"""
A dbm clone using sqlite under the covers.

XXX TO DO:

Everything.
"""

import sqlite3
import collections

__all__ = ["error", "open"]

error = sqlite3.OperationalError

class _Database(collections.MutableMapping):
    def __init__(self, filename, mode):
        self._mode = mode
        self._filename = filename
        self._conn = sqlite3.connect(filename)
        self.initialize_table()

    def initialize_table(self):
        c = self._conn.cursor()
        try:
            c.execute("select count(key) from dict")
        except sqlite3.OperationalError:
            c.execute("""create table dict (key text, value text)""")
            self._conn.commit()
        finally:
            c.close()

    def __getitem__(self, key):
        c = self._conn.cursor()
        try:
            c.execute("select value from dict"
                      "  where key = ?", (key,))
            rows = list(c)
            if not rows:
                raise KeyError(key)
            return rows[0][0]
        finally:
            c.close()

    def __setitem__(self, key, val):
        del self[key]
        c = self._conn.cursor()
        try:
            c.execute("insert into dict"
                      " (key, value) values (?, ?)", (key, val))
            self._conn.commit()
        finally:
            c.close()

    def __delitem__(self, key):
        c = self._conn.cursor()
        try:
            c.execute("delete from dict where key = ?", (key,))
            self._conn.commit()
        finally:
            c.close()

    def keys(self):
        c = self._conn.cursor()
        try:
            c.execute("select key from dict order by key")
            return [e[0] for e in c]
        finally:
            c.close()

    def values(self):
        c = self._conn.cursor()
        try:
            c.execute("select value from dict order by key")
            return [e[0] for e in c]
        finally:
            c.close()

    def items(self):
        c = self._conn.cursor()
        try:
            c.execute("select key, value from dict order by key")
            return list(c)
        finally:
            c.close()

    def __contains__(self, key):
        c = self._conn.cursor()
        try:
            c.execute("select value from dict"
                      "  where key = ?", (key,))
            return not not list(c)
        finally:
            c.close()

    def iterkeys(self):
        return iter(self.keys())
    __iter__ = iterkeys

    def iteritems(self):
        return iter(self.items())

    def itervalues(self):
        return iter(self.values())

    def __len__(self):
        c = self._conn.cursor()
        try:
            c.execute("select count(key) from dict")
            return int(list(c)[0])
        finally:
            c.close()

    def close(self):
        if self._conn is not None:
            self._conn.close()
        self._conn = None

def open(file, flag=None, mode=0o666):
    return _Database(file, mode)