Add SeqSee output format for charting

[JoeyBF]

Closes #191.

Summary

Adds a new charting backend that emits SeqSee-compatible JSON, alongside the existing SVG and TikZ backends. SeqSee is a generic spectral-sequence visualizer that consumes JSON conforming to its schema and renders a self-contained interactive HTML chart.

As #191 notes, this wasn't previously implementable because the Backend API drew lines from raw coordinates rather than naming source/target nodes. The API has since gained a node-aware structline(source, target, …) method, which this backend builds on.

Changes

• crates/sseq/src/charting/seqsee.rs — new SeqSeeBackend<T: Write> implementing the Backend trait:
  • Buffers nodes and edges in memory and writes the JSON document on Drop, since the schema groups all nodes together and all edges together whereas the trait callbacks interleave them (this mirrors how the SVG/TikZ backends finalize output).
  • Node ids are "x,y,idx", shared between node creation and edge endpoints.
  • Grid lines and axis labels are no-ops, because SeqSee draws its own grid from the chart dimensions in the header.
  • Differentials (styles matching d<page>) are given a distinct color to match the other backends; every referenced style is registered as an attribute alias so the output validates against the schema.
• crates/sseq/src/charting/mod.rs — export SeqSeeBackend.
• examples/chart.rs — prompt for the output format (svg/tikz/seqsee) and dispatch to the corresponding backend.

Testing

• cargo test -p sseq passes, including a new snapshot test of the emitted JSON and a unit test for the differential-detection helper.
• cargo clippy -p sseq is clean.
• The emitted JSON was validated against SeqSee's published input schema with jsonschema.

🤖 Generated with Claude Code

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Generated by Claude Code

Summary by CodeRabbit

• New Features

  • Added SeqSee JSON as a chart output format.
  • Chart generation now supports choosing between SVG, TikZ, and SeqSee formats at runtime.
  • SeqSee output includes chart dimensions, connections, and styling information.

• Tests

  • Added coverage validating SeqSee style handling and generated JSON output.

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 7dc0dcf9-6e8f-4edf-95a1-9e5d3de895c2

📥 Commits

Reviewing files that changed from the base of the PR and between 3a1e2ae and b6a86eb.

📒 Files selected for processing (2)

• ext/crates/sseq/src/charting/seqsee.rs
• ext/examples/chart.rs

📝 Walkthrough

Walkthrough

The charting crate adds a SeqSeeBackend that produces SeqSee-compatible JSON, exposes it publicly, tests its output and style aliases, and updates the chart example to select SVG, TikZ, or SeqSee output at runtime.

Changes

SeqSee JSON charting

Layer / File(s)	Summary
Backend contract and graph accumulation ext/crates/sseq/src/charting/mod.rs, ext/crates/sseq/src/charting/seqsee.rs	Adds and exports SeqSeeBackend, which implements Backend, accumulates nodes and edges, ignores unsupported drawing operations, and records referenced styles.
JSON finalization and validation ext/crates/sseq/src/charting/seqsee.rs	Builds the SeqSee document on drop, generates style aliases, writes formatted JSON, and tests graph output plus differential-style detection.
Runtime format dispatch ext/examples/chart.rs	Prompts for svg, tikz, or seqsee, validates the selection, and dispatches graph writing to the corresponding backend.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant User
  participant ChartExample
  participant SeqSeeBackend
  participant Stdout
  User->>ChartExample: choose output format
  ChartExample->>SeqSeeBackend: construct backend for seqsee
  ChartExample->>SeqSeeBackend: write graph nodes and edges
  SeqSeeBackend->>Stdout: emit SeqSee JSON

Loading

Possibly related PRs

• SpectralSequences/sseq#227: Introduced the charting module structure extended by this backend.

Poem

A bunny hops through nodes and lines,
And JSON sparkles in neat designs.
SVG, TikZ, or SeqSee too—
Pick a format; the chart shines through!
o.o

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding SeqSee chart output.
Linked Issues check	✅ Passed	The changes implement SeqSee-compatible JSON export and add the runtime option requested in issue #191.
Out of Scope Changes check	✅ Passed	The PR stays focused on SeqSee chart export and the matching example update, with no obvious unrelated code changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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