taskgraph_ts/tasks/implementation/graph/taskgraph-class.md

id, name, status, depends_on, scope, risk, impact, level

id	name	status	depends_on	scope	risk	impact	level
graph/taskgraph-class	Implement TaskGraph class skeleton with graphology DirectedGraph	completed	schema/enums schema/input-schemas schema/graph-schemas error/error-hierarchy setup/project-init	moderate	medium	phase	implementation

Description

Create the TaskGraph class in src/graph/index.ts that wraps graphology.DirectedGraph. This is the data class that holds the graph instance and provides the foundation for construction, mutation, and query methods. At this stage, implement the constructor, raw getter, and the overall class structure. Actual construction and analysis methods come in dependent tasks.

Acceptance Criteria

• src/graph/index.ts exports TaskGraph class
• Constructor creates an internal graphology.DirectedGraph with options { type: 'directed', multi: false, allowSelfLoops: false }
• get raw(): Graph returns the underlying graphology instance
• Constructor accepts optional TaskGraphSerialized for initializing from serialized data (delegates to fromJSON pattern)
• Class stores edge key format: ${source}->${target} (per ADR-006)
• No parallel edges constraint enforced by multi: false graph option
• No self-loops constraint enforced by allowSelfLoops: false graph option
• Internal _edgeKey(source, target): string method producing deterministic keys
• Re-exported from src/index.ts

References

• docs/architecture/api-surface.md — TaskGraph class API
• docs/architecture/graph-model.md — construction paths, edge direction, constraints
• docs/architecture/decisions/006-deterministic-edge-keys.md — edge key format

Notes

Implementation placed in src/graph/construction.ts (as per existing module structure). The class is re-exported via src/graph/index.ts and src/index.ts. Static methods fromTasks and fromRecords are stubs (throw) pending dependent task implementation. fromJSON is fully implemented since the constructor needs it for deserialization.

Summary

Implemented TaskGraph class skeleton wrapping graphology DirectedGraph.

• Modified: src/graph/construction.ts (full class with constructor, raw getter, _edgeKey, fromJSON, stubs for fromTasks/fromRecords)
• Modified: src/graph/index.ts (added TaskGraphInner type export)
• Modified: test/graph.test.ts (added 20 new tests for class skeleton, preserved 22 existing fixture tests)
• Tests: 42 in graph.test.ts (all passing), 204 total across suite (all passing)