imap-handler

Parses IMAP commands

npm install imap-handler
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IMAP Handler

Parses and compiles IMAP commands. This parser is not suitable for live servers as it requires the entire command (including all literals) to be buffered into one long string before parsing it. It does not tolerate syntax errors as well (an exception is thrown if syntax error occurs). So the module should be suitable for building test IMAP servers.

IMAP Handler parser is not context sensitive, it only makes distinction in data types but not in the values - eg. when an internal date string is expected, the parser identifies this value as a string but does not check if the value has a proper date-time format.

Key-value pairs are also not identified, all lists are parsed into arrays, not objects.

Installation

npm install imap-handler

Usage

Parse IMAP commands

To parse a command you need to have the command as one complete string (including all literals) without the ending <CR><LF>

imapHandler.parser(imapCommand[, options]);

Where

  • imapCommand is an IMAP string without the final line break
  • options is an optional options object (see below)

Options

  • allowUntagged (Boolean) by default parsing "*" tags are not allowed, set this value to true to accept untagged commands
  • allowSection (Array) Not all atoms are allowed to have section (and partial) values, set the command names with this array (default value is ["BODY", "BODY.PEEK"])

The function returns an object in the following form:

{
    tag: "TAG",
    command: "COMMAND",
    attributes: [
        {type: "SEQUENCE", value: "sequence-set"},
        {type: "ATOM", value: "atom", section:[section_elements], partial: [start, end]},
        {type: "STRING", value: "string"},
        {type: "LITERAL", value: "literal"},
        [list_elements]
    ]
}

Where

  • tag is a string containing the tag
  • command is the first element after tag
  • attributes (if present) is an array of next elements

If section or partial values are not specified in the command, the values are also missing from the ATOM element

NB! Sequence numbers are identified as ATOM values if the value contains only numbers. NB! NIL atoms are always identified as null values, even though in some cases it might be an ATOM with value "NIL"

For example

var imapHandler = require("imap-handler");

imapHandler.parser("A1 FETCH *:4 (BODY[HEADER.FIELDS ({4}\r\nDate Subject)]<12.45> UID)");

Results in the following value:

{
    "tag": "A1",
    "command": "FETCH",
    "attributes": [
        [
            {
                "type": "SEQUENCE",
                "value": "*:4"
            },
            {
                "type": "ATOM",
                "value": "BODY",
                "section": [
                    {
                        "type": "ATOM",
                        "value": "HEADER.FIELDS"
                    },
                    [
                        {
                            "type": "LITERAL",
                            "value": "Date"
                        },
                        {
                            "type": "ATOM",
                            "value": "Subject"
                        }
                    ]
                ],
                "partial": [
                    12,
                    45
                ]
            },
            {
                "type": "ATOM",
                "value": "UID"
            }
        ]
    ]
}

Compile command objects into IMAP commands

You can "compile" parsed or self generated IMAP command obejcts to IMAP command strings with

imapHandler.compiler(commandObject);

Where

  • commandObject is an object parsed with imapHandler.parser() or self generated

The function returns a string.

The input object differs from the parsed object with the following aspects:

  • string, number and null (null values are all non-number and non-string falsy values) are allowed to use directly - {type: "STRING", value: "hello"} can be replaced with "hello"
  • Additional types are used: SECTION which is an alias for ATOM and TEXT which returns the input string as given with no modification (useful for server messages).

For example

var command = {
    tag: "*",
    command: "OK",
    attributes: [
        {
            type: "SECTION",
            section: [
                {type: "ATOM", value: "ALERT"}
            ]
        },
        {type:"TEXT", value: "NB! The server is shutting down"}
    ]
};

imapHandler.compiler(command);
// * OK [ALERT] NB! The server is shutting down

License

MIT

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