#!/usr/bin/python
# -*- coding: utf-8 -*-

# This file is part of Ansible
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.

import re

try:
    import psycopg2
except ImportError:
    postgresqldb_found = False
else:
    postgresqldb_found = True

# ===========================================
# PostgreSQL module specific support methods.
#


def user_exists(cursor, user):
    query = "SELECT rolname FROM pg_roles WHERE rolname=%(user)s"
    cursor.execute(query, {'user': user})
    return cursor.rowcount > 0


def user_add(cursor, user, password):
    """Create a new user with write access to the database"""
    query = "CREATE USER %(user)s with PASSWORD '%(password)s'"
    cursor.execute(query % {"user": user, "password": password})
    return True

def user_chpass(cursor, user, password):
    """Change user password"""
    changed = False

    # Handle passwords.
    if password is not None:
        select = "SELECT rolpassword FROM pg_authid where rolname=%(user)s"
        cursor.execute(select, {"user": user})
        current_pass_hash = cursor.fetchone()[0]
        # Not sure how to hash the new password, so we just initiate the
        # change and check if the hash changed
        alter = "ALTER USER %(user)s WITH PASSWORD '%(password)s'"
        cursor.execute(alter % {"user": user, "password": password})
        cursor.execute(select, {"user": user})
        new_pass_hash = cursor.fetchone()[0]
        if current_pass_hash != new_pass_hash:
            changed = True

    return changed

def user_delete(cursor, user):
    """Try to remove a user. Returns True if successful otherwise False"""
    cursor.execute("SAVEPOINT ansible_pgsql_user_delete")
    try:
        cursor.execute("DROP USER %s" % user)
    except:
        cursor.execute("ROLLBACK TO SAVEPOINT ansible_pgsql_user_delete")
        cursor.execute("RELEASE SAVEPOINT ansible_pgsql_user_delete")
        return False
    
    cursor.execute("RELEASE SAVEPOINT ansible_pgsql_user_delete")
    return True

def has_table_privilege(cursor, user, table, priv):
    query = 'SELECT has_table_privilege(%s, %s, %s)'
    cursor.execute(query, (user, table, priv))
    return cursor.fetchone()[0]

def get_table_privileges(cursor, user, table):
    if '.' in table:
        schema, table = table.split('.', 1)
    else:
        schema = 'public'
    query = '''SELECT privilege_type FROM information_schema.role_table_grants
    WHERE grantee=%s AND table_name=%s AND table_schema=%s'''
    cursor.execute(query, (user, table, schema))
    return set([x[0] for x in cursor.fetchall()])
    

def grant_table_privilege(cursor, user, table, priv):
    prev_priv = get_table_privileges(cursor, user, table)
    query = 'GRANT %s ON TABLE %s TO %s' % (priv, table, user)
    cursor.execute(query)
    curr_priv = get_table_privileges(cursor, user, table)
    return len(curr_priv) > len(prev_priv)

def revoke_table_privilege(cursor, user, table, priv):
    prev_priv = get_table_privileges(cursor, user, table)
    query = 'REVOKE %s ON TABLE %s FROM %s' % (priv, table, user)
    cursor.execute(query)
    curr_priv = get_table_privileges(cursor, user, table)
    return len(curr_priv) < len(prev_priv)


def get_database_privileges(cursor, user, db):
    priv_map = {
        'C':'CREATE',
        'T':'TEMPORARY',
        'c':'CONNECT',
    }
    query = 'SELECT datacl FROM pg_database WHERE datname = %s'
    cursor.execute(query, (db,))
    datacl = cursor.fetchone()[0]
    r = re.search('%s=(C?T?c?)/[a-z]+\,?' % user, datacl)
    if r is None:
        return []
    o = []
    for v in r.group(1):
        o.append(priv_map[v])
    return o

def has_database_privilege(cursor, user, db, priv):
    query = 'SELECT has_database_privilege(%s, %s, %s)'
    cursor.execute(query, (user, db, priv))
    return cursor.fetchone()[0]

def grant_database_privilege(cursor, user, db, priv):
    prev_priv = get_database_privileges(cursor, user, db)
    query = 'GRANT %s ON DATABASE %s TO %s' % (priv, db, user)
    cursor.execute(query)
    curr_priv = get_database_privileges(cursor, user, db)
    return len(curr_priv) > len(prev_priv)

def revoke_database_privilege(cursor, user, db, priv):
    prev_priv = get_database_privileges(cursor, user, db)
    query = 'REVOKE %s ON DATABASE %s FROM %s' % (priv, db, user)
    cursor.execute(query)
    curr_priv = get_database_privileges(cursor, user, db)
    return len(curr_priv) < len(prev_priv)

def revoke_privileges(cursor, user, privs):
    if privs is None:
        return False

    changed = False
    for type_ in privs:
        revoke_func = {
            'table':revoke_table_privilege,
            'database':revoke_database_privilege
        }[type_]
        for name, privileges in privs[type_].iteritems():
            for privilege in privileges:
                changed = revoke_func(cursor, user, name, privilege)\
                        or changed

    return changed

def grant_privileges(cursor, user, privs):
    if privs is None:
        return False

    changed = False
    for type_ in privs:
        grant_func = {
            'table':grant_table_privilege,
            'database':grant_database_privilege
        }[type_]
        for name, privileges in privs[type_].iteritems():
            for privilege in privileges:
                changed = grant_func(cursor, user, name, privilege)\
                        or changed

    return changed

def parse_privs(privs, db):
    """
    Parse privilege string to determine permissions for database db.
    Format:

        privileges[/privileges/...]

    Where:

        privileges := DATABASE_PRIVILEGES[,DATABASE_PRIVILEGES,...] |
            TABLE_NAME:TABLE_PRIVILEGES[,TABLE_PRIVILEGES,...]
    """
    if privs is None:
        return privs

    o_privs = {
        'database':{},
        'table':{}
    }
    for token in privs.split('/'):
        if ':' not in token:
            type_ = 'database'
            name = db
            priv_set = set(x.strip() for x in token.split(','))
        else:
            type_ = 'table'
            name, privileges = token.split(':', 1)
            priv_set = set(x.strip() for x in privileges.split(','))
        
        o_privs[type_][name] = priv_set
    
    return o_privs

# ===========================================
# Module execution.
#

def main():
    module = AnsibleModule(
        argument_spec=dict(
            login_user=dict(default="postgres"),
            login_password=dict(default=""),
            login_host=dict(default=""),
            user=dict(required=True, aliases=['name']),
            password=dict(default=None),
            state=dict(default="present", choices=["absent", "present"]),
            priv=dict(default=None),
            db=dict(default=''),
            fail_on_user=dict(default='yes')
        )
    )
    user = module.params["user"]
    password = module.params["password"]
    state = module.params["state"]
    fail_on_user = module.params["fail_on_user"] == 'yes'
    db = module.params["db"]
    if db == '' and module.params["priv"] is not None:
        module.fail_json(msg="privileges require a database to be specified")
    privs = parse_privs(module.params["priv"], db)

    if not postgresqldb_found:
        module.fail_json(msg="the python psycopg2 module is required")
    
    # To use defaults values, keyword arguments must be absent, so 
    # check which values are empty and don't include in the **kw
    # dictionary
    params_map =  {
        "login_host":"host",
        "login_user":"user",
        "login_password":"password",
        "db":"database" 
    }
    kw = dict( (params_map[k], v) for (k, v) in module.params.iteritems() 
              if k in params_map and v != "" )
    try:
        db_connection = psycopg2.connect(**kw)
        cursor = db_connection.cursor()
    except Exception, e:
        module.fail_json(msg="unable to connect to database: %s" % e)
    
    kw = dict(user=user)
    changed = False
    user_removed = False
    if state == "present":
        if user_exists(cursor, user):
            changed = user_chpass(cursor, user, password)
        else:
            if password is None:
                msg = "password parameter required when adding a user"
                module.fail_json(msg=msg)
            changed = user_add(cursor, user, password)
        changed = grant_privileges(cursor, user, privs) or changed
    else:
        if user_exists(cursor, user):
            changed = revoke_privileges(cursor, user, privs)
            user_removed = user_delete(cursor, user)
            changed = changed or user_removed
            if fail_on_user and not user_removed:
                msg = "unabel to remove user"
                module.fail_json(msg=msg)
            kw['user_removed'] = user_removed

    if changed:
        db_connection.commit()

    kw['changed'] = changed
    module.exit_json(**kw)

# this is magic, see lib/ansible/module_common.py
#<<INCLUDE_ANSIBLE_MODULE_COMMON>>
main()