# lib-core.input

P.0 action-mapping lib. Decouples physical keys from logical actions.
Polling-based (`is_action_down`) + edge-based (`was_action_pressed`).
Direction-vector helper composes 4 actions into `{x, y}` ∈ {-1, 0, +1}².

- Lib-ID: `lib-core.input`
- Version: `0.2.0` (breaking change from v0.1.0 — string-keys only, see §Migration)
- Spec v0.2.0 (P.2.6): `meta/docs/superpowers/specs/2026-05-11-engine-input-symbolic-keys-design.md`
- Spec v0.1.0 (P.0): `meta/docs/superpowers/specs/2026-05-09-p0-lib-input-design.md`

Forward-compat stubs (DEPRECATED-MVP) for mouse-button actions, gamepad
bindings, action-context-stack, key-rebinding-config, modifier-combos,
analog-axis, was_action_released edge, right-modifier-keys, function-keys,
special-keys (delete/insert/home/end/pageup/pagedown).

## API

- `input.bind(action_name, {"keyname1", "keyname2", ...})` — bind multi-key array (string-keys only, see §Key-Names)
- `input.unbind(action_name)` — remove binding
- `input.is_action_down(action) → bool` — any bound key currently down
- `input.was_action_pressed(action) → bool` — any bound key just-pressed
- `input.direction(left, right, up, down) → {x, y}` — vec in {-1,0,+1}², Y-down-positive
- `input.action_count() → number` — bound-actions count

## Key-Names (v0.2.0)

Strict-lowercase. Engine-internal `engine.input.KEY_*` integer-args are rejected.

| Category | Names |
|---|---|
| Letters | `a`, `b`, …, `z` |
| Numbers | `0`, `1`, …, `9` |
| Arrows | `left`, `right`, `up`, `down` |
| Whitespace + control | `space`, `tab`, `enter`, `backspace`, `escape` |
| Modifiers (left-side) | `shift` (= `lshift`), `ctrl` (= `lctrl`), `alt` (= `lalt`) |
| Console-toggle | `^` (DE: Zirkumflex / US: backtick — Quake/Source-Tradition) |

Right-modifier-aliases (`rshift`, `rctrl`, `ralt`) + function-keys (`f1`..`f12`) + special-keys (`delete`, `insert`, …) are **forthcoming** — additiv wenn `engine.input` die entsprechenden `KEY_*`-Konstanten exposed.

Unknown key-names raise a Lua-error with hint to this README.

## Conventions

- Y-down-positive per Sporel pixel-convention (ADR-0031).
- Multi-key per action (e.g., `{"a", "left"}` for both A and Left-Arrow).
- Silent-false for undefined actions (debug-friendly; lookup-misuse won't drown the game-loop in errors).
- Lua `error(...)` for `bind()` misuse (caller-bug fast-fail). Atomic: invalid key fails the entire bind without partial-state mutation.

## Consumer pattern

```lua
local input = require("lib-core.input")
input.bind("quit",       { "escape" })
input.bind("move_left",  { "a", "left" })
input.bind("move_right", { "d", "right" })
input.bind("move_up",    { "w", "up" })
input.bind("move_down",  { "s", "down" })

function update(ctx, dt)
    if input.was_action_pressed("quit") then engine.exit(0) end
    local d = input.direction("move_left", "move_right", "move_up", "move_down")
    -- d.x, d.y ∈ {-1, 0, +1}
end
```

## Migration v0.1.0 → v0.2.0

`bind()` switched from integer `engine.input.KEY_*` arguments to lowercase string-keys (per P.2.6). Reason: stop leaking engine-internal namespace into modules; align with ADR-0001 „engine knows verbs, libs bring nouns".

| v0.1.0 | v0.2.0 |
|---|---|
| `bind("quit", { engine.input.KEY_ESCAPE })` | `bind("quit", { "escape" })` |
| `bind("move", { engine.input.KEY_A, engine.input.KEY_LEFT })` | `bind("move", { "a", "left" })` |

`engine.input.KEY_*` constants remain available for direct engine-input use (e.g. `engine.input.is_key_down(engine.input.KEY_F1)` for edge-cases without bind), but `lib-core.input.bind` strict-rejects them.