// Copyright 2013 Gushcha Anton
/*
Boost Software License - Version 1.0 - August 17th, 2003

Permission is hereby granted, free of charge, to any person or organization
obtaining a copy of the software and accompanying documentation covered by
this license (the "Software") to use, reproduce, display, distribute,
execute, and transmit the Software, and to prepare derivative works of the
Software, and to permit third-parties to whom the Software is furnished to
do so, all subject to the following:

The copyright notices in the Software and this entire statement, including
the above license grant, this restriction and the following disclaimer,
must be included in all copies of the Software, in whole or in part, and
all derivative works of the Software, unless such copies or derivative
works are solely in the form of machine-executable object code generated by
a source language processor.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
*/
// Written in D programing language
/**
*   Module provides functions to handle localization. Translated string
*   is searched in special files with .lang extention by exact matching
*   with original string.
*
*   Lang files are loaded in memory at program start up from current 
*   directory. Additional localizations can be loaded with $(B loadLocaleFile) 
*   function.
*
*   Example:
*   --------
*    import std.stdio, std.opt, dtext;
*
*    void main(string[] args) 
*    {
*        string locale;
*        getopt(args,
*            "l|lang", &locale);
*
*        defaultLocale = locale;
*
*        writeln(_("Hello, world!")); \\ or use getdtext instead _
*    }
*   --------
*
*   If text for translation cannot be found in specified locale name, the text will
*   be saved and written down to a special fuzzy texts file at program shutdown. That
*   should help to add new localization fast and without program recompilation.
*
*   TODO:
*   <ul>
*   <li>Load localization files on demand;</li>
*   <li>Add ability to unload unused locales.</li>
*   </ul>
*/
module dtext;

/**
*   Special locale that doesn't have own locale file. System won't
*   create additional information (fuzzy file or locale map).
*/
enum BASE_LOCALE = "en_US";

/**
*   File extention which will be searched in current directory to load locale information.
*/
enum LOCALE_EXTENTION = ".lang";

/**
*   Returns translated string $(B s) for specified $(B locale). If locale is empty default
*   locale will be taken. If locale name is equal to base locale $(B s) string is returned 
*   without modification.
*
*   Localization strings are taken from special files previosly loaded into memory.
*
*   If string $(B s) isn't persists in locale strings it will be put into fuzzy text map.
*   Fuzzy strings is saved in separate file for each locale to be translated later.
*
*   See_Also: BASE_LOCALE, defaultLocale properties.
*
*   Example:
*   --------
*   assert(getdtext("Hello, world!", "ru_RU") == "Привет, мир!");
*   assert(getdtext("Hello, world!", "es_ES") == "Hola, mundo!");
*   assert(getdtext("") == "");
*   --------
*/
string getdtext(string s, string locale = "")
{
    if(locale == "") locale = defaultLocale;
    if(locale == BASE_LOCALE) return s;

    if(locale in localeMap)
    {
        auto map = localeMap[locale];
        if(s in map)
        {
            return map[s];
        }
    } 

    if(locale !in fuzzyText) fuzzyText[locale] = [];
    if(fuzzyText[locale].find(s) == [])
        fuzzyText[locale] ~= s;
    return s;
}

/// Short name for getdtext
alias getdtext _;

/**
*   Setups current locale name. If empty string is passed to
*   $(B getdtext) then default locale will be taken.
*
*   Example:
*   --------
*   defaultLocale = "ru_RU";
*   defaultLocale = BASE_LOCALE;
*   --------
*/
void defaultLocale(string locale) @property
{
    _defaultLocale = locale;
}

/**
*   Returns current locale name. If empty string is passed to
*   $(B getdtext) then default locale will be taken.
*/
string defaultLocale() @property
{
    return _defaultLocale;
}

/**
*   Manuall loads localization file with $(B name). May be usefull to
*   load localization during program execution. 
*
*   Example:
*   --------
*   loadLocaleFile("ru_RU");
*   loadLocaleFile("es_ES");
*   --------
*/
void loadLocaleFile(string name)
{
    if(!name.endsWith(LOCALE_EXTENTION)) name ~= LOCALE_EXTENTION;

    auto data = slurp!(string, string)(name, `"%s" = "%s"`);
    auto localeName = baseName(name, LOCALE_EXTENTION);
    if(localeName !in localeMap) localeMap[localeName] = ["":""];
    auto map = localeMap[localeName];
    foreach(pair; data)
    {
        map[pair[0]] = pair[1];
    }
}

private
{
    import std.file;
    import std.algorithm;
    import std.path;
    import std.stdio;
    
    string _defaultLocale = BASE_LOCALE;

    string[string][string] localeMap;
    string[][string] fuzzyText;
}

private string getFuzzyLocaleFileName(string locale)
{
    return locale~".fuzzy";
}

private void saveFuzzyText()
{
    foreach(locale, strs; fuzzyText)
    {
        try
        {
            auto file = new File(getFuzzyLocaleFileName(locale), "wr");
            scope(exit) file.close;

            foreach(i,s; strs)
                if(i++ == strs.length-1)
                    file.write('"'~s~`" = "`~s~`"`);
                else
                    file.writeln('"'~s~`" = "`~s~`"`);
        }
        catch(Exception e)
        {
            writeln("Failed to save fuzzy text for locale ", locale);
        }
    }
}

private void loadAllLocales()
{
    auto locFiles = filter!`endsWith(a.name,".lang")`(dirEntries(".",SpanMode.breadth));
    foreach(entry; locFiles)
    {
        try
        {
            loadLocaleFile(entry.name);
        } 
        catch(Exception e)
        {
            writeln("Failed to load localization file ", entry.name, ". Reason: ", e.msg);
        }
    }
}

shared static this() 
{
    version(unittest) {}
    else
        loadAllLocales();
}

shared static ~this()
{
    version(unittest) {}
    else
        saveFuzzyText();

}

version(unittest)
{
    import std.getopt;
    import std.typecons;
    import std.file;

    void main(string[] args) 
    {
        string locale;
        getopt(args,
            "l|lang", &locale);

        defaultLocale = locale;
    }
}

unittest
{
    loadLocaleFile("ru_RU");
    loadLocaleFile("es_ES");

    assert(getdtext("Hello, world!", "ru_RU") == "Привет, мир!");
    assert(getdtext("Hello, world!", "es_ES") == "Hola, mundo!");
    assert(getdtext("") == "");

    // test fuzzy
    assert(getdtext("Hello, world!", "unknown_UNKNOWN") == "Hello, world!");
    saveFuzzyText();

    auto data = slurp!(string, string)(getFuzzyLocaleFileName("unknown_UNKNOWN"), `"%s" = "%s"`);
    assert(data == [Tuple!(string, string)("Hello, world!", "Hello, world!")]);

    remove(getFuzzyLocaleFileName("unknown_UNKNOWN"));
}