#!/usr/bin/python3

"""
Best-practices tracker for Tor source code.

Go through the various .c files and collect metrics about them. If the metrics
violate some of our best practices and they are not found in the optional
exceptions file, then log a problem about them.

We currently do metrics about file size, function size and number of includes.

practracker.py should be run with its second argument pointing to the Tor
top-level source directory like this:
  $ python3 ./scripts/maint/practracker/practracker.py .

The exceptions file is meant to be initialized once with the current state of
the source code and then get saved in the repository for ever after:
  $ python3 ./scripts/maint/practracker/practracker.py . > ./scripts/maint/practracker/exceptions.txt
"""

import os, sys

import metrics
import util
import problem

# The filename of the exceptions file (it should be placed in the practracker directory)
EXCEPTIONS_FNAME = "./exceptions.txt"

# Recommended file size
MAX_FILE_SIZE = 3000 # lines
# Recommended function size
MAX_FUNCTION_SIZE = 100 # lines
# Recommended number of #includes
MAX_INCLUDE_COUNT = 50

#######################################################

# ProblemVault singleton
ProblemVault = None

# The Tor source code topdir
TOR_TOPDIR = None

#######################################################

def consider_file_size(fname, f):
    """Consider file size issues for 'f' and return True if a new issue was found"""
    file_size = metrics.get_file_len(f)
    if file_size > MAX_FILE_SIZE:
        p = problem.FileSizeProblem(fname, file_size)
        return ProblemVault.register_problem(p)
    return False

def consider_includes(fname, f):
    """Consider #include issues for 'f' and return True if a new issue was found"""
    include_count = metrics.get_include_count(f)

    if include_count > MAX_INCLUDE_COUNT:
        p = problem.IncludeCountProblem(fname, include_count)
        return ProblemVault.register_problem(p)
    return False

def consider_function_size(fname, f):
    """Consider the function sizes for 'f' and return True if a new issue was found"""
    found_new_issues = False

    for name, lines in metrics.get_function_lines(f):
        # Don't worry about functions within our limits
        if lines <= MAX_FUNCTION_SIZE:
            continue

        # That's a big function! Issue a problem!
        canonical_function_name = "%s:%s()" % (fname, name)
        p = problem.FunctionSizeProblem(canonical_function_name, lines)
        found_new_issues |= ProblemVault.register_problem(p)

    return found_new_issues

#######################################################

def consider_all_metrics(files_list):
    """Consider metrics for all files, and return True if new issues were found"""
    found_new_issues = False
    for fname in files_list:
        with open(fname, 'r') as f:
            found_new_issues |= consider_metrics_for_file(fname, f)
    return found_new_issues

def consider_metrics_for_file(fname, f):
    """
    Consider the various metrics for file with filename 'fname' and file descriptor 'f'.
    Return True if we found new issues.
    """
    # Strip the useless part of the path
    if fname.startswith(TOR_TOPDIR):
        fname = fname[len(TOR_TOPDIR):]

    found_new_issues = False

    # Get file length
    found_new_issues |= consider_file_size(fname, f)

    # Consider number of #includes
    f.seek(0)
    found_new_issues |= consider_includes(fname, f)

    # Get function length
    f.seek(0)
    found_new_issues |= consider_function_size(fname, f)

    return found_new_issues

def main():
    if (len(sys.argv) != 2):
        print("Usage:\n\t$ practracker.py <tor topdir>\n\t(e.g. $ practracker.py ~/tor/)")
        return

    global TOR_TOPDIR
    TOR_TOPDIR = sys.argv[1]
    exceptions_file = os.path.join(TOR_TOPDIR, "scripts/maint/practracker", EXCEPTIONS_FNAME)

    # 1) Get all the .c files we care about
    files_list = util.get_tor_c_files(TOR_TOPDIR)

    # 2) Initialize problem vault and load an optional exceptions file so that
    # we don't warn about the past
    global ProblemVault
    ProblemVault = problem.ProblemVault(exceptions_file)

    # 3) Go through all the files and report problems if they are not exceptions
    found_new_issues = consider_all_metrics(files_list)

    # If new issues were found, try to give out some advice to the developer on how to resolve it.
    if (found_new_issues):
        new_issues_str = "practracker FAILED as indicated by the problem lines above. Please use the exceptions file ({}) to find any previous state of these problems. If you are unable to fix the underlying best-practices issue right now then you need to either update the relevant exception line or add a new one.".format(exceptions_file)
        print(new_issues_str)

    sys.exit(found_new_issues)

if __name__ == '__main__':
    main()