import shlex
from collections import OrderedDict
from io import BufferedIOBase, TextIOBase


class LogParseError(ValueError):
    """Raised when the uploaded log file cannot be parsed."""


def parse_log_file(stream: BufferedIOBase | TextIOBase) -> tuple[list[dict[str, str]], list[str]]:
    """Parse a UTF-8 log file where each line contains shell-like key/value tokens."""
    raw_bytes = stream.read()
    if isinstance(raw_bytes, str):
        content = raw_bytes
    else:
        content = raw_bytes.decode("utf-8")

    records: list[dict[str, str]] = []
    seen_keys: OrderedDict[str, None] = OrderedDict()

    for line_number, raw_line in enumerate(content.splitlines(), start=1):
        line = raw_line.strip()
        if not line:
            continue

        try:
            tokens = shlex.split(line, posix=True)
        except ValueError as exc:
            raise LogParseError(f"Line {line_number}: invalid shell-style quoting.") from exc

        record: dict[str, str] = {}
        for token in tokens:
            if "=" not in token:
                raise LogParseError(
                    f"Line {line_number}: token '{token}' is missing '='."
                )

            key, value = token.split("=", 1)
            if not key:
                raise LogParseError(f"Line {line_number}: empty key is not allowed.")

            record[key] = value
            seen_keys.setdefault(key, None)

        records.append(record)

    return records, list(seen_keys.keys())