#!/usr/bin/env python3
#
# (C) 2017 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
# All rights reserved.
#
# Author: Neels Hofmeyr <nhofmeyr@sysmocom.de>
#
# This program 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.
#
# 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/>.

'''
Common code for VTY and CTRL interface interaction and transcript verification.
This implements all of application interaction, piping and verification.
vty.py and ctrl.py plug VTY and CTRL interface specific bits.
'''

# Our setup.py currently wants everything to be parsable by both py2 and py3.
# IMHO that is not a good idea, but until that changes, let's just keep this
# py2 legacy shim in here so we can syntax-check this py3 module with py2.
from __future__ import print_function

import argparse
import sys
import os
import subprocess
import time
import traceback
import socket
import shlex
import re


class Interact:

    class StepBase:
        command = None
        result = None
        leading_blanks = None

        def __init__(self):
            self.result = []

        def verify_interact_state(self, interact_instance):
            # for example to verify that the last VTY prompt received shows the
            # right node.
            pass

        def command_str(self, interact_instance=None):
            return self.command

        def __str__(self):
            return '%s\n%s' % (self.command_str(), '\n'.join(self.result))

        @staticmethod
        def is_next_step(line, interact_instance):
            assert not "implemented by InteractVty.VtyStep and InteractCtrl.CtrlStep"

    socket = None

    def __init__(self, step_class, port, host, verbose=False, update=False):
        '''
        host is the hostname to connect to.
        port is the CTRL port to connect on.
        '''
        self.Step = step_class
        self.port = port
        self.host = host
        self.verbose = verbose
        self.update = update

        if not port:
            raise Exception("You need to provide port number to connect to")

    def connect(self):
        assert self.socket is None
        retries = 30
        took = 0
        while True:
            took += 1
            try:
                self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                self.socket.setblocking(1)
                self.socket.connect((self.host, int(self.port)))
            except IOError:
                retries -= 1
                if retries <= 0:
                    raise
                time.sleep(.1)
                continue
            break

    def close(self):
        if self.socket is None:
            return
        self.socket.close()
        self.socket = None

    def command(self, command):
        assert not "implemented separately by InteractVty and InteractCtrl"

    def verify_transcript_file(self, transcript_file):
        with open(transcript_file, 'r') as f:
            content = f.read()

        try:
            result = self.verify_transcript(content)
        except:
            print('Error while verifying transcript file %r' % transcript_file, file=sys.stderr)
            sys.stderr.flush()
            raise

        if not self.update:
            return
        content = '\n'.join(result)
        with open(transcript_file, 'w') as f:
            f.write(content)

    def verify_transcript(self, transcript):
        ''''
        transcript is a "screenshot" of a session, a multi-line string
        including commands and expected results.
        Feed commands to self.command() and verify the expected results.
        '''

        # parse steps
        steps = []
        step = None
        blank_lines = 0
        for line in transcript.splitlines():
            if not line:
                blank_lines += 1
                continue
            next_step_started = self.Step.is_next_step(line, self)
            if next_step_started:
                if step:
                    steps.append(step)
                step = next_step_started
                step.leading_blanks = blank_lines
                blank_lines = 0
            elif step:
                # we only count blank lines directly preceding the start of a
                # next step. Insert blank lines in the middle of a response
                # back into the response:
                if blank_lines:
                    step.result.extend([''] * blank_lines)
                blank_lines = 0
                step.result.append(line)
        if step:
            steps.append(step)
        step = None

        actual_result = []

        # run steps
        step_nr = 0
        for step in steps:
            step_nr += 1
            try:
                if self.verbose:
                    if step.leading_blanks:
                        print('\n' * step.leading_blanks, end='')
                    print(step.command_str())
                    sys.stdout.flush()

                step.verify_interact_state(self)

                res = self.command(step.command)
                # trailing empty lines in the command output cannot be preserved because we allow
                # arbitrary newlines between commands. Do not even track these.
                while res and not res[-1]:
                    res = res[:-1]

                if self.verbose:
                    sys.stderr.flush()
                    sys.stdout.flush()
                    print('\n'.join(res))
                    sys.stdout.flush()

                if step.leading_blanks:
                    actual_result.extend([''] * step.leading_blanks)
                actual_result.append(step.command_str(self))

                match_result = self.match_lines(step.result, res)

                if self.update:
                    if match_result is True:
                        # preserve any wildcards
                        actual_result.extend(step.result)
                    else:
                        # mismatch, take exactly what came in
                        actual_result.extend(res)
                    continue
                if match_result is not True:
                    raise Exception('Result mismatch:\n%s\n\nExpected:\n[\n%s\n]\n\nGot:\n[\n%s\n%s\n]'
                                    % (match_result, step, step.command_str(), '\n'.join(res)))
            except:
                print('Error during transcript step %d:\n[\n%s\n]' % (step_nr, step),
                      file=sys.stderr)
                sys.stderr.flush()
                raise

        # final line ending
        actual_result.append('')
        return actual_result

    @staticmethod
    def match_lines(expect, got):
        '''
        Match two lists of strings, allowing certain wildcards:
        - In 'expect', if a line is exactly '...', it matches any number of
          arbitrary lines in 'got'; the implementation is trivial and skips
          lines to the first occurence in 'got' that continues after '...'.
        - If an 'expect' line is '... !regex', it matches any number of
          lines like '...', but the given regex must not match any of those
          lines.

        Return 'True' on match, or a string describing the mismatch.
        '''
        def match_line(expect_line, got_line):
            return expect_line == got_line

        ANY = '...'
        ANY_EXCEPT = '... !'

        e = 0
        g = 0
        while e < len(expect):
            if expect[e] == ANY or expect[e].startswith(ANY_EXCEPT):
                wildcard = expect[e]
                e += 1
                g_end = g

                if e >= len(expect):
                    # anything left in 'got' is accepted.
                    g_end = len(got)

                # look for the next occurence of the expected line in 'got'
                while g_end < len(got) and not match_line(expect[e], got[g_end]):
                    g_end += 1

                if wildcard == ANY:
                    # no restrictions on lines
                    g = g_end

                elif wildcard.startswith(ANY_EXCEPT):
                    except_re = re.compile(wildcard[len(ANY_EXCEPT):])
                    while g < g_end:
                        if except_re.search(got[g]):
                          return ('Got forbidden line for wildcard %r:'
                                  ' did not expect %r in line %d of response'
                                  % (wildcard, got[g], g))
                        g += 1

                continue

            if g >= len(got):
                return 'Cannot find line %r' % expect[e]

            if not match_line(expect[e], got[g]):
                return 'Mismatch:\nExpect:\n%r\nGot:\n%r' % (expect[e], got[g])

            e += 1
            g += 1

        if g < len(got):
            return 'Did not expect line %r' % got[g]
        return True

    def feed_commands(self, output, command_strs):
        for command_str in command_strs:
            for command in command_str.splitlines():
                res = self.command(command)
                output.write('\n'.join(res))
                output.write('\n')

def end_process(proc, quiet=False):
    if not proc:
        return

    rc = proc.poll()
    if rc is not None:
        if not quiet:
            print('Process has already terminated with', rc)
        proc.wait()
        return

    proc.terminate()
    time_to_wait_for_term = 5
    wait_step = 0.001
    waited_time = 0
    while True:
        # poll returns None if proc is still running
        if proc.poll() is not None:
            break
        waited_time += wait_step
        # make wait_step approach 1.0
        wait_step = (1. + 5. * wait_step) / 6.
        if waited_time >= time_to_wait_for_term:
            break
        time.sleep(wait_step)

    if proc.poll() is None:
        # termination seems to be slower than that, let's just kill
        proc.kill()
        if not quiet:
            print("Killed child process")
    elif waited_time > .002:
        if not quiet:
            print("Terminating took %.3fs" % waited_time)
    proc.wait()

class Application:
    proc = None
    _devnull = None

    @staticmethod
    def devnull():
        if Application._devnull is None:
            Application._devnull = open(os.devnull, 'w')
        return Application._devnull

    def __init__(self, run_app_str, purge_output=True, quiet=False):
        self.command_tuple = shlex.split(run_app_str)
        self.purge_output = purge_output
        self.quiet = quiet

    def run(self):
        out_err = None
        if self.purge_output:
            out_err = Application.devnull()

        if not self.quiet:
            print('Launching: cd %r; %s' % (os.getcwd(), ' '.join(self.command_tuple)))
        self.proc = subprocess.Popen(self.command_tuple, stdout=out_err, stderr=out_err)

    def stop(self):
        end_process(self.proc, self.quiet)

def verify_application(run_app_str, interact, transcript_file, verbose):
    passed = None
    application = None

    sys.stdout.flush()
    sys.stderr.flush()

    if run_app_str:
        application = Application(run_app_str, purge_output=not verbose)
        application.run()

    try:
        interact.connect()
        interact.verify_transcript_file(transcript_file)
        passed = True
    except:
        traceback.print_exc()
        passed = False
    interact.close()

    if application:
        application.stop()

    sys.stdout.flush()
    sys.stderr.flush()

    return passed

def common_parser(doc=None):
    parser = argparse.ArgumentParser(description=doc,
                                     formatter_class=argparse.RawDescriptionHelpFormatter)
    parser.add_argument('-r', '--run', dest='run_app_str',
                        help='command to run to launch application to test,'
                        ' including command line arguments. If omitted, no'
                        ' application is launched.')
    parser.add_argument('-p', '--port', dest='port',
                        help="Port to reach the application at.")
    parser.add_argument('-H', '--host', dest='host', default='localhost',
                        help="Host to reach the application at.")
    return parser

def parser_add_verify_args(parser):
    parser.add_argument('-u', '--update', dest='update', action='store_true',
                        help='Do not verify, but OVERWRITE transcripts based on'
                        ' the application\'s current behavior. OVERWRITES TRANSCRIPT'
                        ' FILES.')
    parser.add_argument('-v', '--verbose', action='store_true',
                        help='Print commands and application output')
    parser.add_argument('transcript_files', nargs='*', help='transcript file(s) to verify')
    return parser

def parser_add_run_args(parser):
    parser.add_argument('-O', '--output', dest='output_path',
                        help="Write command results to a file instead of stdout."
                        "('-O -' writes to stdout and is the default)")
    parser.add_argument('-c', '--command', dest='cmd_str',
                        help="Run this command (before reading input files, if any)."
                        " multiple commands may be separated by ';'")
    parser.add_argument('cmd_files', nargs='*', help='file(s) with plain commands to run')
    return parser

def main_run_commands(run_app_str, output_path, cmd_str, cmd_files, interact):
    to_stdout = False
    if not output_path or output_path == '-':
        to_stdout = True
        output = sys.stdout
    else:
        output = open(output_path, 'w')

    application = None

    if run_app_str:
        application = Application(run_app_str, quiet=to_stdout)
        application.run()

    try:
        interact.connect()

        if cmd_str:
            interact.feed_commands(output, cmd_str.split(';'))

        for f_path in (cmd_files or []):
            with open(f_path, 'r') as f:
                interact.feed_commands(output, f.read().splitlines())

        if not (cmd_str or cmd_files):
            while True:
                line = sys.stdin.readline()
                if not line:
                    break;
                interact.feed_commands(output, line.split(';'))
    except:
        traceback.print_exc()
    finally:
        if not to_stdout:
            try:
                output.close()
            except:
                traceback.print_exc()

        try:
            interact.close()
        except:
            traceback.print_exc()

        if application:
            try:
                application.stop()
            except:
                traceback.print_exc()

def main_verify_transcripts(run_app_str, transcript_files, interact, verbose):
    results = []
    for t in transcript_files:
        passed = verify_application(run_app_str=run_app_str,
                                    interact=interact,
                                    transcript_file=t,
                                    verbose=verbose)
        results.append((passed, t))

    print('\nRESULTS:')
    all_passed = True
    for passed, t in results:
        print('%s: %s' % ('pass' if passed else 'FAIL', t))
        all_passed = all_passed and passed
    print()

    if not all_passed:
        sys.exit(1)

# vim: tabstop=4 shiftwidth=4 expandtab nocin ai