import random
import re

import sqlite_static_helper


def _quote_str(text: str) -> str:
  """O'Reilly -> 'O''Reilly'"""
  return "'" + text.replace("'", "''") + "'"


_TOKEN_RE = re.compile(
  r"""
    (?P<line_comment>--[^\n]*)                            |
    (?P<block_comment>/\*.*?\*/)                          |
    (?P<string>'(?:[^']|'')*')                            |
    (?P<dquoted>"(?:[^"]|"")*")                           |
    (?P<bracket>\[[^\]]*\])                               |
    (?P<backtick>`(?:[^`]|``)*`)                          |
    (?P<blob>[xX]'[0-9a-fA-F]*')                          |
    (?P<number>\b\d+(?:\.\d+)?(?:[eE][+-]?\d+)?\b)        |
    (?P<ident>[A-Za-z_][A-Za-z0-9_]*)                     |
    (?P<op>[<>!=]=|<>|\|\||::|->>?|[+\-*/%<>=&|^~,.;()@]) |
    (?P<ws>\s+)                                           |
    (?P<other>.)
  """,
  re.VERBOSE | re.DOTALL,
)


def _tokenize(s: str) -> list[tuple[str | None, str]]:
  """[("line_comment", "-- This is a comment!"), ("number", 0), ...]"""
  return [(m.lastgroup, m.group()) for m in _TOKEN_RE.finditer(s)]


_UNSAFE_KINDS = {
  "line_comment", "block_comment", "string", "dquoted", "bracket", "backtick",
  "blob"
}


def _sub_in_safe(s: str, pattern: re.Pattern, repl, max_subs: int = 1) -> str:
  """Run `pattern.sub(repl, …)` only outside strings/comments/blob literals."""
  if max_subs <= 0:
    return s
  parts: list[str] = []
  done = 0
  for kind, text in _tokenize(s):
    if done >= max_subs or kind in _UNSAFE_KINDS:
      parts.append(text)
      continue
    new_text, n = pattern.subn(repl, text, count=max_subs - done)
    parts.append(new_text)
    done += n
  return ''.join(parts)


_NUM_RE = re.compile(r'\b\d+(?:\.\d+)?(?:[eE][+-]?\d+)?\b')


def mut_replace_num_with_edge_int(s: str) -> str:
  """Replace the left-most number with a random edge-case integer"""
  return _sub_in_safe(
    s, _NUM_RE, lambda m: str(random.choice(sqlite_static_helper.EDGE_INTS)), 1)


def mut_replace_num_with_random_int(s: str) -> str:
  """Replace the left-most number with a random integer"""
  return _sub_in_safe(s, _NUM_RE,
                      lambda m: str(random.randint(-(2**63), 2**63 - 1)), 1)


def mut_replace_num_with_edge_float(s: str) -> str:
  """Replace the left-most number with a random edge-case floating-point number"""
  return _sub_in_safe(
    s, _NUM_RE, lambda m: repr(random.choice(sqlite_static_helper.EDGE_FLOATS)),
    1)


def mut_replace_num_with_edge_string(s: str) -> str:
  """Replace the left-most number with a random edge-case string"""
  return _sub_in_safe(
    s, _NUM_RE,
    lambda m: _quote_str(random.choice(sqlite_static_helper.EDGE_STRINGS)), 1)


def mut_replace_num_with_random_hex(s: str) -> str:
  """Replace the left-most number with a random hex blob"""
  n = random.randint(0, 16)
  val = "x'" + ''.join(random.choices('0123456789abcdef', k=n * 2)) + "'"
  return _sub_in_safe(s, _NUM_RE, lambda m: val, 1)


def mut_replace_num_with_null(s: str) -> str:
  """Replace the left-most number with NULL"""
  return _sub_in_safe(s, _NUM_RE, lambda m: 'NULL', 1)


def mut_wrap_num_in_cast(s: str) -> str:
  """Cast the left-most number to a different data type"""
  target = random.choice(sqlite_static_helper.TYPES)
  return _sub_in_safe(s, _NUM_RE, lambda m: f'CAST({m.group(0)} AS {target})',
                      1)


def _wrap_value(s: str, templates: list[str]) -> str:
  tpl = random.choice(templates)
  return _sub_in_safe(s, _NUM_RE, lambda m: tpl.replace('{v}', m.group(0)), 1)


def mut_wrap_num_in_datetime_func(s: str) -> str:
  """Wrap the left-most number in a date/time function"""
  return _wrap_value(s, sqlite_static_helper.DATETIME_FUNCS)


def mut_wrap_num_in_core_func(s: str) -> str:
  """Wrap the left-most number in core function"""
  return _wrap_value(s, sqlite_static_helper.CORE_FUNCS)


def mut_wrap_num_in_math_func(s: str) -> str:
  """Wrap the left-most number in a math function"""
  return _wrap_value(s, sqlite_static_helper.MATH_FUNCS)


def mut_wrap_num_in_json_func(s: str) -> str:
  """Wrap the left-most number in a JSON function"""
  return _wrap_value(s, sqlite_static_helper.JSON_VALUE_FUNCS)