"""Project service — operative Struktur unter Initiative (AP1.5, AP1.5c)."""

from __future__ import annotations

from datetime import date
from typing import Any, Literal, Optional

from psycopg2.extras import RealDictCursor

from db import get_connection
from services.audit import log_audit
from services.initiatives import get_initiative

ProjectStatus = Literal["active", "paused", "completed", "archived"]
PROJECT_STATUSES = frozenset({"active", "paused", "completed", "archived"})

ContainerKind = Literal["project", "stream", "phase", "release"]
CONTAINER_KINDS = frozenset({"project", "stream", "phase", "release"})

MAX_PROJECT_DEPTH = 5

_PROJECT_COLUMNS = """
    id, tenant_id, initiative_id, parent_project_id, container_kind,
    title, description, status,
    roadmap_item_id, sort_order, target_date, created_at, updated_at
"""


def _serialize_row(row: dict[str, Any]) -> dict[str, Any]:
    result = dict(row)
    for key in ("id", "tenant_id", "initiative_id", "parent_project_id", "roadmap_item_id"):
        if result.get(key):
            result[key] = str(result[key])
    if result.get("target_date"):
        result["target_date"] = (
            result["target_date"].isoformat()
            if hasattr(result["target_date"], "isoformat")
            else str(result["target_date"])
        )
    for ts in ("created_at", "updated_at"):
        if result.get(ts):
            result[ts] = result[ts].isoformat()
    return result


def _validate_status(status: str) -> None:
    if status not in PROJECT_STATUSES:
        raise ValueError(f"Ungültiger Project-Status: {status}")


def _validate_container_kind(container_kind: Optional[str]) -> None:
    if container_kind is not None and container_kind not in CONTAINER_KINDS:
        raise ValueError(f"Ungültiger container_kind: {container_kind}")


def _validate_roadmap_item(
    cur, *, tenant_id: str, initiative_id: str, roadmap_item_id: Optional[str]
) -> None:
    if not roadmap_item_id:
        return
    cur.execute(
        """
        SELECT 1 FROM roadmap_items ri
        JOIN roadmaps r ON r.id = ri.roadmap_id AND r.tenant_id = ri.tenant_id
        WHERE ri.id = %s AND ri.tenant_id = %s AND r.initiative_id = %s
        """,
        (roadmap_item_id, tenant_id, initiative_id),
    )
    if not cur.fetchone():
        raise ValueError("Gate/Plan-Element gehört nicht zu diesem Vorhaben")


def _fetch_project_row(
    cur, *, tenant_id: str, project_id: str, initiative_id: Optional[str] = None
) -> Optional[dict[str, Any]]:
    query = f"""
        SELECT {_PROJECT_COLUMNS}
        FROM projects
        WHERE id = %s AND tenant_id = %s
    """
    params: list[Any] = [project_id, tenant_id]
    if initiative_id is not None:
        query += " AND initiative_id = %s"
        params.append(initiative_id)
    cur.execute(query, params)
    row = cur.fetchone()
    return dict(row) if row else None


def _project_depth_from_map(
    project_id: str, by_id: dict[str, dict[str, Any]], memo: dict[str, int]
) -> int:
    if project_id in memo:
        return memo[project_id]
    project = by_id.get(project_id)
    if not project or not project.get("parent_project_id"):
        memo[project_id] = 1
        return 1
    parent_id = str(project["parent_project_id"])
    if parent_id == project_id:
        raise ValueError("Zyklus in Project-Hierarchie")
    depth = _project_depth_from_map(parent_id, by_id, memo) + 1
    memo[project_id] = depth
    return depth


def _collect_descendant_ids(
    project_id: str, by_parent: dict[str, list[str]]
) -> set[str]:
    result: set[str] = set()
    stack = list(by_parent.get(project_id, []))
    while stack:
        child_id = stack.pop()
        if child_id in result:
            continue
        result.add(child_id)
        stack.extend(by_parent.get(child_id, []))
    return result


def _subtree_height(project_id: str, by_parent: dict[str, list[str]]) -> int:
    children = by_parent.get(project_id, [])
    if not children:
        return 1
    return 1 + max(_subtree_height(child_id, by_parent) for child_id in children)


def _load_initiative_project_maps(
    cur, *, tenant_id: str, initiative_id: str
) -> tuple[dict[str, dict[str, Any]], dict[str, list[str]]]:
    cur.execute(
        f"""
        SELECT {_PROJECT_COLUMNS}
        FROM projects
        WHERE tenant_id = %s AND initiative_id = %s
        """,
        (tenant_id, initiative_id),
    )
    rows = [dict(r) for r in cur.fetchall()]
    by_id = {str(r["id"]): r for r in rows}
    by_parent: dict[str, list[str]] = {}
    for row in rows:
        parent_id = row.get("parent_project_id")
        if parent_id:
            by_parent.setdefault(str(parent_id), []).append(str(row["id"]))
    return by_id, by_parent


def _validate_parent_project(
    cur,
    *,
    tenant_id: str,
    initiative_id: str,
    project_id: Optional[str],
    parent_project_id: Optional[str],
) -> None:
    if not parent_project_id:
        return
    if project_id and parent_project_id == project_id:
        raise ValueError("Projekt kann nicht sein eigener Parent sein")

    parent = _fetch_project_row(
        cur, tenant_id=tenant_id, project_id=parent_project_id, initiative_id=initiative_id
    )
    if not parent:
        raise ValueError("Parent-Projekt gehört nicht zu diesem Vorhaben")

    by_id, by_parent = _load_initiative_project_maps(
        cur, tenant_id=tenant_id, initiative_id=initiative_id
    )
    if project_id:
        descendants = _collect_descendant_ids(project_id, by_parent)
        if parent_project_id in descendants:
            raise ValueError("Zyklus: Parent darf kein Nachfahr sein")

    memo: dict[str, int] = {}
    parent_depth = _project_depth_from_map(parent_project_id, by_id, memo)
    subtree_height = (
        _subtree_height(project_id, by_parent) if project_id else 1
    )
    if parent_depth + subtree_height > MAX_PROJECT_DEPTH:
        raise ValueError(
            f"Maximale Project-Tiefe ({MAX_PROJECT_DEPTH}) würde überschritten"
        )


def _attach_depths(projects: list[dict[str, Any]]) -> list[dict[str, Any]]:
    if not projects:
        return projects
    by_id = {p["id"]: p for p in projects}
    memo: dict[str, int] = {}
    for project in projects:
        project["depth"] = _project_depth_from_map(project["id"], by_id, memo)
        project["has_children"] = any(
            other.get("parent_project_id") == project["id"] for other in projects
        )
        project["is_leaf"] = not project["has_children"]
    return projects


def project_is_leaf(*, tenant_id: str, project_id: str) -> bool:
    conn = get_connection()
    try:
        with conn.cursor() as cur:
            cur.execute(
                """
                SELECT 1 FROM projects
                WHERE parent_project_id = %s AND tenant_id = %s
                LIMIT 1
                """,
                (project_id, tenant_id),
            )
            return cur.fetchone() is None
    finally:
        conn.close()


def create_project(
    *,
    tenant_id: str,
    initiative_id: str,
    title: str,
    description: str = "",
    status: ProjectStatus = "active",
    parent_project_id: Optional[str] = None,
    container_kind: Optional[ContainerKind] = None,
    roadmap_item_id: Optional[str] = None,
    sort_order: int = 0,
    target_date: Optional[date] = None,
    user_id: Optional[str] = None,
) -> dict[str, Any]:
    title = title.strip()
    if not title:
        raise ValueError("Titel ist erforderlich")
    _validate_status(status)
    _validate_container_kind(container_kind)
    if not get_initiative(tenant_id=tenant_id, initiative_id=initiative_id):
        raise ValueError("Initiative nicht gefunden")

    conn = get_connection()
    try:
        with conn.cursor(cursor_factory=RealDictCursor) as cur:
            _validate_roadmap_item(
                cur,
                tenant_id=tenant_id,
                initiative_id=initiative_id,
                roadmap_item_id=roadmap_item_id,
            )
            _validate_parent_project(
                cur,
                tenant_id=tenant_id,
                initiative_id=initiative_id,
                project_id=None,
                parent_project_id=parent_project_id,
            )
            cur.execute(
                f"""
                INSERT INTO projects (
                    tenant_id, initiative_id, parent_project_id, container_kind,
                    title, description, status,
                    roadmap_item_id, sort_order, target_date
                )
                VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s)
                RETURNING {_PROJECT_COLUMNS}
                """,
                (
                    tenant_id,
                    initiative_id,
                    parent_project_id,
                    container_kind,
                    title,
                    description,
                    status,
                    roadmap_item_id,
                    sort_order,
                    target_date,
                ),
            )
            row = _serialize_row(dict(cur.fetchone()))
        conn.commit()
    finally:
        conn.close()

    log_audit(
        "project.created",
        user_id=user_id,
        tenant_id=tenant_id,
        details={
            "project_id": row["id"],
            "initiative_id": initiative_id,
            "title": title,
            "parent_project_id": parent_project_id,
        },
    )
    return row


def list_projects_for_initiative(
    *, tenant_id: str, initiative_id: str
) -> list[dict[str, Any]]:
    if not get_initiative(tenant_id=tenant_id, initiative_id=initiative_id):
        raise ValueError("Initiative nicht gefunden")

    conn = get_connection()
    try:
        with conn.cursor(cursor_factory=RealDictCursor) as cur:
            cur.execute(
                f"""
                SELECT {_PROJECT_COLUMNS}
                FROM projects
                WHERE tenant_id = %s AND initiative_id = %s
                ORDER BY sort_order ASC, updated_at DESC, title
                """,
                (tenant_id, initiative_id),
            )
            rows = [_serialize_row(dict(r)) for r in cur.fetchall()]
            return _attach_depths(rows)
    finally:
        conn.close()


def get_project(*, tenant_id: str, project_id: str) -> Optional[dict[str, Any]]:
    conn = get_connection()
    try:
        with conn.cursor(cursor_factory=RealDictCursor) as cur:
            cur.execute(
                f"""
                SELECT initiative_id
                FROM projects WHERE id = %s AND tenant_id = %s
                """,
                (project_id, tenant_id),
            )
            row = cur.fetchone()
            if not row:
                return None
            initiative_id = str(row["initiative_id"])
    finally:
        conn.close()

    for project in list_projects_for_initiative(
        tenant_id=tenant_id, initiative_id=initiative_id
    ):
        if project["id"] == project_id:
            return project
    return None


def update_project(
    *,
    tenant_id: str,
    project_id: str,
    user_id: Optional[str] = None,
    title: Optional[str] = None,
    description: Optional[str] = None,
    status: Optional[ProjectStatus] = None,
    parent_project_id: Optional[str] = None,
    clear_parent_project: bool = False,
    container_kind: Optional[ContainerKind] = None,
    clear_container_kind: bool = False,
    roadmap_item_id: Optional[str] = None,
    clear_roadmap_item: bool = False,
    sort_order: Optional[int] = None,
    target_date: Optional[date] = None,
    clear_target_date: bool = False,
) -> Optional[dict[str, Any]]:
    existing = get_project(tenant_id=tenant_id, project_id=project_id)
    if not existing:
        return None

    updates: list[str] = []
    params: list[Any] = []

    if title is not None:
        title = title.strip()
        if not title:
            raise ValueError("Titel ist erforderlich")
        updates.append("title = %s")
        params.append(title)
    if description is not None:
        updates.append("description = %s")
        params.append(description)
    if status is not None:
        _validate_status(status)
        updates.append("status = %s")
        params.append(status)
    if clear_parent_project:
        updates.append("parent_project_id = NULL")
    elif parent_project_id is not None:
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                _validate_parent_project(
                    cur,
                    tenant_id=tenant_id,
                    initiative_id=existing["initiative_id"],
                    project_id=project_id,
                    parent_project_id=parent_project_id,
                )
        finally:
            conn.close()
        updates.append("parent_project_id = %s")
        params.append(parent_project_id)
    if clear_container_kind:
        updates.append("container_kind = NULL")
    elif container_kind is not None:
        _validate_container_kind(container_kind)
        updates.append("container_kind = %s")
        params.append(container_kind)
    if clear_roadmap_item:
        updates.append("roadmap_item_id = NULL")
    elif roadmap_item_id is not None:
        conn = get_connection()
        try:
            with conn.cursor() as cur:
                _validate_roadmap_item(
                    cur,
                    tenant_id=tenant_id,
                    initiative_id=existing["initiative_id"],
                    roadmap_item_id=roadmap_item_id,
                )
        finally:
            conn.close()
        updates.append("roadmap_item_id = %s")
        params.append(roadmap_item_id)
    if sort_order is not None:
        updates.append("sort_order = %s")
        params.append(sort_order)
    if clear_target_date:
        updates.append("target_date = NULL")
    elif target_date is not None:
        updates.append("target_date = %s")
        params.append(target_date)

    if not updates:
        return existing

    updates.append("updated_at = NOW()")
    params.extend([project_id, tenant_id])

    conn = get_connection()
    try:
        with conn.cursor(cursor_factory=RealDictCursor) as cur:
            cur.execute(
                f"""
                UPDATE projects SET {", ".join(updates)}
                WHERE id = %s AND tenant_id = %s
                RETURNING {_PROJECT_COLUMNS}
                """,
                params,
            )
            row = cur.fetchone()
            if not row:
                return None
            result = _serialize_row(dict(row))
        conn.commit()
    finally:
        conn.close()

    log_audit(
        "project.updated",
        user_id=user_id,
        tenant_id=tenant_id,
        details={"project_id": project_id},
    )
    return get_project(tenant_id=tenant_id, project_id=project_id)


def delete_project(
    *, tenant_id: str, project_id: str, user_id: Optional[str] = None
) -> bool:
    conn = get_connection()
    try:
        with conn.cursor() as cur:
            cur.execute(
                """
                SELECT 1 FROM projects
                WHERE parent_project_id = %s AND tenant_id = %s
                LIMIT 1
                """,
                (project_id, tenant_id),
            )
            if cur.fetchone():
                raise ValueError(
                    "Projekt hat Unterprojekte — zuerst löschen oder verschieben"
                )
            cur.execute(
                "UPDATE actions SET project_id = NULL WHERE project_id = %s AND tenant_id = %s",
                (project_id, tenant_id),
            )
            cur.execute(
                "DELETE FROM projects WHERE id = %s AND tenant_id = %s RETURNING id",
                (project_id, tenant_id),
            )
            deleted = cur.fetchone() is not None
        conn.commit()
    finally:
        conn.close()

    if deleted:
        log_audit(
            "project.deleted",
            user_id=user_id,
            tenant_id=tenant_id,
            details={"project_id": project_id},
        )
    return deleted