OneCAD-Draft/crates/ocs_doc_api/README.md

ocs_doc_api

Object-oriented, transport-agnostic CAD entity API for OpenCADStudio plugins and hosts (v2). One typed vocabulary — Entity, ObjectId, Operation, Query, Transport — that runs identically in-process and over IPC.

use ocs_doc_api::{DocApi, Solid, OpGroup, ApiResult};

fn intersect_solids(api: &DocApi) -> ApiResult<()> {
    let doc = api.document(api.active_tab());
    let mut grp = OpGroup::new();

    // Each call is ONE atomic host op = one undo step. Per-op autocommit; no
    // multi-op write transactions. OpGroup is best-effort cleanup on failure.
    let block = grp.track(doc.solids().create_cuboid([0.0, 0.0, 0.0], [10.0, 10.0, 10.0]))?;
    let other = grp.track(doc.solids().create_cuboid([5.0, 5.0, 5.0], [10.0, 10.0, 10.0]))?;

    let lens: Solid = match block.intersect(&other) {   // host runs brep::combine
        Ok(l) => { grp.commit(); l }
        Err(e) => { grp.compensate(&doc)?; return Err(e); }
    };

    // Read-only query batch (one round-trip, no revision bump).
    let (bb, vol) = {
        let r = doc.query_batch(|q| { q.bounds(&lens); q.volume(&lens); })?;
        (r.bounds(0)?, r.volume(1)?)
    };
    api.push_info(&format!("lens vol={vol:.1} bounds={bb:?}"));
    Ok(())
}

What it is

• Object-centric facade — DocApi (root) → Document → collections (solids(), curves(), entities()) → typed handles (Solid, Line, Circle, Polyline, Point, Entity) that carry geometric methods (intersect/union/subtract/transform/bounds/volume/centroid/delete).
• Transport-agnostic — the same typed requests run in-process ([InProcess]) or over the ocs_plugin_api IPC channel ([OcsPluginApiIpc]); only the Transport differs. The host executes them through one crate-owned executor.
• Stable across async IPC — handles are Copy, Send, Sync {ObjectId, Arc<Session>} tokens, safe to share across plugin worker threads. A stale handle's methods return ApiError::UnknownId, never a panic.

Core guarantees

• Per-op autocommit, no write transactions. Every write op is ONE atomic host call = one undo step. Multi-op write transactions were removed after a security/integrity review (rollback-correctness of erase_sources + unbounded synchronous batch execution). There is no doc.transaction.
• Per-op atomicity. An op validates its inputs and computes its geometry before any mutation; a failed op applies nothing and records no undo step. brep::combine is pure; erase_sources runs only on success.
• Bulk ops (CreateMany/TransformMany/DeleteMany, and read-only query batching) are single ops, all-or-nothing via upfront validation (no rollback), item-capped — for bulk data (see ARCHITECTURE.md § Performance).
• Structured errors — ApiError::{Validation, Geometry, UnknownId, Unsupported, Transport}, serializable so IPC returns the same error the in-process executor produced.

Scope (v1)

• Solids — primitives (cuboid, sphere, cylinder, cone, torus, wedge), booleans (union/intersect/subtract), transform, and queries (bounds/volume/centroid). Host resolves bodies via the solid_models cache (lift-on-miss from ACIS SAT).
• Minimal 2D — line, circle, polyline, point (construction + bounds); used as boolean/sweep inputs.
• Not yet: sweep/revolve profiles, AddVertex, non-solid transforms, annotations, containers (insert/block), viewports, media. See IMPLEMENTATION.md.

Features

Feature	Pulls	Use
(default)	—	Pure data types (ops/query/envelope/errors) — binding generators, tooling
host	acadrust + cadkernel	The executor + DocApiBackend trait + in-process transport (the host side)
ipc	acadrust + ocs_plugin_api	The IPC transport adapter (the plugin side)

For REPL/scripting bridges (Python, Lua, …)

The object model is handed over as a single versioned schema (binding_schema_json(), generated by build.rs). A bridge in any language is a thin serializer + schema-driven generator + session glue over V4 ExecuteCode — no Rust FFI. See bindings/README.md and bindings/python/generate.py.

Links

• ARCHITECTURE.md — design decisions, the per-op execution model, how to add a new entity/family/method, performance notes.
• IMPLEMENTATION.md — what's supported now vs. the phased roadmap.
• spec/entities.toml — the curated source of truth for codegen.