diff-tools/public/docs/ARCHITECTURE.md

Architecture

Diff Tools is a static React application with a relocatable ./ build. Its comparison pipeline is deliberately separated from the view:

1. The workbench captures strings or decodes a selected file as strict UTF-8 after a byte-size check.
2. A fresh module worker receives a plain comparison request. Changing input cancels and terminates the preceding worker; the last successful result remains on screen until a replacement succeeds.
3. A mode-specific pure comparator produces display rows and diagnostics. Normalized rows are first-class output, not discarded state.
4. The orchestrator adds exact input metadata, a bounded unified patch and a schema-labelled portable report.
5. React renders values as text. The app never consumes or inserts HTML produced by a diff or parser library.

When Worker is unavailable, such as in unit tests, the same pure comparator runs asynchronously on the calling thread.

Comparators

• Text tokenizes lines without losing delimiters, or uses Intl.Segmenter for words and graphemes with bounded fallbacks. diff aligns token arrays.
• JSON uses lossless-json, rejects duplicate and prototype-affecting keys, and compares numbers without converting to IEEE-754. Object member order is semantically ignored but reported.
• XML rejects active declaration/include syntax and preflights structure before @xmldom/xmldom builds an inert DOM. Elements and attributes compare by expanded name when selected.
• CSV/TSV uses Papa Parse in string mode. Unique composite keys align rows; no spreadsheet type inference is performed.

All report and patch formats are generated locally. de.add-ideas.diff-tools.report.v1 is the portable report schema identifier.

The planned shared @add-ideas/toolbox-helpers package is not yet published at a compatible version, so v0.1 keeps its bounded domain functions inside src/core. They can be extracted without changing the worker protocol or report schema.