bUwUma/README.md

bUwUma

bUwUma is a build system that uses GNU make and a preprocessor written in python to build static, multilingual websites.

This readme only documents the preprocessor. For more information and a quickstart guide on how to use bUwUma, please refer to the article on my website.

HTML Preprocessor Documentation

Syntax

Commands

- All commands must be located within a html comment what starts with `<!--` and ends with `-->`.
- Commands start with a `#` character, the command must follow the `#` immediately.
- Everything after the command until the end of the comment or a newline character are considered the argument of the command.
```html
<!-- #command everything here is an argument -->
<!--
    #command everything here is an argument
    #anothercommand more arguments
    While this is a comment right now, it will be UNCOMMENTED in the after the preprocessor finishes!
    #comment This will be a single line html comment after the preprocessor finishes.
-->
```
- All commands return a string, which can be empty.
- If a comment contains a command, the entire comment will replaced with the return value of the command.
- If there are multiple commands in a command, it will be replaced by all the return values added together.

Variables

- Variable names must only consist of these characters: `a-zA-Z0-9_`
- A variable with name `varname` can be used like this: `#$(varname)`
- A variable usage will be replaced by the value of the variable
- Any variable that has is not defined has empty string as value

General

- Whitespaces around a token are ignored, so `<!--#include     dir/file-->` is the same as `<!-- #include dir/file -->`
- If a command-comment takes up a whole line, the whole line including the newline character is replaced.

Commands

include

Include the content of a file at the position of the command.
**Synopsis**:
    `<!-- #include path/to-a-text-file.html -->`
**Argument**:
    A absolute or relative path to a text file
**Return Value**:
    The content of the file or `<!-- Could not include '{args}' -->` empty string if the file can not be opened.

set

Set the value of a variable
**Synopsis**:
    Set the value of `varname` to `this is the value`:
    `<!-- #set varname this is the value -->`
    Set the value of `varname` depending on the value of `othervar`:
    `<!-- #set varname othervar?{*:fallback,key1:val1,key2:val2...}>`
**Argument**:
    The first word is the name of the variable, the rest is the value or a dictionary.
**Return Value**:
    Empty string
You can make the value of `varname` dependant on the value of another variable `othervar` by using a dictionary-like syntax described above.
In this case, `varname` will take the first value from the dictionary that matches tha value of `othervar`. 
`*` always everything and can be used as fallback. General wildcards like `a*` to match everything that starts with a are not supported.
Instead of commas `,` you can also use semicolons `;` as separators, but this must be consistend within the map.

default

Same as `set`, but it sets the variable's value only if it has no value yet.

comment

Comment the arguemnts.
**Synopsis**:
    `<!-- #comment This will stay as comment in the html -->`
**Argument**:
    Any string
**Return Value**:
    The argument in comment tags
This can be useful in multiline comments that contain other commands: In that case, the comment tags will be removed and each command replaced with
its return value, so if you want to just have commented text in there you can use `#comment` 

uncomment

Uncomment the comment.
**Synopsis**:
    `<!-- #uncomment This will not be commented -->`
**Argument**:
    Any string
**Return Value**:
    The argument
This can be useful when you want to look at the unprocessed html without variables or when your syntax highlighting gets confused by a variable.

sidenav

Manage the generation of a content menu which contains links to all headings in your html that have an id. The menu is called sidenav here.
An entry is a html heading with a id: `<h1 id=myheading>This heading will be linked in the sidenav</h1>`
**Synopsis**:
    `<!-- #sidenav sidenav-command arguments -->`
sidenav-command must be one of the following:
#### `include`
    Include the generated sidenav at this position.
    **Argument**:
        Ignored
    **Return Value**:
        The generated sidenav
#### `section`
    Group all following entries in named section.
    **Argument**:
        The name of the section
    **Return Value**
        Empty string
#### `name`
    Use a custom name instead of the heading itself for the link to the next heading.
    **Argument**:
        The link-name of the next heading
    **Return Value**:
        Empty string
#### `custom`
    Include a custom link in the sidenav.
    **Synopsis**:
        `<!-- #sidenav custom href="my-link" name="Go to my link!" -->`
    **Argument**:
        Must be `href="..." name="..."`. Either single `'` or double `"` quotes are required.
    **Return Value**:
        Empty string

Pitfalls

- The `#include` command must not be in the last line of the file
- The maps in `set` have **at least 2** options
- If you want to use variables in markdown, you have to escape the `#` with a backslash, so `#$(var)` becomes `\#$(var)`