#!/usr/bin/env python3
#
# Copyright (C) 2019 VyOS maintainers and contributors
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 or later as
# published by the Free Software Foundation.
#
# This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
#
#

import os
import sys
import grp
import json
import traceback
import threading
import signal

import vyos.config

from flask import Flask, request

from functools import wraps

from vyos.configsession import ConfigSession, ConfigSessionError
from vyos.config import VyOSError


DEFAULT_CONFIG_FILE = '/etc/vyos/http-api.conf'
CFG_GROUP = 'vyattacfg'

app = Flask(__name__)

# Giant lock!
lock = threading.Lock()

def load_server_config():
    with open(DEFAULT_CONFIG_FILE) as f:
        config = json.load(f)
    return config

def check_auth(key_list, key):
    id = None
    for k in key_list:
        if k['key'] == key:
            id = k['id']
    return id

def error(code, msg):
    resp = {"success": False, "error": msg, "data": None}
    return json.dumps(resp), code

def success(data):
    resp = {"success": True, "data": data, "error": None}
    return json.dumps(resp)

def get_command(f):
    @wraps(f)
    def decorated_function(*args, **kwargs):
        cmd = request.form.get("data")
        if not cmd:
            return error(400, "Non-empty data field is required")
        try:
            cmd = json.loads(cmd)
        except Exception as e:
            return error(400, "Failed to parse JSON: {0}".format(e))
        return f(cmd, *args, **kwargs)

    return decorated_function

def auth_required(f):
    @wraps(f)
    def decorated_function(*args, **kwargs):
        key = request.form.get("key")
        api_keys = app.config['vyos_keys']
        id = check_auth(api_keys, key)
        if not id:
            return error(401, "Valid API key is required")
        return f(*args, **kwargs)

    return decorated_function

@app.route('/configure', methods=['POST'])
@get_command
@auth_required
def configure_op(commands):
    session = app.config['vyos_session']
    env = session.get_session_env()
    config = vyos.config.Config(session_env=env)

    strict_field = request.form.get("strict")
    if strict_field == "true":
        strict = True
    else:
        strict = False

    # Allow users to pass just one command
    if not isinstance(commands, list):
        commands = [commands]

    # We don't want multiple people/apps to be able to commit at once,
    # or modify the shared session while someone else is doing the same,
    # so the lock is really global
    lock.acquire()

    status = 200
    error_msg = None
    try:
        for c in commands:
            # What we've got may not even be a dict
            if not isinstance(c, dict):
                raise ConfigSessionError("Malformed command \"{0}\": any command must be a dict".format(json.dumps(c)))

            # Missing op or path is a show stopper
            if not ('op' in c):
                raise ConfigSessionError("Malformed command \"{0}\": missing \"op\" field".format(json.dumps(c)))
            if not ('path' in c):
                raise ConfigSessionError("Malformed command \"{0}\": missing \"path\" field".format(json.dumps(c)))

            # Missing value is fine, substitute for empty string
            if 'value' in c:
                value = c['value']
            else:
                value = ""

            op = c['op']
            path = c['path']

            if not path:
                raise ConfigSessionError("Malformed command \"{0}\": empty path".format(json.dumps(c)))

            # Type checking
            if not isinstance(path, list):
                raise ConfigSessionError("Malformed command \"{0}\": \"path\" field must be a list".format(json.dumps(c)))

            if not isinstance(value, str):
                raise ConfigSessionError("Malformed command \"{0}\": \"value\" field must be a string".format(json.dumps(c)))

            # Account for the case when value field is present and set to null
            if not value:
                value = ""

            # For vyos.configsessios calls that have no separate value arguments,
            # and for type checking too
            try:
                cfg_path = " ".join(path + [value]).strip()
            except TypeError:
                raise ConfigSessionError("Malformed command \"{0}\": \"path\" field must be a list of strings".format(json.dumps(c)))

            if op == 'set':
                # XXX: it would be nice to do a strict check for "path already exists",
                # but there's probably no way to do that
                session.set(path, value=value)
            elif op == 'delete':
                if strict and not config.exists(cfg_path):
                    raise ConfigSessionError("Cannot delete [{0}]: path/value does not exist".format(cfg_path))
                session.delete(path, value=value)
            elif op == 'comment':
                session.comment(path, value=value)
            else:
                raise ConfigSessionError("\"{0}\" is not a valid operation".format(op))
        # end for
        session.commit()
        print("Configuration modified via HTTP API using key \"{0}\"".format(id))
    except ConfigSessionError as e:
        session.discard()
        status = 400
        if app.config['vyos_debug']:
            print(traceback.format_exc(), file=sys.stderr)
        error_msg = str(e)
    except Exception as e:
        session.discard()
        print(traceback.format_exc(), file=sys.stderr)
        status = 500

        # Don't give the details away to the outer world
        error_msg = "An internal error occured. Check the logs for details."
    finally:
        lock.release()

    if status != 200:
        return error(status, error_msg)
    else:
        return success(None)

@app.route('/retrieve', methods=['POST'])
@get_command
@auth_required
def retrieve_op(command):
    session = app.config['vyos_session']
    env = session.get_session_env()
    config = vyos.config.Config(session_env=env)

    try:
        op = command['op']
        path = " ".join(command['path'])
    except KeyError:
        return error(400, "Missing required field. \"op\" and \"path\" fields are required")

    try:
        if op == 'returnValue':
            res = config.return_value(path)
        elif op == 'returnValues':
            res = config.return_values(path)
        elif op == 'exists':
            res = config.exists(path)
        elif op == 'showConfig':
            config_format = 'json'
            if 'configFormat' in command:
                config_format = command['configFormat']

            res = session.show_config(path=command['path'])
            if config_format == 'json':
                config_tree = vyos.configtree.ConfigTree(res)
                res = json.loads(config_tree.to_json())
            elif config_format == 'json_ast':
                config_tree = vyos.configtree.ConfigTree(res)
                res = json.loads(config_tree.to_json_ast())
            elif config_format == 'raw':
                pass
            else:
                return error(400, "\"{0}\" is not a valid config format".format(config_format))
        else:
            return error(400, "\"{0}\" is not a valid operation".format(op))
    except VyOSError as e:
        return error(400, str(e))
    except ConfigSessionError as e:
        return error(400, str(e))
    except Exception as e:
        print(traceback.format_exc(), file=sys.stderr)
        return error(500, "An internal error occured. Check the logs for details.")

    return success(res)

@app.route('/config-file', methods=['POST'])
@get_command
@auth_required
def config_file_op(command):
    session = app.config['vyos_session']

    try:
        op = command['op']
    except KeyError:
        return error(400, "Missing required field \"op\"")

    try:
        if op == 'save':
            try:
                path = command['file']
            except KeyError:
                path = '/config/config.boot'
            res = session.save_config(path)
        elif op == 'load':
            try:
                path = command['file']
            except KeyError:
                return error(400, "Missing required field \"file\"")
            res = session.load_config(path)
            res = session.commit()
        else:
            return error(400, "\"{0}\" is not a valid operation".format(op))
    except ConfigSessionError as e:
        return error(400, str(e))
    except Exception as e:
        print(traceback.format_exc(), file=sys.stderr)
        return error(500, "An internal error occured. Check the logs for details.")

    return success(res)

@app.route('/image', methods=['POST'])
@get_command
@auth_required
def image_op(command):
    session = app.config['vyos_session']

    try:
        op = command['op']
    except KeyError:
        return error(400, "Missing required field \"op\"")

    try:
        if op == 'add':
            try:
                url = command['url']
            except KeyError:
                return error(400, "Missing required field \"url\"")
            res = session.install_image(url)
        elif op == 'delete':
            try:
                name = command['name']
            except KeyError:
                return error(400, "Missing required field \"name\"")
            res = session.remove_image(name)
        else:
            return error(400, "\"{0}\" is not a valid operation".format(op))
    except ConfigSessionError as e:
        return error(400, str(e))
    except Exception as e:
        print(traceback.format_exc(), file=sys.stderr)
        return error(500, "An internal error occured. Check the logs for details.")

    return success(res)


@app.route('/generate', methods=['POST'])
@get_command
@auth_required
def generate_op(command):
    session = app.config['vyos_session']

    try:
        op = command['op']
        path = command['path']
    except KeyError:
        return error(400, "Missing required field. \"op\" and \"path\" fields are required")

    if not isinstance(path, list):
        return error(400, "Malformed command: \"path\" field must be a list of strings")

    try:
        if op == 'generate':
            res = session.generate(path)
        else:
            return error(400, "\"{0}\" is not a valid operation".format(op))
    except ConfigSessionError as e:
        return error(400, str(e))
    except Exception as e:
        print(traceback.format_exc(), file=sys.stderr)
        return error(500, "An internal error occured. Check the logs for details.")

    return success(res)

@app.route('/show', methods=['POST'])
@get_command
@auth_required
def show_op(command):
    session = app.config['vyos_session']

    try:
        op = command['op']
        path = command['path']
    except KeyError:
        return error(400, "Missing required field. \"op\" and \"path\" fields are required")

    if not isinstance(path, list):
        return error(400, "Malformed command: \"path\" field must be a list of strings")

    try:
        if op == 'show':
            res = session.show(path)
        else:
            return error(400, "\"{0}\" is not a valid operation".format(op))
    except ConfigSessionError as e:
        return error(400, str(e))
    except Exception as e:
        print(traceback.format_exc(), file=sys.stderr)
        return error(500, "An internal error occured. Check the logs for details.")

    return success(res)

def shutdown():
    raise KeyboardInterrupt

if __name__ == '__main__':
    # systemd's user and group options don't work, do it by hand here,
    # else no one else will be able to commit
    cfg_group = grp.getgrnam(CFG_GROUP)
    os.setgid(cfg_group.gr_gid)

    # Need to set file permissions to 775 too so that every vyattacfg group member
    # has write access to the running config
    os.umask(0o002)

    try:
        server_config = load_server_config()
    except Exception as e:
        print("Failed to load the HTTP API server config: {0}".format(e))

    session = ConfigSession(os.getpid())

    app.config['vyos_session'] = session
    app.config['vyos_keys'] = server_config['api_keys']
    app.config['vyos_debug'] = server_config['debug']

    def sig_handler(signum, frame):
        shutdown()

    signal.signal(signal.SIGTERM, sig_handler)

    app.run(host=server_config["listen_address"], port=server_config["port"], debug=True)