"""
从 DBHub sql-parser.ts 等价移植：按方言剥离注释/字符串、切分语句。
参见 dbhub/src/utils/sql-parser.ts
"""

from __future__ import annotations

import re
from typing import Callable, Literal, TypedDict

ConnectorType = Literal["postgres", "mysql", "mariadb", "sqlite", "sqlserver"]


class _Token(TypedDict):
    type: int  # 0 Plain, 1 Comment, 2 QuotedBlock
    end: int


_TOKEN_PLAIN = 0
_TOKEN_COMMENT = 1
_TOKEN_QUOTED = 2


def _plain_token(i: int) -> _Token:
    return {"type": _TOKEN_PLAIN, "end": i + 1}


def _scan_single_line_comment(sql: str, i: int) -> _Token | None:
    if i + 1 >= len(sql) or sql[i] != "-" or sql[i + 1] != "-":
        return None
    j = i
    while j < len(sql) and sql[j] != "\n":
        j += 1
    return {"type": _TOKEN_COMMENT, "end": j}


def _scan_multi_line_comment(sql: str, i: int) -> _Token | None:
    if i + 1 >= len(sql) or sql[i] != "/" or sql[i + 1] != "*":
        return None
    j = i + 2
    while j + 1 < len(sql) and not (sql[j] == "*" and sql[j + 1] == "/"):
        j += 1
    if j + 1 < len(sql):
        j += 2
    return {"type": _TOKEN_COMMENT, "end": j}


def _scan_multi_line_comment_mysql(sql: str, i: int) -> _Token | None:
    if i + 1 >= len(sql) or sql[i] != "/" or sql[i + 1] != "*":
        return None
    nxt = sql[i + 2] if i + 2 < len(sql) else ""
    nxt2 = sql[i + 3] if i + 3 < len(sql) else ""
    if nxt == "!" or (nxt == "M" and nxt2 == "!"):
        return None
    return _scan_multi_line_comment(sql, i)


def _scan_nested_multi_line_comment(sql: str, i: int) -> _Token | None:
    if i + 1 >= len(sql) or sql[i] != "/" or sql[i + 1] != "*":
        return None
    j = i + 2
    depth = 1
    while j < len(sql) and depth > 0:
        if j + 1 < len(sql) and sql[j] == "/" and sql[j + 1] == "*":
            depth += 1
            j += 2
        elif j + 1 < len(sql) and sql[j] == "*" and sql[j + 1] == "/":
            depth -= 1
            j += 2
        else:
            j += 1
    return {"type": _TOKEN_COMMENT, "end": j}


def _scan_single_quoted_string(sql: str, i: int) -> _Token | None:
    if sql[i] != "'":
        return None
    j = i + 1
    while j < len(sql):
        if j + 1 < len(sql) and sql[j] == "'" and sql[j + 1] == "'":
            j += 2
        elif sql[j] == "'":
            j += 1
            break
        else:
            j += 1
    return {"type": _TOKEN_QUOTED, "end": j}


def _scan_double_quoted_string(sql: str, i: int) -> _Token | None:
    if sql[i] != '"':
        return None
    j = i + 1
    while j < len(sql):
        if j + 1 < len(sql) and sql[j] == '"' and sql[j + 1] == '"':
            j += 2
        elif sql[j] == '"':
            j += 1
            break
        else:
            j += 1
    return {"type": _TOKEN_QUOTED, "end": j}


_dollar_quote_open_regex = re.compile(r"^\$([a-zA-Z_]\w*)?\$")


def _scan_dollar_quoted_block(sql: str, i: int) -> _Token | None:
    if sql[i] != "$":
        return None
    nxt = sql[i + 1] if i + 1 < len(sql) else ""
    if nxt.isdigit():
        return None
    remaining = sql[i:]
    m = _dollar_quote_open_regex.match(remaining)
    if not m:
        return None
    tag = m.group(0)
    body_start = i + len(tag)
    close_idx = sql.find(tag, body_start)
    end = close_idx + len(tag) if close_idx != -1 else len(sql)
    return {"type": _TOKEN_QUOTED, "end": end}


def _scan_backtick_quoted_identifier(sql: str, i: int) -> _Token | None:
    if sql[i] != "`":
        return None
    j = i + 1
    while j < len(sql):
        if j + 1 < len(sql) and sql[j] == "`" and sql[j + 1] == "`":
            j += 2
        elif sql[j] == "`":
            j += 1
            break
        else:
            j += 1
    return {"type": _TOKEN_QUOTED, "end": j}


def _scan_bracket_quoted_identifier(sql: str, i: int) -> _Token | None:
    if sql[i] != "[":
        return None
    j = i + 1
    while j < len(sql):
        if j + 1 < len(sql) and sql[j] == "]" and sql[j + 1] == "]":
            j += 2
        elif sql[j] == "]":
            j += 1
            break
        else:
            j += 1
    return {"type": _TOKEN_QUOTED, "end": j}


def _scan_token_ansi(sql: str, i: int) -> _Token:
    return (
        _scan_single_line_comment(sql, i)
        or _scan_multi_line_comment(sql, i)
        or _scan_single_quoted_string(sql, i)
        or _scan_double_quoted_string(sql, i)
        or _plain_token(i)
    )


def _scan_token_postgres(sql: str, i: int) -> _Token:
    return (
        _scan_single_line_comment(sql, i)
        or _scan_nested_multi_line_comment(sql, i)
        or _scan_single_quoted_string(sql, i)
        or _scan_double_quoted_string(sql, i)
        or _scan_dollar_quoted_block(sql, i)
        or _plain_token(i)
    )


def _scan_token_mysql(sql: str, i: int) -> _Token:
    return (
        _scan_single_line_comment(sql, i)
        or _scan_multi_line_comment_mysql(sql, i)
        or _scan_single_quoted_string(sql, i)
        or _scan_double_quoted_string(sql, i)
        or _scan_backtick_quoted_identifier(sql, i)
        or _plain_token(i)
    )


def _scan_token_sqlite(sql: str, i: int) -> _Token:
    return (
        _scan_single_line_comment(sql, i)
        or _scan_multi_line_comment(sql, i)
        or _scan_single_quoted_string(sql, i)
        or _scan_double_quoted_string(sql, i)
        or _scan_backtick_quoted_identifier(sql, i)
        or _scan_bracket_quoted_identifier(sql, i)
        or _plain_token(i)
    )


def _scan_token_sqlserver(sql: str, i: int) -> _Token:
    return (
        _scan_single_line_comment(sql, i)
        or _scan_multi_line_comment(sql, i)
        or _scan_single_quoted_string(sql, i)
        or _scan_double_quoted_string(sql, i)
        or _scan_bracket_quoted_identifier(sql, i)
        or _plain_token(i)
    )


_DIALECT_SCANNERS: dict[ConnectorType, Callable[[str, int], _Token]] = {
    "postgres": _scan_token_postgres,
    "mysql": _scan_token_mysql,
    "mariadb": _scan_token_mysql,
    "sqlite": _scan_token_sqlite,
    "sqlserver": _scan_token_sqlserver,
}


def _get_scanner(dialect: ConnectorType | None) -> Callable[[str, int], _Token]:
    if dialect and dialect in _DIALECT_SCANNERS:
        return _DIALECT_SCANNERS[dialect]
    return _scan_token_ansi


def strip_comments_and_strings(sql: str, dialect: ConnectorType | None = None) -> str:
    """Replace comments, string literals, and dialect-specific quoted blocks with a single space each."""
    scan_token = _get_scanner(dialect)
    parts: list[str] = []
    plain_start = -1
    i = 0
    n = len(sql)
    while i < n:
        token = scan_token(sql, i)
        if token["type"] == _TOKEN_PLAIN:
            if plain_start == -1:
                plain_start = i
        else:
            if plain_start != -1:
                parts.append(sql[plain_start:i])
                plain_start = -1
            parts.append(" ")
        i = token["end"]
    if plain_start != -1:
        parts.append(sql[plain_start:])
    return "".join(parts)


def split_sql_statements(sql: str, dialect: ConnectorType | None = None) -> list[str]:
    """Split SQL into individual statements, handling semicolons inside quoted contexts."""
    scan_token = _get_scanner(dialect)
    statements: list[str] = []
    stmt_start = 0
    i = 0
    n = len(sql)
    while i < n:
        if sql[i] == ";":
            trimmed = sql[stmt_start:i].strip()
            if trimmed:
                statements.append(trimmed)
            stmt_start = i + 1
            i += 1
            continue
        token = scan_token(sql, i)
        i = token["end"]
    trimmed = sql[stmt_start:].strip()
    if trimmed:
        statements.append(trimmed)
    return statements