[feat] DocumentRegistry: add getProviders() and preferred by weight

This is step one toward "open with".

References koreader#3345

frontend/document/credocument.lua

@@ -26,6 +26,7 @@ local CreDocument = Document:new{
     fallback_font = G_reader_settings:readSetting("fallback_font") or "Noto Sans CJK SC",
     default_css = "./data/cr3.css",
     options = CreOptions,
+    provider_name = "Cool Reader Engine",
 }
 
 -- NuPogodi, 20.05.12: inspect the zipfile content

frontend/document/djvudocument.lua

@@ -12,6 +12,7 @@ local DjvuDocument = Document:new{
     options = KoptOptions,
     koptinterface = nil,
     color_bb_type = Blitbuffer.TYPE_BBRGB24,
+    provider_name = "DjVu Libre",
 }
 
 -- check DjVu magic string to validate

frontend/document/documentregistry.lua

@@ -9,22 +9,47 @@ local DocumentRegistry = {
     providers = {},
 }
 
-function DocumentRegistry:addProvider(extension, mimetype, provider)
-    table.insert(self.providers, { extension = extension, mimetype = mimetype, provider = provider })
+function DocumentRegistry:addProvider(extension, mimetype, provider, weight)
+    table.insert(self.providers, {
+        extension = extension,
+        mimetype = mimetype,
+        provider = provider,
+        weight = weight or 100,
+    })
 end
 
---- Returns the registered document handler.
+--- Returns the preferred registered document handler.
 -- @string file
 -- @treturn string provider, or nil
 function DocumentRegistry:getProvider(file)
+    local providers = self:getProviders(file)
+
+    if #providers >= 1 then
+        return providers[1].provider
+    end
+end
+
+--- Returns the registered document handlers.
+-- @string file
+-- @treturn string provider, or nil
+function DocumentRegistry:getProviders(file)
+    local providers = {}
+
     -- TODO: some implementation based on mime types?
     for _, provider in ipairs(self.providers) do
         local suffix = string.sub(file, -string.len(provider.extension) - 1)
         if string.lower(suffix) == "."..provider.extension then
         -- if extension == provider.extension then
-            return provider.provider
+            -- stick highest weighted provider at the front
+            if #providers >= 1 and provider.weight > providers[#providers].weight then
+                table.insert(providers, #providers, provider)
+            else
+                table.insert(providers, provider)
+            end
         end
     end
+
+    return providers
 end
 
 function DocumentRegistry:openDocument(file)

frontend/document/pdfdocument.lua

@@ -13,6 +13,7 @@ local PdfDocument = Document:new{
     dc_null = DrawContext.new(),
     options = KoptOptions,
     koptinterface = nil,
+    provider_name = "MuPDF",
 }
 
 function PdfDocument:init()
@@ -237,11 +238,12 @@ function PdfDocument:drawPage(target, x, y, rect, pageno, zoom, rotation, gamma,
 end
 
 function PdfDocument:register(registry)
-    registry:addProvider("pdf", "application/pdf", self)
-    registry:addProvider("cbz", "application/cbz", self)
-    registry:addProvider("cbt", "application/cbt", self)
-    registry:addProvider("zip", "application/zip", self)
-    registry:addProvider("xps", "application/xps", self)
+    registry:addProvider("pdf", "application/pdf", self, 100)
+    registry:addProvider("epub", "application/epub", self, 50)
+    registry:addProvider("cbz", "application/cbz", self, 100)
+    registry:addProvider("cbt", "application/cbt", self, 100)
+    registry:addProvider("zip", "application/zip", self, 100)
+    registry:addProvider("xps", "application/xps", self, 100)
 end
 
 return PdfDocument

frontend/document/picdocument.lua

@@ -6,7 +6,8 @@ local pic = nil
 local PicDocument = Document:new{
     _document = false,
     is_pic = true,
-    dc_null = DrawContext.new()
+    dc_null = DrawContext.new(),
+    provider_name = "Picture Document (MuPDF)",
 }
 
 function PicDocument:init()

spec/unit/document_registry_spec.lua

@@ -0,0 +1,23 @@
+describe("document registry module", function()
+    local DocumentRegistry
+
+    setup(function()
+        require("commonrequire")
+        DocumentRegistry = require("document/documentregistry")
+    end)
+
+    it("should get preferred rendering engine", function()
+        assert.is_equal("Cool Reader Engine",
+                        DocumentRegistry:getProvider("bla.epub").provider_name)
+        assert.is_equal("MuPDF",
+                        DocumentRegistry:getProvider("bla.pdf").provider_name)
+    end)
+
+    it("should return all supported rendering engines", function()
+        local providers = DocumentRegistry:getProviders("bla.epub")
+        assert.is_equal("Cool Reader Engine",
+                        providers[1].provider.provider_name)
+        assert.is_equal("MuPDF",
+                        providers[2].provider.provider_name)
+    end)
+end)