import {
  describe,
  it,
  expect,
  vi,
  beforeAll,
  afterAll,
  beforeEach,
  afterEach,
} from "vitest";
import * as fs from "fs";
import * as os from "os";
import * as path from "path";

/**
 * Unit tests for the RunResult discriminated union returned by runAgent().
 *
 * cross-spawn is mocked so no real process is launched. Each test controls
 * what the fake child process emits (stdout, exit code, error event) to cover
 * all four RunResult status variants.
 */

// ---------------------------------------------------------------------------
// Configurable mock state — mutated per test via setMockBehavior()
// ---------------------------------------------------------------------------
interface MockBehavior {
  /** stdout data to emit (default: valid JSON success payload) */
  stdoutData?: string;
  /** exit code the child closes with (default: 0) */
  exitCode?: number;
  /** if set, child emits an "error" event with this error object */
  spawnError?: NodeJS.ErrnoException;
  /** if true, close event is never emitted (simulates a hanging process) */
  neverClose?: boolean;
  /** delay in ms before emitting close (default: 0) */
  closeDelayMs?: number;
}

let mockBehavior: MockBehavior = {};

function setMockBehavior(b: MockBehavior) {
  mockBehavior = b;
}

vi.mock("cross-spawn", () => {
  function makeMockChild() {
    const listeners: Record<string, Array<(...a: unknown[]) => void>> = {};

    const emit = (event: string, ...args: unknown[]) => {
      for (const cb of listeners[event] ?? []) {
        cb(...args);
      }
    };

    const stdoutListeners: Record<string, Array<(...a: unknown[]) => void>> =
      {};

    const stdoutStream = {
      setEncoding: () => {},
      on: (event: string, cb: (...a: unknown[]) => void) => {
        if (!stdoutListeners[event]) stdoutListeners[event] = [];
        stdoutListeners[event].push(cb);

        if (event === "data" && !mockBehavior.spawnError) {
          const data =
            mockBehavior.stdoutData ??
            JSON.stringify({ result: "hello from agent" });
          Promise.resolve().then(() => {
            for (const handler of stdoutListeners["data"] ?? []) {
              handler(data);
            }
          });
        }
      },
    };

    const child = {
      stdout: stdoutStream,
      stderr: {
        setEncoding: () => {},
        on: () => {},
      },
      stdin: { end: () => {} },
      on: (event: string, cb: (...a: unknown[]) => void) => {
        if (!listeners[event]) listeners[event] = [];
        listeners[event].push(cb);

        if (event === "error" && mockBehavior.spawnError) {
          Promise.resolve().then(() => emit("error", mockBehavior.spawnError));
          return;
        }

        if (event === "close" && !mockBehavior.neverClose) {
          // Emit close after stdout data (two microtask ticks away)
          const delay = mockBehavior.closeDelayMs ?? 0;
          const schedule = delay > 0
            ? (fn: () => void) => setTimeout(fn, delay)
            : (fn: () => void) =>
                Promise.resolve()
                  .then(() => Promise.resolve())
                  .then(fn);

          schedule(() => emit("close", mockBehavior.exitCode ?? 0));
        }
      },
      kill: () => {},
    };

    return child;
  }

  return {
    default: (_cmd: string, _args: string[]) => makeMockChild(),
  };
});

// Import after mock registration
import { runAgent, _resetSemaphore } from "../../src/agent/runner";
import { _resetResolveClaudeCache } from "../../src/runtime/resolve-claude";

// ---------------------------------------------------------------------------
// Shared workspace fixture
// ---------------------------------------------------------------------------

describe("RunResult discriminated union", () => {
  let workspaceDir: string;
  const originalEnv = { ...process.env };

  beforeAll(() => {
    workspaceDir = fs.mkdtempSync(
      path.join(os.tmpdir(), "disclaw-runresult-")
    );

    fs.writeFileSync(
      path.join(workspaceDir, "agent.yaml"),
      `name: result-agent\ndisplay_name: Result Agent\nrole: Testing\nchannel_id: "999"\n`,
      "utf-8"
    );
    fs.writeFileSync(
      path.join(workspaceDir, "CLAUDE.md"),
      "# Result Agent\nYou are a test agent.\n",
      "utf-8"
    );
  });

  beforeEach(() => {
    mockBehavior = {};
    _resetResolveClaudeCache();
    _resetSemaphore(4);
    process.env.CLAUDE_PATH = "/fake/claude";
  });

  afterEach(() => {
    process.env = { ...originalEnv };
    _resetResolveClaudeCache();
  });

  afterAll(() => {
    try {
      fs.rmSync(workspaceDir, { recursive: true, force: true });
    } catch {
      // Best-effort cleanup
    }
  });

  // -------------------------------------------------------------------------
  // (a) success
  // -------------------------------------------------------------------------
  it('(a) success: valid JSON stdout → status "success" with correct text', async () => {
    setMockBehavior({
      stdoutData: JSON.stringify({ result: "Agent says hi!" }),
      exitCode: 0,
    });

    const result = await runAgent({
      workspacePath: workspaceDir,
      channelName: "test",
      userMessage: "hello",
      conversationHistory: [],
    });

    expect(result.status).toBe("success");
    if (result.status === "success") {
      expect(result.text).toBe("Agent says hi!");
    }
  });

  // -------------------------------------------------------------------------
  // (b) timeout
  // -------------------------------------------------------------------------
  it('(b) timeout: process never closes → status "timeout" with timeoutMs', async () => {
    // Never emit close so the timeout fires. Use a very short timeout by
    // writing a disclaw.yaml that sets claude_timeout_seconds to something tiny.
    // Instead we rely on the fact that the timeout logic in runner.ts will kill
    // the child (kill() is a no-op in the mock) and then the close event must
    // still fire. We simulate this by making close fire *after* a delay longer
    // than the timeout but still having `killed = true` set by the timer.
    //
    // The cleanest approach: let the mock emit close immediately but set
    // killed=true before it fires by abusing the AbortController signal to
    // trigger the kill path, and then emit close with code 0.
    //
    // Actually the simplest: set closeDelayMs to something > timeout, but
    // the default timeout is 120s which is way too long for a test. Instead
    // we use a custom disclaw.yaml in the workspace.

    const configPath = path.join(workspaceDir, "disclaw.yaml");
    fs.writeFileSync(
      configPath,
      `workspace_root: /tmp\nmanagement_channel: disclaw\nclaude_command: claude\nclaude_timeout_seconds: 0.05\nmax_concurrent_agents: 4\nenv_blocklist: []\n`,
      "utf-8"
    );

    // The mock's kill() is a no-op, so the close event will never arrive via
    // the normal path. We need close to fire after the timeout kills the child.
    // Set a small delay so close fires *after* the 50ms timeout.
    setMockBehavior({
      neverClose: false,
      closeDelayMs: 200, // fires after the 50ms timeout
      exitCode: 0,
    });

    // Override __dirname resolution: runner.ts resolves rootDir as 2 levels
    // up from __dirname (src/agent -> root). We need to point it to our temp
    // workspace. Use DISCLAW_ROOT env var is not available, so instead we
    // write disclaw.yaml to the project root's expected location. This is
    // tricky in a unit test — easier to just accept the default 120s timeout
    // won't fire and instead mock the behavior differently.
    //
    // Simplest working approach: use AbortController to abort → child.kill()
    // is called → mock emits close immediately with code 0 but killed=true.
    // BUT abort doesn't set `killed` in the timeout branch — it sets it in
    // the abort branch, and close code 0 after abort currently resolves success.
    //
    // The cleanest unit-testable path: just verify the timeout branch by
    // patching the timeout to a very small value via the config file in the
    // project root (since runner.ts uses loadDisclawConfig from 2 levels up).

    // Clean up config to avoid affecting other tests
    try {
      fs.unlinkSync(configPath);
    } catch {
      // ignore
    }

    // Alternative approach: write config to project root temporarily
    const projectRoot = path.resolve(__dirname, "../..");
    const projectConfig = path.join(projectRoot, "disclaw.yaml");
    const originalConfig = fs.existsSync(projectConfig)
      ? fs.readFileSync(projectConfig, "utf-8")
      : null;

    try {
      fs.writeFileSync(
        projectConfig,
        `workspace_root: /tmp\nmanagement_channel: disclaw\nclaude_command: claude\nclaude_timeout_seconds: 0.05\nmax_concurrent_agents: 4\nenv_blocklist: []\n`,
        "utf-8"
      );

      setMockBehavior({
        neverClose: false,
        closeDelayMs: 200,
        exitCode: 0,
      });

      const result = await runAgent({
        workspacePath: workspaceDir,
        channelName: "test",
        userMessage: "hello",
        conversationHistory: [],
      });

      expect(result.status).toBe("timeout");
      if (result.status === "timeout") {
        expect(result.timeoutMs).toBe(50);
      }
    } finally {
      if (originalConfig !== null) {
        fs.writeFileSync(projectConfig, originalConfig, "utf-8");
      } else {
        try {
          fs.unlinkSync(projectConfig);
        } catch {
          // ignore
        }
      }
    }
  }, 10_000);

  // -------------------------------------------------------------------------
  // (c) cli-error: non-zero exit code
  // -------------------------------------------------------------------------
  it('(c) cli-error: exit code != 0 → status "cli-error"', async () => {
    setMockBehavior({
      stdoutData: "",
      exitCode: 1,
    });

    const result = await runAgent({
      workspacePath: workspaceDir,
      channelName: "test",
      userMessage: "hello",
      conversationHistory: [],
    });

    expect(result.status).toBe("cli-error");
    if (result.status === "cli-error") {
      expect(result.message).toMatch(/Claude Code CLI error/);
    }
  });

  // -------------------------------------------------------------------------
  // (d) cli-error ENOENT
  // -------------------------------------------------------------------------
  it('(d) cli-error ENOENT: spawn error → status "cli-error" with "not found" message', async () => {
    const enoentError = Object.assign(new Error("spawn ENOENT"), {
      code: "ENOENT",
    }) as NodeJS.ErrnoException;

    setMockBehavior({
      spawnError: enoentError,
    });

    const result = await runAgent({
      workspacePath: workspaceDir,
      channelName: "test",
      userMessage: "hello",
      conversationHistory: [],
    });

    expect(result.status).toBe("cli-error");
    if (result.status === "cli-error") {
      expect(result.message).toMatch(/not found/i);
      expect(result.stderr).toBeUndefined();
    }
  });
});