/**
 * adapters/pi — Pi coding agent platform adapter.
 *
 * Implements HookAdapter for Pi's MCP-only paradigm at the adapter layer.
 *
 * Pi hook specifics:
 *   - NO JSON-stdio hooks. Pi exposes a JS-callback runtime API
 *     (`pi.on("session_start", fn)`, `pi.on("tool_call", fn)`, …) which is
 *     wired DIRECTLY by `src/adapters/pi/extension.ts`. The HookAdapter
 *     contract here intentionally reports `mcp-only` and all-false
 *     capabilities so harness paths that walk the JSON-stdio matrix do not
 *     try to register stdio hooks for Pi.
 *   - Config root: ~/.pi/
 *   - Settings: ~/.pi/settings.json (kept lightweight — Pi does not
 *     prescribe a canonical settings file, but several internal tools
 *     write one; using settings.json keeps parity with Claude Code).
 *   - Session dir: ~/.pi/context-mode/sessions/  (parallel to ~/.claude/,
 *     ~/.omp/) — this is the data-isolation contract from issue #473.
 *   - Instruction file: AGENTS.md (per configs/pi/AGENTS.md).
 *
 * Why a dedicated adapter is mandatory:
 *   Before this adapter existed, `getAdapter("pi")` fell through to the
 *   `default` arm of the switch in `src/adapters/detect.ts` and returned a
 *   ClaudeCodeAdapter. Pi sessions therefore wrote DBs and event logs into
 *   `~/.claude/context-mode/sessions/`, contaminating Claude Code state and
 *   silently leaking Pi user data into the wrong storage root (issue #473
 *   follow-up). The OMP adapter fixed the same class of bug for OMP; this
 *   adapter closes the gap for Pi.
 */

import {
  readFileSync,
  writeFileSync,
  mkdirSync,
} from "node:fs";
import { resolve, dirname } from "node:path";
import { homedir } from "node:os";

import { BaseAdapter } from "../base.js";

import type {
  HookAdapter,
  HookParadigm,
  PlatformCapabilities,
  DiagnosticResult,
  PreToolUseEvent,
  PostToolUseEvent,
  PreCompactEvent,
  SessionStartEvent,
  PreToolUseResponse,
  PostToolUseResponse,
  PreCompactResponse,
  SessionStartResponse,
  HookRegistration,
} from "../types.js";

// ─────────────────────────────────────────────────────────
// Adapter implementation
// ─────────────────────────────────────────────────────────

export class PiAdapter extends BaseAdapter implements HookAdapter {
  constructor() {
    super([".pi"]);
  }

  readonly name = "Pi";
  readonly paradigm: HookParadigm = "mcp-only";

  readonly capabilities: PlatformCapabilities = {
    preToolUse: false,
    postToolUse: false,
    preCompact: false,
    sessionStart: false,
    canModifyArgs: false,
    canModifyOutput: false,
    canInjectSessionContext: false,
  };

  // ── Input parsing ──────────────────────────────────────
  // Pi does not feed the adapter via JSON-stdio. These methods exist to
  // satisfy the HookAdapter contract and throw if the harness mistakenly
  // routes a JSON-stdio event through the adapter.

  parsePreToolUseInput(_raw: unknown): PreToolUseEvent {
    throw new Error("Pi does not support JSON-stdio hooks (wired via extension.ts)");
  }

  parsePostToolUseInput(_raw: unknown): PostToolUseEvent {
    throw new Error("Pi does not support JSON-stdio hooks (wired via extension.ts)");
  }

  parsePreCompactInput(_raw: unknown): PreCompactEvent {
    throw new Error("Pi does not support JSON-stdio hooks (wired via extension.ts)");
  }

  parseSessionStartInput(_raw: unknown): SessionStartEvent {
    throw new Error("Pi does not support JSON-stdio hooks (wired via extension.ts)");
  }

  // ── Response formatting ────────────────────────────────
  // No JSON-stdio path — return undefined to satisfy the contract.

  formatPreToolUseResponse(_response: PreToolUseResponse): unknown {
    return undefined;
  }

  formatPostToolUseResponse(_response: PostToolUseResponse): unknown {
    return undefined;
  }

  formatPreCompactResponse(_response: PreCompactResponse): unknown {
    return undefined;
  }

  formatSessionStartResponse(_response: SessionStartResponse): unknown {
    return undefined;
  }

  // ── Configuration ──────────────────────────────────────

  getSettingsPath(): string {
    return resolve(homedir(), ".pi", "settings.json");
  }

  getInstructionFiles(): string[] {
    return ["AGENTS.md"];
  }

  generateHookConfig(_pluginRoot: string): HookRegistration {
    return {};
  }

  readSettings(): Record<string, unknown> | null {
    try {
      const raw = readFileSync(this.getSettingsPath(), "utf-8");
      return JSON.parse(raw);
    } catch {
      return null;
    }
  }

  writeSettings(settings: Record<string, unknown>): void {
    const settingsPath = this.getSettingsPath();
    mkdirSync(dirname(settingsPath), { recursive: true });
    writeFileSync(settingsPath, JSON.stringify(settings, null, 2), "utf-8");
  }

  // ── Diagnostics (doctor) ─────────────────────────────────

  validateHooks(_pluginRoot: string): DiagnosticResult[] {
    return [
      {
        check: "Hook support",
        status: "pass",
        message:
          "Pi hooks are wired via the context-mode Pi extension " +
          "(~/.pi/extensions/context-mode/), not via JSON-stdio.",
      },
    ];
  }

  checkPluginRegistration(): DiagnosticResult {
    // Pi registers extensions by directory presence; the version-sync
    // script writes ~/.pi/extensions/context-mode/package.json. We treat
    // that file as the registration signal.
    const pkgPath = resolve(
      homedir(),
      ".pi",
      "extensions",
      "context-mode",
      "package.json",
    );
    try {
      const pkg = JSON.parse(readFileSync(pkgPath, "utf-8"));
      if (pkg?.name === "context-mode") {
        return {
          check: "Pi extension registration",
          status: "pass",
          message: `context-mode extension installed at ${pkgPath}`,
        };
      }
      return {
        check: "Pi extension registration",
        status: "warn",
        message: `Unexpected package at ${pkgPath}`,
      };
    } catch {
      return {
        check: "Pi extension registration",
        status: "fail",
        message: `context-mode not found at ${pkgPath}`,
        fix: "Run: context-mode upgrade",
      };
    }
  }

  getInstalledVersion(): string {
    try {
      const pkgPath = resolve(
        homedir(),
        ".pi",
        "extensions",
        "context-mode",
        "package.json",
      );
      const pkg = JSON.parse(readFileSync(pkgPath, "utf-8"));
      return pkg.version ?? "unknown";
    } catch {
      return "not installed";
    }
  }

  // ── Upgrade ────────────────────────────────────────────
  // Pi does NOT use settings.json hook entries. The extension is the
  // integration point — there is nothing for the harness to register
  // beyond copying the extension into ~/.pi/extensions/context-mode/.

  configureAllHooks(_pluginRoot: string): string[] {
    return [];
  }

  setHookPermissions(_pluginRoot: string): string[] {
    return [];
  }

  updatePluginRegistry(_pluginRoot: string, _version: string): void {
    // Pi extension version is managed by scripts/version-sync.mjs writing
    // to ~/.pi/extensions/context-mode/package.json. No-op here.
  }

  getRoutingInstructions(): string {
    return "# context-mode\n\nUse context-mode MCP tools (ctx_execute, ctx_execute_file, ctx_batch_execute, ctx_fetch_and_index, ctx_search) instead of inline shell/HTTP calls for data-heavy operations.";
  }
}