"""
CSV Import 0.1
==============

Import a Comma Separated Values file and map it to a Django model.

I apologise for the rather clumsy format, but there does not really seem to
be an intuitive way to do this. I hope the documentation will suffice.

Sparse documentation
====================

CSV Import is run from the commandline. It has a few options: --csv, --help,
--mappings, --model, --modelspy, --name-indexes and --test.

--csv
-----

The path reference to the CSV file from which the script will import. Can be
either relative or absolute, as a regular UNIX file reference.

--help
------

Self-explanatory, shows documentation of these options.

--mappings
----------

Definition of the column-to-field mapping. Written in the format 
column=field(ForeignKeyName|field). The foreign key part is optional, and
may be omitted completely, leaving column=field.

--model
-------

The model in which the contents of the CSV file will be inserted.

--modelspy
----------

The path of the models.py file in which the model is located.

--name-indexes
--------------

Whether or not to use the first line of the CSV file as an index, giving the
possibility to refer to a column by its name. If omitted, column references 
are written as [column number]=field, e.g. 1=field.

Example runs
============

An example could look like the following. Please note that all occurences of
-> on the end of a line indicate a hard break, where none should be present.

We have an import.csv file with these contents:
"Contents of first column, first row","Contents of second column, first ->
row","Contents of third column, first row"
"Contents of first column, second row","Contents of second column, second -> 
row","Contents of third column, second row"
"Contents of first column, third row","Contents of second column, third -> 
row","Contents of third column, third row"

We have a models.py with a TestModel looking like this:

class TestModel(models.Model):
    field1 = models.CharField(max_length=255)
    field2 = models.CharField(max_length=255)
    field3 = models.CharField(max_length=255)

Then we run it:

$ python csvimport.py --csv import.csv --mappings 1=field1,2=field2, ->
3=field3 --model TestModel --modelspy .
TestModel.field1 = "Contents of first column, first row"
TestModel.field2 = "Contents of second column, first row"
TestModel.field3 = "Contents of third column, first row"
--------------------
TestModel.field1 = "Contents of first column, second row"
TestModel.field2 = "Contents of second column, second row"
TestModel.field3 = "Contents of third column, second row"
--------------------
TestModel.field1 = "Contents of first column, third row"
TestModel.field2 = "Contents of second column, third row"
TestModel.field3 = "Contents of third column, third row"

Using named indexes
-------------------

It is custom to have the first line of a CSV file serve as a sort of index, 
naming the columns. CSV Import supports this through the --name-indexes 
option. Using this, we can alter the command a bit, the --mappings option 
specifically:

$ python csvimport.py --csv import.csv --mappings column1=field1, -> 
column2=field2,column3=field3 --model TestModel --modelspy .

This asserts that the first line of import.csv looks like this:
"column1","column2","column3"

Version history
===============

*   0.1, 9 March 2008: Initial Release.

Credits
=======

Jonathan Holst <jonathan.holst [at] gmta.info>

Founded in 2003, GMTA ApS is the partnership between three
Danish computer enthusiasts with a strong interest in the
web-phenomenon.

Visit our website: http://www.gmta.info

License
=======

Creative Commons Attribution-Share Alike 3.0 License
http://creativecommons.org/licenses/by-sa/3.0/

When attributing this work, you must maintain the Credits
paragraph above.
"""

__version__ = '0.1'

import sys, os, csv, re

class CSVImport:
    """
    Parse and map a CSV resource to a Django model.
    
    Notice that the doc tests are merely illustrational, and will not run 
    as is.
    """
    def __init__(self, csvfile, mappings, model, modelspy, nameindexes=False):
        # This setting can be overriden at any time through an 
        # instance.debug = True, but this is for the hardcore crowd, and
        # should not polute the API
        self.debug = False
        self.errors = []
    
        self.csvfile = self.__csvfile(csvfile)
        self.mappings = self.__mappings(mappings)
        self.modelspy = self.__modelspy(modelspy)
        self.model = self.__model(model)
        self.nameindexes = bool(nameindexes)
    
    def run(self):
        if self.nameindexes:
            indexes = self.csvfile.pop(0)
            
        for row in self.csvfile:
            model_instance = getattr(self.models, self.model)()
            
            for (column, field, foreignkey) in self.mappings:
                if self.nameindexes:
                    column = indexes.index(column)
                else:
                    column = int(column)-1
                
                if foreignkey:
                    fk_key, fk_field = foreignkey
                try:
                    fk = getattr(self.models, fk_key)
                except AttributeError:
                    self.error('Referenced foreign keys must be in specified models.py', 0)
                
                # If there is corresponding data in the model already,
                # we do not need to add more, since we are dealing with
                # foreign keys, therefore foreign data
                matches = fk.objects.filter(**{fk_field+'__exact': 
                row[column]})
                
                if not matches:
                    key = fk()
                    key.__setattr__(fk_field, row[column])
                    key.save()
                
                row[column] = fk.objects.filter(**{fk_field+'__exact': 
                row[column]})[0]
            
                print '%s.%s = "%s"' % (self.model, field, row[column])
                model_instance.__setattr__(field, row[column])
        
        model_instance.save()
        
        print '-' * 20
        
    def error(self, message, type=1):
        """
        Types:
            0. A fatal error. The most drastic one. Will quit the program.
            1. A notice. Some minor thing is in disorder.
        """
        
        types = (
            ('Fatal error', FatalError),
            ('Notice', None),
        )
        
        self.errors.append((message, type))
        
        if type == 0:
            # There is nothing to do. We have to quite at this point
            raise types[0][1], message
        elif self.debug == True:
            print "%s: %s" % (types[type][0], message)
    
    def __csvfile(self, datafile):
        try:
            csvfile = file(datafile, 'r')
        except IOError:
            self.error('Could not open specified csv file, %s, or it does not exist' % datafile, 0)
        else:
            # CSV Reader returns an iterable, but as we possibly need to
            # perform list commands and since list is an acceptable iterable, 
            # we'll just transform it.
            return list(csv.reader(csvfile))
    
    def __modelspy(self, modelspy):
        # We need the path containing the models.py, so if it's in the
        # specified path, we'll just remove it.
        if modelspy.endswith('models.py'):
            self.error('Specified models.py path has "models.py" in it.', 1)
            modelspy = modelspy[:-9]
        
        if not os.path.exists(modelspy):
            self.error('Specified directory does not contain a models.py', 0)
        
        return modelspy
    
    def __model(self, model):
        # In order to properly import the models, and figure out what settings 
        # to use, we need to figure out the application and project names.
        a_dir = os.path.abspath(self.modelspy)
        a_name = os.path.basename(a_dir)
        p_dir = os.path.dirname(a_dir)
        p_name = os.path.basename(p_dir)
        
        # To import the models.py, it needs to be in sys.path
        sys.path.append(os.path.abspath(self.modelspy))
        # The project path should too
        sys.path.append(os.path.dirname(p_dir))
        
        os.environ['DJANGO_SETTINGS_MODULE'] = '%s.settings' % p_name
        
        try:
            self.models = __import__('%s.%s.models' % (p_name, a_name),
            globals(), locals(), '%s.%s' % (p_name, p_name))
        except ImportError:
            self.error('Specified directory does not exist')
        else:
            return model
    
        def __mappings(mappings):
            """
            Parse the mappings, and return a list of them.
            """
            
            def parse_mapping(args):
                """
                Parse the custom mapping syntax (column1=field1(ForeignKey|field),
                etc.)
                
                >>> parse_mapping('a=b(c|d)')
                [('a', 'b', '(c|d)')]
                """
                
                pattern = re.compile(r'(\w+)=(\w+)(\(\w+\|\w+\))?')
                mappings = pattern.findall(args)
                
                mappings = list(mappings)
                for mapping in mappings:
                    m = mappings.index(mapping)
                    mappings[m] = list(mappings[m])
                    mappings[m][2] = parse_foreignkey(mapping[2])
                    mappings[m] = tuple(mappings[m])
                mappings = list(mappings)
                
                return mappings
                
            def parse_foreignkey(key):
                """
                Parse the foreignkey syntax (Key|field)
                
                >>> parse_foreignkey('(a|b)')
                ('a', 'b')
                """
                
                pattern = re.compile(r'(\w+)\|(\w+)', re.U)
                if key.startswith('(') and key.endswith(')'):
                    key = key[1:-1]
                    
                found = pattern.search(key)
                
                return (found.group(1), found.group(2))
                
            mappings = mappings.replace(',', ' ')
            return parse_mapping(mappings)

class FatalError(Exception):
    """
    Something really bad happened.
    """
    def __init__(self, value):
        self.value = value
        
    def __str__(self):
        return repr(self.value)

if __name__ == '__main__':
    import optparse
    parser = optparse.OptionParser(usage='csvimport.py [args]', version='CSV Import %s' % __version__)
    
    try:
        sys.argv[1]
    except IndexError:
        parser.error('No arguments specified')
        
    parser.add_option('-n', '--name-indexes',
    action='store_true', dest='nameindexes',
    help='If this flag is on, the first line of the CSV file will be used as an index reference, meaning the mapping will appear as columnname=modelname. If it is not on, columns should instead be referred to by their position (first column is 1, second is 2, etc.)')
    
    parser.add_option('-c', '--csv', 
    action='store', type='string', dest='csvfile',
    help='The desired CSV file to import from')
    
    parser.add_option('-p', '--modelspy',
    action='store', type='string', dest='modelspy', 
    help='The mapping, to specify which columns from the CSV file that go with which models.')
    
    parser.add_option('-m', '--model',
    action='store', type='string', dest='model',
    help='The model to perform the mapping on. Must be in the specified models.py')
    
    parser.add_option('-a', '--mappings', 
    action='store', type='string', dest='mappings', 
    help='The mapping, to specify which columns from the CSV file that go with which models. Written as a list of column=field, eg. column1=field1,column2=field2. No spaces. Foreign keys are specified by appending (key|field), where key is the name of the foreign key, and field is the attribute in the foreign key, that holds the data specified in the CSV column.')
    
    opts, args = parser.parse_args()
    
    if not opts.csvfile or not opts.modelspy or not opts.model or not\
    opts.mappings:
        parser.error('Not enough arguments specified.')
    
    try:
        c = CSVImport(opts.csvfile, opts.mappings, opts.model, opts.modelspy,
        opts.nameindexes)
        c.run()
    except FatalError, e:
        parser.error(e)