Kronos-Integration/kronos-interceptor-line-header

== Header Check
This modules consumes an object stream as created by https://github.com/darlenya/stream-line-tokenizer-csv[stream-line-tokenizer-csv]
The consumed objects have the following format.

.Line object example
[source,json]
----
{
  "lineNumber": 1,
  "data": "['any', 'line', 'data']"
}
----

After the header is checked the module will emit an event ''header'' which defines which columns where found
and on which position they are. All errors found on the header where emitted as ''error'' events.

An error event has this format:

.Error event
[source,json]
----
{
  "errorCode": "CHECK_HEADER_NO_STRICT_MATCH",
  "severity": "abort_file",
    "message": "The expected header [<expectedHeader>] has a different column count to the actual header [<actualHeader>]"
}
----


This module is for checking the header line of such tokens. It will only read the object
where ''lineNumber'' is ''0''. All other objects will not be considered.

=== Install
[source,bash]
----
$ npm install stream-line-header
----


=== Usage
The following code shows example for the option given to the module. For more information what optiona are mandatory
and what they does refer to the later chaper which describe the json schema for the options.

.Options for the parser
[source,js]
----
{
    "expectedHeader": ["col_1", "col_2", "col_3", ["col_4", "col 4", "c4"], "col_5", "col_6"],
  "fieldNames": ["c1", "c2", "c3", "c4", "c5", "c6"],
  "caseSensitive": true,
  "strict": {
    "val": true,
    "severity": "skip_record"
  },
  "additionalColumns": false,
  "missingColumns": false,
  "mandatoryColumns": ["c1", "c2", "c3"],
  "severity": "abort_file"
}
----


.Usage example
[source,js]
----
const fs = require('fs');
const lp = require('stream-line-parser');
const tk = require('stream-line-tokenizer-csv');
const header = require('stream-line-tokenizer-csv');

let parser = lp({
  "allow_new_line_in_cell" : true,
    "line_separator": "\n",
  "quote_char" : '"',
  "skip_empty_lines" : true
});

let tokenizer = tk({
  "separator_list" : [',', ';'],
  "quote_char" : '"',
  "use_quotes" : true,
  "trim" : true
  });

let headerCheck = header(options, validate);   // <1>

fs.createReadStream('filename.csv').pipe(parser).pipe(tokenizer).pipe(headerCheck);
----
<1> If validate is set to a true value the format of the given options will be validated.


This will read the file 'filename.csv'. The stream will be piped to the parser which
will split the stream in to objects. The parser emits an object stream. This object
stream will then be piped to the line tokenizer.
Then the header format will be checked. These checks depends on the defined options.

include::schema/header.adoc[]