# -*- coding: utf-8 -*-
#
# PgDataCopy - copy data between tables
#
# Copyright (c) 2012  Radek Brich <radek.brich@devl.cz>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.


import io


class TargetNotEmptyError(Exception):
    
    pass


class PgDataCopy:
    
    def __init__(self, conn1, conn2):
        self.conn1 = conn1
        self.conn2 = conn2
        self.fulltable1 = None
        self.fulltable2 = None
   
    def set_source(self, table, schema='public'):
        self.schema1 = schema
        self.table1 = table
        self.fulltable1 = '"' + schema + '"."'+ table + '"'
    
    def set_destination(self, table, schema='public'):
        self.schema2 = schema
        self.table2 = table
        self.fulltable2 = '"' + schema + '"."'+ table + '"'
    
    def copy(self):
        self.check()
        
        buf = io.StringIO()
        try:
            self.read(buf)
            data = buf.getvalue()
        finally:
            buf.close()
        
        buf = io.StringIO(data)
        try:
            self.write(buf)
        finally:
            buf.close()
        
        self.analyze()
    
    def check(self):
        '''Check that target table does not contain any data (otherwise cannot copy).'''
        q = self._compose_check(self.fulltable2)
        curs = self.conn2.cursor()
        curs.execute(q)
        curs.connection.commit()
        if curs.rowcount > 0:
            raise TargetNotEmptyError('Target table contains data: %s' % self.fulltable2)
        self.cols = [desc[0] for desc in curs.description]
    
    def read(self, tmpfile):
        '''Read contents from source table.'''
        q = self._compose_read(self.fulltable1, self.cols)
        curs = self.conn1.cursor()
        curs.copy_expert(q, tmpfile)
        curs.connection.commit()
    
    def write(self, tmpfile):
        '''Write source table contents to target table.'''
        q = self._compose_write(self.fulltable2, self.cols)
        curs = self.conn2.cursor()
        curs.copy_expert(q, tmpfile)
        curs.connection.commit()
    
    def analyze(self):
        '''Analyze target table.'''
        q = self._compose_analyze(self.fulltable2)
        curs = self.conn2.cursor()
        curs.execute(q)
        curs.connection.commit()
    
    def _compose_check(self, table):
        return 'SELECT * FROM %s LIMIT 1' % table
    
    def _compose_read(self, table, cols):
        collist = ', '.join(['"%s"' % col for col in cols])
        return 'COPY %s (%s) TO STDOUT' % (table, collist)
    
    def _compose_write(self, table, cols):
        collist = ', '.join(['"%s"' % col for col in cols])
        return 'COPY %s (%s) FROM STDIN' % (table, collist)
    
    def _compose_analyze(self, table):
        return 'ANALYZE %s' % table