from __future__ import annotations

from dataclasses import dataclass, field
from typing import Iterable, List, Sequence

from fastapi import Request

from models.navigation import NavigationLink
from services.repositories import NavigationRepository
from services.session import AuthSession


@dataclass(slots=True)
class NavigationLinkDTO:
    id: int
    label: str
    href: str
    match_prefix: str | None
    icon: str | None
    tooltip: str | None
    is_external: bool
    children: List["NavigationLinkDTO"] = field(default_factory=list)


@dataclass(slots=True)
class NavigationGroupDTO:
    id: int
    label: str
    icon: str | None
    tooltip: str | None
    links: List[NavigationLinkDTO] = field(default_factory=list)


@dataclass(slots=True)
class NavigationSidebarDTO:
    groups: List[NavigationGroupDTO]
    roles: tuple[str, ...]


class NavigationService:
    """Build navigation payloads filtered for the current session."""

    def __init__(self, repository: NavigationRepository) -> None:
        self._repository = repository

    def build_sidebar(
        self,
        *,
        session: AuthSession,
        request: Request | None = None,
        include_disabled: bool = False,
    ) -> NavigationSidebarDTO:
        roles = self._collect_roles(session)
        groups = self._repository.list_groups_with_links(
            include_disabled=include_disabled
        )
        context = self._derive_context(request)

        mapped_groups: List[NavigationGroupDTO] = []
        for group in groups:
            if not include_disabled and not group.is_enabled:
                continue
            mapped_links = self._map_links(
                group.links,
                roles,
                request=request,
                include_disabled=include_disabled,
                context=context,
            )
            if not mapped_links and not include_disabled:
                continue
            mapped_groups.append(
                NavigationGroupDTO(
                    id=group.id,
                    label=group.label,
                    icon=group.icon,
                    tooltip=group.tooltip,
                    links=mapped_links,
                )
            )
        return NavigationSidebarDTO(groups=mapped_groups, roles=roles)

    def _map_links(
        self,
        links: Sequence[NavigationLink],
        roles: Iterable[str],
        *,
        request: Request | None,
        include_disabled: bool,
        context: dict[str, str | None],
        include_children: bool = False,
    ) -> List[NavigationLinkDTO]:
        resolved_roles = tuple(roles)
        mapped: List[NavigationLinkDTO] = []
        for link in sorted(links, key=lambda x: (x.sort_order, x.id)):
            if not include_children and link.parent_link_id is not None:
                continue
            if not include_disabled and (not link.is_enabled):
                continue
            if not self._link_visible(link, resolved_roles, include_disabled):
                continue
            href = self._resolve_href(link, request=request, context=context)
            if not href:
                continue
            children = self._map_links(
                link.children,
                resolved_roles,
                request=request,
                include_disabled=include_disabled,
                context=context,
                include_children=True,
            )
            match_prefix = link.match_prefix or href
            mapped.append(
                NavigationLinkDTO(
                    id=link.id,
                    label=link.label,
                    href=href,
                    match_prefix=match_prefix,
                    icon=link.icon,
                    tooltip=link.tooltip,
                    is_external=link.is_external,
                    children=children,
                )
            )
        return mapped

    @staticmethod
    def _collect_roles(session: AuthSession) -> tuple[str, ...]:
        roles = tuple((session.role_slugs or ()) if session else ())
        if session and session.is_authenticated:
            return roles
        if "anonymous" in roles:
            return roles
        return roles + ("anonymous",)

    @staticmethod
    def _derive_context(request: Request | None) -> dict[str, str | None]:
        if request is None:
            return {"project_id": None, "scenario_id": None}
        project_id = request.path_params.get(
            "project_id") if hasattr(request, "path_params") else None
        scenario_id = request.path_params.get(
            "scenario_id") if hasattr(request, "path_params") else None
        if not project_id:
            project_id = request.query_params.get("project_id")
        if not scenario_id:
            scenario_id = request.query_params.get("scenario_id")
        return {"project_id": project_id, "scenario_id": scenario_id}

    def _resolve_href(
        self,
        link: NavigationLink,
        *,
        request: Request | None,
        context: dict[str, str | None],
    ) -> str | None:
        if link.route_name:
            if request is None:
                fallback = link.href_override
                if fallback:
                    return fallback
                # Fallback to route name when no request is available
                return f"/{link.route_name.replace('.', '/')}"
            requires_context = link.slug in {
                "profitability",
                "profitability-calculator",
                "opex",
                "capex",
            }
            if requires_context:
                project_id = context.get("project_id")
                scenario_id = context.get("scenario_id")
                if project_id and scenario_id:
                    try:
                        return str(
                            request.url_for(
                                link.route_name,
                                project_id=project_id,
                                scenario_id=scenario_id,
                            )
                        )
                    except Exception:  # pragma: no cover - defensive
                        pass
            try:
                return str(request.url_for(link.route_name))
            except Exception:  # pragma: no cover - defensive
                return link.href_override
        return link.href_override

    @staticmethod
    def _link_visible(
        link: NavigationLink,
        roles: Iterable[str],
        include_disabled: bool,
    ) -> bool:
        role_tuple = tuple(roles)
        if not include_disabled and not link.is_enabled:
            return False
        if not link.required_roles:
            return True
        role_set = set(role_tuple)
        return any(role in role_set for role in link.required_roles)