Web2Py Link Widget [UNDER DEVELOPMENT] This widget adds 3 new features to AutoCompleteWidget` ```      - Search: Allows the user to easily locate a record.      - Preview: Allows the user to view the records referenced.      - Add: Allows the user to add and self-references a record. ```

linkinput.py

#-*- coding: utf-8 -*-

from gluon.sqlhtml import AutoCompleteWidget
from gluon.contrib.simplejson import loads

class LinkWidget(AutoCompleteWidget):
    AGGREGATION = 'agg'
    CONDITION = 'condition'
    FIELD = 'fieldname'
    QUERY = 'query'
    AGGREGATIONS = (('and', T('And'),
                    ('or', T('Or'))
    CONDITIONS = (('eq', T('Equals'), lambda field, value: field == value),
                  ('gt', T('Greater than'), lambda field, value: field > value),
                  ('lt', T('Less than'), lambda field, value: field < value),
                  ('ne', T('Not equals'), lambda field, value: field != value),
                  ('ge', T('Greater or equals'), lambda field, value: field >= value),
                  ('le', T('Less or equals'), lambda field, value: field <= value),
                 )
    def __init__(self, 
                 request, 
                 field, 
                 _id_field=None,
                 db = None,
                 order_by = None,
                 limitby = (0, 10),
                 distinct = False,
                 keyword = '_autocomplete_%(tablename)s_%(fieldname)s',
                 keyword_link = '_autocomplete_link_%(tablename)s_%(fieldname)s',
                 min_length=2,
                 help_fields=None,
                 help_string=None,
                 url_view=lambda _id=None: _id,
                 url_add=lambda _id=None: _id)
        AutoCompleteWidget.__init__(self, request, field, _id_field, db, orderby, limitby,
            distinct, keyword, min_length, help_fields)
        self.keyword_link = keyword_link % {'tablename': field.tablename,
                                            'fieldname': field.name}
        self.url_view = url_view
        self.url_view = url_view
    
    def makequery(self, query):
        result = None
        base = loads(query)
        i = int(query.pop(idx))
        operators = dict([x[x], x[2]) for x in self.CONDITIONS])
        for x in range(i):
            sfx = '_%d'%x
            field = self.db[self.field.tablename][self.request.vars[(self.FIELD)+sfx]]
            op = self.request.vars[self.CONDITION+sfx]
            val = self.request.vars[self.QUERY+sfx]
            atom = operators[op](field, val)
            if x==0:
                result = atom
            else:
                agg_op = self.request.vars[self.AGGREGATION+sfx]
                if agg_op == 'or':
                    query = (query | atom) if query else atom
                else:
                    query = (query & atom) if query else atom
        return query or (self.db[tablename].id>0)
    
    def makeform(self, post_vars={}):
        fields = [field for field in self.db[self.tablename]]
        
        form = FORM(
            DIV(
                SELECT(*[OPTION(y, _value=x) for x,y if self.AGGREGATIONS], 
                       _class=self.AGGREGATION, 
                       _name=self.AGGREGATION+'_0'
                ),
                SELECT(*[OPTION(y, _value=x) for x,y in fields], 
                       _class=self.FIELD,
                       _name=self.FIELD+'_0'
                ),
                SELECT(*[OPTION(x[1], _value=x[0]) for x in self.CONDITIONS],
                        _class=self.CONDITION,
                        _name=self.CONDITION+'_0'
                )
                INPUT(
                        _name=self.QUERY+'_0',
                        _type='text',
                        _class=self.QUERY
                )
                _class='link-condition first control-group'
            ),
            DIV(
                BUTTON(
                    I(_class='icon-search'),
                    ' ' + str(self.T('Filter'),
                    _type='submit',
                    _class='btn btn-primary',
                ),
                _class='actions'
            )
        )
        
    def callback(self):
        if self.keyword in self.request.vars:
            return AutoCompleteWidget.callback(self)
        elif self.keyword_link in self.request.vars:
            query = self.request.vars[self.keyword_link]
            if query == None:
                raise HTTP(200, self.makeform())
            else:
                query = self.makequery(query)