BloomJS
====

A javascript search engine.

## Basic idea
I have a static weblog, generated thanks to [Blogit](https://github.com/phyks/blogit, caution this code is ugly) and, as I only want to have html files on my server, I needed to find a way to enable users to search my blog.

An index is generated by a Python script, upon generation of the pages, and is dynamically downloaded by the client when he wants to search for contents.

## Files

### Index generation (`index_generation/` folder)

* `generate_index.py`: Python script to generate the index (runs only at page generation) in a nice format for Javascript
* `pybloom.py`: Library to handle bloom filters in Python
* `stemmer.py`: Implementation of Porter Stemming algorithm in Python, from Vivake Gupta.

### Example html search form

* `index.html`
* `js/bloom.js`: main JS code
* `js/bloomfilters.js`: JS library to use BloomFilters

### Examples

* `samples/`: samples for testing purpose (taken from my blog articles)

## Data storing

One of the main problem was to transmit the binary data from the Python script to the JS script. I found [an article about handling binary data in JavaScript](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/Sending_and_Receiving_Binary_Data) which helped me a lot.

Data from the python script is just the array of bloomfilters bitarray written as a binary file (`data/search_index`), which I open with JS. The list of articles is also written in JSON form in a specific file (`data/pages_index.json`).

Here's the format of the output from the python script:

* [16 bits] : number of articles (== number of bitarrays)
* for each bitarray:
    * [16 bits] : length of the bitarray
    * […] : the bitarray itself

## Notes
* I got the idea while reading [this page](http://www.stavros.io/posts/bloom-filter-search-engine/?print) found on [Sebsauvage's shaarli](http://sebsauvage.net/links/). I searched a bit for code doing what I wanted and found these ones:

    * https://github.com/olivernn/lunr.js
    * https://github.com/reyesr/fullproof

    But I wasn't fully satisfied by the first one, and I found the second one too heavy and complicated for my purpose, so I ended up coding this.

* This code is mainly a proof of concept. As such, it is not fully optimized (actually, I just tweaked until the resulted files and calculations could be considered "acceptable"). For those looking for more effective solutions, here are a few things I found while looking for information on the web:

    * The stemming algorithm used may not be the most efficient one. People wanting to work with non-English languages or to optimize the overall computation of the index can easily move to a more effective algorithm. See [Wikipedia](http://en.wikipedia.org/wiki/Stemming) and [the stemming library in Python](https://pypi.python.org/pypi/stemming/1.0) which has C wrappers for best performances.