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67 lines
2.3 KiB
67 lines
2.3 KiB
9 years ago
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# Text Moderation with Firebase Cloud Functions
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This template shows how to perform server side moderation of text written to a Firebase DB.
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For instance if a user added the message "I DON'T LIKE THIS APP!! This is POOP!!!" this will get moderated to a - more civilized - non uppercase message: "I don't like this app. This is ****".
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## Cloud Function Code
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See file [index.js](index.js) and [moderation-string-utils.js](moderation-string-utils.js) for the moderation code.
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Moderation of the messages is performed using [bad-words](https://www.npmjs.com/package/bad-words) a bad words remover that uses an external [list of bad-words](https://github.com/web-mech/badwords-list) and is currently mostly aimed at filtering english bad words. Also messages that contains mostly upper case characters are re-capitalized correctly using [capitalize-sentence](https://www.npmjs.com/package/capitalize-sentence).
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The dependencies are listed in [package.json](package.json).
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## Sample Database Structure
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Users anonymously add a message text to the `/messages` list:
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```
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/functions-project-12345
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/messages
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/key-123456
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text: "This is my first message!"
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/key-123457
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text: "This is my second message!"
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```
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## Trigger rules
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Below is the trigger rule for the `moderator` function making sure it's triggered only when a new message is created and not every time it's updated.
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```
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"functions": {
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".source": "functions",
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"moderator": {
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"triggers": {
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"database": {
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"path": "/messages/$message",
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"condition": "!data.exists()" // Only run the function once on new messages
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}
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}
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}
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}
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```
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## Security Rules
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The following security rules ensures users cannot read a message before it has been sanitized. The function adds a `sanitize` attribute (boolean) to the messages once they have been moderated.
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Also we make sure that users can only create a message and not edit them. We also make sure they cannot set the sanitized flag already.
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```
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{
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"rules": {
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"messages": {
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"$message": {
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// Users can only add new messages. Not modify or delete them. Also makes sure they cannot mark a message as
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// already sanitized.
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".write": "!data.exists() && !newData.child('sanitized').exists()'"
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".read": "data.child('sanitized').val() === true"
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}
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}
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}
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}
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```
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