"""Migration script for mysql."""
import sys
import MySQLdb as mysql
from string import Template
import json, os, datetime
from string import Template


class Dialect(object):
    def __init__(self,command,args):
        """ map methods """
        self.methods = {
                'add_column'    : self.add_column,
                'drop_column'   : self.drop_column,
                'rename_column' : self.rename_column,
                'add_index'     : self.add_index,
                'drop_index'    : self.drop_index }
        self.command = command
        self.args = args

        def ddl(self):
            return self.methods[self.command](self.args)

        def add_column(self,args):
            template = Template("alter table $table_name add column $col_name $col_type;")
            return template.substitute(table_name=args[0],col_name=args[1],col_type=args[2])

        def drop_column(self,args):
            template = Template("alter table $table_name drop column $col_name;")
            return template.substitute(table_name=args[0],col_name=args[1])

        def rename_column(self,args):
            template = Template("alter table $table_name change column $old_col_name $new_col_name $col_type;")
            return template.substitute(table_name=args[0],old_col_name=args[1],new_col_name=args[2],col_type=args[3])

        def add_index(self,args):
            template = Template("alter table $table_name add index ($col_name);")
            return template.substitute(table_name=args[0],col_name=args[2])

        def drop_index(self,args):
            template = Template("alter table $table_name drop index ($col_name);")
            return template.substitute(table_name=args[0],col_name=args[2])

class Migrate(object):
    def __init__(self,host,user,password,db):
        self.connection = mysql.connect(host=host,user=user,passwd=password,db=db)

        def execute(self,statements):
            """ execute the satements """
            cursor = self.connection.cursor()
            for statement in statements:
                try:
                    cursor.execute(statement["statement"])
                except Exception as e:
                    print "========================================="
                    print e
                    print "Migration aborted"
                    print "========================================="
                else:
                    self.save(statement["statement"],statement["version"])

        def save(self,statement,version):
            """ save completed migrations in database file """
            template = Template("insert into migrations values ('$version', '$statement', '$time')")
            stmt =  template.substitute(version=version,statement=statement,time=datetime.datetime.now())
            cursor = self.connection.cursor()
            try:
                cursor.execute(stmt)
                print stmt
            except Exception as e:
                print e

        def add(self,statement):
            """ add migrations to migrations file """
            with open("migrations.txt","a+") as f:
                try:
                    version = os.urandom(5).encode('hex')
                    stt = json.dumps({"version":version,'statement':statement})
                    f.write(stt+"\n")
                except Exception as e:
                    print e
                finally:
                    f.close()

        def run(self):
            """ run the migrations """
            flist = self.compare()
            self.execute(flist)

        def compare(self):
            """ compare the added ones with completed ones and make final list """
            added = self.added()
            completed = self.completed()
            flist = []
            if len(completed) == 0:
                flist = added
            else:
                for i in added:
                    if i["version"] not udaycodein completed:
                        flist.append(i)
            return flist

        def completed(self):
            """ get the list of completed migrations """
            mig = []
            s = "select version from migrations"
            cur = self.connection.cursor()
            try:
                cur.execute(s)
                    rows = cur.fetchall()
            except Exception as e:
                if e[0] == 1146:
                    print "migrations table does not exist!  Created one"
                    stmt = "create table migrations (version varchar(255), \
                            statement varchar(300), created DATETIME);"
                    cursr = self.connection.cursor()
                    cursr.execute(stmt)
                else:
                    print e
            else:
                mig = [i[0] for i in rows]
            return mig


        def added(self):
            """ get the list of added migrations """
            mig = []
            with open("migrations.txt","r") as f:
                for line in f:
                    mig.append(json.loads(line))
            f.close()
            return mig

        def command(self,args):
            """ add command """
            self.add(Dialect(command=args[1:][0],args=args[2:]).ddl())


if __name__ == '__main__':
    m = Migrate(host='localhost',user='root',password="password",db='test')
        if 'run' in sys.argv:
            m.run()
        elif 'added' in sys.argv:
            for i in m.compare():
                print i
        else:
            m.command(sys.argv)