#!/usr/bin/env python2
# -*- coding: utf-8 -*-
"""
    Blockstack-client
    ~~~~~
    copyright: (c) 2014-2015 by Halfmoon Labs, Inc.
    copyright: (c) 2016-2017 by Blockstack.org

    This file is part of Blockstack-client.

    Blockstack-client 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.

    Blockstack-client 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 Blockstack-client.  If not, see <http://www.gnu.org/licenses/>.
"""
import os
import sys

if sys.version_info.major != 2:
    raise Exception("Python 3 is not supported")

if sys.version_info.minor < 7:
    raise Exception("Python 2.7 or greater is required")

import traceback
import json

# Hack around absolute paths
current_dir = os.path.abspath(os.path.dirname(__file__))
parent_dir = os.path.abspath(current_dir + "/../")

import errno
import socket
import posixpath
import SocketServer
from SimpleHTTPServer import SimpleHTTPRequestHandler
import re
import jsonschema
from jsonschema import ValidationError

import keylib

import blockstack_client.schemas as schemas

class BlockstackSnapshotHandler(SimpleHTTPRequestHandler):
    """
    Snapshot server request handler.

    Endpoints are:
        POST /v1/snapshot       Sign a snapshot digest if it is signed by a trusted key

    server variables:
        self.server.trusted_public_key
        self.server.private_key
    """

    def _send_headers(self, status_code=200, content_type='application/json'):
        """
        Generate and reply headers
        """
        self.send_response(status_code)
        self.send_header('content-type', content_type)
        self.send_header('Access-Control-Allow-Origin', '*')    # CORS
        self.end_headers()


    def _reply_json(self, json_payload, status_code=200):
        """
        Return a JSON-serializable data structure
        """
        self._send_headers(status_code=status_code)
        json_str = json.dumps(json_payload)
        self.wfile.write(json_str)


    def _read_payload(self, maxlen=None):
        """
        Read raw uploaded data.
        Return the data on success
        Return None on I/O error, or if maxlen is not None and the number of bytes read is too big
        """

        client_address_str = "{}:{}".format(self.client_address[0], self.client_address[1])

        # check length
        read_len = self.headers.get('content-length', None)
        if read_len is None:
            log.error("No content-length given from {}".format(client_address_str))
            return None

        try:
            read_len = int(read_len)
        except:
            log.error("Invalid content-length")
            return None

        if maxlen is not None and read_len >= maxlen:
            log.error("Request from {} is too long ({} >= {})".format(client_address_str, read_len, maxlen))
            return None

        # get the payload
        request_str = self.rfile.read(read_len)
        return request_str


    def _read_json(self, schema=None):
        """
        Read a JSON payload from the requester
        Return the parsed payload on success
        Return None on error
        """
        # JSON post?
        request_type = self.headers.get('content-type', None)
        client_address_str = "{}:{}".format(self.client_address[0], self.client_address[1])

        if request_type != 'application/json':
            log.error("Invalid request of type {} from {}".format(request_type, client_address_str))
            return None

        request_str = self._read_payload(maxlen=self.JSONRPC_MAX_SIZE)
        if request_str is None:
            log.error("Failed to read request")
            return None

        # parse the payload
        request = None
        try:
            request = json.loads( request_str )
            if schema is not None:
                jsonschema.validate( request, schema )

        except (TypeError, ValueError, ValidationError) as ve:
            if BLOCKSTACK_DEBUG:
                log.exception(ve)

            return None

        return request


    def get_path_and_qs(self):
        """
        Parse and obtain the path and query values.
        We don't care about fragments.

        Return {'path': ..., 'qs_values': ...} on success
        Return {'error': ...} on error
        """
        path_parts = self.path.split("?", 1)

        if len(path_parts) > 1:
            qs = path_parts[1].split("#", 1)[0]
        else:
            qs = ""

        path = path_parts[0].split("#", 1)[0]
        path = posixpath.normpath(urllib.unquote(path))

        qs_values = self.parse_qs( qs )
        if qs_values is None:
            return {'error': 'Failed to parse query string'}

        parts = path.strip('/').split('/')

        return {'path': path, 'qs_values': qs_values, 'parts': parts}


    def sign_snapshot( self ):
        """
        Read a snapshot digest, sign it, and return the signature.
        Return 200 with {'sigb64': sigb64} on success
        Return 401 on invalid request structure
        Return 403 on invalid signature

        TODO: if this server is colocated with a blockstack server, then
        it should verify that independently calculated the same snapshot.
        Use `block_height` for that.
        """
        snapshot_schema = {
            'type': 'object',
            'properties': {
                'block_height': {
                    'type': 'integer',
                },
                'file_hash': {
                    'type': 'string',
                    'pattern': schemas.OP_HEX_PATTERN,
                },
                'sigb64': {
                    'type': 'string',
                    'pattern': schemas.OP_BASE64_PATTERN,
                },
            },
            'required': [
                'file_hash',
                'sigb64',
            ],
            'additionalProperties': False,
        }

        request = _read_json(schema=snapshot_schema)
        if request is None:
            return self._reply_json({'error': 'Invalid snapshot request'}, status_code=401)
            
        block_height = request['block_height']
        hash_bin = request['file_hash'].decode('hex')
        sigb64 = request['sigb64']

        # TODO: check to see that we (1) have this snapshot, and (2) it has the given hash 

        # did our trusted public key sign it?
        valid = blockstack_client.storage.verify_raw_data( hash_bin, self.server.trusted_public_key, sigb64 )
        if not valid:
            return self._reply_json({'error': 'Invalid signature'}, status_code=403)

        # can sign 
        sigb64 = blockstack_client.storage.sign_raw_data( hash_bin, self.server.private_key )
        assert sigb64

        return self._reply_json({'sigb64': sigb64})


    def do_POST(self):
        """
        Handle POST request
        """
        path_info = self.get_path_and_qs()
        if 'error' in path_info:
            return self._reply_json({'error': 'Invalid request'}, status_code=401)

        path = path_info['path']
        if path == '/v1/snapshots':
            return self.sign_snapshot()
        else:
            return self._reply_json({'error': 'No such method'}, status_code=404)


class BlockstackSnapshotServer(SocketServer.TCPServer):
    """
    Snapshot server implementation
    """
    def __init__(self, trusted_public_key, private_key ):
        """
        Set up a snapshot server
        """
        self.trusted_public_key = keylib.ECPublicKey(trusted_public_key).to_hex()
        self.private_key = keylib.ECPrivateKey(private_key).to_hex()


def usage():
    print >> sys.stderr, "Usage: {} /path/to/private/key /path/to/trusted/public/key".format(sys.argv[0])
    sys.exit(1)


if __name__ == '__main__':
    # usage: $0 /path/to/private/key /path/to/trusted/public/key
    if len(sys.argv) != 3:
        usage()

    for path in sys.argv[1:]:
        if not os.path.exists(path):
            usage()

    private_key = None
    trusted_public_key = None

    with open(sys.argv[1]) as f:
        private_key = f.read().strip()

    with open(sys.argv[2]) as f:
        trusted_public_key = f.read().strip()

    try:
        keylib.ECPrivateKey(private_key)
        keylib.ECPublicKey(trusted_public_key)
    except:
        print >> sys.stderr, "Invalid key data"
        usage()

    srv = BlocksatckSnapshotServer( trusted_public_key, private_key )
    srv.serve_forever()