reikhelm/.dev/2026-05-28-procgen-map-core/tasks/02-geometry.md

Task 2: Geometry

Depends on: Task 1

Context Files

• .dev/2026-05-28-procgen-map-core/spec/design.md — §4.1 (geometry).
• reikhelm-core/src/lib.rs — append the module declaration here.

Files

• Create: reikhelm-core/src/geometry.rs — Point, Rect, Line.
• Modify: reikhelm-core/src/lib.rs — append pub mod geometry;.

What to Build

Integer grid-coordinate geometry types (spec §4.1). All types derive Clone, Copy, Debug, PartialEq, Eq and serde::{Serialize, Deserialize}. These are the foundation reused by the grid, regions, and every pass — keep them small and total (no panics on valid input).

Interface Dependencies

• Produces:
  • Point { x: i32, y: i32 } — new, manhattan(&self, other: Point) -> i32, and offset helpers for the four/eight neighbor directions.
  • Rect { x: i32, y: i32, w: i32, h: i32 } — new, center() -> Point, contains(Point) -> bool, intersects(&Rect) -> bool, inflate(by: i32) -> Rect, iter() -> impl Iterator<Item = Point> (all contained cells).
  • Line { from: Point, to: Point } — cells() -> impl Iterator<Item = Point> yielding the grid cells along the segment (a straight horizontal/vertical run is sufficient for v1 corridors; document the behavior).

Tests

• Rect::contains is true for corners/interior and false just outside.
• Rect::intersects is symmetric; true for overlap, false for adjacent-but-disjoint rects.
• Rect::iter yields exactly w * h distinct points, all contained.
• Rect::center returns an interior point.
• Point::manhattan is correct and symmetric.
• Line::cells yields a contiguous run from from to to inclusive for a horizontal and a vertical line.

Success Criteria

• All listed types and methods exist with the signatures above and derive serde.
• pub mod geometry; added to lib.rs.
• All tests pass: cargo test -p reikhelm-core geometry

Commit

"feat(core): geometry primitives (Point, Rect, Line)"