"""
Unit Tests für Workflow Engine (Phase 0: Foundation)

Tests für:
- Graph-Parsing
- Topologische Sortierung
- DAG-Validierung (Zyklen-Erkennung)
- Erreichbarkeits-Prüfungen

Run with: pytest tests/backend/test_workflow_engine.py -v
"""
import pytest
import sys
import os

# Add backend to path
sys.path.insert(0, os.path.join(os.path.dirname(__file__), '../../backend'))

from workflow_models import WorkflowGraph, WorkflowNode, WorkflowEdge, NodeType, Position
from workflow_engine import WorkflowEngine, parse_workflow_graph, validate_workflow_graph
from fastapi import HTTPException


# ── Fixtures ──────────────────────────────────────────────────────────────────

@pytest.fixture
def simple_valid_graph():
    """Einfacher gültiger Graph: START → ANALYSIS → END"""
    return WorkflowGraph(
        nodes=[
            WorkflowNode(id="start", type=NodeType.START, position=Position(x=0, y=0)),
            WorkflowNode(id="analysis1", type=NodeType.ANALYSIS, position=Position(x=100, y=0), prompt_slug="test_prompt"),
            WorkflowNode(id="end", type=NodeType.END, position=Position(x=200, y=0))
        ],
        edges=[
            WorkflowEdge(id="e1", from_node="start", to_node="analysis1"),
            WorkflowEdge(id="e2", from_node="analysis1", to_node="end")
        ]
    )


@pytest.fixture
def parallel_graph():
    """Graph mit Parallelität: START → (A1 || A2) → JOIN → END"""
    return WorkflowGraph(
        nodes=[
            WorkflowNode(id="start", type=NodeType.START, position=Position(x=0, y=50)),
            WorkflowNode(id="analysis1", type=NodeType.ANALYSIS, position=Position(x=100, y=0), prompt_slug="prompt1"),
            WorkflowNode(id="analysis2", type=NodeType.ANALYSIS, position=Position(x=100, y=100), prompt_slug="prompt2"),
            WorkflowNode(id="join", type=NodeType.JOIN, position=Position(x=200, y=50)),
            WorkflowNode(id="end", type=NodeType.END, position=Position(x=300, y=50))
        ],
        edges=[
            WorkflowEdge(id="e1", from_node="start", to_node="analysis1"),
            WorkflowEdge(id="e2", from_node="start", to_node="analysis2"),
            WorkflowEdge(id="e3", from_node="analysis1", to_node="join"),
            WorkflowEdge(id="e4", from_node="analysis2", to_node="join"),
            WorkflowEdge(id="e5", from_node="join", to_node="end")
        ]
    )


@pytest.fixture
def branching_graph():
    """Graph mit Verzweigung: START → LOGIC → (A1 | A2) → END"""
    return WorkflowGraph(
        nodes=[
            WorkflowNode(id="start", type=NodeType.START, position=Position(x=0, y=50)),
            WorkflowNode(id="logic1", type=NodeType.LOGIC, position=Position(x=100, y=50)),
            WorkflowNode(id="analysis1", type=NodeType.ANALYSIS, position=Position(x=200, y=0), prompt_slug="prompt1"),
            WorkflowNode(id="analysis2", type=NodeType.ANALYSIS, position=Position(x=200, y=100), prompt_slug="prompt2"),
            WorkflowNode(id="end", type=NodeType.END, position=Position(x=300, y=50))
        ],
        edges=[
            WorkflowEdge(id="e1", from_node="start", to_node="logic1"),
            WorkflowEdge(id="e2", from_node="logic1", to_node="analysis1", label="then"),
            WorkflowEdge(id="e3", from_node="logic1", to_node="analysis2", label="else"),
            WorkflowEdge(id="e4", from_node="analysis1", to_node="end"),
            WorkflowEdge(id="e5", from_node="analysis2", to_node="end")
        ]
    )


# ── Test: Graph-Parsing ───────────────────────────────────────────────────────

def test_parse_workflow_graph_valid(simple_valid_graph):
    """Test: Gültiger Graph wird korrekt geparst"""
    graph_dict = simple_valid_graph.model_dump()
    parsed = parse_workflow_graph(graph_dict)

    assert len(parsed.nodes) == 3
    assert len(parsed.edges) == 2
    assert parsed.nodes[0].type == NodeType.START
    assert parsed.nodes[2].type == NodeType.END


def test_parse_workflow_graph_invalid_format():
    """Test: Ungültiges Format wirft ValidationError"""
    invalid_graph = {"nodes": "not a list", "edges": []}

    with pytest.raises(Exception):  # Pydantic ValidationError
        parse_workflow_graph(invalid_graph)


# ── Test: Graph-Validierung ──────────────────────────────────────────────────

def test_valid_graph_initialization(simple_valid_graph):
    """Test: Gültiger Graph kann initialisiert werden"""
    engine = WorkflowEngine(simple_valid_graph)

    assert len(engine.nodes_by_id) == 3
    assert len(engine.edges_by_id) == 2
    assert engine.topological_order == ["start", "analysis1", "end"]


def test_validate_graph_no_start_node():
    """Test: Graph ohne START-Knoten wird abgelehnt"""
    graph = WorkflowGraph(
        nodes=[
            WorkflowNode(id="analysis1", type=NodeType.ANALYSIS, position=Position(x=0, y=0), prompt_slug="test"),
            WorkflowNode(id="end", type=NodeType.END, position=Position(x=100, y=0))
        ],
        edges=[WorkflowEdge(id="e1", from_node="analysis1", to_node="end")]
    )

    with pytest.raises(HTTPException) as exc_info:
        WorkflowEngine(graph)

    assert exc_info.value.status_code == 400
    assert "Kein START-Knoten" in str(exc_info.value.detail)


def test_validate_graph_no_end_node():
    """Test: Graph ohne END-Knoten wird abgelehnt"""
    graph = WorkflowGraph(
        nodes=[
            WorkflowNode(id="start", type=NodeType.START, position=Position(x=0, y=0)),
            WorkflowNode(id="analysis1", type=NodeType.ANALYSIS, position=Position(x=100, y=0), prompt_slug="test")
        ],
        edges=[WorkflowEdge(id="e1", from_node="start", to_node="analysis1")]
    )

    with pytest.raises(HTTPException) as exc_info:
        WorkflowEngine(graph)

    assert exc_info.value.status_code == 400
    assert "Kein END-Knoten" in str(exc_info.value.detail)


def test_validate_graph_multiple_start_nodes():
    """Test: Graph mit mehreren START-Knoten wird abgelehnt"""
    graph = WorkflowGraph(
        nodes=[
            WorkflowNode(id="start1", type=NodeType.START, position=Position(x=0, y=0)),
            WorkflowNode(id="start2", type=NodeType.START, position=Position(x=0, y=100)),
            WorkflowNode(id="end", type=NodeType.END, position=Position(x=100, y=0))
        ],
        edges=[
            WorkflowEdge(id="e1", from_node="start1", to_node="end"),
            WorkflowEdge(id="e2", from_node="start2", to_node="end")
        ]
    )

    with pytest.raises(HTTPException) as exc_info:
        WorkflowEngine(graph)

    assert exc_info.value.status_code == 400
    assert "Mehrere START-Knoten" in str(exc_info.value.detail)


def test_validate_graph_missing_node_reference():
    """Test: Edge referenziert nicht-existierenden Knoten"""
    graph = WorkflowGraph(
        nodes=[
            WorkflowNode(id="start", type=NodeType.START, position=Position(x=0, y=0)),
            WorkflowNode(id="end", type=NodeType.END, position=Position(x=100, y=0))
        ],
        edges=[WorkflowEdge(id="e1", from_node="start", to_node="nonexistent")]
    )

    with pytest.raises(HTTPException) as exc_info:
        WorkflowEngine(graph)

    assert exc_info.value.status_code == 400
    assert "existiert nicht" in str(exc_info.value.detail)


# ── Test: Zyklen-Erkennung ────────────────────────────────────────────────────

def test_detect_cycle_simple():
    """Test: Einfacher Zyklus wird erkannt (A → B → A)"""
    graph = WorkflowGraph(
        nodes=[
            WorkflowNode(id="start", type=NodeType.START, position=Position(x=0, y=0)),
            WorkflowNode(id="a", type=NodeType.ANALYSIS, position=Position(x=100, y=0), prompt_slug="test"),
            WorkflowNode(id="b", type=NodeType.ANALYSIS, position=Position(x=200, y=0), prompt_slug="test"),
            WorkflowNode(id="end", type=NodeType.END, position=Position(x=300, y=0))
        ],
        edges=[
            WorkflowEdge(id="e1", from_node="start", to_node="a"),
            WorkflowEdge(id="e2", from_node="a", to_node="b"),
            WorkflowEdge(id="e3", from_node="b", to_node="a"),  # Zyklus!
            WorkflowEdge(id="e4", from_node="b", to_node="end")
        ]
    )

    with pytest.raises(HTTPException) as exc_info:
        WorkflowEngine(graph)

    assert exc_info.value.status_code == 400
    assert "Zyklus erkannt" in str(exc_info.value.detail)


def test_detect_cycle_self_loop():
    """Test: Selbst-Zyklus wird erkannt (A → A)"""
    graph = WorkflowGraph(
        nodes=[
            WorkflowNode(id="start", type=NodeType.START, position=Position(x=0, y=0)),
            WorkflowNode(id="a", type=NodeType.ANALYSIS, position=Position(x=100, y=0), prompt_slug="test"),
            WorkflowNode(id="end", type=NodeType.END, position=Position(x=200, y=0))
        ],
        edges=[
            WorkflowEdge(id="e1", from_node="start", to_node="a"),
            WorkflowEdge(id="e2", from_node="a", to_node="a"),  # Selbst-Zyklus!
            WorkflowEdge(id="e3", from_node="a", to_node="end")
        ]
    )

    with pytest.raises(HTTPException) as exc_info:
        WorkflowEngine(graph)

    assert exc_info.value.status_code == 400
    assert "Zyklus erkannt" in str(exc_info.value.detail)


def test_no_cycle_branching(branching_graph):
    """Test: Verzweigung ohne Zyklus wird akzeptiert"""
    engine = WorkflowEngine(branching_graph)
    assert engine is not None  # Kein Fehler


# ── Test: Erreichbarkeit ──────────────────────────────────────────────────────

def test_unreachable_node_from_start():
    """Test: Nicht vom START erreichbarer Knoten wird erkannt"""
    graph = WorkflowGraph(
        nodes=[
            WorkflowNode(id="start", type=NodeType.START, position=Position(x=0, y=0)),
            WorkflowNode(id="a", type=NodeType.ANALYSIS, position=Position(x=100, y=0), prompt_slug="test"),
            WorkflowNode(id="isolated", type=NodeType.ANALYSIS, position=Position(x=100, y=100), prompt_slug="test"),  # Isoliert!
            WorkflowNode(id="end", type=NodeType.END, position=Position(x=200, y=0))
        ],
        edges=[
            WorkflowEdge(id="e1", from_node="start", to_node="a"),
            WorkflowEdge(id="e2", from_node="a", to_node="end")
            # 'isolated' ist nicht verbunden
        ]
    )

    with pytest.raises(HTTPException) as exc_info:
        WorkflowEngine(graph)

    assert exc_info.value.status_code == 400
    assert "nicht erreichbar vom START" in str(exc_info.value.detail)


def test_node_cannot_reach_end():
    """Test: Knoten der END nicht erreichen kann wird erkannt"""
    graph = WorkflowGraph(
        nodes=[
            WorkflowNode(id="start", type=NodeType.START, position=Position(x=0, y=0)),
            WorkflowNode(id="a", type=NodeType.ANALYSIS, position=Position(x=100, y=0), prompt_slug="test"),
            WorkflowNode(id="dead_end", type=NodeType.ANALYSIS, position=Position(x=200, y=0), prompt_slug="test"),
            WorkflowNode(id="end", type=NodeType.END, position=Position(x=200, y=100))
        ],
        edges=[
            WorkflowEdge(id="e1", from_node="start", to_node="a"),
            WorkflowEdge(id="e2", from_node="a", to_node="dead_end")
            # 'dead_end' kann END nicht erreichen (keine Verbindung)
        ]
    )

    with pytest.raises(HTTPException) as exc_info:
        WorkflowEngine(graph)

    assert exc_info.value.status_code == 400
    assert "END nicht erreichen" in str(exc_info.value.detail)


# ── Test: Topologische Sortierung ─────────────────────────────────────────────

def test_topological_sort_simple(simple_valid_graph):
    """Test: Einfacher linearer Graph hat korrekte topologische Sortierung"""
    engine = WorkflowEngine(simple_valid_graph)
    assert engine.topological_order == ["start", "analysis1", "end"]


def test_topological_sort_parallel(parallel_graph):
    """Test: Paralleler Graph - Topologische Sortierung"""
    engine = WorkflowEngine(parallel_graph)

    # START muss zuerst kommen
    assert engine.topological_order[0] == "start"

    # analysis1 und analysis2 können in beliebiger Reihenfolge kommen (parallel)
    assert set(engine.topological_order[1:3]) == {"analysis1", "analysis2"}

    # JOIN kommt nach beiden Analysen
    assert engine.topological_order[3] == "join"

    # END kommt zuletzt
    assert engine.topological_order[4] == "end"


def test_topological_sort_branching(branching_graph):
    """Test: Verzweigter Graph - Topologische Sortierung"""
    engine = WorkflowEngine(branching_graph)

    # START → LOGIC muss zuerst kommen
    assert engine.topological_order[:2] == ["start", "logic1"]

    # analysis1 und analysis2 können in beliebiger Reihenfolge kommen (alternative Pfade)
    assert set(engine.topological_order[2:4]) == {"analysis1", "analysis2"}

    # END kommt zuletzt
    assert engine.topological_order[4] == "end"


# ── Test: Ausführungs-Ebenen (Parallelität) ───────────────────────────────────

def test_execution_order_simple(simple_valid_graph):
    """Test: Einfacher Graph hat 3 Ebenen (keine Parallelität)"""
    engine = WorkflowEngine(simple_valid_graph)
    execution_order = engine.get_execution_order()

    assert len(execution_order) == 3
    assert execution_order[0] == ["start"]
    assert execution_order[1] == ["analysis1"]
    assert execution_order[2] == ["end"]


def test_execution_order_parallel(parallel_graph):
    """Test: Paralleler Graph - Ebene 2 hat 2 Knoten (können parallel laufen)"""
    engine = WorkflowEngine(parallel_graph)
    execution_order = engine.get_execution_order()

    assert len(execution_order) == 4
    assert execution_order[0] == ["start"]
    assert set(execution_order[1]) == {"analysis1", "analysis2"}  # Parallel!
    assert execution_order[2] == ["join"]
    assert execution_order[3] == ["end"]


def test_execution_order_branching(branching_graph):
    """Test: Verzweigter Graph - Alternative Pfade sind auf derselben Ebene"""
    engine = WorkflowEngine(branching_graph)
    execution_order = engine.get_execution_order()

    assert len(execution_order) == 4
    assert execution_order[0] == ["start"]
    assert execution_order[1] == ["logic1"]
    assert set(execution_order[2]) == {"analysis1", "analysis2"}  # Alternative Pfade
    assert execution_order[3] == ["end"]


# ── Test: Validierungs-Hilfsfunktion ──────────────────────────────────────────

def test_validate_workflow_graph_valid(simple_valid_graph):
    """Test: Hilfsfunktion validate_workflow_graph für gültigen Graph"""
    is_valid, errors = validate_workflow_graph(simple_valid_graph)

    assert is_valid is True
    assert errors == []


def test_validate_workflow_graph_invalid():
    """Test: Hilfsfunktion validate_workflow_graph für ungültigen Graph"""
    graph = WorkflowGraph(
        nodes=[
            WorkflowNode(id="start", type=NodeType.START, position=Position(x=0, y=0))
            # Kein END-Knoten!
        ],
        edges=[]
    )

    is_valid, errors = validate_workflow_graph(graph)

    assert is_valid is False
    assert len(errors) > 0
    assert any("END-Knoten" in str(e) for e in errors)


# ── Test: Adjacency Lists ─────────────────────────────────────────────────────

def test_adjacency_lists_creation(parallel_graph):
    """Test: Adjacency Lists werden korrekt erstellt"""
    engine = WorkflowEngine(parallel_graph)

    # Outgoing edges vom START
    start_outgoing = engine.outgoing_edges.get("start", [])
    assert len(start_outgoing) == 2
    assert set(e.to_node for e in start_outgoing) == {"analysis1", "analysis2"}

    # Incoming edges zu JOIN
    join_incoming = engine.incoming_edges.get("join", [])
    assert len(join_incoming) == 2
    assert set(e.from_node for e in join_incoming) == {"analysis1", "analysis2"}


# ── Run Tests ─────────────────────────────────────────────────────────────────

if __name__ == "__main__":
    pytest.main([__file__, "-v"])