Here is a detailed checklist of all items to be implemented for the DTS tool.

Phase 1: Setup and Configuration

• Project: Create dts directory.
• Project: Initialize Go module github.com/fluxnull/dts.
• Code: Create main.go with initial boilerplate (imports, constants).
• Config: Define the config struct to hold all runtime parameters.

Phase 2: User Interface

• CLI: Implement parsing for all command-line flags (-f, -l, -r, -nh, -q, -o, -n, -h).
• CLI: Ensure -r/--range flag correctly parses the START...END format.
• CLI: Implement validation to ensure exactly one of -f or -l is used.
• CLI: Implement the printHelp() function with the full, specified help text.
• Interactive Mode (Windows):
  • Implement logic in main() to detect when to enter interactive mode.
  • Create the runInteractiveMode() function.
  • In interactive mode, display file stats (name, path, total lines).
  • Implement the series of interactive prompts for header, split mode, and count.
  • Implement the animated processing spinner.
  • Implement the "Press ENTER to exit" prompt on completion.

Phase 3: Core Functionality

• Helpers: Implement the parseLineCount() function to handle K/M suffixes.
• File I/O: Implement file opening with syscall optimizations for Windows and Linux.
• Core Logic: Implement the countLinesAndIndex() function for concurrent, chunk-based line counting and sparse index creation.
• Core Logic: Implement resolveRange() to parse keywords (BOF, COF, EOF) and numbers.
• Core Logic: Implement header extraction logic to read and store the first line as a byte slice.
• Core Logic: Implement the splitting algorithm for -lines mode (single-pass streaming).
• Core Logic: Implement the splitting algorithm for -files mode (two-pass, concurrent writers).
• Core Logic: Implement the generateName() function for creating formatted output filenames.

Phase 4: Finalization and Verification

• Assembly: Tie all components together in the main() function to handle all execution paths.
• Error Handling: Ensure robust error handling and that partial output files are deleted on failure.
• Testing:
  • Test -f mode with a sample file.
  • Test -l mode with a sample file.
  • Test -r mode with various ranges (numeric, keyword, mixed).
  • Test -nh and -q flags.
  • On Windows, test the interactive drag-and-drop mode.
  • Verify output files are byte-for-byte correct.
• Build: Create final cross-platform executables for Linux, Windows, and macOS.