from PLC.Faults import *
from PLC.Parameter import Parameter

class Row(dict):
    """
    Representation of a row in a database table. To use, optionally
    instantiate with a dict of values. Update as you would a
    dict. Commit to the database with sync().
    """

    # Set this to the name of the table that stores the row.
    table_name = None

    # Set this to the name of the primary key of the table. It is
    # assumed that the this key is a sequence if it is not set when
    # sync() is called.
    primary_key = None

    # Set this to a dict of the valid fields of this object. Not all
    # fields (e.g., joined fields) may be updated via sync().
    fields = {}

    def validate(self):
        """
        Validates values. Will validate a value with a custom function
        if a function named 'validate_[key]' exists.
        """

        # Warn about mandatory fields
        mandatory_fields = self.api.db.fields(self.table_name, notnull = True, hasdef = False)
        for field in mandatory_fields:
            if not self.has_key(field) or self[field] is None:
                raise PLCInvalidArgument, field + " must be specified and cannot be unset"

        # Validate values before committing
        for key, value in self.iteritems():
            if value is not None and hasattr(self, 'validate_' + key):
                validate = getattr(self, 'validate_' + key)
                self[key] = validate(value)

    def sync(self, commit = True):
        """
        Flush changes back to the database.
        """

        # Validate all specified fields
        self.validate()

        # Filter out fields that cannot be set or updated directly
        all_fields = self.api.db.fields(self.table_name)
        fields = dict(filter(lambda (key, value): \
                             key in all_fields and \
                             (key not in self.fields or \
                              not isinstance(self.fields[key], Parameter) or \
                              not self.fields[key].ro),
                             self.items()))

        # Parameterize for safety
        keys = fields.keys()
        values = [self.api.db.param(key, value) for (key, value) in fields.items()]

        if not self.has_key(self.primary_key):
            # Insert new row
            sql = "INSERT INTO %s (%s) VALUES (%s);" % \
                  (self.table_name, ", ".join(keys), ", ".join(values))
        else:
            # Update existing row
            columns = ["%s = %s" % (key, value) for (key, value) in zip(keys, values)]
            sql = "UPDATE %s SET " % self.table_name + \
                  ", ".join(columns) + \
                  " WHERE %s = %s" % \
                  (self.primary_key,
                   self.api.db.param(self.primary_key, self[self.primary_key]))

        self.api.db.do(sql, fields)

        if not self.has_key(self.primary_key):
            self[self.primary_key] = self.api.db.last_insert_id(self.table_name, self.primary_key)

        if commit:
            self.api.db.commit()

    def delete(self, commit = True):
        """
        Delete row from its primary table.
        """

        assert self.primary_key in self

        sql = "DELETE FROM %s" % self.table_name + \
              " WHERE %s = %s" % \
              (self.primary_key,
               self.api.db.param(self.primary_key, self[self.primary_key]))

        self.api.db.do(sql, self)

        if commit:
            self.api.db.commit()

class Table(dict):
    """
    Representation of row(s) in a database table.
    """

    def sync(self, commit = True):
        """
        Flush changes back to the database.
        """

        for row in self.values():
            row.sync(commit)