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docs/security-stack/security/password-strength/src/matchers/keyboard/keyboard.md

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+# `keyboard` — keyboard adjacency matcher
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+## Purpose
+
+Detects spatial walks across a physical keyboard layout (QWERTY, DVORAK,
+AZERTY, or any caller-supplied adjacency graph) per Wheeler 2016 section
+3.5. A password like `qwerty` traces a straight horizontal walk along the
+top row; the matcher reports its length, the number of times the walker
+changed direction, and how many shift-required presses it contained — all
+inputs to the keyboard guess estimate in section 4.5.
+
+## Features
+
+- Pluggable graph map via the `graphs` option
+- Counts both `turns` (direction changes) and `shiftedCount` (capital /
+  symbol presses)
+- Default graph is QWERTY; alternative layouts ship under
+  `graphs/{dvorak,azerty}` subpaths
+- Rejects malformed graphs (self-adjacency or asymmetric edges) via
+  `validateGraph` → `PWSTRENGTH.GRAPH_INVALID`
+
+## Usage: Basic Example
+
+```ts
+import { keyboardMatch } from "@suaveplan/password-strength/matchers/keyboard";
+
+const matches = keyboardMatch("qwerty");
+console.log(matches[0]); // { graph: "qwerty", turns: 0, shiftedCount: 0, … }
+```
+
+## Usage: Advanced Example
+
+```ts
+import { keyboardMatch } from "@suaveplan/password-strength/matchers/keyboard";
+import { DVORAK_GRAPH } from "@suaveplan/password-strength/graphs/dvorak";
+
+const matches = keyboardMatch("aoeuhtns", { graphs: { dvorak: DVORAK_GRAPH } });
+for (const m of matches) {
+ console.log(m.token, m.graph, m.turns, m.shiftedCount);
+}
+```
+
+## API Reference
+
+- `keyboardMatch(password: string, opts?: KeyboardMatchOptions): KeyboardMatch[]`
+  - `opts.graphs`: `Record<string, KeyboardGraph>` — override the default
+    QWERTY-only graph set. Each graph is validated before use.
+- `KeyboardMatchOptions`: `{ graphs?: KeyboardGraphMap }`
+
+## Implementation Notes
+
+Each walk advances character by character; a transition is accepted iff the
+target character appears in the current key's adjacency slots (six slots
+per key, encoding the six surrounding keys on a staggered layout). A
+direction change increments `turns`; a press whose target matches the
+shifted half of the slot increments `shiftedCount`. The walk continues
+greedily until the chain breaks; the matcher then restarts at the
+following index. Graph validation rejects malformed graphs upfront so the
+matcher never produces self-loops or asymmetric walks.