<p><strong>HTML entity parser</strong> is the parser that takes HTML code as input and replace all the entities of the special characters by the characters itself.</p>

<p>The special characters and their entities for HTML are:</p>

<ul>
	<li><strong>Quotation Mark:</strong> the entity is <code>&amp;quot;</code> and symbol character is <code>&quot;</code>.</li>
	<li><strong>Single Quote Mark:</strong> the entity is <code>&amp;apos;</code> and symbol character is <code>&#39;</code>.</li>
	<li><strong>Ampersand:</strong> the entity is <code>&amp;amp;</code> and symbol character is <code>&amp;</code>.</li>
	<li><strong>Greater Than Sign:</strong> the entity is <code>&amp;gt;</code> and symbol character is <code>&gt;</code>.</li>
	<li><strong>Less Than Sign:</strong> the entity is <code>&amp;lt;</code> and symbol character is <code>&lt;</code>.</li>
	<li><strong>Slash:</strong> the entity is <code>&amp;frasl;</code> and symbol character is <code>/</code>.</li>
</ul>

<p>Given the input <code>text</code> string to the HTML parser, you have to implement the entity parser.</p>

<p>Return <em>the text after replacing the entities by the special characters</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> text = &quot;&amp;amp; is an HTML entity but &amp;ambassador; is not.&quot;
<strong>Output:</strong> &quot;&amp; is an HTML entity but &amp;ambassador; is not.&quot;
<strong>Explanation:</strong> The parser will replace the &amp;amp; entity by &amp;
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> text = &quot;and I quote: &amp;quot;...&amp;quot;&quot;
<strong>Output:</strong> &quot;and I quote: \&quot;...\&quot;&quot;
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= text.length &lt;= 10<sup>5</sup></code></li>
	<li>The string may contain any possible characters out of all the 256 ASCII characters.</li>
</ul>

class Solution:
    def entityParser(self, text: str) -> str:

        entitySymbol = {
            '&quot': "\"",
            "&apos": "\'",
            "&amp": "&",
            "&gt": ">",
            "&lt": "<",
            "&frasl": "/"
        }


        # iterate through each char in the text
        # previous chars equals a key: pop and replace with entity symbol
        # then join again

        output = []
        buffer = ''

        for char in text:
            # possible ending of special character
            if char == ';':
                # buffer matches entity: replace with symbol
                if buffer in entitySymbol:
                    output.append(entitySymbol[buffer])
                
                # buffer does not represent a special character: add as normal
                else:
                    output.extend(buffer + ";")

                # erase buffer
                buffer = ''
                

            elif char == "&":
                # previous apostrophe has been detected
                # apostrophe and following characters are part of string
                if buffer:
                    output.append(buffer)
                    buffer = ""

                buffer += '&'
 
            else:
                # following characters may make up special character
                if buffer:
                    buffer += char
                
                # add regular characters to output
                else:
                    output.append(char)

        # add buffer at the end
        # edge case of '&' at the end without following ';'
        return ''.join(output) + buffer
            
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