private Lang Lookup(Lang langDef)
{
Lang retval;
HashSet <Lang> copy;
lock (supported)
{
retval = this.defaultLang;
copy = GetSupportedListClone();
}
//1st step: all language whose language subtag does not match are not match
string lang = langDef.Language.Subtag;
//1.1 if a language is not a match, a better match than the default could be another language that is a macrolanguage for this one
if (!copy.Any(a => a.Language.Subtag == lang))
{
//no one language is matching, as a second chanche we will try to see if the requested language have any macrolanguage
//in this case we will match against the macrolanguage instead of the language
if (langDef.Language.MacroLanguage != "") //Macrolanguage cant be null, see Record constructor
{
lang = langDef.Language.MacroLanguage;
}
}
//now lang is the subtag of the requested language or of the macrolanguage
//1.2 now we see if we have some match
if (copy.Any(a => a.Language.Subtag == lang))
{
//we have at least a match.. remove mismatch from the list
copy.RemoveWhere(a => a.Language.Subtag != lang);
}
else
{
//there is no match, we should return default language, but,
//as last resort try to see if there is any language on the bunch that share the same macrolanguage
//remove from the list all language that are not on the same family
copy.RemoveWhere(a => a.Language.MacroLanguage != lang);
}
//now the list contains the best possible match for the given language or contains nothing
if (copy.Count == 0)
{
return(retval);
}
if (copy.Count == 1)
{
return(copy.First()); //we matched at least the language, this is better than the default, so return this
}
//2nd step, we have some match, now see if we can refine using extlang... btw the extlang should have been canonicalized, so 99% wil do nothing
string extlang = langDef.ExtLang.Subtag;
if (copy.Any(a => a.ExtLang.Subtag == extlang))
{
//ok we can refine the list using the extlang
copy.RemoveWhere(a => a.ExtLang.Subtag != extlang);
if (copy.Count == 1)
{
return(copy.First()); //we cannot find any better match
}
}
//3rd step, we have some match, now go to see the scripts
string script = langDef.Script.Subtag;
//note that script value is blank only if the language supports many scripts and the user have not choosen one, otherwise the
//registry provide a SuppressScript for the language tag so even if the user have not specified it the script value does contain the
//default script value
//3.1 if we do match any script, remove all other languages that does not match
if (copy.Any(a => a.Script.Subtag == script))
{
copy.RemoveWhere(a => a.Script.Subtag != script);
if (copy.Count == 1)
{
return(copy.First()); //we cannot find any better match
}
}
//4th step, we have more than 1 match and we see if we can refine it by using the region
string region = langDef.Region.Subtag;
if (copy.Any(a => a.Region.Subtag == region))
{
//ok we can refine the list using the extlang
copy.RemoveWhere(a => a.Region.Subtag != region);
if (copy.Count == 1)
{
return(copy.First()); //we cannot find any better match
}
}
else
{
if (copy.Any(a => a.Region.Subtag == ""))
{
//we keep those language that have generic region and remove those with unmatching specific regions
copy.RemoveWhere(a => a.Region.Subtag != "");
if (copy.Count == 1)
{
return(copy.First()); //we cannot find any better match
}
}
}
//5th step, we still have more than 1 match, try to refine using the VARIANTS
var variants = new HashSet <string>(langDef.Variants.Select(a => a.Subtag));
//now, let's see who is the supported language that have the greatest number of variants and filter the other
var queryVariants = copy.Select
(
a =>
new
{
Language = a,
Num = a.Variants.Count(b => variants.Contains(b.Subtag))
}
).Where(c => c.Num > 0).ToList();
int maxVariants = queryVariants.Count == 0 ? 0 : queryVariants.Select(a => a.Num).Max();
if (maxVariants > 0)
{
var bestVariants = new HashSet <Lang>(queryVariants.Where(a => a.Num == maxVariants).Select(a => a.Language));
//ok we have a set of elements that best fits user requested language... remove other languages from the set
copy.RemoveWhere(a => !bestVariants.Contains(a));
if (copy.Count == 1)
{
return(copy.First()); //we cannot find any better match
}
}
//6th step, this is becoming a long task, we might find if we are matching some extension
Dictionary <char, HashSet <string> > extensions = langDef.Extensions.ToDictionary(a => a.Key, b => new HashSet <string>(b.Value));
//now, let's see who is the supported language that have the greatest number of extension matching and filter out others
var queryExtensions = copy.Select
(
a => new
{
Language = a,
Num = a.Extensions.Sum(b => b.Value.Count(c => extensions.ContainsKey(b.Key) && extensions[b.Key].Contains(c)))
}
).Where(d => d.Num > 0).ToList();
int maxExtensions = queryExtensions.Count == 0 ? 0 : queryExtensions.Select(a => a.Num).Max();
if (maxExtensions > 0)
{
var bestExtensions = new HashSet <Lang>(queryExtensions.Where(a => a.Num == maxExtensions).Select(a => a.Language));
//ok we have a set of elements that best fits user requested language... remove other languages from the set
copy.RemoveWhere(a => !bestExtensions.Contains(a));
if (copy.Count == 1)
{
return(copy.First()); //we cannot find any better match
}
}
//7th step, last resort is matching the private section, we will not do that...
//8th step, consider languages with shorter name to be better match than ones with long names
//for example when matching "de-Qaaa" against "de" and "de-Qaab" prefer "de"
return(copy.OrderBy(a => a.Private.Length).ThenBy(s => s.Canonical.Length).ThenBy(a => a.Canonical).First());
}
/// <summary>
/// Return the language closest to langDef in the supported list
/// </summary>
/// <param name="langDef">language to find </param>
/// <returns>best match found or default</returns>
/// <remarks>
/// The idea is to find the closest language using this policy:
///
/// - a language whose is in the same family of the searched language is always better than another language
///
/// for example
///
/// xx-xxx-Xxxx-XX-x-xxxxxxxx-xxxxx-xxxxxx-x-xxxxxx-xxxx
/// is a better match to
/// yy-yyy-Yyyy-YY-y-yyyyyyyy-yyyyy
///
/// if yy is a sublanguage of the same macrolanguage than the default
///
/// and so on the same policy is applied in cascade
///
/// example: ( X = Y means X match Y, X = Y > Z means that Y match X better than Z)
///
/// de-CH is a better match to de-DE than the default
///
///
/// de-CH-1901 = de-CH > de > default ; cause it match language and region even if orthography is old.
///
/// to match the variants: greater number of variant matches is always better than lower match of matches
///
/// In the case of equal matching, the shortest one is preferred
/// </remarks>
public Lang Lookup(string language)
{
return(Lookup(Lang.Parse(language)));
}