from __future__ import annotations

from django.contrib.auth import get_user_model
from django.db.models import Q, QuerySet
from django.utils import timezone
from rest_framework.exceptions import PermissionDenied, ValidationError

from apps.projects.models import Project, ProjectAccess, ProjectUserRate
from apps.workspaces.models import Workspace, WorkspaceMembership, WorkspaceUserRate
from apps.workspaces.services import PROJECTS_EDIT, get_workspace_role, has_workspace_capability

User = get_user_model()

PROJECT_ACCESS_MANAGED_ROLES = {
    WorkspaceMembership.Role.MEMBER,
    WorkspaceMembership.Role.GUEST,
}
PROJECT_ACCESS_IMPLICIT_ROLES = {
    WorkspaceMembership.Role.OWNER,
    WorkspaceMembership.Role.ADMIN,
}


def user_has_implicit_project_access(user, workspace: Workspace) -> bool:
    return get_workspace_role(user, workspace) in PROJECT_ACCESS_IMPLICIT_ROLES


def user_has_project_access(user, project: Project) -> bool:
    if not user or not getattr(user, "is_authenticated", False):
        return False
    if user_has_implicit_project_access(user, project.workspace):
        return True
    return ProjectAccess.objects.filter(project=project, user=user).exists()


def filter_projects_for_user(user, queryset: QuerySet[Project] | None = None) -> QuerySet[Project]:
    if queryset is None:
        queryset = Project.objects.all()

    if not user or not getattr(user, "is_authenticated", False):
        return queryset.none()

    return queryset.filter(
        Q(workspace__owner=user)
        | Q(
            workspace__memberships__user=user,
            workspace__memberships__is_active=True,
            workspace__memberships__role__in=PROJECT_ACCESS_IMPLICIT_ROLES,
        )
        | Q(
            workspace__memberships__user=user,
            workspace__memberships__is_active=True,
            workspace__memberships__role__in=PROJECT_ACCESS_MANAGED_ROLES,
            access_memberships__user=user,
        )
    ).distinct()


def ensure_project_access(user, project: Project, *, message: str = "Selected project is unavailable.") -> None:
    if not user_has_project_access(user, project):
        raise ValidationError({"project_id": message})


def ensure_workspace_project_access(user, workspace: Workspace) -> None:
    if not has_workspace_capability(user, workspace, PROJECTS_EDIT):
        raise PermissionDenied("You do not have permission to manage project access in this workspace.")


def get_access_managed_membership(workspace: Workspace, user_id: str) -> WorkspaceMembership:
    membership = WorkspaceMembership.objects.filter(
        workspace=workspace,
        user_id=user_id,
        is_active=True,
        is_deleted=False,
    ).select_related("user").first()
    if not membership:
        raise ValidationError({"user": "Selected user is not an active member of this workspace."})
    if membership.role not in PROJECT_ACCESS_MANAGED_ROLES:
        raise ValidationError({"user": "Owners and admins have implicit access to all projects."})
    return membership


def serialize_rate(rate) -> dict | None:
    if not rate:
        return None
    return {
        "id": str(rate.id),
        "hourly_rate": str(rate.hourly_rate),
        "currency": rate.currency,
        "effective_from": rate.effective_from.isoformat() if rate.effective_from else None,
    }


def build_project_access_item(*, project: Project, has_access: bool, workspace_rate, project_rate) -> dict:
    return {
        "id": str(project.id),
        "name": project.name,
        "description": project.description,
        "color": project.color,
        "is_archived": project.is_archived,
        "client": (
            {"id": str(project.client_id), "name": project.client.name}
            if project.client_id and project.client
            else None
        ),
        "has_access": has_access,
        "workspace_rate": serialize_rate(workspace_rate),
        "project_rate": serialize_rate(project_rate),
    }


def build_project_access_items(*, workspace: Workspace, target_user) -> list[dict]:
    explicit_access_ids = {
        str(project_id)
        for project_id in ProjectAccess.objects.filter(
            project__workspace=workspace,
            user=target_user,
        ).values_list("project_id", flat=True)
    }
    workspace_rate = (
        WorkspaceUserRate.objects.filter(
            workspace=workspace,
            user=target_user,
            is_deleted=False,
        )
        .order_by("-effective_from", "-updated_at")
        .first()
    )
    project_rates: dict[str, ProjectUserRate] = {}
    for rate in (
        ProjectUserRate.objects.filter(
            project__workspace=workspace,
            user=target_user,
            is_active=True,
            is_deleted=False,
        )
        .select_related("project")
        .order_by("project_id", "-effective_from", "-updated_at")
    ):
        project_rates.setdefault(str(rate.project_id), rate)
    projects = (
        Project.objects.filter(workspace=workspace, is_deleted=False)
        .select_related("client")
        .order_by("client__name", "name")
    )
    return [
        build_project_access_item(
            project=project,
            has_access=str(project.id) in explicit_access_ids,
            workspace_rate=workspace_rate,
            project_rate=project_rates.get(str(project.id)),
        )
        for project in projects
    ]


def grant_project_accesses(*, actor, workspace: Workspace, target_user, project_ids: list[str]) -> int:
    ensure_workspace_project_access(actor, workspace)
    get_access_managed_membership(workspace, str(target_user.id))

    projects = list(Project.objects.filter(workspace=workspace, id__in=project_ids, is_deleted=False))
    if len(projects) != len(set(project_ids)):
        raise ValidationError({"project_ids": "One or more selected projects do not belong to this workspace."})

    changed = 0
    for project in projects:
        access, created, restored = ProjectAccess.get_or_restore(project=project, user=target_user)
        if created or restored:
            access.is_active = True
            access.updated_at = timezone.now()
            access.save(update_fields=["is_active", "updated_at"])
            changed += 1
    return changed


def revoke_project_accesses(*, actor, workspace: Workspace, target_user, project_ids: list[str]) -> int:
    ensure_workspace_project_access(actor, workspace)
    get_access_managed_membership(workspace, str(target_user.id))

    accesses = list(
        ProjectAccess.objects.filter(
            project__workspace=workspace,
            user=target_user,
            project_id__in=project_ids,
        ).select_related("project")
    )
    changed = 0
    for access in accesses:
        access.delete()
        changed += 1
    return changed