Editing Anatomy of a request (section)

===EPrint IDs, Documents and EP_TRIGGER_DOC_URL_REWRITE===

[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L377-493 Lines 377-493] This block of code looks for requests starting with e.g. <code><nowiki>http://repository.blah/123</nowiki></code> - where '123' is an EPrintID.

There are some <code>redir</code>ects in this block to account for older URL that may be requested that had EPrintIDs and/or document positions zero-padded <code><nowiki>http://repository.blah/00000123</nowiki></code> or <code><nowiki>http://repository.blah/00000123/01/Document.txt</nowiki></code>.

Each subsequent match on the <code>$uri</code> consumes part of it - e.g. 

[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L377 Line 377]
<source lang="perl">$uri =~ s! ^$urlpath/(0*)([1-9][0-9]*)\b !!x</source>
will remove the EPrintID from the start of <code>$uri</code>.

[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L398-467 Lines 398-467] deal with document requests. 

[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L398 Line 398]
<source lang="perl">$uri =~ s! ^/(0*)([1-9][0-9]*)\b !!x</source>
will match elements '''after''' the EPrintID in the original URL - matching '45' in
*<code><nowiki>http://repository.blah/123/45/Document.txt</nowiki></code> or 
*<code><nowiki>http://repository.blah/123/45.hassmallThumbnailVersion/Document.txt</nowiki></code> 
(the second example shows the use of a 'relationship' that is processed using a EP_TRIGGER_DOC_URL_REWRITE trigger).

[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L418-419 Lines 418-419] may be a bit confusing at first glance.
<source lang="perl">
$uri =~ s! ^([^/]*)/ !!x;
my @relations = grep { length($_) } split /\./, $1;
</source>
They deal with document relationships - that are of the form <code>.../DocID.relationship1.relationship2.relationshipN/...</code>.

For documents, thumbnails are presented as related documents, the relationship is e.g. 'hassmallThumbnailVersion'.

The first line gets anything from the start of <code>$uri</code> (the DocID already having been removed by line 398), to the next '/'.

The second line (possibly the least readable line of code in EPrints?):
*takes the captured match ($1): <code>.relationship1.relationship2.relationshipN</code>
*splits on '.'s: <code>"","relationship1","relationship2","relationshipN"</code>
*for each of the split values (referenced as $_): grep for the length of the value. This effectively strips out empty elements (length = 0, grep doesn't return the value).
*@relationships = <code>"relationship1","relationship2","relationshipN"</code>

[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L421 Line 421] then assigns whatever is left of the URL as the filename.

[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L423-426 Lines 423-426] use 'pnotes' (http://perl.apache.org/docs/2.0/api/Apache2/RequestUtil.html#C_pnotes_) to pass objects to the request handler.

[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L433-436 Lines 433-436] call document specific authen and authz methods. These deal with the 'security' flag on the document, and are part of the core EPrints that needs to be addressed with ACL.
<source lang="perl">
$r->push_handlers(PerlAccessHandler => [
	\&EPrints::Apache::Auth::authen_doc,
	\&EPrints::Apache::Auth::authz_doc
] );
</source>

[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L440 Line 440] add the document-download log handler to the request cleanup phase:
<source lang="perl">$r->pool->cleanup_register(\&EPrints::Apache::LogHandler::document, $r);</source>

[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L443-459 Lines 443-458] call the EP_TRIGGER_DOC_URL_REWRITE triggers.
There is one default trigger for this - in <code>~/lib/cfg.d/doc_rewrite.pl</code> that handles the relationship-based document requests.

[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L470-490 Lines 470-490] If the URL has an EPrint, but doesn't have a document, we reach this block - which updates the abstract page if necessary, and uses the EPrints templating system to render the page. It also logs the page view using <code>EPrints::Apache::LogHandler::eprint</code>.