__doc__="""helper for importing pdf structures into a ReportLab generated document

"""

from reportlab.pdfbase.pdfdoc import format

class PDFPattern:

    __PDFObject__ = True

    __RefOnly__ = 1

    def __init__(self, pattern_sequence, **keywordargs):

        """

        Description of a kind of PDF object using a pattern.

        Pattern sequence should contain strings or singletons of form [string].

        Strings are literal strings to be used in the object.

        Singletons are names of keyword arguments to include.

        Keyword arguments can be non-instances which are substituted directly in string conversion,

        or they can be object instances in which case they should be pdfdoc.* style

        objects with a x.format(doc) method.

        Keyword arguments may be set on initialization or subsequently using __setitem__, before format.

        "constant object" instances can also be inserted in the patterns.

        """

        self.pattern = pattern_sequence

        self.arguments = keywordargs

        from types import StringType, InstanceType

        toptypes = (StringType, InstanceType)

        for x in pattern_sequence:

            if type(x) not in toptypes:

                if len(x)!=1:

                    raise ValueError("sequence elts must be strings or singletons containing strings: "+repr(x))

                if type(x[0]) is not StringType:

                    raise ValueError("Singletons must contain strings or instances only: "+repr(x[0]))

    def __setitem__(self, item, value):

        self.arguments[item] = value

    def __getitem__(self, item):

        return self.arguments[item]

    def format(self, document):

        L = []

        arguments = self.arguments

        from types import StringType, InstanceType

        for x in self.pattern:

            tx = type(x)

            if tx is StringType:

                L.append(x)

            elif tx is InstanceType:

                L.append( x.format(document) )

            else:

                name = x[0]

                value = arguments.get(name, None)

                if value is None:

                    raise ValueError("%s value not defined" % repr(name))

                if type(value) is InstanceType:

                    #L.append( value.format(document) )

                    L.append(format(value, document))

                else:

                    L.append( str(value) )