How to manage documents?

jIO is mapped after the CouchDB APIs and extends them to provide unified, scalable and high performance access via JavaScript to a wide variety of different storage backends.

If you are not familiar with Apache CouchDB: it is a scalable, fault-tolerant, and schema-free document-oriented database. It is used in large and small organizations for a variety of applications where traditional SQL databases are not the best solution for the problem at hand. CouchDB provides a RESTful HTTP/JSON API accessible by many programming libraries and tools (like curl or Pouchdb) and has its own conflict management system.

What is a document?

A document is an association of metadata and attachment(s). The metadata is the set of properties of the document and the attachments are the binaries of the content of the document.

In jIO, metadata is just a dictionary with keys and values (JSON object), and attachments are just simple strings.

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{
    // document metadata
    "_id"   : "Identifier",
    "title" : "A Title!",
    "creator": "Mr.Author"
}

You can also retrieve document attachment metadata in this object.

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{
    // document metadata
    "_id"   : "Identifier",
    "title" : "A Title!",
    "creator": "Mr.Author",
    "_attachments": {
        // attachment metadata
        "body.html": {
            "length": 12893,
            "digest": "sha256-XXXX...",
            "content_type": "text/html"
        }
    }
}

Here is a draft about metadata to use with jIO.

Basic Methods

Below you can see examples of the main jIO methods. All examples are using revisions (as in revision storage or replicate revision storage), so you can see how method calls should be made with either of these storages.

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// Create a new jIO instance
var jio_instance = jIO.newJio(storage tree description);

// create and store new document
jio_instance.post({"title": "some title"}).
  then(function (response) {
    // console.log(response);
  });

// create or update an existing document
jio_instance.put({"_id": "my_document", "title": "New Title"}).
  then(function (response) {
    // console.log(response);
  });

// add an attachment to a document
jio_instance.putAttachment({"_id": "my_document", "_attachment": "its_attachment",
                            "_data": "abc", "_mimetype": "text/plain"}).
  then(function (response) {
    // console.log(response);
  });

// read a document
jio_instance.get({"_id": "my_document"}).
  then(function (response) {
    // console.log(response);
  });

// read an attachment
jio_instance.getAttachment({"_id": "my_document", "_attachment": "its_attachment"}).
  then(function (response) {
    // console.log(response);
  });

// delete a document and its attachment(s)
jio_instance.remove({"_id": "my_document"}).
  then(function (response) {
    // console.log(response);
  });

// delete an attachment
jio_instance.removeAttachment({"_id": "my_document", "_attachment": "its_attachment"}).
  then(function (response) {
    // console.log(response);
  });

// get all documents
jio_instance.allDocs().then(function (response) {
  // console.log(response);
});

Promises

Each jIO method returns a Promise object, which allows us to get responses into callback parameters and to chain callbacks with other returned values.

jIO uses a custom version of RSVP.js, adding canceler and progression features.

You can read more about promises:

Method Options and Callback Responses

To retrieve jIO responses, you have to provide callbacks like this:

jio_instance.post(metadata, [options]).
    then([responseCallback], [errorCallback], [progressionCallback]);
  • On command success, responseCallback will be called with the jIO response as first parameter.
  • On command error, errorCallback will be called with the jIO error as first parameter.
  • On command notification, progressionCallback will be called with the storage notification.

Here is a list of responses returned by jIO according to methods and options:

Option Available for Response (Callback first parameter)
No options post(), put(), remove()
{
  "result": "success",
  "method": "post",
  // or put or remove
  "id": "my_doc_id",
  "status": 204,
  "statusText": "No Content"
}
No options putAttachment(), removeAttachment()
{
  "result": "success",
  "method": "putAttachment",
  // or removeAttachment
  "id": "my_doc_id",
  "attachment": "my_attachment_id",
  "status": 204,
  "statusText": "No Content"
}
No options get()
{
  "result": "success",
  "method": "get",
  "id": "my_doc_id",
  "status": 200,
  "statusText": "Ok",
  "data": {
    // Here, the document metadata
  }
}
No options getAttachment()
{
  "result": "success",
  "method": "getAttachment",
  "id": "my_doc_id",
  "attachment": "my_attachment_id",
  "status": 200,
  "statusText": "Ok",
  "data": Blob // Here, the attachment content
}
No option allDocs()
{
  "result": "success",
  "method": "allDocs",
  "id": "my_doc_id",
  "status": 200,
  "statusText": "Ok",
  "data":  {
    "total_rows": 1,
    "rows": [{
      "id": "mydoc",
      "key": "mydoc", // optional
      "value": {},
    }]
  }
}
include_docs: true allDocs()
{
  "result": "success",
  "method": "allDocs",
  "id": "my_doc_id",
  "status": 200,
  "statusText": "Ok",
  "data":  {
    "total_rows": 1,
    "rows": [{
      "id": "mydoc",
      "key": "mydoc", // optional
      "value": {},
      "doc": {
        // Here, "mydoc" metadata
      }
    }]
  }
}

In case of error, the errorCallback first parameter will look like:

{
  "result": "error",
  "method": "get",
  "status": 404,
  "statusText": "Not Found",
  "error": "not_found",
  "reason": "document missing",
  "message": "Unable to get the requseted document"
}

Example: How to store a video on localStorage

The following shows how to create a new jIO in localStorage and then post a document with two attachments.

// create a new jIO
var jio_instance = jIO.newJio({
  "type": "local",
  "username": "usr",
  "application_name":"app"
});
// post the document "metadata"
jio_instance.post({
  "title"       : "My Video",
  "type"        : "MovingImage",
  "format"      : "video/ogg",
  "description" : "Images Compilation"
}, function (err, response) {
  var id;
  if (err) {
    return alert('Error posting the document meta');
  }
  id = response.id;
  // post a thumbnail attachment
  jio_instance.putAttachment({
    "_id": id,
    "_attachment": "thumbnail",
    "_data": my_image,
    "_mimetype": "image/jpeg"
  }, function (err, response) {
    if (err) {
      return alert('Error attaching thumbnail');
    }
    // post video attachment
    jio_instance.putAttachment({
      "_id": id,
      "_attachment": "video",
      "_data": my_video,
      "_mimetype":"video/ogg"
    }, function (err, response) {
      if (err) {
        return alert('Error attaching the video');
      }
      alert('Video Stored');
    });
  });
});

localStorage contents:

{
  "jio/local/usr/app/12345678-1234-1234-1234-123456789012": {
    "_id": "12345678-1234-1234-1234-123456789012",
    "title": "My Video",
    "type": "MovingImage",
    "format": "video/ogg",
    "description": "Images Compilation",
    "_attachments":{
      "thumbnail":{
        "digest": "md5-3ue...",
        "content_type": "image/jpeg",
        "length": 17863
      },
      "video":{
        "digest": "md5-0oe...",
        "content_type": "video/ogg",
        "length": 2840824
      }
    }
  },
  "jio/local/usr/app/myVideo/thumbnail": "/9j/4AAQSkZ...",
  "jio/local/usr/app/myVideo/video": "..."
}