from core_domain import InitialNodeContract, WorkflowVersionContract
from core_shared import JSONValue


def derive_initial_node(workflow_version: WorkflowVersionContract) -> InitialNodeContract | None:
    dsl = workflow_version.dsl_json
    if not isinstance(dsl, dict):
        return None

    nodes_value = dsl.get("nodes")
    if not isinstance(nodes_value, list):
        return None

    nodes: list[dict[str, JSONValue]] = [
        item for item in nodes_value if isinstance(item, dict)
    ]
    if not nodes:
        return None

    edges_value = dsl.get("edges")
    incoming_targets = _collect_incoming_targets(edges_value)

    for node in nodes:
        node_id = node.get("id")
        node_type = node.get("type")
        if isinstance(node_id, str) and isinstance(node_type, str) and node_id not in incoming_targets:
            return InitialNodeContract(node_id=node_id, node_type=node_type, status="queued")

    first = nodes[0]
    first_id = first.get("id")
    first_type = first.get("type")
    if isinstance(first_id, str) and isinstance(first_type, str):
        return InitialNodeContract(node_id=first_id, node_type=first_type, status="queued")

    return None


def derive_successor_nodes(
    workflow_version: WorkflowVersionContract,
    current_node_id: str,
) -> list[InitialNodeContract]:
    dsl = workflow_version.dsl_json
    if not isinstance(dsl, dict):
        return []

    nodes_value = dsl.get("nodes")
    edges_value = dsl.get("edges")
    if not isinstance(nodes_value, list) or not isinstance(edges_value, list):
        return []

    node_type_map = _build_node_type_map(nodes_value)
    successor_ids = _collect_successor_ids(edges_value, current_node_id)

    successors: list[InitialNodeContract] = []
    for successor_id in successor_ids:
        node_type = node_type_map.get(successor_id)
        if node_type is None:
            continue
        successors.append(
            InitialNodeContract(
                node_id=successor_id,
                node_type=node_type,
                status="queued",
            )
        )
    return successors


def _collect_incoming_targets(edges_value: JSONValue | None) -> set[str]:
    if not isinstance(edges_value, list):
        return set()

    incoming_targets: set[str] = set()
    for item in edges_value:
        if not isinstance(item, dict):
            continue
        target = item.get("target")
        if isinstance(target, str):
            incoming_targets.add(target)
    return incoming_targets


def _build_node_type_map(nodes_value: list[JSONValue]) -> dict[str, str]:
    node_type_map: dict[str, str] = {}
    for item in nodes_value:
        if not isinstance(item, dict):
            continue
        node_id = item.get("id")
        node_type = item.get("type")
        if isinstance(node_id, str) and isinstance(node_type, str):
            node_type_map[node_id] = node_type
    return node_type_map


def _collect_successor_ids(edges_value: list[JSONValue], current_node_id: str) -> list[str]:
    successor_ids: list[str] = []
    for item in edges_value:
        if not isinstance(item, dict):
            continue
        source = item.get("source")
        target = item.get("target")
        if isinstance(source, str) and isinstance(target, str) and source == current_node_id:
            successor_ids.append(target)
    return successor_ids