"""Roadmap gate graph read models — Plan-Zielzustand, kein Workflow (AP1.4d)."""

from __future__ import annotations

from typing import Any, Optional

TERMINAL_STATUSES = frozenset({"reached", "moved", "discarded"})
ACTIVE_STATUSES = frozenset({"planned", "active", "at_risk"})
BLOCKING_STATUSES = frozenset({"planned", "active", "at_risk"})


def _is_prerequisite_satisfied(status: str) -> bool:
    return status == "reached"


def _fulfillment_ratio(progress: Optional[dict[str, int]]) -> Optional[float]:
    if not progress:
        return None
    total = progress.get("total", 0)
    if total <= 0:
        return None
    closed = progress.get("closed", 0)
    return round(closed / total, 4)


def _sort_items(items: list[dict[str, Any]]) -> list[dict[str, Any]]:
    return sorted(
        items,
        key=lambda item: (
            item.get("sort_order", 0),
            item.get("title") or "",
            str(item.get("id", "")),
        ),
    )


def _sequential_order_blocked_by(
    item: dict[str, Any],
    sorted_items: list[dict[str, Any]],
) -> list[str]:
    """Fallback wenn keine Kanten: sequenzielle Items nach sort_order."""
    blocked_by: list[str] = []
    item_id = str(item["id"])
    for prev in sorted_items:
        if str(prev["id"]) == item_id:
            break
        if prev.get("sequencing_mode", "sequential") != "sequential":
            continue
        if not _is_prerequisite_satisfied(prev.get("status", "planned")):
            blocked_by.append(str(prev["id"]))
    return blocked_by


def compute_initiative_graph_state(
    *,
    items: list[dict[str, Any]],
    dependencies: list[dict[str, Any]],
    criteria_progress: Optional[dict[str, dict[str, int]]] = None,
) -> dict[str, Any]:
    """
    Read Model pro Initiative: blocked / ready / fulfillment_ratio.

    Kanten-Semantik (from → to):
    - requires: from benötigt to (Voraussetzung) als reached
    - optional_branch: wie requires, blockiert aber nicht (nur Metadaten)
    - blocks: from blockiert to solange from noch aktiv ist
    - parallel_group / related: keine Blockade
    """
    criteria_progress = criteria_progress or {}
    sorted_items = _sort_items(items)
    item_by_id = {str(item["id"]): item for item in items}
    has_any_deps = len(dependencies) > 0

    blocked_by_map: dict[str, list[str]] = {item_id: [] for item_id in item_by_id}

    for dep in dependencies:
        dep_type = dep.get("dependency_type") or dep.get("edge_kind") or "requires"
        from_id = str(dep["from_item_id"])
        to_id = str(dep["to_item_id"])
        if from_id not in item_by_id or to_id not in item_by_id:
            continue

        if dep_type == "requires":
            prereq = item_by_id[to_id]
            if not _is_prerequisite_satisfied(prereq.get("status", "planned")):
                if to_id not in blocked_by_map[from_id]:
                    blocked_by_map[from_id].append(to_id)
        elif dep_type == "blocks":
            blocker = item_by_id[from_id]
            if blocker.get("status", "planned") in BLOCKING_STATUSES:
                if from_id not in blocked_by_map[to_id]:
                    blocked_by_map[to_id].append(from_id)

    if not has_any_deps:
        for item in sorted_items:
            item_id = str(item["id"])
            if item.get("sequencing_mode", "sequential") == "sequential":
                for prereq_id in _sequential_order_blocked_by(item, sorted_items):
                    if prereq_id not in blocked_by_map[item_id]:
                        blocked_by_map[item_id].append(prereq_id)

    item_states: dict[str, dict[str, Any]] = {}
    blocked_items: list[str] = []
    ready_items: list[str] = []

    for item_id, item in item_by_id.items():
        status = item.get("status", "planned")
        blocked_by = blocked_by_map.get(item_id, [])
        blocked = len(blocked_by) > 0
        ready = (
            status in ACTIVE_STATUSES
            and not blocked
        )

        ratio = _fulfillment_ratio(criteria_progress.get(item_id))
        item_states[item_id] = {
            "blocked": blocked,
            "ready": ready,
            "blocked_by": blocked_by,
            "fulfillment_ratio": ratio,
        }
        if blocked and status in ACTIVE_STATUSES:
            blocked_items.append(item_id)
        if ready:
            ready_items.append(item_id)

    return {
        "items": item_states,
        "blocked_items": blocked_items,
        "ready_items": ready_items,
    }


def load_initiative_graph_state(
    *, tenant_id: str, initiative_id: str
) -> dict[str, Any]:
    """Lädt Items, Kanten und Kriterien-Fortschritt und berechnet Graph-State."""
    from services import roadmap as roadmap_service
    from services import roadmap_criteria as criteria_service

    items = roadmap_service.list_roadmap_items_for_initiative(
        tenant_id=tenant_id, initiative_id=initiative_id
    )
    dependencies = roadmap_service.list_dependencies_for_initiative(
        tenant_id=tenant_id, initiative_id=initiative_id
    )
    criteria_progress = criteria_service.criteria_progress_for_initiative(
        tenant_id=tenant_id, initiative_id=initiative_id
    )
    return compute_initiative_graph_state(
        items=items,
        dependencies=dependencies,
        criteria_progress=criteria_progress,
    )