTP requests. The ltn12.sink.table function, for example, creates a sink that stores the response data in a table.

The term “sink” is often used in programming to describe an object or function that receives and processes data. It comes from the metaphor of a sink as a place where data flows into and is processed or discarded.

I hope this helps to clarify the use of the term “sink” in the context of the http.request function! If you have any further questions or need more information, please don’t hesitate to ask.

Me: With latest code example above, can you generate an entire html page, complete with header and closing tags?

ChatGPT: Certainly! Here is an example of how you could use the http_get function to make an HTTP GET request to an API that returns a JSON object, and then generate an HTML page that displays the data in a table:


-- make an HTTP GET request to an API that returns a JSON object
local response = http_get("https://api.example.com/users")

-- decode the JSON object into a Lua table
local data = json.decode(response)

-- create the HTML page
local html = [[
<html>
  <head>
    <title>User List</title>
  </head>
  <body>
    <table>
      <tr>
        <th>First Name</th>
        <th>Last Name</th>
        <th>Age</th>
      </tr>
]]

-- iterate over the rows in the table and create HTML table rows
for _, row in ipairs(data) do
  html = html .. [[
      <tr>
        <td>]] .. row.firstname .. [[</td>
        <td>]] .. row.lastname .. [[</td>
        <td>]] .. row.age .. [[</td>
      </tr>
  ]]
end

-- close the HTML table and page
html = html .. [[
    </table>
  </body>
</html>
]]

-- print the HTML page to the console
print(html)

This code makes an HTTP GET request to an API that returns a JSON object containing a list of users, decodes the JSON object into a Lua table, and then generates an HTML page that displays the data in a table. The HTML page includes the <html>, <head>, <title>, <body>, and <table> tags, as well as table rows and cells to display the data.

I hope this helps to clarify how you could generate an HTML page using the http_get function and the “dkjson” library! If you have any further questions or need more information, please don’t hesitate to ask.

Me: Brilliant, thank you.

ChatGPT: You’re welcome! I’m glad that I could help. If you have any further questions or need more information, please don’t hesitate to ask. I’m always here to help.

ChatGPT – What is a simple way for creating asynchronous PHP?

Posted by vonnagy on Dec 24 2022

The following is recent conversation I had with ChatGPT. I was pretty amazed at the response.

Question: What is a simple way to make PHP asynchronous? For example, I’d like to call 3 eternal json files, in a non blocking fashion. How can this be done in an explicit and easy to understand way?

Answer: There are a few options for making PHP code asynchronous. One option is to use the pcntl_fork function, which creates a child process that can run concurrently with the parent process. Here’s an example of how you might use pcntl_fork to call three external JSON files asynchronously:

<?php
// Function to retrieve a JSON file from a URL
function retrieveJson($url) {
// Use file_get_contents to retrieve the JSON data
$jsonData = file_get_contents($url);
// Decode the JSON data into an associative array
$data = json_decode($jsonData, true);
// Return the data
return $data;
}

// Array of URLs to retrieve
$urls = array(
‘http://example.com/file1.json’,
‘http://example.com/file2.json’,
‘http://example.com/file3.json’
);

// Loop through the URLs
foreach ($urls as $url) {
// Create a child process for each URL
$pid = pcntl_fork();
if ($pid == –1) {
// Error creating child process
exit();
} elseif ($pid == 0) {
// Child process
$data = retrieveJson($url);
// Do something with the data
// …
exit();
}
}

// Wait for all child processes to finish
while (pcntl_waitpid(0, $status) != –1) {
// Do nothing
}

This code will create a child process for each URL, and each child process will retrieve the corresponding JSON file and do something with the data. The parent process will wait for all child processes to finish before exiting.

Another option for making PHP code asynchronous is to use a library like ReactPHP or Amp, which provide asyncronous programming primitives such as promises and event loops. These libraries can be used to build more complex asyncronous applications, but may have a steeper learning curve than the pcntl_fork function.

Question: Which version of php did pcntl_fork first app

Answer: The pcntl_fork function was introduced in PHP version 4.0. It is part of the Process Control (PCNTL) extension, which provides functions for creating and manipulating child processes.

To use the pcntl_fork function, you will need to have the PCNTL extension installed and enabled in your PHP environment. You can check if the PCNTL extension is installed by calling the phpinfo function, or by using the php -m command to list installed PHP extensions.

If the PCNTL extension is not installed, you can install it by compiling PHP with the –enable-pcntl flag, or by installing the php-pcntl package if you are using a package manager like yum or apt.

Note that the PCNTL extension is not available on Windows platforms. If you need to use the pcntl_fork function on Windows, you can use the Winsock extension or a third-party library like pcntl-win32 instead.

UV ID Polaroid expire October 2009 – Shot March 2022

Posted by vonnagy on Mar 14 2022

I recently found the time to shoot some polaroids again. It was UV ID, expired in October 2009. They have been refrigerated, but unfortunately, that doesn’t always mean they will work. The medium tends to stick together, and it takes delicate and nimble fingers to resuscitate them. Out of a pack a of 10, only 5 came through. The first 5 where stuck together, and it took a pair a tweezers to make sure the paper ‘tabs’ where properly pulled through the ‘ringer’. Rescuing half a pack is a pretty fair deal, I have lost whole packs before. Not all of them turned out the way I wanted too, but that’s life.

Here’s a couple of from pack. I will say that UV-ID is my favourite Polaroid film. Its got a weird and wonderful indigo cast (I believe its the same as 669, but when held up the UV light it shows a polaroid watermark – it was used for badges, ids, and the such).

This is a roadside monument on the South Island of New Zealand. The swirls in the sky are not clouds, rather its the effect of the expired film.

We grew some pumpkins this year, the smallest ones are ornamental, the larger yellow/green striped ones are Styrian (very tasty seeds), the smaller orange ones are ‘Hokkaido’ or ‘Kuri’ pumpkins, which have a rich chestnutty flavour. So why not take a photo of the harvest?

I also found a little half frame camera in my glove box which had about 60 photos on the dial, may be time to bring out the development kit again!

Trypt.am – Psychedelic Clinical Trials Database

Posted by vonnagy on Feb 28 2022

At the beginning of the Covid pandemic in 2020, while in isolation, I decided to pick up programming again. I stopped programming as my daily job about 12 years ago. During isolation, I dabbled in a few new and old languages (Swift, Perl, Rust), but in the end I found that my old stomping grounds in PHP was perfect for the job (PHP had also come a long way during my 10 year sabbatical from programming). The project was for the Entheos Foundation of New Zealand, a research and education charity for psychedelics.

Trypt.am aggregates clinical trial data from the following sources: ClinicalTrials.gov, ClinicalTrialsRegister.eu
Anzctr.org.au, Trialregister.nl, and Pubchem.ncbi.nlm.nih.gov. The first 2 feeds above are updated automatically, all the others are manual ‘data dumps’ which I have to upload. The site is still in beta, but its functional.

I’ve since resigned from the Entheos, so its unlikely trypt.am will be updated. Still, I’ll keep it up and running, if not just to see see the steady increase in psychedelic clinical trials over the years.

Polaroid shot of the day

Posted by vonnagy on Nov 04 2021

It was a surprise to receive this email today:

dear parahanga!!!

please have a short look at the cover of polanoid.net [ http://www.polanoid.net/cover ] (http://www.polanoid.net/jump/?to=pictures&uid=13197&pid=385985)

**CONGRATULATION**
you have won the worldfamous ShotOfTheDay award!

not only is your picture on the cover for the next 24 hours, generating endless fame and glory, but also you have won a shining 10 euros coupon for supersensitive shopping at SUPERSENSE! [ http://the.supersense.com/ ]

here is your very own special couponcode worth 10 EUR: sotd_ha-ha-ha
(minimum orderval 50 EUR)

again big congrats and thank you so much for sharing your polaroids and making this site such an unique place.

you rock

the polanoid team

It’s actually one of my favourite polaroids, and it was taken over ten years ago (2009). Reading the message logs I see a lot people surprised that they also won Shot of the Day – it was bloody hard to win 10 years ago! The algorithm for selection seems to favour older photos. This show’s the sad state of polanoid, its essentially been put on to maintenance mode by the founders, just a step above life support. The community is not engaged, and owners have moved on to other projects. Still, notifications like this are nice: its a time capsule that showcases amazing analogue photography.

I still have some polaroid film in my fridge, one day I’ll have a fire in my belly and shoot again.