protected ResourceMeta deriveResourceMeta()

in impl/src/main/java/org/apache/myfaces/application/ResourceHandlerImpl.java [1135:1300]
133 lines of code
32 McCabe index (conditional complexity)

    protected ResourceMeta deriveResourceMeta(FacesContext context, ResourceLoader resourceLoader,
            String resourceId)
    {
        ResourceMeta resourceMeta = null;
        String token = null;
        String localePrefix = null;
        String libraryName = null;
        String libraryVersion = null;
        String resourceName = null;
        String resourceVersion = null;

        int lastSlash = resourceId.lastIndexOf('/');
        if (lastSlash < 0)
        {
            //no slashes, so it is just a plain resource.
            resourceName = resourceId;
        }
        else
        {
            token = resourceId.substring(lastSlash+1);
            if (RESOURCE_VERSION_CHECKER.matcher(token).matches())
            {
                int secondLastSlash = resourceId.lastIndexOf('/', lastSlash-1);
                if (secondLastSlash < 0)
                {
                    secondLastSlash = 0;
                }

                String rnToken = resourceId.substring(secondLastSlash+1, lastSlash);
                int lastPoint = rnToken.lastIndexOf('.');
                // lastPoint < 0 means it does not match, the token is not a resource version
                if (lastPoint >= 0)
                {
                    String ext = rnToken.substring(lastPoint);
                    if (token.endsWith(ext))
                    {
                        //It match a versioned resource
                        resourceVersion = token.substring(0,token.length()-ext.length());
                    }
                }
            }

            // 1. Extract the library path and locale prefix if necessary
            int start = 0;
            int firstSlash = resourceId.indexOf('/');

            // At least one slash, check if the start is locale prefix.
            String bundleName = context.getApplication().getMessageBundle();
            //If no bundle set, it can't be localePrefix
            if (null != bundleName)
            {
                token = resourceId.substring(start, firstSlash);
                //Try to derive a locale object
                Locale locale = LocaleUtils.deriveLocale(token);

                // If the locale was derived and it is available, 
                // assume that portion of the resourceId it as a locale prefix.
                if (locale != null && LocaleUtils.isAvailableLocale(locale))
                {
                    localePrefix = token;
                    start = firstSlash+1;
                }
            }

            //Check slash again from start
            firstSlash = resourceId.indexOf('/', start);
            if (firstSlash < 0)
            {
                //no slashes.
                resourceName = resourceId.substring(start);
            }
            else
            {
                //check libraryName
                token = resourceId.substring(start, firstSlash);
                int minResourceNameSlash = (resourceVersion != null) ?
                    resourceId.lastIndexOf('/', lastSlash-1) : lastSlash;

                if (start < minResourceNameSlash)
                {
                    libraryName = token;
                    start = firstSlash+1;

                    //Now that libraryName exists, check libraryVersion
                    firstSlash = resourceId.indexOf('/', start);
                    if (firstSlash >= 0)
                    {
                        token = resourceId.substring(start, firstSlash);
                        if (LIBRARY_VERSION_CHECKER.matcher(token).matches())
                        {
                            libraryVersion = token;
                            start = firstSlash+1;
                        }
                    }
                }

                firstSlash = resourceId.indexOf('/', start);
                if (firstSlash < 0)
                {
                    //no slashes.
                    resourceName = resourceId.substring(start);
                }
                else
                {
                    // Check resource version. 
                    if (resourceVersion != null)
                    {
                        resourceName = resourceId.substring(start,lastSlash);
                    }
                    else
                    {
                        //no resource version, assume the remaining to be resource name
                        resourceName = resourceId.substring(start);
                    }
                }
            }
        }

        //Check libraryName and resourceName
        if (resourceName == null)
        {
            return null;
        }
        if (!ResourceValidationUtils.isValidResourceName(resourceName))
        {
            return null;
        }

        if (libraryName != null && !ResourceValidationUtils.isValidLibraryName(
                libraryName, isAllowSlashesLibraryName()))
        {
            return null;
        }

        // If some variable is "" set it as null.
        if (localePrefix != null && localePrefix.length() == 0)
        {
            localePrefix = null;
        }
        if (libraryName != null && libraryName.length() == 0)
        {
            libraryName = null;
        }
        if (libraryVersion != null && libraryVersion.length() == 0)
        {
            libraryVersion = null;
        }
        if (resourceName != null && resourceName.length() == 0)
        {
            resourceName = null;
        }
        if (resourceVersion != null && resourceVersion.length() == 0)
        {
            resourceVersion = null;
        }

        resourceMeta = resourceLoader.createResourceMeta(
            localePrefix, libraryName, libraryVersion, resourceName, resourceVersion);

        if (resourceMeta != null && !resourceLoader.resourceExists(resourceMeta))
        {
            resourceMeta = null;
        }

        return resourceMeta;
    }