Added converter for PlantUML builtin functions

[ThirtySomething]

Hi,

as mentionend and proposed in issue #400 this is a substitution mechanism for your extension. In this pull request there is a very quick and dirty draft version as proof of concept. I'm looking forward to your comments and hopefully your support. I'm not so familiar with reqular expressions in TypeScript and how to pass matches (groups) of the find-part to the replace-part. Also I don't know it the place where I've hooked this in is the right place.

Regards

Jochen

[qjebbs]

Thanks. Basically, you're going to implement a compatible preprocessor within the extension, which I think it not worthwhile to do it. Here is my tips:

1. execute the preprocessor before the original title processing, since the process may bring in unwanted characters for title
2. Do replace like following:

   let text = `%lighten("red",20)`;
   let reg = /%([a-z_]+)\((.+?)(?:,(.+?))*\)/ig;
   
   text.replace(reg, (substring, ...args) => {
       let func = substring
       let paras = args.slice(1, args.length - 2)
       console.log(`full: ${substring}}, func: ${func}, paras: ${paras}`)
       switch (func) {
           case "lighten":
               return isDarkPreprocessor(paras[0], paras[1])
           // ...
           default:
               break;
       }
   })
   
   function isDarkPreprocessor(color: String, offset: number): string {
       return "..."
   }

[ThirtySomething]

Hi,

thanks for your valuable tipps. I've done a complete rewrite of the preprocessor based on your tipps. From my point of view nearly all possible preprocessing is done. There is one point left:

• Basically I want to use the package ts-expression-evaluator, but I don't know if you agree to this. Additionally I don't know how to set this dependency. Without this package I have to use the Javascript eval function which is basically dangerous. I've marked all relevant code parts with // 001.

Also I've changed the place where I've hooked the preprocessing in. As you mentioned, the preprocessor is called before the title.Deal function.

Regards

Jochen