from django.contrib.auth import get_user_model


def _get_model(app_label, model_name):
    from django.apps import apps

    return apps.get_model(app_label, model_name)


def _object_label(app_label, model_name, pk, formatter=None):
    if pk in (None, ""):
        return None
    try:
        obj = _get_model(app_label, model_name).objects.get(pk=pk)
    except Exception:
        return None
    if formatter is not None:
        return formatter(obj)
    return str(obj)


def user_label(user):
    full_name = user.get_full_name()
    if full_name:
        return f"{user.username} ({full_name})"
    return user.username


def user_profile_label(user_profile):
    try:
        return user_label(user_profile.user)
    except Exception:
        return f"UserProfile id {user_profile.pk} (user not found)"


def user_profile_label_from_id(user_profile_id):
    try:
        user_profile = _get_model("user", "UserProfile").objects.select_related("user").get(pk=user_profile_id)
    except Exception:
        return f"UserProfile id {user_profile_id} (user not found)"
    return user_profile_label(user_profile)


def _resource_allocation_prefix(resource_names):
    names = [name for name in resource_names if name]
    if not names:
        return "Allocation"
    if len(names) <= 2:
        return f"{', '.join(names)} allocation"
    return f"{', '.join(names[:2])} + {len(names) - 2} more allocation"


def allocation_label_from_parts(resource_names, project_reference):
    return f"{_resource_allocation_prefix(resource_names)} for {project_reference}"


def project_label_from_id(project_id):
    if project_id in (None, ""):
        return "Project unknown"
    try:
        return project_label(_get_model("project", "Project").objects.get(pk=project_id))
    except Exception:
        return f"Project id {project_id} (not found)"


def allocation_label(allocation):
    resources = list(allocation.resources.values_list("name", flat=True).order_by("name"))
    try:
        project_reference = project_label(allocation.project)
    except Exception:
        project_reference = project_label_from_id(getattr(allocation, "project_id", None))
    return allocation_label_from_parts(resources, project_reference)


def allocation_change_label(allocation_change):
    return f"change request for {allocation_label(allocation_change.allocation)}"


def project_user_label(project_user):
    return f"{project_user.user.username} on {project_label(project_user.project)}"


def project_review_label(project_review):
    return f"review for {project_label(project_review.project)}"


def project_label(project):
    label = f"Project: {project.title}"
    if getattr(project, "project_code", ""):
        label = f"{label} (code {project.project_code})"
    return label


def resolve_target_label(target_type, target_id):
    formatter_map = {
        "allocation.allocation": lambda obj: allocation_label(obj),
        "allocation.allocationchangerequest": lambda obj: allocation_change_label(obj),
        "auth.user": lambda obj: user_label(obj),
        "user.userprofile": lambda obj: user_profile_label(obj),
        "project.project": lambda obj: project_label(obj),
        "project.projectuser": lambda obj: project_user_label(obj),
        "project.projectreview": lambda obj: project_review_label(obj),
        "resource.resource": lambda obj: obj.name,
    }
    if "." not in target_type:
        return None
    app_label, model_name = target_type.split(".", 1)
    if target_type == "project.project":
        return project_label_from_id(target_id)
    return _object_label(app_label, model_name, target_id, formatter_map.get(target_type))


def _resolve_id(key, value):
    if key in {"project_id", "project"}:
        label = _object_label("project", "Project", value, lambda obj: project_label(obj))
    elif key in {"user_id", "user"}:
        label = _object_label("auth", "User", value, lambda obj: user_label(obj))
    elif key in {"allocation_id", "allocation"}:
        label = _object_label("allocation", "Allocation", value, lambda obj: allocation_label(obj))
    elif key in {"allocation_change_request_id", "allocation_change_request"}:
        label = _object_label(
            "allocation",
            "AllocationChangeRequest",
            value,
            lambda obj: allocation_change_label(obj),
        )
    elif key in {"resource_type_id", "resource_type"}:
        label = _object_label("resource", "ResourceType", value)
    elif key in {"parent_resource_id", "parent_resource"}:
        label = _object_label("resource", "Resource", value, lambda obj: obj.name)
    else:
        label = None

    if not label:
        return value
    return f"{label} (id {value})"


def _resolve_id_list(key, values):
    if key == "resource_ids":
        labels = []
        for value in values:
            label = _object_label("resource", "Resource", value, lambda obj: obj.name)
            labels.append(f"{label} (id {value})" if label else value)
        return labels
    return values


def resolve_value_labels(values):
    if not isinstance(values, dict):
        return values

    resolved = {}
    for key, value in values.items():
        if isinstance(value, list):
            resolved[key] = _resolve_id_list(key, value)
        elif key.endswith("_id") or key in {"project", "user", "allocation", "resource_type", "parent_resource"}:
            resolved[key] = _resolve_id(key, value)
        else:
            resolved[key] = value
    return resolved


def actor_label(actor):
    if actor is None:
        return "programmatic"
    return user_label(actor)


def username_from_id(user_id):
    try:
        return user_label(get_user_model().objects.get(pk=user_id))
    except Exception:
        return str(user_id)