"""Tests for the pipeline orchestrator's wiring and control flow.

These tests replace each stage's ``run_*`` function with a fake so we can
verify:
    * Artifact paths are passed correctly between stages
    * A failing gate aborts the pipeline (bail_on_failure=True)
    * ``--from`` and ``--only`` flags skip the right stages
    * ``pipeline_summary.json`` is written with the right shape

Run on CPU only.
"""
from __future__ import annotations

import json
import sys
from pathlib import Path
from unittest.mock import patch

_ROOT = Path(__file__).resolve().parent.parent
if str(_ROOT) not in sys.path:
    sys.path.insert(0, str(_ROOT))

from training.config import TrainingConfig
from training.pipeline import STAGES, run_pipeline


def _fake_stage(ok: bool = True, extra: dict | None = None):
    def fake(config, *args, **kwargs):
        return {"ok": ok, **(extra or {})}
    return fake


def test_stages_list_is_ordered():
    """Pipeline stages run in this exact order: sft → gate → grpo → eval."""
    assert STAGES == ["sft", "gate", "grpo", "eval"]


def test_pipeline_runs_all_stages_when_all_pass():
    """Happy path: every stage returns ok=True, pipeline completes."""
    cfg = TrainingConfig()

    with patch("training.stages.stage_1_sft.run_sft", _fake_stage(True)), \
         patch("training.stages.stage_2_gate.run_gate", _fake_stage(True, {"coverage": 1.0})), \
         patch("training.stages.stage_3_grpo.run_grpo", _fake_stage(True, {"mean_reward": 0.8})), \
         patch("training.stages.stage_4_eval.run_eval", _fake_stage(True)):
        summary = run_pipeline(cfg, list(STAGES), bail_on_failure=True)

    assert summary["final_status"] == "completed"
    assert set(summary["stages"].keys()) == set(STAGES)
    for stage in STAGES:
        assert summary["stages"][stage]["ok"] is True


def test_pipeline_bails_when_gate_fails():
    """If the gate fails, GRPO and eval must NOT run — this is the whole
    point of the gate: fail fast, don't burn GPU on a broken SFT."""
    cfg = TrainingConfig()

    grpo_called = [False]
    eval_called = [False]

    def track_grpo(*args, **kwargs):
        grpo_called[0] = True
        return {"ok": True}

    def track_eval(*args, **kwargs):
        eval_called[0] = True
        return {"ok": True}

    with patch("training.stages.stage_1_sft.run_sft", _fake_stage(True)), \
         patch("training.stages.stage_2_gate.run_gate", _fake_stage(False, {"coverage": 0.5})), \
         patch("training.stages.stage_3_grpo.run_grpo", track_grpo), \
         patch("training.stages.stage_4_eval.run_eval", track_eval):
        summary = run_pipeline(cfg, list(STAGES), bail_on_failure=True)

    assert summary["final_status"] == "failed_at_gate"
    assert grpo_called[0] is False, "GRPO ran even though gate failed!"
    assert eval_called[0] is False, "Eval ran even though gate failed!"


def test_pipeline_bails_when_sft_fails():
    """Even earlier: if SFT fails (loss too high), nothing downstream runs."""
    cfg = TrainingConfig()

    gate_called = [False]

    with patch("training.stages.stage_1_sft.run_sft", _fake_stage(False, {"final_training_loss": 2.5})), \
         patch("training.stages.stage_2_gate.run_gate", lambda *a, **k: gate_called.__setitem__(0, True) or {"ok": True}):
        summary = run_pipeline(cfg, list(STAGES), bail_on_failure=True)

    assert summary["final_status"] == "failed_at_sft"
    assert gate_called[0] is False


def test_pipeline_no_bail_runs_all_stages_even_on_failure():
    """With bail_on_failure=False, each stage runs regardless of prior
    failures. Used for post-mortem runs where we want partial artifacts."""
    cfg = TrainingConfig()

    with patch("training.stages.stage_1_sft.run_sft", _fake_stage(False)), \
         patch("training.stages.stage_2_gate.run_gate", _fake_stage(False)), \
         patch("training.stages.stage_3_grpo.run_grpo", _fake_stage(False)), \
         patch("training.stages.stage_4_eval.run_eval", _fake_stage(True)):
        summary = run_pipeline(cfg, list(STAGES), bail_on_failure=False)

    assert summary["final_status"] == "completed"
    assert all(stage in summary["stages"] for stage in STAGES)


def test_pipeline_with_subset_of_stages():
    """``--only grpo`` or ``--from gate`` narrows the stage list. Pipeline
    runs exactly those stages."""
    cfg = TrainingConfig()

    with patch("training.stages.stage_3_grpo.run_grpo", _fake_stage(True)):
        summary = run_pipeline(cfg, ["grpo"], bail_on_failure=True)

    assert list(summary["stages"].keys()) == ["grpo"]
    assert summary["final_status"] == "completed"


def test_exception_in_stage_surfaces_cleanly():
    """If a stage's run function raises (not returns ok=False), the
    orchestrator must catch it and record ``final_status=fatal``."""
    cfg = TrainingConfig()

    def raiser(*args, **kwargs):
        raise RuntimeError("simulated stage crash")

    with patch("training.stages.stage_1_sft.run_sft", raiser):
        summary = run_pipeline(cfg, ["sft"], bail_on_failure=True)

    assert summary["final_status"] == "fatal"
    assert "error" in summary["stages"]["sft"]


def test_pipeline_summary_is_json_serializable():
    """The final summary must round-trip through JSON so it can be written
    to artifacts/pipeline_summary.json."""
    cfg = TrainingConfig()

    with patch("training.stages.stage_1_sft.run_sft", _fake_stage(True, {"custom_metric": 0.42})):
        summary = run_pipeline(cfg, ["sft"], bail_on_failure=True)

    # This serialization is what pipeline.py main() does; if it fails,
    # the artifact won't be written.
    s = json.dumps(summary, default=str)
    assert len(s) > 10
    # And re-parses
    parsed = json.loads(s)
    assert parsed["final_status"] == "completed"