'''
hashdb.py
'''
import collections
import hashlib
import sqlite3
import uuid

# TODO: l o g g i n g
HASH_CHUNK_SIZE = 10485760 # 10mb
SQL_AND = ' AND '
SQL_OR = ' OR '

# TODO: Figure out how to do some kind of type checking for these named tuples.
# TODO: Switch these over to using traditional classes.
# TODO: UUID generation/editing is probably best done in here.
ImageData = collections.namedtuple('ImageData', 'UUID, sha1sum, filename, release_group')
ReleaseGroupData = collections.namedtuple('ReleaseGroupData', 'UUID, name, platform')
PlatformData = collections.namedtuple('PlatformData', 'UUID, name, shortcode')
DatData = collections.namedtuple('DatData', 'UUID, name, website, version, image_list')

# TODO: This should go in the eventual romdb class.
def get_file_sha1sum(filename):
    sha1sum = hashlib.sha1()
    with open(filename, 'rb') as file_contents:
        while True:
            chunk = file_contents.read(HASH_CHUNK_SIZE)
            if not chunk:
                break
            sha1sum.update(chunk)

    return sha1sum.hexdigest()

def _build_sql_constraints(inclusive, constraints):
    '''Build an SQL constraint clause out of a dictionary.

    inclusive   - If True, uses SQL AND operator, otherwise OR will be used.
    constraints - A dictionary of arbitrary constraints

    returns a tuple containing the appropriately formatted SQL string and a list of parameters
    '''
    if constraints == {}:
        return ('', [])

    if inclusive:
        logical_separator = SQL_AND
    else:
        logical_separator = SQL_OR

    sql_constraint_string = 'WHERE '
    sql_parameter_list = []
    for key, value in constraints.items():
        sql_constraint_string += '%s=?%s' % (key, logical_separator)
        sql_parameter_list.append(value)

    # Trim off the last ', '
    sql_constraint_string = sql_constraint_string[0:-len(logical_separator)]

    return (sql_constraint_string, sql_parameter_list)


class MetadataDB:
    def __init__(self, db_path):
        '''
        If db file does not exist, create it and create necessary tables.
        Either way, create a connection object.
        '''
        # TODO: This process needs real error handling.
        self._connection = sqlite3.connect(db_path)

        with self._connection:
            self._connection.execute('CREATE TABLE IF NOT EXISTS images (uuid PRIMARY KEY, '
                                     'sha1sum UNIQUE NOT NULL, filename NOT NULL, release_group);') 

            self._connection.execute('CREATE TABLE IF NOT EXISTS release_groups (UUID PRIMARY KEY, '
                                     'name NOT NULL, platform NOT NULL);')

            self._connection.execute('CREATE TABLE IF NOT EXISTS platforms (UUID PRIMARY KEY, '
                                     'name NOT NULL, shortcode UNIQUE NOT NULL);')

            # TODO: Add DAT import support.

            print('Database initialized.')

    def add_image(self, image_data):
        pass

    def update_image(self, image_data):
        pass

    def remove_image(self, image_data):
        pass

    def add_release_group(self, release_group_data):
        pass

    def update_release_group(self, release_group_data):
        pass

    def remove_release_group(self, release_group_data):
        pass

    def add_platform(self, platform_data):
        ''' Add a platform shortcode to the database. '''
        with self._connection:
            self._connection.execute('INSERT INTO platforms VALUES (?, ?, ?);', platform_data)

    def update_platform(self, platform_data):
        pass

    # TODO: Switch this to use more generic constraints language
    def remove_platform(self, platform_shortcode):
        with self._connection:
            self._connection.execute('DELETE FROM platforms WHERE shortcode=?;', platform_shortcode)

    def search_platforms(self, inclusive=True, **constraints):
        '''Search for platforms, given the parameters. '''

        sql_where_clause, sql_parameters = _build_sql_constraints(inclusive, constraints)

        platform_data_list = []
        with self._connection:
            cursor = self._connection.cursor()
            sql_query = 'SELECT * FROM platforms %s;' % sql_where_clause
            cursor.execute(sql_query, sql_parameters)
            rows = cursor.fetchall()

            for row in rows:
                platform_data = PlatformData(*row)
                platform_data_list.append(platform_data)

        return platform_data_list

    def add_dat(self, dat_data):
        pass

    def update_dat(self, dat_data):
        pass

    def remove_dat(self, dat_data):
        pass