feat(pi-fff): support global config file

packages/pi-fff/README.md

@@ -127,7 +127,36 @@ Parameters:
 Mode precedence:
 1. `--fff-mode <mode>` CLI flag
 2. `PI_FFF_MODE=<mode>` environment variable
-3. default (`tools-and-ui`)
+3. `mode` in the global config file
+4. default (`tools-and-ui`)
+
+## Configuration
+
+For persistent global configuration, create `pi-fff.json` in pi's agent directory (`~/.pi/agent/pi-fff.json` by default; `PI_CODING_AGENT_DIR` is respected):
+
+```json
+{
+  "mode": "override",
+  "frecencyDbPath": "/path/to/frecency",
+  "historyDbPath": "/path/to/history",
+  "enableFsRootScanning": false,
+  "enableHomeDirScanning": true
+}
+```
+
+All fields are optional:
+
+| Field | Type | Default |
+|---|---|---|
+| `mode` | `tools-and-ui`, `tools-only`, or `override` | `tools-and-ui` |
+| `frecencyDbPath` | non-empty string | See [Data](#data) |
+| `historyDbPath` | non-empty string | See [Data](#data) |
+| `enableFsRootScanning` | boolean | `false` |
+| `enableHomeDirScanning` | boolean | `true` |
+
+CLI flags take precedence over environment variables, which take precedence over this file. A missing file is ignored. Malformed JSON, unknown fields, and invalid values stop the extension from loading and report the file path and error. `/fff-mode` changes the current session; it does not edit this file.
+
+The file is global only. Project-level config cannot safely control tool names because pi decides which tools an extension registers before project configuration can be trusted.
 
 ## Flags
 
@@ -147,11 +176,12 @@ Each path is resolved independently, in this order:
 
 1. CLI flag — `--fff-frecency-db` / `--fff-history-db`
 2. Env var — `FFF_FRECENCY_DB` / `FFF_HISTORY_DB`
-3. An existing [fff.nvim](https://github.com/dmtrKovalenko/fff.nvim) database, so pi reuses the frecency you built up in your editor:
+3. Global config — `frecencyDbPath` / `historyDbPath`
+4. An existing [fff.nvim](https://github.com/dmtrKovalenko/fff.nvim) database, so pi reuses the frecency you built up in your editor:
    - frecency: `$XDG_CACHE_HOME/nvim/fff_nvim`
    - history: `$XDG_DATA_HOME/nvim/fff_queries`
    - `XDG_CACHE_HOME` defaults to `~/.cache` and `XDG_DATA_HOME` to `~/.local/share`; on Windows both fall back under `%LOCALAPPDATA%\nvim-data`. Only directories count — a plain file at those paths is ignored.
-4. pi-local directory, created on demand — `$PI_CODING_AGENT_DIR/fff/{frecency,history}`, defaulting to `~/.pi/agent/fff/{frecency,history}`
+5. pi-local directory, created on demand — `$PI_CODING_AGENT_DIR/fff/{frecency,history}`, defaulting to `~/.pi/agent/fff/{frecency,history}`
 
 The extension only reads these databases; it never records the agent's own searches into your Neovim history. If a database cannot be opened, the finder starts without persistence and pi shows a warning instead of failing.
 

packages/pi-fff/src/config.ts

@@ -0,0 +1,100 @@
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+import { piDataDir } from "./paths";
+
+export const CONFIG_FILE_NAME = "pi-fff.json";
+export const VALID_MODES = ["tools-and-ui", "tools-only", "override"] as const;
+
+export type FffMode = (typeof VALID_MODES)[number];
+
+export interface FffConfig {
+  mode?: FffMode;
+  frecencyDbPath?: string;
+  historyDbPath?: string;
+  enableFsRootScanning?: boolean;
+  enableHomeDirScanning?: boolean;
+}
+
+const CONFIG_KEYS = new Set<keyof FffConfig>([
+  "mode",
+  "frecencyDbPath",
+  "historyDbPath",
+  "enableFsRootScanning",
+  "enableHomeDirScanning",
+]);
+
+export function loadConfig(agentDir = piDataDir()): FffConfig {
+  const configPath = join(agentDir, CONFIG_FILE_NAME);
+  let contents: string;
+
+  try {
+    contents = readFileSync(configPath, "utf8");
+  } catch (error: unknown) {
+    if ((error as NodeJS.ErrnoException).code === "ENOENT") return {};
+    throw new Error(
+      `Could not read pi-fff config at ${configPath}: ${errorMessage(error)}`,
+    );
+  }
+
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(contents);
+  } catch (error: unknown) {
+    throw invalidConfig(configPath, `not valid JSON (${errorMessage(error)})`);
+  }
+
+  if (!isRecord(parsed)) {
+    throw invalidConfig(configPath, "expected a JSON object");
+  }
+
+  for (const key of Object.keys(parsed)) {
+    if (!CONFIG_KEYS.has(key as keyof FffConfig)) {
+      throw invalidConfig(configPath, `unknown option "${key}"`);
+    }
+  }
+
+  if (parsed.mode !== undefined && !VALID_MODES.includes(parsed.mode as FffMode)) {
+    throw invalidConfig(configPath, `"mode" must be one of ${VALID_MODES.join(", ")}`);
+  }
+
+  validateString(configPath, parsed, "frecencyDbPath");
+  validateString(configPath, parsed, "historyDbPath");
+  validateBoolean(configPath, parsed, "enableFsRootScanning");
+  validateBoolean(configPath, parsed, "enableHomeDirScanning");
+
+  return parsed as FffConfig;
+}
+
+function invalidConfig(configPath: string, reason: string): Error {
+  return new Error(`Invalid pi-fff config at ${configPath}: ${reason}`);
+}
+
+function errorMessage(error: unknown): string {
+  return error instanceof Error ? error.message : String(error);
+}
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null && !Array.isArray(value);
+}
+
+function validateString(
+  configPath: string,
+  config: Record<string, unknown>,
+  key: "frecencyDbPath" | "historyDbPath",
+): void {
+  const value = config[key];
+  if (value !== undefined && (typeof value !== "string" || value.length === 0)) {
+    throw invalidConfig(configPath, `"${key}" must be a non-empty string`);
+  }
+}
+
+function validateBoolean(
+  configPath: string,
+  config: Record<string, unknown>,
+  key: "enableFsRootScanning" | "enableHomeDirScanning",
+): void {
+  const value = config[key];
+  if (value !== undefined && typeof value !== "boolean") {
+    throw invalidConfig(configPath, `"${key}" must be a boolean`);
+  }
+}

packages/pi-fff/src/index.ts

@@ -22,6 +22,7 @@ import type {
 } from "@ff-labs/fff-node";
 import { Type } from "@sinclair/typebox";
 import { AuxFinderPool, routePathConstraint } from "./aux-finders";
+import { type FffMode, loadConfig, VALID_MODES } from "./config";
 import { FilePickerFactory } from "./file-picker";
 import { isHomeDir, resolveDbPaths } from "./paths";
 import { buildQuery } from "./query";
@@ -45,11 +46,7 @@ const GREP_TIME_BUDGET_MS = 10_000;
 const HOME_SCAN_STATUS_KEY = "fff";
 const HOME_SCAN_POLL_MS = 1_000;
 const HOME_SCAN_DISABLE_HINT =
-  "You can prevent home dir indexing with --fff-enable-home-scan=false (or FFF_ENABLE_HOME_SCAN=0).";
-
-type FffMode = "tools-and-ui" | "tools-only" | "override";
-
-const VALID_MODES: FffMode[] = ["tools-and-ui", "tools-only", "override"];
+  "You can prevent home dir indexing with --fff-enable-home-scan=false, FFF_ENABLE_HOME_SCAN=0, or enableHomeDirScanning in pi-fff.json.";
 
 interface ToolNames {
   grep: string;
@@ -299,44 +296,77 @@ export default function fffExtension(pi: ExtensionAPI) {
   let finderPromise: Promise<FileFinderApi> | null = null;
   let activeCwd = process.cwd();
 
-  // Mode resolution: flag > env > default
-  let currentMode: FffMode =
-    (pi.getFlag("fff-mode") as FffMode) ??
-    (process.env.PI_FFF_MODE as FffMode) ??
-    "tools-and-ui";
+  const config = loadConfig();
+
+  // All startup options use the same flag > env > file > fallback order.
+  function getConfigValue<T>(
+    flagName: string,
+    envName: string,
+    fileValue: T | undefined,
+    fallback: T,
+    parse: (value: unknown) => T | undefined = (value) => value as T,
+  ): T {
+    const flagValue = pi.getFlag(flagName);
+    if (flagValue !== undefined) {
+      const value = parse(flagValue);
+      if (value !== undefined) return value;
+    }
+
+    const envValue = process.env[envName];
+    if (envValue !== undefined) {
+      const value = parse(envValue);
+      if (value !== undefined) return value;
+    }
+
+    return fileValue ?? fallback;
+  }
 
+  function parseBoolean(value: unknown): boolean | undefined {
+    if (typeof value === "boolean") return value;
+    if (value === "1" || value === "true") return true;
+    if (value === "0" || value === "false") return false;
+    return undefined;
+  }
+
+  let currentMode = getConfigValue(
+    "fff-mode",
+    "PI_FFF_MODE",
+    config.mode,
+    "tools-and-ui",
+  );
   const toolNames = resolveToolNames(currentMode);
 
-  // DB path resolution: flag > env > existing fff.nvim db > pi-local data dir.
   const resolvedDbPaths = resolveDbPaths({
-    frecency:
-      (pi.getFlag("fff-frecency-db") as string | undefined) ??
-      process.env.FFF_FRECENCY_DB,
-    history:
-      (pi.getFlag("fff-history-db") as string | undefined) ?? process.env.FFF_HISTORY_DB,
+    frecency: getConfigValue(
+      "fff-frecency-db",
+      "FFF_FRECENCY_DB",
+      config.frecencyDbPath,
+      undefined,
+    ),
+    history: getConfigValue(
+      "fff-history-db",
+      "FFF_HISTORY_DB",
+      config.historyDbPath,
+      undefined,
+    ),
   });
 
-  // flag (boolean) > env ("1"/"true", or "0"/"false") > default.
-  function resolveBoolOpt(flagName: string, envName: string, fallback = false): boolean {
-    const flag = pi.getFlag(flagName);
-    if (typeof flag === "boolean") return flag;
-    if (typeof flag === "string") return flag === "true" || flag === "1";
-    const env = process.env[envName];
-    if (env === "1" || env === "true") return true;
-    if (env === "0" || env === "false") return false;
-    return fallback;
-  }
   // Root scanning opt-in: FFF refuses to init at / unless this is set.
-  const enableFsRootScanning = resolveBoolOpt(
+  const enableFsRootScanning = getConfigValue(
     "fff-enable-root-scan",
     "FFF_ENABLE_ROOT_SCAN",
+    config.enableFsRootScanning,
+    false,
+    parseBoolean,
   );
   // Home dir scanning is on by default (launching pi from $HOME is a normal
   // flow), but configurable so users with huge $HOME trees can opt out.
-  const enableHomeDirScanning = resolveBoolOpt(
+  const enableHomeDirScanning = getConfigValue(
     "fff-enable-home-scan",
     "FFF_ENABLE_HOME_SCAN",
+    config.enableHomeDirScanning,
     true,
+    parseBoolean,
   );
 
   function getMode(): FffMode {

packages/pi-fff/src/paths.ts

@@ -52,7 +52,7 @@ function nvimDataDir(): string {
   return path.join(HOME_DIR, ".local", "share", "nvim");
 }
 
-function piDataDir(): string {
+export function piDataDir(): string {
   return process.env.PI_CODING_AGENT_DIR ?? path.join(HOME_DIR, ".pi", "agent");
 }
 

packages/pi-fff/test/config.test.ts

@@ -0,0 +1,84 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+import { CONFIG_FILE_NAME, loadConfig } from "../src/config";
+
+describe("loadConfig", () => {
+  let agentDir: string;
+  let configPath: string;
+
+  beforeEach(() => {
+    agentDir = fs.mkdtempSync(path.join(os.tmpdir(), "pi-fff-config-"));
+    configPath = path.join(agentDir, CONFIG_FILE_NAME);
+  });
+
+  afterEach(() => {
+    fs.rmSync(agentDir, { recursive: true, force: true });
+  });
+
+  test("returns an empty config when the file does not exist", () => {
+    expect(loadConfig(agentDir)).toEqual({});
+  });
+
+  test("loads every supported option", () => {
+    const config = {
+      mode: "override" as const,
+      frecencyDbPath: "/data/frecency",
+      historyDbPath: "/data/history",
+      enableFsRootScanning: true,
+      enableHomeDirScanning: false,
+    };
+    writeConfig(config);
+
+    expect(loadConfig(agentDir)).toEqual(config);
+  });
+
+  test("rejects malformed JSON", () => {
+    fs.writeFileSync(configPath, '{"mode":');
+
+    expect(() => loadConfig(agentDir)).toThrow(
+      `Invalid pi-fff config at ${configPath}: not valid JSON`,
+    );
+  });
+
+  test("rejects non-object config", () => {
+    writeConfig(["override"]);
+
+    expect(() => loadConfig(agentDir)).toThrow("expected a JSON object");
+  });
+
+  test("rejects unknown options", () => {
+    writeConfig({ mode: "override", typo: true });
+
+    expect(() => loadConfig(agentDir)).toThrow('unknown option "typo"');
+  });
+
+  test("rejects invalid option values", () => {
+    const cases: [Record<string, unknown>, string][] = [
+      [{ mode: "replace" }, '"mode" must be one of'],
+      [{ frecencyDbPath: "" }, '"frecencyDbPath" must be a non-empty string'],
+      [{ historyDbPath: false }, '"historyDbPath" must be a non-empty string'],
+      [{ enableFsRootScanning: 1 }, '"enableFsRootScanning" must be a boolean'],
+      [{ enableHomeDirScanning: "false" }, '"enableHomeDirScanning" must be a boolean'],
+    ];
+
+    for (const [config, message] of cases) {
+      writeConfig(config);
+      expect(() => loadConfig(agentDir)).toThrow(message);
+    }
+  });
+
+  test("reports file read failures", () => {
+    fs.mkdirSync(configPath);
+
+    expect(() => loadConfig(agentDir)).toThrow(
+      `Could not read pi-fff config at ${configPath}`,
+    );
+  });
+
+  function writeConfig(config: unknown): void {
+    fs.writeFileSync(configPath, JSON.stringify(config));
+  }
+});