/**
 * T12 tests — session/session.ts (single-session lifecycle).
 *
 * ARCHITECTURE §3.4 / §4.4 + the cross-validated fixes:
 *  - M4: spawn failure THROWS, never swallowed.
 *  - M5: every ws.send is guarded by `ws.readyState === WS_OPEN`.
 *  - L1: detach-then-exit keeps the session (exit not delivered when attachedWs is null).
 *  - L4: writeInput/resize are no-ops once the PTY has exited.
 *
 * node-pty is mocked (`vi.mock`) so `spawn` returns a MockIPty — the sandbox blocks
 * real posix_spawn, and the mock lets us drive onData/onExit deterministically and
 * assert lifecycle without a real shell.
 */

import { describe, it, expect, beforeEach, vi } from 'vitest';

import type { Config, Dims, Session, ServerMessage, WebSocketLike } from '../src/types.js';
import { WS_OPEN } from '../src/types.js';
import { createMockPty, type MockIPty } from './helpers/mock-pty.js';

// ── node-pty mock ───────────────────────────────────────────────────────────
// spawn returns whatever `nextPty` points at, and records its call args so we
// can assert how createSession invoked it (and force it to throw for M4).
let nextPty: MockIPty;
let spawnError: Error | null = null;
const spawnCalls: Array<{ file: string; args: string[] | string; options: unknown }> = [];

vi.mock('node-pty', () => ({
  spawn: (file: string, args: string[] | string, options: unknown) => {
    spawnCalls.push({ file, args, options });
    if (spawnError) throw spawnError;
    return nextPty;
  },
}));

// Imported AFTER vi.mock so the module under test binds to the mocked spawn.
const { createSession, attachWs, detachWs, writeInput, resize, kill } = await import(
  '../src/session/session.js'
);

// ── helpers ─────────────────────────────────────────────────────────────────
const CFG: Config = {
  port: 3000,
  bindHost: '0.0.0.0',
  shellPath: '/bin/zsh',
  homeDir: '/home/tester',
  idleTtlMs: 86_400_000,
  scrollbackBytes: 2 * 1024 * 1024,
  maxPayloadBytes: 1024 * 1024,
  wsPath: '/term',
  allowedOrigins: [],
};

const DIMS: Dims = { cols: 80, rows: 24 };

interface MockWs extends WebSocketLike {
  readyState: number;
  sent: string[];
  closed: boolean;
}

function createMockWs(readyState: number = WS_OPEN): MockWs {
  const sent: string[] = [];
  return {
    readyState,
    sent,
    closed: false,
    send(data: string) {
      sent.push(data);
    },
    close() {
      this.closed = true;
    },
  };
}

/** Decode the JSON frames a ws received back into ServerMessages. */
function received(ws: MockWs): ServerMessage[] {
  return ws.sent.map((s) => JSON.parse(s) as ServerMessage);
}

function newSession(onExit: (s: Session) => void = () => {}): Session {
  nextPty = createMockPty();
  return createSession(CFG, DIMS, 1_000, onExit);
}

beforeEach(() => {
  spawnError = null;
  spawnCalls.length = 0;
});

// ── createSession / spawn ─────────────────────────────────────────────────────
describe('createSession', () => {
  it('spawns the PTY via node-pty with shellPath, cwd and dims', () => {
    const s = newSession();

    expect(spawnCalls).toHaveLength(1);
    expect(spawnCalls[0]!.file).toBe(CFG.shellPath);
    const opts = spawnCalls[0]!.options as { cwd?: string; cols?: number; rows?: number };
    expect(opts.cwd).toBe(CFG.homeDir);
    expect(opts.cols).toBe(DIMS.cols);
    expect(opts.rows).toBe(DIMS.rows);

    expect(s.pty).toBe(nextPty);
    expect(s.meta.shellPath).toBe(CFG.shellPath);
    expect(s.meta.createdAt).toBe(1_000);
    expect(s.attachedWs).toBeNull();
    expect(s.exitedAt).toBeNull();
    expect(s.exitCode).toBeNull();
  });

  it('THROWS (does not swallow) when spawn fails (M4)', () => {
    spawnError = new Error('spawn failed: /no/such/shell ENOENT');
    nextPty = createMockPty();

    expect(() => createSession(CFG, DIMS, 1_000, () => {})).toThrow(/spawn failed/);
  });
});

// ── onData → buffer + forward ──────────────────────────────────────────────────
describe('onData', () => {
  it('appends output to the ring buffer and refreshes lastOutputAt', () => {
    const s = newSession();
    const pty = s.pty as MockIPty;

    pty.emitData('hello ');
    pty.emitData('world');

    // buffer snapshot prepends the M2 soft-reset, then the verbatim output.
    expect(s.buffer.snapshot()).toBe('\x1b[0mhello world');
    expect(s.lastOutputAt).toBeGreaterThanOrEqual(1_000);
  });

  it('forwards output to the attached ws as an `output` message', () => {
    const s = newSession();
    const ws = createMockWs();
    attachWs(s, ws);
    ws.sent.length = 0; // drop the replay frame from attach

    (s.pty as MockIPty).emitData('abc');

    expect(received(ws)).toEqual([{ type: 'output', data: 'abc' }]);
  });

  it('still buffers output when no ws is attached (does not throw)', () => {
    const s = newSession();
    expect(() => (s.pty as MockIPty).emitData('orphan')).not.toThrow();
    expect(s.buffer.snapshot()).toContain('orphan');
  });

  it('does NOT send to a ws whose readyState is not OPEN (M5)', () => {
    const s = newSession();
    const ws = createMockWs(WS_OPEN);
    attachWs(s, ws);
    ws.sent.length = 0;

    ws.readyState = 3; // CLOSED
    (s.pty as MockIPty).emitData('lost');

    expect(ws.sent).toHaveLength(0);
  });
});

// ── attachWs ──────────────────────────────────────────────────────────────────
describe('attachWs', () => {
  it('replays the buffer snapshot to the newly attached ws', () => {
    const s = newSession();
    (s.pty as MockIPty).emitData('prior output');

    const ws = createMockWs();
    const kicked = attachWs(s, ws);

    expect(kicked).toBeNull();
    expect(s.attachedWs).toBe(ws);
    expect(received(ws)).toEqual([{ type: 'output', data: '\x1b[0mprior output' }]);
  });

  it('points attachedWs at the new ws BEFORE returning the kicked old ws (later wins)', () => {
    const s = newSession();
    const oldWs = createMockWs();
    attachWs(s, oldWs);

    const newWs = createMockWs();
    const kicked = attachWs(s, newWs);

    // pointer is swapped first; caller is responsible for closing the kicked ws.
    expect(s.attachedWs).toBe(newWs);
    expect(kicked).toBe(oldWs);
    expect(oldWs.closed).toBe(false); // attachWs must NOT close it itself

    // forwarding now only ever reaches the new ws.
    newWs.sent.length = 0;
    (s.pty as MockIPty).emitData('after kick');
    expect(received(newWs)).toEqual([{ type: 'output', data: 'after kick' }]);
    expect(oldWs.sent.some((f) => f.includes('after kick'))).toBe(false);
  });
});

// ── detachWs ──────────────────────────────────────────────────────────────────
describe('detachWs', () => {
  it('clears attachedWs and stamps detachedAt but NEVER kills the PTY', () => {
    const s = newSession();
    const ws = createMockWs();
    attachWs(s, ws);

    detachWs(s, 5_000);

    expect(s.attachedWs).toBeNull();
    expect(s.detachedAt).toBe(5_000);
    expect((s.pty as MockIPty).killed).toBe(false);
  });

  it('keeps the PTY alive after detach: further onData still fills the buffer', () => {
    const s = newSession();
    const ws = createMockWs();
    attachWs(s, ws);
    detachWs(s, 5_000);

    (s.pty as MockIPty).emitData('background work');

    expect((s.pty as MockIPty).killed).toBe(false);
    expect(s.buffer.snapshot()).toContain('background work');
  });
});

// ── onExit ────────────────────────────────────────────────────────────────────
describe('onExit', () => {
  it('sets exitedAt/exitCode, sends `exit` to the attached ws, and calls injected onExit', () => {
    const onExit = vi.fn();
    nextPty = createMockPty();
    const s = createSession(CFG, DIMS, 1_000, onExit);

    const ws = createMockWs();
    attachWs(s, ws);
    ws.sent.length = 0;

    (s.pty as MockIPty).emitExit(0);

    expect(s.exitedAt).not.toBeNull();
    expect(s.exitCode).toBe(0);
    expect(received(ws)).toEqual([{ type: 'exit', code: 0 }]);
    expect(onExit).toHaveBeenCalledWith(s);
  });

  it('after detach, exit is NOT delivered but the session is preserved (L1)', () => {
    const onExit = vi.fn();
    nextPty = createMockPty();
    const s = createSession(CFG, DIMS, 1_000, onExit);

    const ws = createMockWs();
    attachWs(s, ws);
    detachWs(s, 5_000);
    ws.sent.length = 0;

    (s.pty as MockIPty).emitExit(137);

    // exit happened: state recorded, but no ws to notify → nothing delivered.
    expect(s.exitedAt).not.toBeNull();
    expect(s.exitCode).toBe(137);
    expect(ws.sent).toHaveLength(0);
    // session preserved: buffer intact (caller/manager decides removal via onExit).
    expect(onExit).toHaveBeenCalledWith(s);
  });

  it('does not send exit to a ws whose readyState is not OPEN (M5)', () => {
    nextPty = createMockPty();
    const s = createSession(CFG, DIMS, 1_000, () => {});
    const ws = createMockWs(WS_OPEN);
    attachWs(s, ws);
    ws.sent.length = 0;
    ws.readyState = 3; // CLOSED

    (s.pty as MockIPty).emitExit(1);

    expect(ws.sent).toHaveLength(0);
  });
});

// ── writeInput / resize after exit (L4) + resize idempotence ──────────────────
describe('writeInput / resize', () => {
  it('writeInput forwards to pty.write while alive', () => {
    const s = newSession();
    writeInput(s, 'ls\r');
    expect((s.pty as MockIPty).writes).toEqual(['ls\r']);
  });

  it('resize forwards to pty.resize while alive', () => {
    const s = newSession();
    resize(s, 100, 40);
    expect((s.pty as MockIPty).resizes).toEqual([{ cols: 100, rows: 40 }]);
  });

  it('resize is idempotent: same cols/rows are skipped', () => {
    const s = newSession();
    resize(s, 80, 24); // equal to the spawn dims → no-op
    expect((s.pty as MockIPty).resizes).toHaveLength(0);

    resize(s, 90, 24); // changed → applied
    resize(s, 90, 24); // unchanged again → skipped
    expect((s.pty as MockIPty).resizes).toEqual([{ cols: 90, rows: 24 }]);
  });

  it('ignores writeInput once the PTY has exited (L4)', () => {
    const s = newSession();
    (s.pty as MockIPty).emitExit(0);

    writeInput(s, 'should be dropped');
    expect((s.pty as MockIPty).writes).toHaveLength(0);
  });

  it('ignores resize once the PTY has exited (L4)', () => {
    const s = newSession();
    (s.pty as MockIPty).emitExit(0);

    resize(s, 200, 50);
    expect((s.pty as MockIPty).resizes).toHaveLength(0);
  });
});

// ── kill ──────────────────────────────────────────────────────────────────────
describe('kill', () => {
  it('kills the underlying PTY', () => {
    const s = newSession();
    kill(s);
    expect((s.pty as MockIPty).killed).toBe(true);
  });
});