Problem Statement

Create a Logger that receives an ordered collection of handlers. When log(message) is invoked, the message must pass through those handlers in sequence.

Provide these handlers:

1. RemoveStringHandler
   • Deletes every instance of a configured substring before any output.
2. TruncateHandler
   • Limits a message to a configured maximum character count before output.
3. CapitalizeHandler
   • Converts the whole message to uppercase before output.
   • In this exercise, “capitalize” refers to uppercasing every character, rather than changing only the first character.
4. StoreHandler
   • Adds messages to an internal list and does not print them.

Suggested Interface

from typing import Optional

class Logger:
    def __init__(self, handlers: list["LogHandler"]):
        pass

    def log(self, message: str) -> Optional[str]:
        """
        Process one log message.

        Returns the printed message when the logger prints.
        Returns None when output is suppressed, such as by StoreHandler.
        """
        pass

class LogHandler:
    def handle(self, message: str) -> tuple[str, bool]:
        """
        Returns:
            (new_message, should_print)
        """
        pass

Example Usage

logger = Logger([
    RemoveStringHandler("trace: "),
    TruncateHandler(11),
    CapitalizeHandler(),
])

logger.log("trace: daily report generated")

Expected Output

DAILY REPOR

The handlers change the text in this order:

1. Remove "trace: ": "daily report generated"
2. Keep only 11 characters: "daily repor"
3. Convert to uppercase: "DAILY REPOR"

Store Example

store = StoreHandler()
logger = Logger([
    RemoveStringHandler("[private] "),
    CapitalizeHandler(),
    store,
])

logger.log("[private] invoice batch delayed")
logger.log("[private] account update finished")

print(store.messages)

Expected Output

['INVOICE BATCH DELAYED', 'ACCOUNT UPDATE FINISHED']

The calls to logger.log(...) produce no printed output because StoreHandler retains the processed messages and disables printing.

---

Problem Statement

Assume that the logger now keeps messages internally. Add, or describe, a keyword-search capability.

A simple initial request may be:

def search(self, keyword: str) -> list[str]:
    """
    Return stored messages that contain keyword.
    """
    pass

A later question may ask for a faster design.