1 files changed, 85 insertions, 0 deletions
diff --git a/content_scripts/mode_normal.coffee b/content_scripts/mode_normal.coffee
index 9a03e9d0..8dad4b63 100644
--- a/content_scripts/mode_normal.coffee
+++ b/content_scripts/mode_normal.coffee
@@ -217,6 +217,91 @@ textInputXPath = (->
   DomUtils.makeXPath(inputElements)
 )()
 
+# used by the findAndFollow* functions.
+followLink = (linkElement) ->
+  if (linkElement.nodeName.toLowerCase() == "link")
+    window.location.href = linkElement.href
+  else
+    # if we can click on it, don't simply set location.href: some next/prev links are meant to trigger AJAX
+    # calls, like the 'more' button on GitHub's newsfeed.
+    linkElement.scrollIntoView()
+    DomUtils.simulateClick(linkElement)
+
+#
+# Find and follow a link which matches any one of a list of strings. If there are multiple such links, they
+# are prioritized for shortness, by their position in :linkStrings, how far down the page they are located,
+# and finally by whether the match is exact. Practically speaking, this means we favor 'next page' over 'the
+# next big thing', and 'more' over 'nextcompany', even if 'next' occurs before 'more' in :linkStrings.
+#
+findAndFollowLink = (linkStrings) ->
+  linksXPath = DomUtils.makeXPath(["a", "*[@onclick or @role='link' or contains(@class, 'button')]"])
+  links = DomUtils.evaluateXPath(linksXPath, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE)
+  candidateLinks = []
+
+  # at the end of this loop, candidateLinks will contain all visible links that match our patterns
+  # links lower in the page are more likely to be the ones we want, so we loop through the snapshot backwards
+  for i in [(links.snapshotLength - 1)..0] by -1
+    link = links.snapshotItem(i)
+
+    # ensure link is visible (we don't mind if it is scrolled offscreen)
+    boundingClientRect = link.getBoundingClientRect()
+    if (boundingClientRect.width == 0 || boundingClientRect.height == 0)
+      continue
+    computedStyle = window.getComputedStyle(link, null)
+    if (computedStyle.getPropertyValue("visibility") != "visible" ||
+        computedStyle.getPropertyValue("display") == "none")
+      continue
+
+    linkMatches = false
+    for linkString in linkStrings
+      if link.innerText.toLowerCase().indexOf(linkString) != -1 ||
+          0 <= link.value?.indexOf? linkString
+        linkMatches = true
+        break
+    continue unless linkMatches
+
+    candidateLinks.push(link)
+
+  return if (candidateLinks.length == 0)
+
+  for link in candidateLinks
+    link.wordCount = link.innerText.trim().split(/\s+/).length
+
+  # We can use this trick to ensure that Array.sort is stable. We need this property to retain the reverse
+  # in-page order of the links.
+
+  candidateLinks.forEach((a,i) -> a.originalIndex = i)
+
+  # favor shorter links, and ignore those that are more than one word longer than the shortest link
+  candidateLinks =
+    candidateLinks
+      .sort((a, b) ->
+        if (a.wordCount == b.wordCount) then a.originalIndex - b.originalIndex else a.wordCount - b.wordCount
+      )
+      .filter((a) -> a.wordCount <= candidateLinks[0].wordCount + 1)
+
+  for linkString in linkStrings
+    exactWordRegex =
+      if /\b/.test(linkString[0]) or /\b/.test(linkString[linkString.length - 1])
+        new RegExp "\\b" + linkString + "\\b", "i"
+      else
+        new RegExp linkString, "i"
+    for candidateLink in candidateLinks
+      if exactWordRegex.test(candidateLink.innerText) ||
+          (candidateLink.value && exactWordRegex.test(candidateLink.value))
+        followLink(candidateLink)
+        return true
+  false
+
+findAndFollowRel = (value) ->
+  relTags = ["link", "a", "area"]
+  for tag in relTags
+    elements = document.getElementsByTagName(tag)
+    for element in elements
+      if (element.hasAttribute("rel") && element.rel.toLowerCase() == value)
+        followLink(element)
+        return true
+
 class FocusSelector extends Mode
   constructor: (hints, visibleInputs, selectedInputIndex) ->
     super