[all] all simulation output written to a single configurable directory

[EskoDijk]

For running multiple OTNS simulations in sequence, an issue is that presently output files from previous runs may be overwritten. Not all output artefacts are stored in the 'tmp' directory also. This PR ensures that all output files are written to into a single, configurable directory. The default name is 'tmp' but this can be changed by the commandline argument -output. Furthermore, also the OTNS main log which was previously not saved is stored as a file in this directory.

Particular commandline argument changes:
-logfile is changed to -lognode which better expresses its purpose: the log level for OT node logs. -noreplay is changed to -replay, with the default being that the replay file is not generated. Typically,
this file is not used, so now it needs to be explicitly requested.

For logging to terminal, there's now an improved check for whether stdout is a terminal (accepting ANSI sequences) or not a terminal. The dispatcher socket is also stored in the output directory. Because this might be a long name, and socket paths are limited, there's a length check added also.

[gemini-code-assist]

Code Review

This pull request refactors the logging and output management system, introducing a configurable output directory for logs, PCAP files, and simulation replays. Key changes include a revamped logger with file support, updated CLI arguments in otns_main, and adjustments to the dispatcher and simulation logic to respect the new output structure. Feedback highlights a potential compilation error in ensureOutputDirExists due to an incorrect errors package import and redundant logic. Additionally, the Python library implementation currently hardcodes the output path, which breaks consistency with the Go changes and existing methods like save_pcap. There is also a concern regarding the log file being opened twice—once manually and once via Zap—which could lead to interleaved output.

[EskoDijk]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a configurable output directory for simulation results, logs, and PCAP files, moving away from hardcoded paths like /tmp and current.pcap. It includes a significant refactor of the logging system to support simultaneous output to console and files, along with updated CLI flags and environment variable support (OTNS_DATA_PATH) for node flash storage. Feedback suggests ensuring consistent timestamping in the Println function for better event correlation and increasing the file path buffer size in the C-based flash implementation to handle longer paths more robustly.

[gemini-code-assist]

The Println function writes directly to the log file without any timestamping or formatting, whereas Logf uses Zap which includes a timestamp. This results in an inconsistent log file where some lines (like echoed commands and node UART output) lack timestamps, making it harder to correlate events during post-simulation analysis. Consider adding a timestamp to Println when toLogFile is true, similar to how it's done manually in SetLevel.

Suggested change

	func Println(msg string, toConsole bool, toLogFile bool) {
	if toConsole {
	if isLogToTerminal {
	_, _ = fmt.Fprint(os.Stdout, "\033[2K\r") // ANSI sequence to clear the CLI line
	}
	_, _ = fmt.Fprintln(os.Stdout, msg)
	if isLogToTerminal && cbStdout != nil {
	cbStdout.OnStdout()
	}
	}
	_, _ = fmt.Fprint(os.Stdout, msg+"\n")
	if isLogToTerminal && cbStdout != nil {
	cbStdout.OnStdout()
	if toLogFile && logFileHandle != nil {
	_, _ = logFileHandle.WriteString(msg + "\n")
	}
	}
	func Println(msg string, toConsole bool, toLogFile bool) {
	if toConsole {
	if isLogToTerminal {
	_, _ = fmt.Fprint(os.Stdout, "\033[2K\r") // ANSI sequence to clear the CLI line
	}
	_, _ = fmt.Fprintln(os.Stdout, msg)
	if isLogToTerminal && cbStdout != nil {
	cbStdout.OnStdout()
	}
	}
	if toLogFile && logFileHandle != nil {
	ts := time.Now().Format(dateTimeFormat)
	_, _ = logFileHandle.WriteString(ts + " " + msg + "\n")
	}
	}

[gemini-code-assist]

While 512 bytes is often sufficient for file paths in a simulation environment, it is smaller than the standard PATH_MAX (usually 4096 on Linux). If a user provides a very long path via the -output argument, snprintf will safely truncate the string, but the resulting path might be invalid or point to the wrong location. Consider using PATH_MAX for the buffer size to be more robust.

    char        fileName[4096];