#!/usr/bin/env python3
"""Produce a report of all assertions in the MongoDB server codebase.

Parses .cpp files for assertions and verifies assertion codes are distinct.
Optionally replaces zero codes in source code with new distinct values.
"""

import bisect
import os.path
import sys
from collections import defaultdict, namedtuple
from functools import reduce
from optparse import OptionParser
from pathlib import Path

# Get relative imports to work when the package is not installed on the PYTHONPATH.
if __name__ == "__main__" and __package__ is None:
    sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

try:
    import regex as re
except ImportError:
    print("*** Run 'pip3 install --user regex' to speed up error code checking")
    import re  # type: ignore

MAXIMUM_CODE = 99999999  # JIRA Ticket + XX
MIN_EXTENSION_RESERVED_CODE = 65000
MAX_EXTENSION_RESERVED_CODE = 71000

codes = []  # type: ignore

# Each AssertLocation identifies the C++ source location of an assertion
AssertLocation = namedtuple("AssertLocation", ["sourceFile", "byteOffset", "lines", "code"])

list_files = False

# Using multiple patterns is faster than one pattern with | in it with both re and regex libraries
# since they use backtracking regex engines. Re-evaluate if we ever switch to an NFA-based regex
# engine.
_CODE_PATTERNS = [
    re.compile(p + r"\s*(?P<code>\d+)", re.MULTILINE | re.VERBOSE)
    for p in [
        # All the asserts and their optional variant suffixes
        r"""
            (?:f|i|m|t|u)(?:assert)
            (?:ed)?
            (?:Failed)?
            (?:WithStatus)?
            (?:NoTrace)?
            (?:StatusOK)?
            (?:WithContext)?
            \s*\(
        """,
        r"MONGO_UN(?:REACHABLE|IMPLEMENTED)_TASSERT\(",
        # DBException and AssertionException constructors
        r"(?:DB|Assertion)Exception\s*[({]",
        # Calls to all LOGV2* variants
        r"LOGV2(?:\w*)?\s*\(",
        # Forwards a dynamic code to LOGV2
        r"logAndBackoff\(",
        r"logWTErrorMessage\(",
        # Error coersions
        r"ErrorCodes::Error\s*[({]",
    ]
]

_DIR_EXCLUDE_RE = re.compile(r"(pcre2.*|debian.*)")

_FILE_INCLUDE_RE = re.compile(r".*\.(cpp|c|h|py|idl)")


def get_all_source_files(prefix="."):
    """Return source files."""

    def walk(path):
        for fx in path.iterdir():
            if fx.is_dir():
                if fx.is_symlink() and fx.parent.name != "modules":
                    continue
                if _DIR_EXCLUDE_RE.fullmatch(fx.name):
                    continue
                for child in walk(fx):
                    yield child
            elif fx.is_file() and _FILE_INCLUDE_RE.fullmatch(fx.name):
                yield fx

    for child in walk(Path(prefix)):
        yield str(child)


def foreach_source_file(callback, src_root):
    """Invoke a callback on the text of each source file."""
    for source_file in get_all_source_files(prefix=src_root):
        if list_files:
            print("scanning file: " + source_file)
        with open(source_file, "r", encoding="utf-8") as fh:
            callback(source_file, fh.read())


def parse_source_files(callback, src_root):
    """Walk MongoDB sourcefiles and invoke a callback for each AssertLocation found."""

    def scan_for_codes(source_file, text):
        for pat in _CODE_PATTERNS:
            for match in pat.finditer(text):
                # Note that this will include the text of the full match but will report the
                # position of the beginning of the code portion rather than the beginning of the
                # match. This is to position editors on the spot that needs to change.
                loc = AssertLocation(
                    source_file, match.start("code"), match.group(0), match.group("code")
                )
                callback(loc)

    foreach_source_file(scan_for_codes, src_root)


def get_line_and_column_for_position(loc, _file_cache=None):
    """Convert an absolute position in a file into a line number."""
    if _file_cache is None:
        _file_cache = {}
    if loc.sourceFile not in _file_cache:
        with open(loc.sourceFile) as fh:
            text = fh.read()
            line_offsets = [0]
            for line in text.splitlines(True):
                line_offsets.append(line_offsets[-1] + len(line))
            _file_cache[loc.sourceFile] = line_offsets

    # These are both 1-based, but line is handled by starting the list with 0.
    line = bisect.bisect(_file_cache[loc.sourceFile], loc.byteOffset)
    column = loc.byteOffset - _file_cache[loc.sourceFile][line - 1] + 1
    return (line, column)


def is_terminated(lines):
    """Determine if assert is terminated, from .cpp/.h source lines as text."""
    code_block = " ".join(lines)
    return ";" in code_block or code_block.count("(") - code_block.count(")") <= 0


def get_next_code(seen, server_ticket=0):
    """Find next unused assertion code."""
    if not codes:
        (_, _, seen) = read_error_codes()

    if server_ticket:
        # Each SERVER ticket is allocated 100 error codes ranging from TICKET_00 -> TICKET_99.
        def generator(seen, ticket):
            avail_codes = list(range(ticket * 100, (ticket + 1) * 100))
            avail_codes.reverse()
            while avail_codes:
                code = avail_codes.pop()
                if str(code) in seen:
                    continue
                yield code
            return "No more available codes for ticket. Ticket: {}".format(ticket)

        return generator(seen, server_ticket)

    # No server ticket. Return a generator that counts starting at highest + 1.
    highest = reduce(lambda x, y: max(int(x), int(y)), (loc.code for loc in codes))
    return iter(range(highest + 1, MAXIMUM_CODE))


def read_error_codes(src_root="src/mongo"):
    """Define callback, call parse_source_files() with callback, save matches to global codes list."""
    seen = {}
    errors = []
    dups = defaultdict(list)
    skips = []
    malformed = []  # type: ignore
    reserved = []

    # define validation callbacks
    def check_dups(assert_loc):
        """Check for duplicates."""
        codes.append(assert_loc)
        code = assert_loc.code

        if code not in seen:
            seen[code] = assert_loc
        else:
            if code not in dups:
                # on first duplicate, add original to dups, errors
                dups[code].append(seen[code])
                errors.append(seen[code])

            dups[code].append(assert_loc)
            errors.append(assert_loc)

    def validate_code(assert_loc):
        """Check for malformed codes or pre-reserved codes."""
        code = int(assert_loc.code)
        if code > MAXIMUM_CODE:
            malformed.append(assert_loc)
            errors.append(assert_loc)
        elif code >= MIN_EXTENSION_RESERVED_CODE and code < MAX_EXTENSION_RESERVED_CODE:
            reserved.append(assert_loc)
            errors.append(assert_loc)

    def callback(assert_loc):
        validate_code(assert_loc)
        check_dups(assert_loc)

    parse_source_files(callback, src_root)

    if "0" in seen:
        code = "0"
        bad = seen[code]
        errors.append(bad)
        line, col = get_line_and_column_for_position(bad)
        print("ZERO_CODE:")
        print("  %s:%d:%d:%s" % (bad.sourceFile, line, col, bad.lines))

    for loc in skips:
        line, col = get_line_and_column_for_position(loc)
        print("EXCESSIVE SKIPPING OF ERROR CODES:")
        print("  %s:%d:%d:%s" % (loc.sourceFile, line, col, loc.lines))

    for code, locations in list(dups.items()):
        print("DUPLICATE IDS: %s" % code)
        for loc in locations:
            line, col = get_line_and_column_for_position(loc)
            print("  %s:%d:%d:%s" % (loc.sourceFile, line, col, loc.lines))

    for loc in malformed:
        line, col = get_line_and_column_for_position(loc)
        print("MALFORMED ID: %s" % loc.code)
        print("  %s:%d:%d:%s" % (loc.sourceFile, line, col, loc.lines))

    for loc in reserved:
        line, col = get_line_and_column_for_position(loc)
        print("USE OF ALREADY RESERVED ID: %s" % loc.code)
        print("  %s:%d:%d:%s" % (loc.sourceFile, line, col, loc.lines))

    return (codes, errors, seen)


def replace_bad_codes(errors, next_code_generator):
    """
    Modify C++ source files to replace invalid assertion codes.

    For now, we only modify zero codes.

    :param errors: list of AssertLocation
    :param next_code_generator: generator -> int, next non-conflicting assertion code
    """

    zero_errors = [e for e in errors if int(e.code) == 0]
    skip_errors = [e for e in errors if int(e.code) != 0]

    for loc in skip_errors:
        line, col = get_line_and_column_for_position(loc)
        print("SKIPPING NONZERO code=%s: %s:%d:%d" % (loc.code, loc.sourceFile, line, col))

    # Dedupe, sort, and reverse so we don't have to update offsets as we go.
    for assert_loc in reversed(sorted(set(zero_errors))):
        (source_file, byte_offset, _, _) = assert_loc
        line_num, _ = get_line_and_column_for_position(assert_loc)
        print("UPDATING_FILE: %s:%s" % (source_file, line_num))

        ln = line_num - 1

        with open(source_file, "r+") as fh:
            print("LINE_%d_BEFORE:%s" % (line_num, fh.readlines()[ln].rstrip()))

            fh.seek(0)
            text = fh.read()
            assert text[byte_offset] == "0"
            fh.seek(0)
            fh.write(text[:byte_offset])
            fh.write(str(next(next_code_generator)))
            fh.write(text[byte_offset + 1 :])
            fh.seek(0)

            print("LINE_%d_AFTER :%s" % (line_num, fh.readlines()[ln].rstrip()))


def coerce_to_number(ticket_value):
    """Coerce the input into a number.

    If the input is a number, return itself. Otherwise parses input strings of two forms.
    'SERVER-12345' and '12345' will both return 12345'.
    """
    if isinstance(ticket_value, int):
        return ticket_value

    ticket_re = re.compile(r"(?:SERVER-)?(\d+)", re.IGNORECASE)
    matches = ticket_re.fullmatch(ticket_value)
    if not matches:
        print("Unknown ticket number. Input: " + ticket_value)
        return -1

    return int(matches.group(1))


def main():
    """Validate error codes."""

    os.chdir(os.environ.get("BUILD_WORKSPACE_DIRECTORY", "."))

    parser = OptionParser(description=__doc__.strip())
    parser.add_option(
        "--fix",
        dest="replace",
        action="store_true",
        default=False,
        help="Fix zero codes in source files [default: %default]",
    )
    parser.add_option(
        "-q",
        "--quiet",
        dest="quiet",
        action="store_true",
        default=False,
        help="Suppress output on success [default: %default]",
    )
    parser.add_option(
        "--list-files",
        dest="list_files",
        action="store_true",
        default=False,
        help="Print the name of each file as it is scanned [default: %default]",
    )
    parser.add_option(
        "--ticket",
        dest="ticket",
        type="str",
        action="store",
        default=None,
        help="Generate error codes for a given SERVER ticket number. Inputs can be of"
        " the form: `--ticket=12345` or `--ticket=SERVER-12345`.",
    )
    options, extra = parser.parse_args()
    if extra:
        parser.error(f"Unrecognized arguments: {' '.join(extra)}")

    global list_files
    list_files = options.list_files

    (_, errors, seen) = read_error_codes()
    ok = len(errors) == 0

    if ok and options.quiet:
        return

    print("ok: %s" % ok)

    if options.ticket:
        next_code_gen = get_next_code(seen, coerce_to_number(options.ticket))
    else:
        next_code_gen = get_next_code(seen, 0)

    if ok:
        sys.exit(0)
    elif options.replace:
        replace_bad_codes(errors, next_code_gen)
    else:
        print(ERROR_HELP)
        sys.exit(1)


ERROR_HELP = """
ERRORS DETECTED. To correct, run "buildscripts/errorcodes.py --fix" to replace zero codes.
Other errors require manual correction.
"""

if __name__ == "__main__":
    main()