o8_pics_size/.github/copilot-instructions.md

Copilot Instructions for o8_pics_size

Build, test, and lint commands

• Build: cargo build
• Run app: cargo run
• Run all tests: cargo test
• Run a single test: cargo test <test_name>
• Formatting check: cargo fmt --check
• Lint (if available in your toolchain): cargo clippy -- -D warnings

High-level architecture

The application is a single-binary Rust CLI (src/main.rs) built as a staged pipeline:

1. Pick an input Excel file (.xls/.xlsx) via rfd::FileDialog.
2. Read workbook/sheet data with calamine.
3. Use terminal UI selectors (dialoguer::Select) to choose:
   • sheet
   • Cikkszám column
   • Url column
   • img_sequence column
4. Build input rows from sheet data (header row is row 0, data starts from row 1).
5. Download images from URLs using blocking reqwest.
6. Decode image bytes with image to extract dimensions; compute size from downloaded byte length.
7. Export results to a new workbook with rust_xlsxwriter, saved as result_[uuid].xlsx next to the input file.

Core helper responsibilities are split into functions in main.rs:

• selection helpers: prompt_sheet_selection, prompt_column_selection
• sheet parsing helpers: extract_headers, collect_input_rows, cell_string
• image metadata fetch: fetch_image_metadata
• output generation: build_output_path, write_results_excel

Key conventions in this repository

• Fail-fast error handling: most failures print a clear eprintln! message and exit with status 1.
• Column naming is contract-like: output headers are currently written as:
  • Cikkszám
  • Sqeuence (keep this spelling unless intentionally changed)
  • Url
  • Width (px)
  • Height (px)
  • Size (KB)
• Interactive flow is TUI-driven: keep sheet/column selection cursor-based (dialoguer::Select), not numeric text prompts.
• Output path pattern is fixed: write result files as result_[uuid].xlsx in the same directory as the source workbook.