feat(S-202): Test-drive and implement src/detect.ts

tools/ai-cli-dispatch/src/detect.ts

@@ -0,0 +1,73 @@
+import { spawnSync as defaultSpawnSync } from "node:child_process";
+import { existsSync as defaultExistsSync } from "node:fs";
+import { join } from "node:path";
+import { type ClientName, type ClientInfo } from "./types.js";
+
+const CLIENT_NAMES: ClientName[] = ["codex", "claude", "opencode"];
+
+export interface DetectOptions {
+  pathEnv?: string;
+  spawnSync?: typeof defaultSpawnSync;
+  existsSync?: typeof defaultExistsSync;
+}
+
+function parseVersion(stdout: string): string | undefined {
+  const match = stdout.match(/v?\d+\.\d+\.\d+(?:[-+.]\w+)*/);
+  return match ? match[0] : undefined;
+}
+
+function findBinary(
+  name: string,
+  pathEnv: string,
+  spawnSyncImpl: typeof defaultSpawnSync,
+  existsSyncImpl: typeof defaultExistsSync
+): string | undefined {
+  const isWin = process.platform === "win32";
+
+  // Try system `which` / `where` first
+  const whichResult = spawnSyncImpl(isWin ? "where" : "which", [name], {
+    encoding: "utf-8",
+    env: { ...process.env, PATH: pathEnv },
+  });
+  if (whichResult.status === 0) {
+    const line = whichResult.stdout.trim().split("\n")[0];
+    if (line) return line;
+  }
+
+  // Fallback: walk PATH directories manually
+  const sep = isWin ? ";" : ":";
+  const ext = isWin ? ".exe" : "";
+  const dirs = pathEnv.split(sep);
+  for (const dir of dirs) {
+    if (!dir) continue;
+    const fullPath = join(dir, name + ext);
+    if (existsSyncImpl(fullPath)) {
+      return fullPath;
+    }
+  }
+
+  return undefined;
+}
+
+export function detectClients(options?: DetectOptions): ClientInfo[] {
+  const spawnSyncImpl = options?.spawnSync ?? defaultSpawnSync;
+  const existsSyncImpl = options?.existsSync ?? defaultExistsSync;
+  const pathEnv = options?.pathEnv ?? process.env.PATH ?? "";
+
+  return CLIENT_NAMES.map((name) => {
+    const path = findBinary(name, pathEnv, spawnSyncImpl, existsSyncImpl);
+    if (!path) {
+      return { name, found: false };
+    }
+
+    const versionResult = spawnSyncImpl(path, ["--version"], {
+      encoding: "utf-8",
+    });
+    const version =
+      versionResult.status === 0
+        ? parseVersion(versionResult.stdout)
+        : undefined;
+
+    return { name, path, version, found: true };
+  });
+}