Added a pure Lua gettext implementation

frontend/gettext.lua

@@ -1,16 +1,96 @@
-lua_gettext.init("./i18n", "koreader")
+local DEBUG = require("dbg")
 
-local GetText = {}
-local GetText_mt = {}
+local GetText = {
+    translation = {},
+    current_lang = "C",
+    dirname = "l10n",
+    textdomain = "koreader"
+}
+
+local GetText_mt = {
+    __index = {}
+}
 
 function GetText_mt.__call(gettext, string)
-    return lua_gettext.translate(string)
+    return gettext.translation[string] or string
+end
+
+local function c_escape(what)
+    if what == "\n" then return ""
+    elseif what == "a" then return "\a"
+    elseif what == "b" then return "\b"
+    elseif what == "f" then return "\f"
+    elseif what == "n" then return "\n"
+    elseif what == "r" then return "\r"
+    elseif what == "t" then return "\t"
+    elseif what == "v" then return "\v"
+    elseif what == "0" then return "\0" -- shouldn't happen, though
+    else
+        return what
+    end
 end
 
-function GetText.changeLang(new_lang)
-    lua_gettext.change_lang(new_lang)
+-- for PO file syntax, see
+-- https://www.gnu.org/software/gettext/manual/html_node/PO-Files.html
+-- we only implement a sane subset for now
+
+function GetText_mt.__index.changeLang(new_lang)
+    GetText.translation = {}
+    GetText.current_lang = "C"
+
+    -- the "C" locale disables localization alltogether
+    if new_lang == "C" then return end
+
+    local file = GetText.dirname .. "/" .. new_lang .. "/" .. GetText.textdomain .. ".po"
+    local po = io.open(file, "r")
+
+    if not po then
+        DEBUG("cannot open translation file " .. file)
+        return
+    end
+
+    local data = {}
+    local what = nil
+    while true do
+        local line = po:read("*l")
+        if line == nil or line == "" then
+            if data.msgid and data.msgstr then
+                GetText.translation[data.msgid] = string.gsub(data.msgstr, "\\(.)", c_escape)
+            end
+            -- stop at EOF:
+            if line == nil then break end
+            data = {}
+            what = nil
+        else
+            -- comment
+            if not line:match("^#") then
+                -- new data item (msgid, msgstr, ...
+                local w, s = line:match("^%s*(%a+)%s+\"(.*)\"%s*$")
+                if w then
+                    what = w
+                else
+                    -- string continuation
+                    s = line:match("^%s*\"(.*)\"%s*$")
+                end
+                if what and s then
+                    data[what] = (data[what] or "") .. s
+                end
+            end
+        end
+    end
+    GetText.current_lang = new_lang
 end
 
 setmetatable(GetText, GetText_mt)
 
+if os.getenv("LANGUAGE") then
+    GetText.changeLang(os.getenv("LANGUAGE"))
+elseif os.getenv("LC_ALL") then
+    GetText.changeLang(os.getenv("LC_ALL"))
+elseif os.getenv("LC_MESSAGES") then
+    GetText.changeLang(os.getenv("LC_MESSAGES"))
+elseif os.getenv("LANG") then
+    GetText.changeLang(os.getenv("LANG"))
+end
+
 return GetText