From d59099aab49cc059c57669031530facb518d75d0 Mon Sep 17 00:00:00 2001
From: Adam Vessey <adam@discoverygarden.ca>
Date: Thu, 22 Aug 2013 20:28:34 +0000
Subject: [PATCH 01/18] Add response headers.

... Still need to react to requests.
---
 includes/datastream.inc | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/includes/datastream.inc b/includes/datastream.inc
index 585fa2f5..74831fd3 100644
--- a/includes/datastream.inc
+++ b/includes/datastream.inc
@@ -46,9 +46,20 @@ function islandora_view_datastream(AbstractDatastream $datastream, $download = F
     }
   }
 
-  header_remove('Cache-Control');
   header_remove('Expires');
   header('Content-type: ' . $datastream->mimetype);
+  $cache_control = array();
+  if ($datastream->parent->repository->api->connection->username == 'anonymous') {
+    $cache_control[] = 'public';
+  }
+  else {
+    $cache_control[] = 'private';
+  }
+  $cache_control[] = 'must-revalidate';
+  header('Cache-Control: ' . implode(', ', $cache_control));
+  header('Last-Modified: '. $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'));
+  header('Etag: "' . $datastream->createdDate->format('Uu') . '"');
+
   if ($datastream->controlGroup == 'M' || $datastream->controlGroup == 'X') {
     header('Content-length: ' . $datastream->size);
   }

From 630ab0e5ae6965add81a90f1ec866d9a3e870998 Mon Sep 17 00:00:00 2001
From: Adam Vessey <adam@discoverygarden.ca>
Date: Fri, 23 Aug 2013 13:36:47 +0000
Subject: [PATCH 02/18] Implement the HTTP cache validation shenanigans.

---
 includes/datastream.inc | 143 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 128 insertions(+), 15 deletions(-)

diff --git a/includes/datastream.inc b/includes/datastream.inc
index 74831fd3..f52ed3a5 100644
--- a/includes/datastream.inc
+++ b/includes/datastream.inc
@@ -46,20 +46,7 @@ function islandora_view_datastream(AbstractDatastream $datastream, $download = F
     }
   }
 
-  header_remove('Expires');
   header('Content-type: ' . $datastream->mimetype);
-  $cache_control = array();
-  if ($datastream->parent->repository->api->connection->username == 'anonymous') {
-    $cache_control[] = 'public';
-  }
-  else {
-    $cache_control[] = 'private';
-  }
-  $cache_control[] = 'must-revalidate';
-  header('Cache-Control: ' . implode(', ', $cache_control));
-  header('Last-Modified: '. $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'));
-  header('Etag: "' . $datastream->createdDate->format('Uu') . '"');
-
   if ($datastream->controlGroup == 'M' || $datastream->controlGroup == 'X') {
     header('Content-length: ' . $datastream->size);
   }
@@ -70,13 +57,139 @@ function islandora_view_datastream(AbstractDatastream $datastream, $download = F
     $filename = $datastream->label . '.' . $extension;
     header("Content-Disposition: attachment; filename=\"$filename\"");
   }
+
+  $cache_check = islandora_view_datastream_cache_check($datastream);
+  if ($cache_check !== 200) {
+    if ($cache_check === 304) {
+      header('HTTP/1.1 304 Not Modified');
+    }
+    elseif ($cache_check === 412) {
+      header('HTTP/1.0 412 Precondition Failed'); 
+    }
+  }
+  islandora_view_datastream_set_cache_headers($datastream);
+
   drupal_page_is_cacheable(FALSE);
   // Try not to load the file into PHP memory!
-  ob_end_flush();
-  $datastream->getContent('php://output');
+  // Close and flush ALL the output buffers!
+  while(@ob_end_flush()) {};
+
+  // New content needed.
+  if ($cache_check === 200) {
+    $datastream->getContent('php://output');
+  }
   exit();
 }
 
+/**
+ * Parse "etags" from HTTP If-Match or If-None-Match headers.
+ *
+ * @param string $header_value
+ *   The value from the headers.
+ *
+ * @return array
+ *   An array containing all the etags present.
+ */
+function islandora_parse_http_match_headers($header_value) {
+  $matches = array();
+  $count = preg_match_all('/(((W\/)?("?)(\*|.+?)\4)(, +)?)/', $header_value, $matches);
+  return $matches[5];  
+}
+
+/**
+ * Validate cache headers.
+ *
+ * @param AbstractDatastream $datastrea
+ *
+ * @return int
+ *   An integer representing the HTTP response code. One of:
+ *   - 200: Proceed as normal.
+ *   - 304: Resource hasn't changed; pass cache validation.
+ *   - 412: Resource has channged; fail cache validation.
+ * 
+ * @see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
+ */
+function islandora_view_datastream_cache_check(AbstractDatastream $datastream) {
+  // Let's assume that if we get here, we'll be able to complete the request.
+  $return = 200;
+
+  if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
+    $modified_since = DateTime::createFromFormat('D, d M Y H:i:s e', $_SERVER['HTTP_IF_MODIFIED_SINCE']);
+    if ($datastream->createdDate->getTimestamp() - $modified_since->getTimestamp() > 0) {
+      // Changed!
+      return $return;
+    }
+    else {
+      $return = 304;
+    }
+  }
+  if ($return === 200 && isset($_SERVER['HTTP_IF_UNMODIFIED_SINCE'])) {
+    $unmodified_since = DateTime::createFromFormat('D, d M Y H:i:s e', $_SERVER['HTTP_IF_UNMODIFIED_SINCE']);
+    if ($datastream->createdDate->getTimestamp() !== $unmodified_since->getTimestamp()) {
+      // Changed!
+      $return = 412;
+    }
+    else {
+      return $return;
+    }
+  }
+
+  // Only consider Etags we have provided.
+  if (isset($datastream->checksum)) {
+    $tags = array();
+    foreach ($datastream as $offset => $version) {
+      if (isset($version->checksum)) {
+        $tags[$offset] = $version->checksum;
+      }
+    }
+
+    if ($return === 200 && isset($_SERVER['HTTP_IF_MATCH'])) {
+      $request_tags = islandora_parse_http_match_headers($_SERVER['HTTP_IF_MATCH']);
+      if (in_array('*', $request_tags) || count(array_intersect($tags, $request_tags)) > 0) {
+        // There's a match... Let things go ahead.
+        return $return;
+      }
+      else {
+        $return = 412;
+      }
+    }
+    if (in_array($return, array(200, 304), TRUE) && isset($_SERVER['HTTP_IF_NONE_MATCH'])) {
+      $request_tags = islandora_parse_http_match_headers($_SERVER['HTTP_IF_NONE_MATCH']);
+      if (in_array('*', $request_tags) || count(array_intersect($tags, $request_tags)) > 0) {
+        $return = 304;
+      }
+      else {
+        $return = 200;
+      }
+    }
+  }
+
+  return $return;
+}
+
+/**
+ * Set various HTTP headers for caching.
+ *
+ * @param AbstractDatastream $datastream
+ *   The datastream being viewed/downloaded.
+ */
+function islandora_view_datastream_set_cache_headers(AbstractDatastream $datastream) {
+  header_remove('Expires');
+  $cache_control = array();
+  if ($datastream->parent->repository->api->connection->username == 'anonymous') {
+    $cache_control[] = 'public';
+  }
+  else {
+    $cache_control[] = 'private';
+  }
+  $cache_control[] = 'must-revalidate';
+  header('Cache-Control: ' . implode(', ', $cache_control));
+  header('Last-Modified: '. $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'));
+  if (isset($datastream->checksum)) {
+    header("Etag: \"{$datastream->checksum}\"");
+  }
+}
+
 /**
  * Get the human readable size of the given datastream.
  *

From 55c3fc0b9055d90d4128d548019ee1bedfd94604 Mon Sep 17 00:00:00 2001
From: Adam Vessey <adam@discoverygarden.ca>
Date: Fri, 23 Aug 2013 14:13:18 +0000
Subject: [PATCH 03/18] Force cache revalidation.

---
 includes/datastream.inc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/includes/datastream.inc b/includes/datastream.inc
index f52ed3a5..43f05478 100644
--- a/includes/datastream.inc
+++ b/includes/datastream.inc
@@ -174,7 +174,7 @@ function islandora_view_datastream_cache_check(AbstractDatastream $datastream) {
  *   The datastream being viewed/downloaded.
  */
 function islandora_view_datastream_set_cache_headers(AbstractDatastream $datastream) {
-  header_remove('Expires');
+  header('Expires: Sun, 19 Nov 1978 05:00:00 GMT');
   $cache_control = array();
   if ($datastream->parent->repository->api->connection->username == 'anonymous') {
     $cache_control[] = 'public';
@@ -183,6 +183,7 @@ function islandora_view_datastream_set_cache_headers(AbstractDatastream $datastr
     $cache_control[] = 'private';
   }
   $cache_control[] = 'must-revalidate';
+  $cache_control[] = 'max-age=0';
   header('Cache-Control: ' . implode(', ', $cache_control));
   header('Last-Modified: '. $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'));
   if (isset($datastream->checksum)) {

From 64c90936d9f1f67a87d1d9d8d1403e6790e181fd Mon Sep 17 00:00:00 2001
From: Adam Vessey <adam@discoverygarden.ca>
Date: Fri, 23 Aug 2013 16:01:01 +0000
Subject: [PATCH 04/18] Coding standards.

---
 includes/datastream.inc | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/includes/datastream.inc b/includes/datastream.inc
index 43f05478..27a25f6e 100644
--- a/includes/datastream.inc
+++ b/includes/datastream.inc
@@ -64,7 +64,7 @@ function islandora_view_datastream(AbstractDatastream $datastream, $download = F
       header('HTTP/1.1 304 Not Modified');
     }
     elseif ($cache_check === 412) {
-      header('HTTP/1.0 412 Precondition Failed'); 
+      header('HTTP/1.0 412 Precondition Failed');
     }
   }
   islandora_view_datastream_set_cache_headers($datastream);
@@ -72,7 +72,8 @@ function islandora_view_datastream(AbstractDatastream $datastream, $download = F
   drupal_page_is_cacheable(FALSE);
   // Try not to load the file into PHP memory!
   // Close and flush ALL the output buffers!
-  while(@ob_end_flush()) {};
+  while (@ob_end_flush()) {
+  };
 
   // New content needed.
   if ($cache_check === 200) {
@@ -93,13 +94,13 @@ function islandora_view_datastream(AbstractDatastream $datastream, $download = F
 function islandora_parse_http_match_headers($header_value) {
   $matches = array();
   $count = preg_match_all('/(((W\/)?("?)(\*|.+?)\4)(, +)?)/', $header_value, $matches);
-  return $matches[5];  
+  return $matches[5];
 }
 
 /**
  * Validate cache headers.
  *
- * @param AbstractDatastream $datastrea
+ * @param AbstractDatastream $datastream
  *
  * @return int
  *   An integer representing the HTTP response code. One of:
@@ -174,6 +175,7 @@ function islandora_view_datastream_cache_check(AbstractDatastream $datastream) {
  *   The datastream being viewed/downloaded.
  */
 function islandora_view_datastream_set_cache_headers(AbstractDatastream $datastream) {
+  // Force cache revalidation.
   header('Expires: Sun, 19 Nov 1978 05:00:00 GMT');
   $cache_control = array();
   if ($datastream->parent->repository->api->connection->username == 'anonymous') {
@@ -185,7 +187,7 @@ function islandora_view_datastream_set_cache_headers(AbstractDatastream $datastr
   $cache_control[] = 'must-revalidate';
   $cache_control[] = 'max-age=0';
   header('Cache-Control: ' . implode(', ', $cache_control));
-  header('Last-Modified: '. $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'));
+  header('Last-Modified: ' . $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'));
   if (isset($datastream->checksum)) {
     header("Etag: \"{$datastream->checksum}\"");
   }

From f0c2e2dd88ddf78bea23a603aab6d00d169f1ac6 Mon Sep 17 00:00:00 2001
From: Adam Vessey <adam@discoverygarden.ca>
Date: Fri, 23 Aug 2013 17:22:33 +0000
Subject: [PATCH 05/18] Code standards, again.

---
 includes/datastream.inc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/includes/datastream.inc b/includes/datastream.inc
index 27a25f6e..0eda5d4d 100644
--- a/includes/datastream.inc
+++ b/includes/datastream.inc
@@ -101,6 +101,7 @@ function islandora_parse_http_match_headers($header_value) {
  * Validate cache headers.
  *
  * @param AbstractDatastream $datastream
+ *   The datastream for which to check the request headers against.
  *
  * @return int
  *   An integer representing the HTTP response code. One of:

From b002191085827a8482bd8c6cddeae921598e85e4 Mon Sep 17 00:00:00 2001
From: MorganDawe <morgandawe@hotmail.com>
Date: Tue, 27 Aug 2013 13:46:26 -0300
Subject: [PATCH 06/18] Added the previously removed print callback, as it was
 required by another module and was breaking clipping.

---
 islandora.module | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/islandora.module b/islandora.module
index 1a53aebf..ed2268db 100644
--- a/islandora.module
+++ b/islandora.module
@@ -297,6 +297,15 @@ function islandora_menu() {
     'access arguments' => array(ISLANDORA_VIEW_DATASTREAM_HISTORY, 4),
     'load arguments' => array(2),
   );
+  $items['islandora/object/%islandora_object/printer'] = array(
+    'title' => 'Print Object',
+    'page callback' => 'islandora_print_object',
+    'page arguments' => array(2),
+    'type' => MENU_CALLBACK,
+    'access callback' => 'islandora_object_access',
+    'access arguments' => array(FEDORA_VIEW_OBJECTS, 2),
+    'load arguments' => array(2),
+  );
   $items['islandora/object/%islandora_object/download_clip'] = array(
     'page callback' => 'islandora_download_clip',
     'page arguments' => array(2),
@@ -341,6 +350,12 @@ function islandora_theme() {
       'variables' => array('islandora_object' => NULL),
     ),
     // Default edit page.
+    'islandora_default_print' => array(
+      'file' => 'theme/theme.inc',
+      'template' => 'theme/islandora-object-print',
+      'variables' => array('islandora_object' => NULL),
+    ),
+    // Default edit page.
     'islandora_default_edit' => array(
       'file' => 'theme/theme.inc',
       'template' => 'theme/islandora-object-edit',
@@ -454,6 +469,22 @@ function islandora_permission() {
   );
 }
 
+/**
+ * Renders the print page for the given object.
+ *
+ * Modules can either implement preprocess functions to append content onto the
+ * 'content' variable, or override the display by providing a theme suggestion.
+ *
+ * @param AbstractObject $object
+ *   The object.
+ *
+ * @return array
+ *   A renderable array.
+ */
+function islandora_print_object(AbstractObject $object) {
+  drupal_set_title($object->label);
+  return theme('islandora_object_print', array('object' => $object));
+}
 /**
  * Implements hook_forms().
  */

From fcb2bf280573ef275c8004eb2a91490c9ff9d095 Mon Sep 17 00:00:00 2001
From: Nigel Banks <nigel.g.banks@gmail.com>
Date: Tue, 27 Aug 2013 23:41:57 +0200
Subject: [PATCH 07/18] Prevents a white screen when a viewer is set but not
 enabled.

If a user selects a viewer and then disables that module, but does
not change any solution packs viewers settings this can occur.
---
 includes/solution_packs.inc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/includes/solution_packs.inc b/includes/solution_packs.inc
index a80c41a5..7cf0351a 100644
--- a/includes/solution_packs.inc
+++ b/includes/solution_packs.inc
@@ -745,7 +745,9 @@ function islandora_get_viewer($params = NULL, $variable_id = NULL, $fedora_objec
     $viewer_id = islandora_get_viewer_id($variable_id);
     if ($viewer_id AND $params !== NULL) {
       $callback = islandora_get_viewer_callback($viewer_id);
-      return $callback($params, $fedora_object);
+      if (function_exists($callback)) {
+        return $callback($params, $fedora_object);
+      }
     }
   }
   return FALSE;

From 76e09b2471f3bd0259769be5ed74d093cc8807db Mon Sep 17 00:00:00 2001
From: MorganDawe <morgandawe@hotmail.com>
Date: Wed, 28 Aug 2013 09:50:56 -0300
Subject: [PATCH 08/18] Fixed Menu path conflicts with printing dc_data and
 clipping large image and newspaper.

---
 islandora.module | 42 +++++++++++++++++++-----------------------
 js/add_print.js  |  1 +
 2 files changed, 20 insertions(+), 23 deletions(-)

diff --git a/islandora.module b/islandora.module
index ed2268db..a8250fcc 100644
--- a/islandora.module
+++ b/islandora.module
@@ -119,13 +119,22 @@ function islandora_menu() {
     'access callback' => 'islandora_object_access_callback',
     'access arguments' => array(ISLANDORA_VIEW_OBJECTS, 2),
   );
-  $items['islandora/object/%islandora_object/print'] = array(
+  $items['islandora/object/%islandora_object/print_object'] = array(
     'page callback' => 'islandora_printer_object',
     'page arguments' => array(2),
     'type' => MENU_NORMAL_ITEM,
-    'access callback' => 'islandora_object_access_callback',
+    'access callback' => 'islandora_object_access',
     'access arguments' => array(ISLANDORA_VIEW_OBJECTS, 2),
   );
+  $items['islandora/object/%islandora_object/print'] = array(
+    'title' => 'Print Object',
+    'page callback' => 'islandora_print_object',
+    'page arguments' => array(2),
+    'type' => MENU_CALLBACK,
+    'access callback' => 'islandora_object_access',
+    'access arguments' => array(FEDORA_VIEW_OBJECTS, 2),
+    'load arguments' => array(2),
+  );
   $items['islandora/object/%islandora_object/view'] = array(
     'title' => 'View',
     'type' => MENU_DEFAULT_LOCAL_TASK,
@@ -151,13 +160,11 @@ function islandora_menu() {
         ISLANDORA_INGEST,
       ), 2),
   );
-
   $items['islandora/object/%islandora_object/manage/overview'] = array(
     'title' => 'Overview',
     'type' => MENU_DEFAULT_LOCAL_TASK,
     'weight' => -20,
   );
-
   $items['islandora/object/%islandora_object/manage/datastreams'] = array(
     'title' => 'Datastreams',
     'type' => MENU_LOCAL_TASK,
@@ -172,7 +179,6 @@ function islandora_menu() {
       ), 2),
     'weight' => -10,
   );
-
   $items['islandora/object/%islandora_object/manage/properties'] = array(
     'title' => 'Properties',
     'page callback' => 'drupal_get_form',
@@ -297,15 +303,6 @@ function islandora_menu() {
     'access arguments' => array(ISLANDORA_VIEW_DATASTREAM_HISTORY, 4),
     'load arguments' => array(2),
   );
-  $items['islandora/object/%islandora_object/printer'] = array(
-    'title' => 'Print Object',
-    'page callback' => 'islandora_print_object',
-    'page arguments' => array(2),
-    'type' => MENU_CALLBACK,
-    'access callback' => 'islandora_object_access',
-    'access arguments' => array(FEDORA_VIEW_OBJECTS, 2),
-    'load arguments' => array(2),
-  );
   $items['islandora/object/%islandora_object/download_clip'] = array(
     'page callback' => 'islandora_download_clip',
     'page arguments' => array(2),
@@ -350,12 +347,6 @@ function islandora_theme() {
       'variables' => array('islandora_object' => NULL),
     ),
     // Default edit page.
-    'islandora_default_print' => array(
-      'file' => 'theme/theme.inc',
-      'template' => 'theme/islandora-object-print',
-      'variables' => array('islandora_object' => NULL),
-    ),
-    // Default edit page.
     'islandora_default_edit' => array(
       'file' => 'theme/theme.inc',
       'template' => 'theme/islandora-object-edit',
@@ -366,8 +357,13 @@ function islandora_theme() {
       'file' => 'includes/solution_packs.inc',
       'render element' => 'form',
     ),
-    // Print object view.
+    // Print used by the clipper.
     'islandora_object_print' => array(
+      'file' => 'theme/theme.inc',
+      'variables' => array('object' => NULL, 'content' => array()),
+    ),
+    // Print object view, prints islandora objects.
+    'islandora_object_print_object' => array(
       'file' => 'theme/theme.inc',
       'template' => 'theme/islandora-object-print',
       'variables' => array(
@@ -866,7 +862,7 @@ function islandora_view_object(AbstractObject $object) {
 
   drupal_add_js(array(
     'islandora' => array(
-      'print_link' => 'islandora/object/' . $object->id . '/print')),
+      'print_link' => 'islandora/object/' . $object->id . '/print_object')),
     array('type' => 'setting'));
   drupal_add_js($path . '/js/add_print.js');
 
@@ -999,7 +995,7 @@ function islandora_default_islandora_printer_object($object, $alter) {
   }
 
   $variables = isset($dc_object) ? $dc_object->asArray() : array();
-  $output = theme('islandora_object_print', array(
+  $output = theme('islandora_object_print_object', array(
     'object' => $object,
     'dc_array' => $variables,
     'islandora_content' => $alter));
diff --git a/js/add_print.js b/js/add_print.js
index 0059ed88..014ec2e3 100644
--- a/js/add_print.js
+++ b/js/add_print.js
@@ -10,6 +10,7 @@
   $(document).ready(function() {
     $('.tabs .primary').append('<img id="print_btn" title="Print" src="' + Drupal.settings.basePath + Drupal.settings.islandora.print_img + '"></img>');
     $('#print_btn').css("cursor","pointer");
+    console.log(Drupal.settings.basePath + Drupal.settings.islandora.print_link);
     $('#print_btn').click(function() {
       window.location=Drupal.settings.basePath + Drupal.settings.islandora.print_link;
     });

From 81cc6be97748b359e8cf4543cca10b18c83e6ce0 Mon Sep 17 00:00:00 2001
From: MorganDawe <morgandawe@hotmail.com>
Date: Wed, 28 Aug 2013 09:58:21 -0300
Subject: [PATCH 09/18] Removed console log function and reference to old view
 object permission.

---
 islandora.module | 2 +-
 js/add_print.js  | 1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/islandora.module b/islandora.module
index a8250fcc..8fa20898 100644
--- a/islandora.module
+++ b/islandora.module
@@ -132,7 +132,7 @@ function islandora_menu() {
     'page arguments' => array(2),
     'type' => MENU_CALLBACK,
     'access callback' => 'islandora_object_access',
-    'access arguments' => array(FEDORA_VIEW_OBJECTS, 2),
+    'access arguments' => array(ISLANDORA_VIEW_OBJECTS, 2),
     'load arguments' => array(2),
   );
   $items['islandora/object/%islandora_object/view'] = array(
diff --git a/js/add_print.js b/js/add_print.js
index 014ec2e3..0059ed88 100644
--- a/js/add_print.js
+++ b/js/add_print.js
@@ -10,7 +10,6 @@
   $(document).ready(function() {
     $('.tabs .primary').append('<img id="print_btn" title="Print" src="' + Drupal.settings.basePath + Drupal.settings.islandora.print_img + '"></img>');
     $('#print_btn').css("cursor","pointer");
-    console.log(Drupal.settings.basePath + Drupal.settings.islandora.print_link);
     $('#print_btn').click(function() {
       window.location=Drupal.settings.basePath + Drupal.settings.islandora.print_link;
     });

From 9335fc3b3a96a16eb0d71aff7eb04214e2ec7d2e Mon Sep 17 00:00:00 2001
From: William Panting <willtp87@hotmail.com>
Date: Wed, 28 Aug 2013 10:33:00 -0300
Subject: [PATCH 10/18] api doc clarification

---
 islandora.api.php | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/islandora.api.php b/islandora.api.php
index 6d25bae3..7fe54828 100644
--- a/islandora.api.php
+++ b/islandora.api.php
@@ -86,7 +86,7 @@ function hook_CMODEL_PID_islandora_view_object_alter(&$object, &$rendered) {
 }
 
 /**
- * Generate an object's management display.
+ * Generate an object's datastreams management display.
  *
  * @param AbstractObject $object
  *   A Tuque FedoraObject
@@ -98,7 +98,7 @@ function hook_islandora_edit_object($object) {
 }
 
 /**
- * Generate an object's management display for the given content model.
+ * Generate an object's datastreams management display based on content model.
  *
  * Content models PIDs have colons and hyphens changed to underscores, to
  * create the hook name.
@@ -113,7 +113,7 @@ function hook_CMODEL_PID_islandora_edit_object($object) {
 }
 
 /**
- * Allow management display output to be altered.
+ * Allow datastreams management display output to be altered.
  *
  * @param AbstractObject $object
  *   A Tuque FedoraObject

From 67999de1e788aa37d138222f6c26b1da1b8798f0 Mon Sep 17 00:00:00 2001
From: Adam Vessey <adam@discoverygarden.ca>
Date: Wed, 28 Aug 2013 17:04:34 +0000
Subject: [PATCH 11/18] Add checkbox to disable caching functionality.

---
 includes/admin.form.inc |  6 ++++++
 includes/datastream.inc | 17 ++++++++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/includes/admin.form.inc b/includes/admin.form.inc
index d34bd5d5..b0bb0642 100644
--- a/includes/admin.form.inc
+++ b/includes/admin.form.inc
@@ -55,6 +55,12 @@ function islandora_repository_admin(array $form, array &$form_state) {
           '#description' => t('The PID of the Root Collection Object'),
           '#required' => TRUE,
         ),
+        'islandora_use_datastream_cache_headers' => array(
+          '#type' => 'checkbox',
+          '#title' => t('Generate/parse datastream HTTP cache headers'),
+          '#description' => t('HTTP caching can reduce network traffic, by allowing clients to used cached copies.'),
+          '#default_value' => variable_get('islandora_use_datastream_cache_headers', TRUE),
+        ),
       ),
       'islandora_namespace' => array(
         '#type' => 'fieldset',
diff --git a/includes/datastream.inc b/includes/datastream.inc
index 0eda5d4d..6a537c2b 100644
--- a/includes/datastream.inc
+++ b/includes/datastream.inc
@@ -85,6 +85,15 @@ function islandora_view_datastream(AbstractDatastream $datastream, $download = F
 /**
  * Parse "etags" from HTTP If-Match or If-None-Match headers.
  *
+ * Parses from the CSV-like struture supported by HTTP headers into an array,
+ * so `"asdf", "fdsa", W/"2132"` should become an array containing the strings:
+ * - asdf
+ * - fdsa
+ * - 2132
+ *
+ * @see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.24
+ * @see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.26
+ *
  * @param string $header_value
  *   The value from the headers.
  *
@@ -93,7 +102,9 @@ function islandora_view_datastream(AbstractDatastream $datastream, $download = F
  */
 function islandora_parse_http_match_headers($header_value) {
   $matches = array();
+  // Match the CSV-like structure supported by the HTTP headers.
   $count = preg_match_all('/(((W\/)?("?)(\*|.+?)\4)(, +)?)/', $header_value, $matches);
+  // The fifth sub-expression/group is which will contain the etags.
   return $matches[5];
 }
 
@@ -105,13 +116,17 @@ function islandora_parse_http_match_headers($header_value) {
  *
  * @return int
  *   An integer representing the HTTP response code. One of:
- *   - 200: Proceed as normal.
+ *   - 200: Proceed as normal. (Full download).
  *   - 304: Resource hasn't changed; pass cache validation.
  *   - 412: Resource has channged; fail cache validation.
  * 
  * @see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
  */
 function islandora_view_datastream_cache_check(AbstractDatastream $datastream) {
+  if (!variable_get('islandora_use_datastream_cache_headers', TRUE)) {
+    return 200;
+  }
+
   // Let's assume that if we get here, we'll be able to complete the request.
   $return = 200;
 

From cc5c9825408c2ae09e51c6b178ac2278fb9b2269 Mon Sep 17 00:00:00 2001
From: Adam Vessey <adam@discoverygarden.ca>
Date: Wed, 28 Aug 2013 19:03:55 +0000
Subject: [PATCH 12/18] Add test to test datastream cache responses.

---
 islandora.info              |   1 +
 tests/datastream_cache.test | 163 ++++++++++++++++++++++++++++++++++++
 2 files changed, 164 insertions(+)
 create mode 100644 tests/datastream_cache.test

diff --git a/islandora.info b/islandora.info
index 4b48bc29..36ed0dff 100644
--- a/islandora.info
+++ b/islandora.info
@@ -18,5 +18,6 @@ files[] = tests/ingest.test
 files[] = tests/hooked_access.test
 files[] = tests/islandora_manage_permissions.test
 files[] = tests/datastream_versions.test
+files[] = tests/datastream_cache.test
 files[] = tests/derivatives.test
 php = 5.3
diff --git a/tests/datastream_cache.test b/tests/datastream_cache.test
new file mode 100644
index 00000000..ffd752c5
--- /dev/null
+++ b/tests/datastream_cache.test
@@ -0,0 +1,163 @@
+<?php
+
+/**
+ * @file
+ * Tests to see if the hooks get called when appropriate.
+ *
+ * In the test module 'islandora_hooks_test' there are implementations
+ * of hooks being tested. These implementations modifies the session, and
+ * that's how we test if the hook gets called.
+ *
+ * To make sense of these tests reference islandora_hooks_test.module.
+ */
+
+class IslandoraDatastreamCacheTestCase extends IslandoraWebTestCase {
+
+  /**
+   * Gets info to display to describe this test.
+   *
+   * @see IslandoraWebTestCase::getInfo()
+   */
+  public static function getInfo() {
+    return array(
+      'name' => 'Datastream Cache Headers',
+      'description' => 'Check our headers work as we expect them to.',
+      'group' => 'Islandora',
+    );
+  }
+
+  /**
+   * Creates an admin user and a connection to a fedora repository.
+   *
+   * @see IslandoraWebTestCase::setUp()
+   */
+  public function setUp() {
+    parent::setUp();
+    $this->repository = $this->admin->repository;
+    $this->purgeTestObjects();
+  }
+
+  /**
+   * Free any objects/resources created for this test.
+   *
+   * @see IslandoraWebTestCase::tearDown()
+   */
+  public function tearDown() {
+    $this->purgeTestObjects();
+    parent::tearDown();
+  }
+
+  /**
+   * Purge any objects created by the test's in this class.
+   */
+  public function purgeTestObjects() {
+    $objects = array(
+      'test:test',
+    );
+    foreach ($objects as $object) {
+      try {
+        $object = $this->repository->getObject($object);
+        $this->repository->purgeObject($object->id);
+      }
+      catch (Exception $e) {
+        // Meh... Either it didn't exist or the purge failed.
+      }
+    }
+  }
+
+  public function createTestObject() {
+    $object = $this->repository->constructObject('test:test');
+    $object->label = 'Test object';
+    $object->models = 'test:model';
+    $datastream = $object->constructDatastream('asdf', 'M');
+    $datastream->label = 'datastream of doom';
+    $datastream->mimetype = 'text/plain';
+    $datastream->content = 'And then things happened.';
+    $datastream->checksumType = 'SHA-1';
+    $object->ingestDatastream($datastream);
+    $this->repository->ingestObject($object);
+    return $object;
+  }
+
+  /**
+   * Test HTTP cache headers.
+   */
+  public function testCacheHeaders() {
+    $object = $this->createTestObject();
+    $datastream = $object['asdf'];
+
+    $user = $this->drupalCreateUser(array(ISLANDORA_VIEW_OBJECTS));
+    $this->drupalLogin($user);
+
+    // Test If-Modified-Since.
+    $result = $this->drupalGet("islandora/object/{$object->id}/datastream/{$datastream->id}/view", array(), array(
+      'If-Modified-Since: ' . $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'),
+    ));
+    $this->assertResponse(304);
+    $result = $this->drupalGet("islandora/object/{$object->id}/datastream/{$datastream->id}/view", array(), array(
+      'If-Modified-Since: ' . $datastream->createdDate->sub(new DateInterval('P1M'))->format('D, d M Y H:i:s \G\M\T'),
+    ));
+    $this->assertResponse(200);
+
+    // Test If-Unmodified-Since.
+    $result = $this->drupalGet("islandora/object/{$object->id}/datastream/{$datastream->id}/view", array(), array(
+      'If-Unmodified-Since: ' . $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'),
+    ));
+    $this->assertResponse(200);
+    $result = $this->drupalGet("islandora/object/{$object->id}/datastream/{$datastream->id}/view", array(), array(
+      'If-Unmodified-Since: ' . $datastream->createdDate->sub(new DateInterval('P1M'))->format('D, d M Y H:i:s \G\M\T'),
+    ));
+    $this->assertResponse(412);
+
+    // Test If-Match.
+    $result = $this->drupalGet("islandora/object/{$object->id}/datastream/{$datastream->id}/view", array(), array(
+      format_string('If-Match: "!checksum"', array(
+        '!checksum' => $datastream->checksum,
+      )),
+    ));
+    $this->assertResponse(200);
+    $result = $this->drupalGet("islandora/object/{$object->id}/datastream/{$datastream->id}/view", array(), array(
+      format_string('If-Match: "!checksum"', array(
+        '!checksum' => 'dont-match' . $datastream->checksum,
+      )),
+    ));
+    $this->assertResponse(412);
+
+    // Test If-None-Match.
+    $result = $this->drupalGet("islandora/object/{$object->id}/datastream/{$datastream->id}/view", array(), array(
+      format_string('If-None-Match: "!checksum"', array(
+        '!checksum' => $datastream->checksum,
+      )),
+    ));
+    $this->assertResponse(304);
+    $result = $this->drupalGet("islandora/object/{$object->id}/datastream/{$datastream->id}/view", array(), array(
+      format_string('If-None-Match: "!checksum"', array(
+        '!checksum' => 'dont-match' . $datastream->checksum,
+      )),
+    ));
+    $this->assertResponse(200);
+
+    // Test combination of If-None-Match and If-Modified-Since
+    $result = $this->drupalGet("islandora/object/{$object->id}/datastream/{$datastream->id}/view", array(), array(
+      'If-Modified-Since: ' . $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'),
+      format_string('If-None-Match: "!checksum"', array(
+        '!checksum' => $datastream->checksum,
+      )),
+    ));
+    $this->assertResponse(304);
+    $result = $this->drupalGet("islandora/object/{$object->id}/datastream/{$datastream->id}/view", array(), array(
+      'If-Modified-Since: ' . $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'),
+      format_string('If-None-Match: "!checksum"', array(
+        '!checksum' => 'dont-match' . $datastream->checksum,
+      )),
+    ));
+    $this->assertResponse(200);
+    $result = $this->drupalGet("islandora/object/{$object->id}/datastream/{$datastream->id}/view", array(), array(
+      'If-Modified-Since: ' . $datastream->createdDate->sub(new DateInterval('P1M'))->format('D, d M Y H:i:s \G\M\T'),
+      format_string('If-None-Match: "!checksum"', array(
+        '!checksum' => $datastream->checksum,
+      )),
+    ));
+    $this->assertResponse(200);
+  }
+}

From 6b4768d9f69834da35d132132c46ae18853db009 Mon Sep 17 00:00:00 2001
From: Adam Vessey <adam@discoverygarden.ca>
Date: Wed, 28 Aug 2013 19:29:46 +0000
Subject: [PATCH 13/18] Add missing function comment.

---
 tests/datastream_cache.test | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tests/datastream_cache.test b/tests/datastream_cache.test
index ffd752c5..0be7dd54 100644
--- a/tests/datastream_cache.test
+++ b/tests/datastream_cache.test
@@ -65,7 +65,10 @@ class IslandoraDatastreamCacheTestCase extends IslandoraWebTestCase {
     }
   }
 
-  public function createTestObject() {
+  /**
+   * Create our test object.
+   */
+  protected function createTestObject() {
     $object = $this->repository->constructObject('test:test');
     $object->label = 'Test object';
     $object->models = 'test:model';

From 44d83c7ed90468d31f1badb49f750648aa513789 Mon Sep 17 00:00:00 2001
From: Adam Vessey <adam@discoverygarden.ca>
Date: Thu, 29 Aug 2013 12:49:46 +0000
Subject: [PATCH 14/18] Fix some comments for Jordan.

---
 includes/datastream.inc     | 4 ++--
 tests/datastream_cache.test | 8 +-------
 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/includes/datastream.inc b/includes/datastream.inc
index 6a537c2b..f7e20b27 100644
--- a/includes/datastream.inc
+++ b/includes/datastream.inc
@@ -118,8 +118,8 @@ function islandora_parse_http_match_headers($header_value) {
  *   An integer representing the HTTP response code. One of:
  *   - 200: Proceed as normal. (Full download).
  *   - 304: Resource hasn't changed; pass cache validation.
- *   - 412: Resource has channged; fail cache validation.
- * 
+ *   - 412: Resource has changed; fail cache validation.
+ *
  * @see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
  */
 function islandora_view_datastream_cache_check(AbstractDatastream $datastream) {
diff --git a/tests/datastream_cache.test b/tests/datastream_cache.test
index 0be7dd54..8118c08a 100644
--- a/tests/datastream_cache.test
+++ b/tests/datastream_cache.test
@@ -2,13 +2,7 @@
 
 /**
  * @file
- * Tests to see if the hooks get called when appropriate.
- *
- * In the test module 'islandora_hooks_test' there are implementations
- * of hooks being tested. These implementations modifies the session, and
- * that's how we test if the hook gets called.
- *
- * To make sense of these tests reference islandora_hooks_test.module.
+ * Tests to verify the cache headers we provide.
  */
 
 class IslandoraDatastreamCacheTestCase extends IslandoraWebTestCase {

From dca15b1ccdd2df044298b3a7126000a41e2c0a05 Mon Sep 17 00:00:00 2001
From: Adam Vessey <adam@discoverygarden.ca>
Date: Thu, 29 Aug 2013 19:52:28 +0000
Subject: [PATCH 15/18] Respond with the same headers as we did before, if
 caching is disabled.

---
 includes/datastream.inc | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/includes/datastream.inc b/includes/datastream.inc
index f7e20b27..1de45581 100644
--- a/includes/datastream.inc
+++ b/includes/datastream.inc
@@ -191,21 +191,27 @@ function islandora_view_datastream_cache_check(AbstractDatastream $datastream) {
  *   The datastream being viewed/downloaded.
  */
 function islandora_view_datastream_set_cache_headers(AbstractDatastream $datastream) {
-  // Force cache revalidation.
-  header('Expires: Sun, 19 Nov 1978 05:00:00 GMT');
-  $cache_control = array();
-  if ($datastream->parent->repository->api->connection->username == 'anonymous') {
-    $cache_control[] = 'public';
+  if (variable_get('islandora_use_datastream_cache_headers', TRUE)) {
+    // Force cache revalidation.
+    header('Expires: Sun, 19 Nov 1978 05:00:00 GMT');
+    $cache_control = array();
+    if ($datastream->parent->repository->api->connection->username == 'anonymous') {
+      $cache_control[] = 'public';
+    }
+    else {
+      $cache_control[] = 'private';
+    }
+    $cache_control[] = 'must-revalidate';
+    $cache_control[] = 'max-age=0';
+    header('Cache-Control: ' . implode(', ', $cache_control));
+    header('Last-Modified: ' . $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'));
+    if (isset($datastream->checksum)) {
+      header("Etag: \"{$datastream->checksum}\"");
+    }
   }
   else {
-    $cache_control[] = 'private';
-  }
-  $cache_control[] = 'must-revalidate';
-  $cache_control[] = 'max-age=0';
-  header('Cache-Control: ' . implode(', ', $cache_control));
-  header('Last-Modified: ' . $datastream->createdDate->format('D, d M Y H:i:s \G\M\T'));
-  if (isset($datastream->checksum)) {
-    header("Etag: \"{$datastream->checksum}\"");
+    header_remove('Cache-Control');
+    header_remove('Expires'); 
   }
 }
 

From a653a25c9c81b7e9a795db6ffba21d1c4b0cd671 Mon Sep 17 00:00:00 2001
From: Adam Vessey <adam@discoverygarden.ca>
Date: Thu, 29 Aug 2013 20:04:44 +0000
Subject: [PATCH 16/18] Coding standards... Trailing space.

---
 includes/datastream.inc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/includes/datastream.inc b/includes/datastream.inc
index 1de45581..1d506e3d 100644
--- a/includes/datastream.inc
+++ b/includes/datastream.inc
@@ -211,7 +211,7 @@ function islandora_view_datastream_set_cache_headers(AbstractDatastream $datastr
   }
   else {
     header_remove('Cache-Control');
-    header_remove('Expires'); 
+    header_remove('Expires');
   }
 }
 

From 7fef116c00f55abbaa9dbbe6dd638e3bbb0c2927 Mon Sep 17 00:00:00 2001
From: Jordan Dukart <jordan@discoverygarden.ca>
Date: Tue, 3 Sep 2013 19:39:00 +0000
Subject: [PATCH 17/18] Add alterable breadcrumbs to Islandora.

---
 includes/breadcrumb.inc | 1 +
 islandora.api.php       | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/includes/breadcrumb.inc b/includes/breadcrumb.inc
index 872eb70a..24b9fbbe 100644
--- a/includes/breadcrumb.inc
+++ b/includes/breadcrumb.inc
@@ -27,6 +27,7 @@
 function islandora_get_breadcrumbs($object) {
   $breadcrumbs = islandora_get_breadcrumbs_recursive($object->id, $object->repository);
   array_pop($breadcrumbs);
+  drupal_alter('islandora_breadcrumbs', $breadcrumbs);
   return $breadcrumbs;
 }
 
diff --git a/islandora.api.php b/islandora.api.php
index 6d25bae3..1d6754c9 100644
--- a/islandora.api.php
+++ b/islandora.api.php
@@ -648,3 +648,10 @@ function hook_islandora_derivative() {
 function hook_CMODEL_PID_islandora_derivative() {
 
 }
+
+/**
+ * Alters breadcrumbs used on Solr search results and collection views.
+ */
+function hook_islandora_breadcrumbs_alter(&$breadcrumbs) {
+
+}

From 0c50962a63e91276f21a543f098ff1f9a37d8815 Mon Sep 17 00:00:00 2001
From: Jordan Dukart <jordan@discoverygarden.ca>
Date: Tue, 3 Sep 2013 19:55:07 +0000
Subject: [PATCH 18/18] Add context for ease of use.

---
 includes/breadcrumb.inc | 3 ++-
 islandora.api.php       | 9 +++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/includes/breadcrumb.inc b/includes/breadcrumb.inc
index 24b9fbbe..05ab1bac 100644
--- a/includes/breadcrumb.inc
+++ b/includes/breadcrumb.inc
@@ -27,7 +27,8 @@
 function islandora_get_breadcrumbs($object) {
   $breadcrumbs = islandora_get_breadcrumbs_recursive($object->id, $object->repository);
   array_pop($breadcrumbs);
-  drupal_alter('islandora_breadcrumbs', $breadcrumbs);
+  $context = 'islandora';
+  drupal_alter('islandora_breadcrumbs', $breadcrumbs, $context);
   return $breadcrumbs;
 }
 
diff --git a/islandora.api.php b/islandora.api.php
index 1d6754c9..3a773e2b 100644
--- a/islandora.api.php
+++ b/islandora.api.php
@@ -650,8 +650,13 @@ function hook_CMODEL_PID_islandora_derivative() {
 }
 
 /**
- * Alters breadcrumbs used on Solr search results and collection views.
+ * Alters breadcrumbs used on Solr search results and within Islandora views.
+ *
+ * @param array $breadcrumbs
+ *   Breadcrumbs array to be altered by reference. Each element is markup.
+ * @param string $context
+ *   Where the alter is originating from for distinguishing.
  */
-function hook_islandora_breadcrumbs_alter(&$breadcrumbs) {
+function hook_islandora_breadcrumbs_alter(&$breadcrumbs, $context) {
 
 }