"""
test_env.py — Simulation Runner & Sanity Tests
================================================

Provides two entry-points:

  run_simulation(mode)  – Run one full episode and print a formatted report.
  run_all()             – Run all three difficulty modes and compare.
  run_sanity_checks()   – Fast correctness assertions (no pytest needed).

Usage
-----
    python test_env.py            # runs all modes + sanity checks
    python test_env.py easy       # run a single mode
"""

from __future__ import annotations

import sys
import builtins
from typing import Dict, Any

from env import TrafficEnv
from tasks import get_config
from baseline_agent import RuleBasedAgent


# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------

_COL = 80  # separator width


def _separator(char: str = "─") -> str:
    return char * _COL


_ASCII_FALLBACKS = (
    ("\u2550", "="),
    ("\u2500", "-"),
    ("\u2502", "|"),
    ("\u00b7", "-"),
    ("\U0001F6A8", "EV"),
    ("\u2713", "PASS"),
    ("\u2717", "FAIL"),
    ("\u26a0\ufe0f", "WARNING"),
    ("\u2705", "PASS"),
    ("\u2014", "-"),
    ("\u2265", ">="),
    ("\u2264", "<="),
    ("\u2208", "in"),
)


def _safe_text(text: str) -> str:
    encoding = getattr(sys.stdout, "encoding", None) or "utf-8"
    try:
        text.encode(encoding)
        return text
    except UnicodeEncodeError:
        for src, dest in _ASCII_FALLBACKS:
            text = text.replace(src, dest)
        return text


def print(*args, **kwargs) -> None:  # type: ignore[override]
    """
    Safe local print wrapper:
    - keeps rich Unicode output when supported
    - falls back to ASCII-safe glyphs on limited encodings (e.g. cp1252)
    """
    file = kwargs.get("file", sys.stdout)
    if file is not sys.stdout:
        builtins.print(*args, **kwargs)
        return

    sep = kwargs.get("sep", " ")
    end = kwargs.get("end", "\n")
    flush = kwargs.get("flush", False)
    text = sep.join(str(arg) for arg in args)
    builtins.print(_safe_text(text), end=end, flush=flush, file=file)


def _fmt_metric(key: str, value: Any) -> str:
    label = key.replace("_", " ").title()
    if isinstance(value, float):
        return f"  {label:<30} {value:.4f}"
    return f"  {label:<30} {value}"


# ---------------------------------------------------------------------------
# Single-mode simulation
# ---------------------------------------------------------------------------

def run_simulation(mode: str = "medium", verbose: bool = True) -> Dict[str, Any]:
    """
    Run one complete episode in the specified difficulty mode.

    Parameters
    ----------
    mode : str
        "easy", "medium", or "hard"
    verbose : bool
        Print step-by-step output if True.

    Returns
    -------
    dict
        Final info metrics plus 'cumulative_reward' and 'mode'.
    """
    config = get_config(mode)
    env    = TrafficEnv(config)
    agent  = RuleBasedAgent(
        min_green_time=5,
        imbalance_threshold=5,
        max_green_time=15,
        emergency_min_green=2,
    )

    state = env.reset()
    agent.reset()
    done          = False
    total_reward  = 0.0
    step_rewards  = []

    if verbose:
        print()
        print(_separator("═"))
        print(f"  TRAFFIC SIGNAL SIMULATION  ·  Mode: {mode.upper()}")
        print(_separator("═"))
        header = (
            f"{'Step':<6} │ {'Phase':<4} │ "
            f"{'N':>4} {'S':>4} {'E':>4} {'W':>4} │ "
            f"{'NS':>4} {'EW':>4} │ "
            f"{'Reward':>8} │ EV"
        )
        print(header)
        print(_separator())

    while not done:
        action = agent.select_action(state)
        next_state, reward, done, info = env.step(action)
        total_reward += reward
        step_rewards.append(reward)

        if verbose:
            phase_str = "NS" if next_state["phase"] == 0 else "EW"
            ns_q = next_state["north_cars"] + next_state["south_cars"]
            ew_q = next_state["east_cars"]  + next_state["west_cars"]
            ev_flags = next_state["emergency_flags"]
            ev_active = "🚨" if any(ev_flags.values()) else "  "

            # Print every 5 steps, or whenever there's an emergency
            if env.step_count % 5 == 0 or any(ev_flags.values()):
                print(
                    f"{env.step_count:<6} │ {phase_str:<4} │ "
                    f"{next_state['north_cars']:>4} "
                    f"{next_state['south_cars']:>4} "
                    f"{next_state['east_cars']:>4} "
                    f"{next_state['west_cars']:>4} │ "
                    f"{ns_q:>4} {ew_q:>4} │ "
                    f"{reward:>8.3f} │ {ev_active}"
                )

        state = next_state

    if verbose:
        print(_separator())
        print(f"\n  FINAL METRICS  ({mode.upper()})")
        print(_separator())
        for k, v in info.items():
            print(_fmt_metric(k, v))
        print(_fmt_metric("cumulative_reward", total_reward))
        if step_rewards:
            print(_fmt_metric("min_step_reward",  min(step_rewards)))
            print(_fmt_metric("max_step_reward",  max(step_rewards)))
        print()

    result = dict(info)
    result["cumulative_reward"] = total_reward
    result["mode"] = mode
    return result


# ---------------------------------------------------------------------------
# Run all modes and print comparison table
# ---------------------------------------------------------------------------

def run_all() -> None:
    """Run easy, medium and hard in sequence; print a comparison table."""
    results = {}
    for mode in ("easy", "medium", "hard"):
        results[mode] = run_simulation(mode, verbose=True)

    print()
    print(_separator("═"))
    print("  CROSS-MODE COMPARISON")
    print(_separator("═"))
    metrics = [
        "total_cleared", "avg_waiting_time",
        "max_queue_length", "signal_switch_count",
        "congestion_score", "avg_ev_clear_time",
        "fairness_score", "cumulative_reward",
    ]
    col_w = 18
    header = f"  {'Metric':<30}" + "".join(f"{m.upper():>{col_w}}" for m in ("easy", "medium", "hard"))
    print(header)
    print(_separator())
    for m in metrics:
        row = f"  {m.replace('_',' ').title():<30}"
        for mode in ("easy", "medium", "hard"):
            val = results[mode].get(m, "—")
            if isinstance(val, float):
                row += f"{val:>{col_w}.3f}"
            else:
                row += f"{val:>{col_w}}"
        print(row)
    print(_separator("═"))
    print()


# ---------------------------------------------------------------------------
# Sanity / correctness checks (no external test runner needed)
# ---------------------------------------------------------------------------

def run_sanity_checks() -> None:
    """Assert basic correctness invariants for all difficulty modes."""
    print()
    print(_separator("═"))
    print("  SANITY CHECKS")
    print(_separator("═"))

    passed = 0
    failed = 0

    def check(name: str, condition: bool) -> None:
        nonlocal passed, failed
        status = "✓ PASS" if condition else "✗ FAIL"
        print(f"  [{status}]  {name}")
        if condition:
            passed += 1
        else:
            failed += 1

    for mode in ("easy", "medium", "hard"):
        cfg = get_config(mode)
        env = TrafficEnv(cfg)
        agent = RuleBasedAgent()

        # 1. reset() returns valid state
        state = env.reset()
        agent.reset()
        check(
            f"[{mode}] reset() returns all-zero queues",
            all(state[f"{d}_cars"] == 0 for d in ("north", "south", "east", "west")),
        )

        # 2. Step returns correct tuple length
        action = agent.select_action(state)
        result = env.step(action)
        check(f"[{mode}] step() returns 4-tuple", len(result) == 4)

        ns, reward, done, info = result

        # 3. Reward is clipped
        check(f"[{mode}] reward in [-1, 1]", -1.0 <= reward <= 1.0)

        # 4. State keys present
        required_keys = {
            "north_cars", "south_cars", "east_cars", "west_cars",
            "waiting_times", "phase", "emergency_flags", "step_count",
        }
        check(f"[{mode}] state has required keys", required_keys.issubset(ns.keys()))

        # 5. Info keys present
        required_info = {
            "total_cleared", "avg_waiting_time",
            "max_queue_length", "signal_switch_count",
            "congestion_score", "avg_ev_clear_time",
            "fairness_score",
        }
        check(f"[{mode}] info has required keys", required_info.issubset(info.keys()))

        # 6. Queues never go negative
        for _ in range(cfg["max_steps"]):
            a = agent.select_action(ns)
            ns, _, done, _ = env.step(a)
            if done:
                break
        all_non_neg = all(v >= 0 for v in env.queues.values())
        check(f"[{mode}] queues never go negative (full episode)", all_non_neg)

        # 7. Queues never exceed max_queue
        check(
            f"[{mode}] queues never exceed max_queue ({cfg['max_queue']})",
            all(v <= cfg["max_queue"] for v in env.queues.values()),
        )

        # 8. Signal phase is always 0 or 1
        check(f"[{mode}] phase is always 0 or 1", env.phase in (0, 1))

        # 9. total_cleared is non-negative
        check(f"[{mode}] total_cleared ≥ 0", env.total_cleared >= 0)

        # 10. congestion_score in [0, 1]
        score = info["congestion_score"]
        check(f"[{mode}] congestion_score ∈ [0, 1]", 0.0 <= score <= 1.0)

        print()

    print(_separator())
    print(f"  Results: {passed} passed, {failed} failed")
    print(_separator("═"))
    if failed:
        print("  ⚠️  Some checks failed — review the environment logic.")
    else:
        print("  ✅  All sanity checks passed.")
    print()


# ---------------------------------------------------------------------------
# CLI entry-point
# ---------------------------------------------------------------------------

if __name__ == "__main__":
    if len(sys.argv) == 2 and sys.argv[1].lower() in ("easy", "medium", "hard"):
        run_simulation(sys.argv[1].lower(), verbose=True)
    else:
        run_all()
        run_sanity_checks()