import regex from '../regex'

export default class Highlight {

constructor(output, options) {

if (!options.plugins.highlightjs && !this.isPrism()) {

throw new ReferenceError(

`'hljs is not defined. HighlightJS library is needed to highlight code. Visit https://highlightjs.org/'`

);

}

this.output = output;

this.options = options;

this.regex = regex.highlightCode;

this.inlineCodeRegex = regex.inlineCode;

}

/**

* Encodes the characters like <, > and space and replaces them with

* &lt;, &gt; and &gt; respectively.

* @param {string} code The string that has to be encoded.

* @return {string} The encoded string

*/

static encode(code) {

code = code.replace(/&amp;/gm, '');

code = code.replace(/&lt;/g, '<');

code = code.replace(/&gt;/g, '>');

return code;

}

/**

* removes whitespace characters

* @param {string} code The string from which the whitespace has to be removed

* @return {string}

*/

static trimSpace(code) {

code = code.replace(/^([ \t]*)/g, ''); // leading whitespace

code = code.replace(/[ \t]*$/g, ''); // trailing whitespace

return code;

}

/**

* Places the code and the language name in the required template

* @param {string} processedCode

* @param {string} language

* @return {string}

*/

static addTemplate(processedCode, language) {

return `<pre><code class="ejs-code hljs ${language}">${processedCode.value || processedCode}</code></pre>`

}

/**

* Replaces the code block with the pre tags and returns a string having the code

* formatting using Highlight.js.

* => Matches the string with the regex and finds the code written in three back-ticks ```

* => Detects whether any language has been provided by the user.

* The format supported by embed.js is

* ```[language-name]

* var a = 2;

* ```

* => Trims all the unnecessary spaces and newlines from the code.

* => Passes the code to `hljs.highlightAuto(code, language)` which returns a formatted string

* having the html tags for styling. The `language` here is optional. In case we don't pass the

* language, it tries to detect the language itself.

* => Replaces the code string in the template with the formatted string

* @return {string} The string in which the code is formatted

*/

process() {

this.output = this.output.replace(this.inlineCodeRegex, function (match, group1, group2) {

return `<code>${group2}</code>`

});

return this.output.replace(this.regex, (match, group1, group2, group3) => {

let code = group3;

code = Highlight.trimSpace(code);

code = Highlight.encode(code);

// to prevent auto-linking. Not necessary in code

// *blocks*, but in code spans. Will be converted

// back after the auto-linker runs.

code = code.replace(/:\/\//g, '~P');

let language = group2.split('\n')[0];

let highlightedCode;

const HighlightJS = this.options.plugins.highlightjs;

if (language) {

highlightedCode = HighlightJS.highlightAuto(code, [language]);

} else {

highlightedCode = HighlightJS.highlightAuto(code);

language = highlightedCode.language;

}

return Highlight.addTemplate(highlightedCode, language);

});

}

}