Better handling of tap on invalid/external links

Tap on external urls or invalid links would jump to
document's 1st page. We check first the validity of the
link, and deal with wikipedia links or just show the external
url.
ConfirmBox: allow dismissing/cancelling by taping outside,
to keep UX consistent.

frontend/apps/reader/modules/readerlink.lua

@@ -5,8 +5,10 @@ local UIManager = require("ui/uimanager")
 local Geom = require("ui/geometry")
 local Screen = require("device").screen
 local Device = require("device")
+local logger = require("logger")
 local Event = require("ui/event")
 local _ = require("gettext")
+local T = require("ffi/util").template
 
 local ReaderLink = InputContainer:new{
     location_stack = {}
@@ -141,13 +143,57 @@ function ReaderLink:onTap(_, ges)
 end
 
 function ReaderLink:onGotoLink(link)
+    logger.dbg("onGotoLink:", link)
     if self.ui.document.info.has_pages then
-        table.insert(self.location_stack, self.ui.paging:getBookLocation())
-        self.ui:handleEvent(Event:new("GotoPage", link.page + 1))
+        -- internal pdf links have a "page" attribute, while external ones have an "uri" attribute
+        if link.page then -- Internal link
+            logger.dbg("Internal link:", link)
+            table.insert(self.location_stack, self.ui.paging:getBookLocation())
+            self.ui:handleEvent(Event:new("GotoPage", link.page + 1))
+            return true
+        end
+        link = link.uri -- external link
     else
-        table.insert(self.location_stack, self.ui.rolling:getBookLocation())
-        self.ui:handleEvent(Event:new("GotoXPointer", link))
+        -- For crengine, internal links may look like :
+        --   #_doc_fragment_0_Organisation (link from anchor)
+        --   /body/DocFragment/body/ul[2]/li[5]/text()[3].16 (xpointer from full-text search)
+        -- If the XPointer does not exist (or is a full url), we will jump to page 1
+        -- Best to check that this link exists in document with the following,
+        -- which accepts both of the above legitimate xpointer as input.
+        if self.ui.document:isXPointerInDocument(link) then
+            logger.dbg("Internal link:", link)
+            table.insert(self.location_stack, self.ui.rolling:getBookLocation())
+            self.ui:handleEvent(Event:new("GotoXPointer", link))
+            return true
+        end
     end
+    logger.dbg("External link:", link)
+    -- Check if it is a wikipedia link
+    local wiki_lang, wiki_page = link:match([[https?://([^%.]+).wikipedia.org/wiki/([^/]+)]])
+    if wiki_lang and wiki_page then
+        logger.dbg("Wikipedia link:", wiki_lang, wiki_page)
+        -- Ask for user confirmation before launching lookup (on a
+        -- wikipedia page saved as epub, full of wikipedia links, it's
+        -- too easy to click on links when wanting to change page...)
+        local ConfirmBox = require("ui/widget/confirmbox")
+        UIManager:show(ConfirmBox:new{
+            text = T(_("Would you like to read this Wikipedia %1 full page?\n\n%2\n"), wiki_lang:upper(), wiki_page:gsub("_", " ")),
+            cancel_on_tap_outside = true,
+            ok_callback = function()
+                UIManager:nextTick(function()
+                    self.ui:handleEvent(Event:new("LookupWikipedia", wiki_page, false, true, wiki_lang))
+                end)
+            end
+        })
+    else
+        -- local Notification = require("ui/widget/notification")
+        local InfoMessage = require("ui/widget/infomessage")
+        UIManager:show(InfoMessage:new{
+            text = T(_("Invalid or external link:\n%1"), link),
+            timeout = 1.0,
+        })
+    end
+    -- don't propagate, user will notice and tap elsewhere if he wants to change page
     return true
 end