# Decisions — tofu-core

Architectural choices and rationales discovered during work on this plan.

_Auto-scaffolded by /start-work. Append new entries below - never overwrite._

---

### Task 4: `version` → `ver` rename
`version` is a reserved keyword in D (conditional compilation). All struct fields bearing this name are renamed to `ver` — PackageIndex.ver, Recipe.ver, DepConstraint.ver, CacheManifest.ver, BinaryCheckResult.ver. This keeps the API readable while avoiding the keyword conflict. Downstream modules referencing these structs must use `.ver` for the version field.

### Task 4: DepConstraint uses typed `DepOp` enum, not string op
The Lua reference stores `op` as a string (`nil`, `">="`, `"=="`, etc.). In D we use a typed `DepOp` enum (`ge, le, eq, ne, gt, lt, none`) for type safety and exhaustive switching. The `parse` factory handles string-to-enum conversion at parse time.

### Task 4: BuildPlan is a plain container — no sorting
The plan specifies that `order()` returns entries in deps-first order *guaranteed by the caller*. The struct itself is just a container with `add()` and `order()` — no topological sort or dependency resolution. Sorting logic belongs in a later module (`tofu.resolver` or similar).

### Task 4: Single exception type `TypesException`
One exception class for the entire types module — no separate subclasses per error category. The parse failures (bad dep spec, invalid pool) all throw `TypesException` with a descriptive message. Callers catch `TypesException` for all type-parsing errors.

### Task 4: Manual char scanning for dep spec parsing
Rather than pulling in `std.regex`, the parser uses hand-written `isNameChar()` and `isWhite()` helpers with a simple position cursor. This keeps the module dependency-light (only `std.ascii`). The logic is a direct 1:1 port of the Lua reference patterns: `[A-Za-z0-9_.+-]` for names/versions, whitespace `[ \t]` for separators.

### Task 12: `delegate` keyword in test lambdas for delegate-typed parameters
D non-capturing lambdas infer as `function` pointers, which cannot implicitly convert to `delegate`-typed parameters. The explicit `delegate` keyword (`scope f = delegate (...) { ... };`) forces the correct type. This pattern is needed for resolution seam delegates that production code will instantiate with captures (e.g. closing over `Config cfg`).

---