# REQUIREMENTS.md

Numbered, categorized requirements list — short form. The companion to USER-GUIDE.md and TECHNICAL.md; updated with every shipped capability.

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## 1. File handling

1.1 File size: ≤ 1 GB (target; bigger files work but the gate's full-DataFrame Apply pass scales linearly).
1.2 Input formats: CSV, TSV, XLSX, XLS.
1.3 Output formats: CSV, TSV.
1.4 Excel: multi-sheet workbook picker.
1.5 Empty file: detected, blocks gate with `empty_input` error finding.

## 2. Input encodings (auto-detected)

2.1 Unicode: UTF-8, UTF-8 with BOM, UTF-16 LE/BE with BOM, UTF-16 LE without BOM (best-effort).
2.2 Western: cp1252, ISO-8859-1, ISO-8859-15, Mac Roman.
2.3 Eastern European: cp1250, ISO-8859-2.
2.4 Cyrillic: cp1251, KOI8-R.
2.5 CJK: Shift_JIS / cp932, GB18030, Big5, EUC-KR / cp949.
2.6 ASCII: detected as UTF-8 (byte-equivalent).
2.7 User override: any Python codec name typed in the Review page.
2.8 BOM: stripped on read, never written.
2.9 Decode failure: surfaced as `encoding_decode_failed` (error severity).
2.10 Replacement char (U+FFFD) in output: surfaced as `encoding_uncertain` (error).

## 3. Output encodings

3.1 UTF-8 (default).
3.2 UTF-8 with BOM (Excel-friendly).
3.3 cp1252, ISO-8859-1, ISO-8859-15, cp1250, ISO-8859-2, cp1251.
3.4 Shift_JIS, GB18030, Big5, EUC-KR, UTF-16 LE.
3.5 Lossy fallback: `?` replacement + warning shown when chosen codec can't represent a character.

## 4. Delimiters

4.1 Auto-detect (input): `,`, `\t`, `;`, `|`.
4.2 Output: `,` (default), `\t`, `;`, `|`.
4.3 File extension: `.tsv` for tab, `.csv` otherwise.

## 5. Line endings

5.1 Input: LF, CRLF, bare CR (all normalized to LF on read).
5.2 Embedded in quoted cells: also normalized to LF.
5.3 Output: LF (default), CRLF, CR.
5.4 Mixed line endings: surfaced as `mixed_line_endings` finding.

## 6. Analyzer detectors

6.1 File-level (audit log of read-time fixes): `csv_bom_stripped`, `csv_nul_stripped`, `csv_smart_quotes_folded`, `csv_line_endings_normalized`, `csv_transcoded_to_utf8`, `csv_unquoted_delimiters_repaired`, `csv_unrepairable_rows`.
6.2 Cell-level: `smart_punctuation_in_data`, `nbsp_or_unicode_whitespace`, `zero_width_or_invisible`, `dirty_column_headers`, `whitespace_padding`, `null_like_sentinels`, `suspected_mojibake`, `mixed_case_email_column`, `near_duplicate_rows`, `leading_zero_ids`.
6.3 Encoding integrity: `encoding_uncertain`, `encoding_decode_failed`, `empty_input`.
6.4 Sample size (default): 1,000 rows; configurable.

## 7. Finding fields

7.1 `id` — stable identifier.
7.2 `severity` — info / warn / error (error blocks gate).
7.3 `confidence` — high / medium / low (auto-fixability).
7.4 `fix_action` — id of the algorithm in `src/core/fixes.py`.
7.5 `pre_applied` — true if fixed during read pass.
7.6 `tool` — owning tool id (or empty).
7.7 `count`, `description`, `column`, `samples` (≤5).

## 8. Confidence tiers

8.1 **high** — round-trip safe; one-click auto-fix.
8.2 **medium** — preview before applying.
8.3 **low** — opt-in only; can corrupt data if wrong.
8.4 **error** — must resolve or waive before tool pages unlock.

## 9. Decision actions per finding

9.1 `auto` — apply the registered fix.
9.2 `skip` — waive (no change, audit-logged).
9.3 `modified` — apply with custom payload (e.g. user-edited null sentinels).

## 10. Performance (1 GB input)

10.1 Initial scan (`analyze` sample-mode): < 2 s.
10.2 Peak RSS during initial scan: ~110 MB.
10.3 Full-file `repair_bytes`: ~30–40 s (when triggered).
10.4 Full-DataFrame analyze: ~4 min (~25 µs/cell).
10.5 Full-DataFrame `auto_fix`: ~5 min (~30 µs/cell).
10.6 Output write: ~10 s for 1 GB UTF-8 CSV.
10.7 RAM headroom recommended: 4× input file size for the full-Apply path.

## 11. Tools shipped

11.1 Deduplicator — Ready.
11.2 Text Cleaner — Ready.
11.3 Format Standardizer — Coming Soon.
11.4 Missing Value Handler — Coming Soon.
11.5 Column Mapper — Coming Soon.
11.6 Outlier Detector — Coming Soon.
11.7 Multi-File Merger — Coming Soon.
11.8 Validator & Reporter — Coming Soon.
11.9 Pipeline Runner — Coming Soon.

## 12. Gate (Review & Normalize)

12.1 Gates every tool page; tool pages refuse to load until passed.
12.2 Auto-fix button applies all `confidence=high` findings in one click.
12.3 Per-finding controls: Auto-fix / Skip / Customize.
12.4 Live before/after preview per finding (≤5 sample rows).
12.5 Audit log: every fix tagged with finding id, decision, cells changed.
12.6 Encoding override picker (16 codepages + custom).
12.7 Advanced output options expander: encoding + delimiter + line terminator.
12.8 Result keyed by upload SHA-256; survives page reloads, invalidated on re-upload.

## 13. Interfaces

13.1 GUI: Streamlit, runs locally, browser-based, no internet required.
13.2 CLI: Typer apps — `python -m src.cli`, `src.cli_text_clean`, `src.cli_analyze`.
13.3 Python API: `from src.core import …` (analyze, repair_bytes, clean_dataframe, deduplicate, etc.).
13.4 JSON output: `--json` flag on `cli_analyze`; full Finding schema.

## 14. Platforms

14.1 Python: ≥ 3.10.
14.2 OS: Linux, macOS, Windows.
14.3 Display: any modern browser (Streamlit GUI).
14.4 Network: not required at runtime.

## 15. Dependencies

15.1 Core: pandas, openpyxl, charset-normalizer, typer, loguru.
15.2 Dedup: rapidfuzz, phonenumbers.
15.3 GUI: streamlit.
15.4 Optional: ftfy (mojibake repair, `repair_mojibake` fix).
15.5 Dev: pytest, tox.

## 16. Test coverage

16.1 Unit + integration: 765 tests passing.
16.2 Documented gaps: 17 xfail (charset-normalizer label drift on byte-equivalent codepages, byte-level smart-quote fold expectation).
16.3 Fixture corpora: 21 text-cleaner fixtures, 31 encoding fixtures, 9 reference UTF-8 files.
16.4 CI surface: `python run_tests.py [--tool …] [--fixtures] [--coverage]`.

## 17. Privacy / data handling

17.1 All processing local; no network calls in the data path.
17.2 No telemetry, no usage analytics shipped.
17.3 Original input file never modified — outputs go to a separate path.
17.4 Audit logs written to `logs/` next to each run (timestamped).