"""
Progressionsgraph zwischen Übungen (Übung → Übung), Migration 032–034.
Optional Übungsvarianten als Knoten-Endpunkte; Sequenz-Bulk-Anlage.
AuthZ analog training_plan_templates: Bearbeiten/Löschen wie Übungen; Governance-Übergänge zentral.
"""
import json
from typing import Any, Dict, List, Mapping, Optional

from fastapi import APIRouter, Depends, HTTPException, Query
from pydantic import BaseModel, Field, model_validator
from psycopg2 import IntegrityError
from psycopg2.extras import Json

from db import get_db, get_cursor, r2d
from progression_graph_planning_artifact import normalize_planning_roadmap_payload
from tenant_context import TenantContext, get_tenant_context, library_content_visibility_sql
from club_tenancy import (
    assert_library_content_deletable,
    assert_library_content_editable,
    assert_library_content_governance_transition,
    assert_valid_governance_visibility,
    is_platform_admin,
    library_content_visible_to_profile,
)

from routers.training_planning import _has_planning_role

router = APIRouter(prefix="/api", tags=["exercises"])


class ProgressionGraphCreate(BaseModel):
    name: str = Field(..., min_length=1, max_length=200)
    description: Optional[str] = None
    visibility: str = Field(default="private", pattern="^(private|club|official)$")
    club_id: Optional[int] = None


class ProgressionGraphUpdate(BaseModel):
    name: Optional[str] = Field(None, min_length=1, max_length=200)
    description: Optional[str] = None
    visibility: Optional[str] = Field(None, pattern="^(private|club|official)$")
    club_id: Optional[int] = None
    planning_roadmap: Optional[Dict[str, Any]] = None


class ProgressionEdgeCreate(BaseModel):
    from_exercise_id: int = Field(..., gt=0)
    to_exercise_id: int = Field(..., gt=0)
    from_exercise_variant_id: Optional[int] = Field(default=None)
    to_exercise_variant_id: Optional[int] = Field(default=None)
    edge_type: str = Field(default="next_exercise", min_length=1, max_length=50)
    notes: Optional[str] = Field(None, max_length=4000)


class ProgressionEdgeUpdate(BaseModel):
    notes: Optional[str] = Field(None, max_length=4000)


class SequenceStep(BaseModel):
    exercise_id: int = Field(..., gt=0)
    variant_id: Optional[int] = Field(default=None)


class ProgressionSequenceCreate(BaseModel):
    steps: List[SequenceStep] = Field(..., min_length=2)
    segment_notes: Optional[List[Optional[str]]] = None
    planning_roadmap: Optional[Dict[str, Any]] = None
    """Länge muss len(steps)-1 sein, wenn gesetzt; Notiz pro Kante Zwischen je zwei Schritten."""

    @model_validator(mode="after")
    def check_segment_notes_len(self):
        if self.segment_notes is not None and len(self.segment_notes) != len(self.steps) - 1:
            raise ValueError(
                f"segment_notes muss genau {len(self.steps) - 1} Einträge haben (len(steps)-1)"
            )
        return self


class EdgeIdsBatch(BaseModel):
    edge_ids: List[int] = Field(..., min_length=1)


_EDGE_SELECT = """
    SELECT e.id, e.graph_id,
           e.from_exercise_id, e.from_exercise_variant_id,
           e.to_exercise_id, e.to_exercise_variant_id,
           e.edge_type, e.notes, e.created_at,
           ef.title AS from_exercise_title, et.title AS to_exercise_title,
           vf.variant_name AS from_variant_name, vt.variant_name AS to_variant_name
    FROM exercise_progression_edges e
    JOIN exercises ef ON ef.id = e.from_exercise_id
    JOIN exercises et ON et.id = e.to_exercise_id
    LEFT JOIN exercise_variants vf ON vf.id = e.from_exercise_variant_id
    LEFT JOIN exercise_variants vt ON vt.id = e.to_exercise_variant_id
"""


def _graph_row(cur, graph_id: int) -> dict:
    cur.execute(
        "SELECT * FROM exercise_progression_graphs WHERE id = %s",
        (graph_id,),
    )
    r = cur.fetchone()
    if not r:
        raise HTTPException(status_code=404, detail="Progressionsgraph nicht gefunden")
    return r2d(r)


def _assert_graph_readable(cur, row: dict, profile_id: int, role: str) -> None:
    vis = (row.get("visibility") or "private").strip().lower()
    cid = row.get("club_id")
    if cid is not None:
        cid = int(cid)
    cr = row.get("created_by")
    if cr is not None:
        cr = int(cr)
    if not library_content_visible_to_profile(cur, profile_id, vis, cid, cr, role):
        raise HTTPException(status_code=403, detail="Keine Berechtigung für diesen Progressionsgraph")


def _assert_graph_writable(cur, row: dict, profile_id: int, role: str) -> None:
    assert_library_content_editable(cur, profile_id, role, row)


def _persist_graph_planning_roadmap(cur, graph_id: int, raw: Optional[Dict[str, Any]]) -> None:
    try:
        normalized = normalize_planning_roadmap_payload(raw)
    except ValueError as exc:
        raise HTTPException(status_code=400, detail=str(exc)) from exc
    cur.execute(
        "UPDATE exercise_progression_graphs SET planning_roadmap = %s WHERE id = %s",
        (Json(normalized) if normalized is not None else None, graph_id),
    )


def _require_graph_read(cur, graph_id: int, profile_id: int, role: str) -> dict:
    row = _graph_row(cur, graph_id)
    _assert_graph_readable(cur, row, profile_id, role)
    return row


def _require_graph_write(cur, graph_id: int, profile_id: int, role: str) -> dict:
    row = _graph_row(cur, graph_id)
    _assert_graph_writable(cur, row, profile_id, role)
    return row


def _assert_exercises_exist(cur, *exercise_ids: int) -> None:
    unique_ids = list(dict.fromkeys(exercise_ids))
    if not unique_ids:
        return
    cur.execute(
        f"SELECT id FROM exercises WHERE id IN ({','.join(['%s'] * len(unique_ids))})",
        tuple(unique_ids),
    )
    found = {r["id"] if isinstance(r, dict) else r[0] for r in cur.fetchall()}
    missing = set(unique_ids) - found
    if missing:
        raise HTTPException(
            status_code=400,
            detail=f"Unbekannte Übung(en): {sorted(missing)}",
        )


def _assert_variant_for_exercise(cur, exercise_id: int, variant_id: Optional[int]) -> None:
    if variant_id is None:
        return
    cur.execute(
        "SELECT exercise_id FROM exercise_variants WHERE id = %s",
        (variant_id,),
    )
    row = cur.fetchone()
    if not row:
        raise HTTPException(status_code=400, detail=f"Unbekannte Variante: {variant_id}")
    ev_ex = row["exercise_id"] if isinstance(row, dict) else row[0]
    if ev_ex != exercise_id:
        raise HTTPException(status_code=400, detail="Variante gehört nicht zur gewählten Übung")


def _exercise_allowed_in_progression_graph(
    exercise_row: Mapping[str, Any],
    *,
    graph_visibility: str,
    graph_club_id: Optional[int],
    profile_id: int,
    role: str,
) -> bool:
    """Prüft, ob eine Übung zur Sichtbarkeit des Progressionsgraphen passt."""
    ex_vis = (exercise_row.get("visibility") or "private").strip().lower()
    gvis = (graph_visibility or "private").strip().lower()
    if gvis == "private":
        if ex_vis == "official":
            return True
        if ex_vis == "club":
            return True
        if ex_vis == "private":
            if is_platform_admin(role):
                return True
            try:
                return int(exercise_row.get("created_by") or 0) == int(profile_id)
            except (TypeError, ValueError):
                return False
        return False
    if gvis == "club":
        if ex_vis == "official":
            return True
        if ex_vis != "club":
            return False
        ex_club = exercise_row.get("club_id")
        if ex_club is None:
            return False
        if graph_club_id is None:
            return True
        return int(ex_club) == int(graph_club_id)
    return ex_vis == "official"


def _assert_exercises_allowed_in_graph(
    cur,
    graph_id: int,
    profile_id: int,
    role: str,
    *exercise_ids: int,
) -> None:
    """400 wenn eine Übung nicht zur Graph-Sichtbarkeit passt."""
    row = _graph_row(cur, graph_id)
    gvis = (row.get("visibility") or "private").strip().lower()
    gclub_raw = row.get("club_id")
    gclub = int(gclub_raw) if gclub_raw is not None else None
    unique = list(dict.fromkeys(exercise_ids))
    if not unique:
        return
    ph = ",".join(["%s"] * len(unique))
    cur.execute(
        f"SELECT id, title, visibility, club_id, created_by FROM exercises WHERE id IN ({ph})",
        tuple(unique),
    )
    by_id = {int(r2d(r)["id"]): r2d(r) for r in cur.fetchall()}
    for eid in unique:
        ex = by_id.get(int(eid))
        if not ex:
            continue
        if _exercise_allowed_in_progression_graph(
            ex,
            graph_visibility=gvis,
            graph_club_id=gclub,
            profile_id=profile_id,
            role=role,
        ):
            continue
        title = (ex.get("title") or "").strip() or f"#{eid}"
        raise HTTPException(
            status_code=400,
            detail=(
                f"Übung „{title}“ (Sichtbarkeit: {ex.get('visibility') or 'private'}) "
                f"passt nicht zum Progressionsgraphen ({gvis})."
            ),
        )


def _insert_edge_row(
    cur,
    graph_id: int,
    from_exercise_id: int,
    from_variant_id: Optional[int],
    to_exercise_id: int,
    to_variant_id: Optional[int],
    edge_type: str,
    notes: Optional[str],
) -> dict:
    cur.execute(
        """
        INSERT INTO exercise_progression_edges (
            graph_id,
            from_exercise_id, from_exercise_variant_id,
            to_exercise_id, to_exercise_variant_id,
            edge_type, notes
        )
        VALUES (%s, %s, %s, %s, %s, %s, %s)
        RETURNING id
        """,
        (
            graph_id,
            from_exercise_id,
            from_variant_id,
            to_exercise_id,
            to_variant_id,
            edge_type,
            notes,
        ),
    )
    new_id = cur.fetchone()["id"]
    cur.execute(_EDGE_SELECT + " WHERE e.id = %s", (new_id,))
    return r2d(cur.fetchone())


@router.get("/exercise-progression-graphs")
def list_progression_graphs(tenant: TenantContext = Depends(get_tenant_context)):
    profile_id = tenant.profile_id
    role = tenant.global_role
    with get_db() as conn:
        cur = get_cursor(conn)
        vis_sql, vis_params = library_content_visibility_sql(
            alias="g",
            profile_id=profile_id,
            role=role,
            effective_club_id=tenant.effective_club_id,
        )
        cur.execute(
            f"""
            SELECT g.*,
                (SELECT COUNT(*) FROM exercise_progression_edges e WHERE e.graph_id = g.id) AS edges_count
            FROM exercise_progression_graphs g
            WHERE ({vis_sql})
            ORDER BY g.updated_at DESC NULLS LAST, g.name
            """,
            vis_params,
        )
        return [r2d(r) for r in cur.fetchall()]


@router.get("/exercise-progression-graphs/{graph_id}")
def get_progression_graph(
    graph_id: int,
    include_edges: bool = Query(default=False),
    tenant: TenantContext = Depends(get_tenant_context),
):
    profile_id = tenant.profile_id
    role = tenant.global_role
    with get_db() as conn:
        cur = get_cursor(conn)
        row = _require_graph_read(cur, graph_id, profile_id, role)
        if include_edges:
            cur.execute(
                _EDGE_SELECT + " WHERE e.graph_id = %s ORDER BY e.id",
                (graph_id,),
            )
            row["edges"] = [r2d(r) for r in cur.fetchall()]
        return row


def _exercise_ids_from_planning_roadmap(artifact: Optional[Dict[str, Any]]) -> set[int]:
    ids: set[int] = set()
    if not artifact or not isinstance(artifact, dict):
        return ids
    for slot in artifact.get("slot_contents") or []:
        if not isinstance(slot, dict):
            continue
        primary = slot.get("primary") if isinstance(slot.get("primary"), dict) else {}
        if primary.get("kind") == "library" and primary.get("exercise_id") is not None:
            try:
                ids.add(int(primary["exercise_id"]))
            except (TypeError, ValueError):
                pass
        for sib in slot.get("siblings") or []:
            if not isinstance(sib, dict):
                continue
            if sib.get("kind") == "library" and sib.get("exercise_id") is not None:
                try:
                    ids.add(int(sib["exercise_id"]))
                except (TypeError, ValueError):
                    pass
    return ids


def _collect_graph_referenced_exercise_ids(cur, graph_id: int) -> set[int]:
    ids: set[int] = set()
    cur.execute(
        """
        SELECT from_exercise_id, to_exercise_id
        FROM exercise_progression_edges
        WHERE graph_id = %s
        """,
        (graph_id,),
    )
    for row in cur.fetchall():
        for key in ("from_exercise_id", "to_exercise_id"):
            raw = row.get(key)
            if raw is not None:
                ids.add(int(raw))
    cur.execute(
        "SELECT planning_roadmap FROM exercise_progression_graphs WHERE id = %s",
        (graph_id,),
    )
    prow = cur.fetchone()
    if prow and prow.get("planning_roadmap"):
        art = prow["planning_roadmap"]
        if isinstance(art, str):
            try:
                art = json.loads(art)
            except json.JSONDecodeError:
                art = None
        ids |= _exercise_ids_from_planning_roadmap(art if isinstance(art, dict) else None)
    return ids


def _graph_promotion_transition(graph_visibility: str, target_visibility: str) -> Optional[tuple[str, ...]]:
    """
    Erlaubte Graph-Promotions und welche Übungs-Sichtbarkeiten mit angehoben werden müssen.

    Returns None wenn kein Übungs-Promotion-Hinweis nötig.
    """
    gvis = (graph_visibility or "private").strip().lower()
    tvis = (target_visibility or "").strip().lower()
    transitions: Dict[tuple[str, str], tuple[str, ...]] = {
        ("private", "club"): ("private",),
        ("private", "official"): ("private", "club"),
        ("club", "official"): ("private", "club"),
    }
    return transitions.get((gvis, tvis))


@router.get("/exercise-progression-graphs/{graph_id}/visibility-promotion-candidates")
def list_visibility_promotion_candidates(
    graph_id: int,
    target_visibility: str = Query(default="club", pattern="^(club|official)$"),
    tenant: TenantContext = Depends(get_tenant_context),
):
    """
    Übungen im Graph, die bei Promotion des Graphen mit angehoben werden müssten.

    Unterstützt: private→club, private→official, club→official.
    """
    profile_id = tenant.profile_id
    role = tenant.global_role
    with get_db() as conn:
        cur = get_cursor(conn)
        row = _require_graph_read(cur, graph_id, profile_id, role)
        graph_vis = (row.get("visibility") or "private").strip().lower()
        target_vis = (target_visibility or "club").strip().lower()
        need_vis = _graph_promotion_transition(graph_vis, target_vis)
        if not need_vis:
            return {
                "graph_id": graph_id,
                "graph_visibility": graph_vis,
                "target_visibility": target_vis,
                "exercises": [],
            }
        ref_ids = _collect_graph_referenced_exercise_ids(cur, graph_id)
        if not ref_ids:
            return {
                "graph_id": graph_id,
                "graph_visibility": graph_vis,
                "target_visibility": target_vis,
                "exercises": [],
            }
        vis_placeholders = ",".join(["%s"] * len(need_vis))
        ph = ",".join(["%s"] * len(ref_ids))
        cur.execute(
            f"""
            SELECT id, title, visibility, club_id, created_by
            FROM exercises
            WHERE id IN ({ph})
              AND LOWER(TRIM(COALESCE(visibility, ''))) IN ({vis_placeholders})
            ORDER BY title
            """,
            list(ref_ids) + list(need_vis),
        )
        exercises = []
        for ex in cur.fetchall():
            exd = r2d(ex)
            if not library_content_visible_to_profile(
                cur,
                profile_id,
                (exd.get("visibility") or "private").strip().lower(),
                exd.get("club_id"),
                exd.get("created_by"),
                role,
            ):
                continue
            exercises.append(
                {
                    "id": exd["id"],
                    "title": exd.get("title"),
                    "visibility": exd.get("visibility"),
                }
            )
    return {
        "graph_id": graph_id,
        "graph_visibility": graph_vis,
        "target_visibility": target_vis,
        "exercises": exercises,
    }


@router.post("/exercise-progression-graphs", status_code=201)
def create_progression_graph(
    body: ProgressionGraphCreate,
    tenant: TenantContext = Depends(get_tenant_context),
):
    profile_id = tenant.profile_id
    role = tenant.global_role
    if not _has_planning_role(role):
        raise HTTPException(status_code=403, detail="Keine Berechtigung zum Anlegen von Progressionsgraphen")

    name = body.name.strip()
    if not name:
        raise HTTPException(status_code=400, detail="name ist Pflicht")

    vis = (body.visibility or "private").strip().lower()
    cid = body.club_id
    if vis == "club":
        if cid is None:
            cid = tenant.effective_club_id
        if cid is None:
            raise HTTPException(
                status_code=400,
                detail="Vereins-Graph: club_id angeben oder aktiven Verein wählen (X-Active-Club-Id).",
            )

    gov_club = cid if vis == "club" else None

    with get_db() as conn:
        cur = get_cursor(conn)
        assert_valid_governance_visibility(cur, profile_id, role, vis, gov_club)
        cur.execute(
            """
            INSERT INTO exercise_progression_graphs (name, description, visibility, club_id, created_by)
            VALUES (%s, %s, %s, %s, %s)
            RETURNING id
            """,
            (name, body.description, vis, cid if vis == "club" else None, profile_id),
        )
        gid = cur.fetchone()["id"]
        conn.commit()

    return get_progression_graph(gid, include_edges=False, tenant=tenant)


@router.put("/exercise-progression-graphs/{graph_id}")
def update_progression_graph(
    graph_id: int,
    body: ProgressionGraphUpdate,
    tenant: TenantContext = Depends(get_tenant_context),
):
    profile_id = tenant.profile_id
    role = tenant.global_role
    original = body.model_dump(exclude_unset=True)
    if not original:
        raise HTTPException(status_code=400, detail="Keine Felder zum Aktualisieren")

    with get_db() as conn:
        cur = get_cursor(conn)
        row = _require_graph_write(cur, graph_id, profile_id, role)

        ex_vis = (row.get("visibility") or "private").strip().lower()
        ex_cid_raw = row.get("club_id")
        ex_cid = int(ex_cid_raw) if ex_cid_raw is not None else None

        next_vis = ex_vis
        if "visibility" in original and original["visibility"] is not None:
            v_raw = str(original["visibility"]).strip().lower()
            if v_raw:
                next_vis = v_raw

        next_club = ex_cid
        if "club_id" in original:
            raw_c = original["club_id"]
            if raw_c in (None, "", []):
                next_club = None
            else:
                next_club = int(raw_c)

        if next_vis == "club":
            if next_club is None:
                next_club = tenant.effective_club_id
            if next_club is None:
                raise HTTPException(
                    status_code=400,
                    detail="Vereins-Graph: club_id angeben oder aktiven Verein wählen (X-Active-Club-Id).",
                )

        gov_club = next_club if next_vis == "club" else None
        assert_library_content_governance_transition(cur, profile_id, role, row, next_vis, gov_club)
        assert_valid_governance_visibility(cur, profile_id, role, next_vis, gov_club)

        fields: List[str] = []
        params: List[Any] = []
        if "name" in original:
            n = (original["name"] or "").strip()
            if not n:
                raise HTTPException(status_code=400, detail="name ist Pflicht")
            fields.append("name = %s")
            params.append(n)
        if "description" in original:
            fields.append("description = %s")
            params.append(original["description"])

        vis_changed = next_vis != ex_vis
        if "visibility" in original or vis_changed:
            fields.append("visibility = %s")
            params.append(next_vis)

        if "club_id" in original or vis_changed:
            fields.append("club_id = %s")
            params.append(next_club if next_vis == "club" else None)

        if "planning_roadmap" in original:
            _persist_graph_planning_roadmap(cur, graph_id, original.get("planning_roadmap"))

        if not fields and "planning_roadmap" not in original:
            return get_progression_graph(graph_id, include_edges=False, tenant=tenant)

        if fields:
            fields.append("updated_at = NOW()")
            params.append(graph_id)
            cur.execute(
                f"UPDATE exercise_progression_graphs SET {', '.join(fields)} WHERE id = %s",
                tuple(params),
            )
        elif "planning_roadmap" in original:
            cur.execute(
                "UPDATE exercise_progression_graphs SET updated_at = NOW() WHERE id = %s",
                (graph_id,),
            )
        conn.commit()

    return get_progression_graph(graph_id, include_edges=False, tenant=tenant)


@router.delete("/exercise-progression-graphs/{graph_id}")
def delete_progression_graph(graph_id: int, tenant: TenantContext = Depends(get_tenant_context)):
    profile_id = tenant.profile_id
    role = tenant.global_role
    with get_db() as conn:
        cur = get_cursor(conn)
        row = _graph_row(cur, graph_id)
        _assert_graph_readable(cur, row, profile_id, role)
        assert_library_content_deletable(cur, profile_id, role, row)
        cur.execute("DELETE FROM exercise_progression_graphs WHERE id = %s", (graph_id,))
        conn.commit()
    return {"ok": True}


@router.get("/exercise-progression-graphs/{graph_id}/edges")
def list_progression_edges(
    graph_id: int,
    from_exercise_id: Optional[int] = Query(default=None),
    to_exercise_id: Optional[int] = Query(default=None),
    tenant: TenantContext = Depends(get_tenant_context),
):
    profile_id = tenant.profile_id
    role = tenant.global_role
    with get_db() as conn:
        cur = get_cursor(conn)
        _require_graph_read(cur, graph_id, profile_id, role)
        q = _EDGE_SELECT + " WHERE e.graph_id = %s"
        params: List[Any] = [graph_id]
        if from_exercise_id is not None:
            q += " AND e.from_exercise_id = %s"
            params.append(from_exercise_id)
        if to_exercise_id is not None:
            q += " AND e.to_exercise_id = %s"
            params.append(to_exercise_id)
        q += " ORDER BY e.id"
        cur.execute(q, tuple(params))
        return [r2d(r) for r in cur.fetchall()]


@router.post("/exercise-progression-graphs/{graph_id}/edges", status_code=201)
def create_progression_edge(
    graph_id: int,
    body: ProgressionEdgeCreate,
    tenant: TenantContext = Depends(get_tenant_context),
):
    profile_id = tenant.profile_id
    role = tenant.global_role

    with get_db() as conn:
        cur = get_cursor(conn)
        _require_graph_write(cur, graph_id, profile_id, role)
        _assert_exercises_exist(cur, body.from_exercise_id, body.to_exercise_id)
        _assert_exercises_allowed_in_graph(
            cur, graph_id, profile_id, role, body.from_exercise_id, body.to_exercise_id
        )
        fv = body.from_exercise_variant_id
        tv = body.to_exercise_variant_id
        _assert_variant_for_exercise(cur, body.from_exercise_id, fv)
        _assert_variant_for_exercise(cur, body.to_exercise_id, tv)
        et = (body.edge_type or "next_exercise").strip() or "next_exercise"
        notes = (body.notes or "").strip() or None
        try:
            row = _insert_edge_row(
                cur,
                graph_id,
                body.from_exercise_id,
                fv,
                body.to_exercise_id,
                tv,
                et,
                notes,
            )
            conn.commit()
        except IntegrityError as e:
            conn.rollback()
            raise HTTPException(
                status_code=409,
                detail="Kante existiert bereits oder Endpunkte unzulässig (gleiche Übung ohne zwei Varianten)",
            ) from e

    return row


@router.post("/exercise-progression-graphs/{graph_id}/edges/sequence", status_code=201)
def create_progression_sequence(
    graph_id: int,
    body: ProgressionSequenceCreate,
    tenant: TenantContext = Depends(get_tenant_context),
):
    """Legt n−1 Nachfolger-Kanten (next_exercise) für eine geordnete Schrittliste an."""
    profile_id = tenant.profile_id
    role = tenant.global_role
    steps = body.steps
    n_seg = len(steps) - 1
    seg_notes = body.segment_notes

    created: List[dict] = []
    with get_db() as conn:
        cur = get_cursor(conn)
        _require_graph_write(cur, graph_id, profile_id, role)

        ex_ids = [s.exercise_id for s in steps]
        _assert_exercises_exist(cur, *ex_ids)
        _assert_exercises_allowed_in_graph(cur, graph_id, profile_id, role, *ex_ids)

        try:
            for i in range(n_seg):
                a, b = steps[i], steps[i + 1]
                _assert_variant_for_exercise(cur, a.exercise_id, a.variant_id)
                _assert_variant_for_exercise(cur, b.exercise_id, b.variant_id)
                note = None
                if seg_notes is not None:
                    raw = seg_notes[i]
                    note = (raw or "").strip() or None if raw is not None else None
                row = _insert_edge_row(
                    cur,
                    graph_id,
                    a.exercise_id,
                    a.variant_id,
                    b.exercise_id,
                    b.variant_id,
                    "next_exercise",
                    note,
                )
                created.append(row)
            if body.planning_roadmap is not None:
                _persist_graph_planning_roadmap(cur, graph_id, body.planning_roadmap)
                cur.execute(
                    "UPDATE exercise_progression_graphs SET updated_at = NOW() WHERE id = %s",
                    (graph_id,),
                )
            conn.commit()
        except IntegrityError as e:
            conn.rollback()
            raise HTTPException(
                status_code=409,
                detail="Sequenz konnte nicht vollständig angelegt werden (Duplikat oder ungültige Endpunkte). Keine Teilmenge gespeichert.",
            ) from e

    return {"created": created, "count": len(created)}


@router.put("/exercise-progression-graphs/{graph_id}/edges/{edge_id}")
def update_progression_edge(
    graph_id: int,
    edge_id: int,
    body: ProgressionEdgeUpdate,
    tenant: TenantContext = Depends(get_tenant_context),
):
    profile_id = tenant.profile_id
    role = tenant.global_role
    data = body.model_dump(exclude_unset=True)
    if not data:
        raise HTTPException(status_code=400, detail="Keine Felder zum Aktualisieren")

    with get_db() as conn:
        cur = get_cursor(conn)
        _require_graph_write(cur, graph_id, profile_id, role)
        cur.execute(
            "SELECT id FROM exercise_progression_edges WHERE id = %s AND graph_id = %s",
            (edge_id, graph_id),
        )
        if not cur.fetchone():
            raise HTTPException(status_code=404, detail="Kante nicht gefunden")

        if "notes" in data:
            n = data["notes"]
            notes_val = (n or "").strip() or None if n is not None else None
            cur.execute(
                "UPDATE exercise_progression_edges SET notes = %s WHERE id = %s AND graph_id = %s",
                (notes_val, edge_id, graph_id),
            )
        conn.commit()
        cur.execute(_EDGE_SELECT + " WHERE e.id = %s AND e.graph_id = %s", (edge_id, graph_id))
        return r2d(cur.fetchone())


@router.delete("/exercise-progression-graphs/{graph_id}/edges/{edge_id}")
def delete_progression_edge(
    graph_id: int,
    edge_id: int,
    tenant: TenantContext = Depends(get_tenant_context),
):
    profile_id = tenant.profile_id
    role = tenant.global_role
    with get_db() as conn:
        cur = get_cursor(conn)
        _require_graph_write(cur, graph_id, profile_id, role)
        cur.execute(
            """
            DELETE FROM exercise_progression_edges
            WHERE id = %s AND graph_id = %s
            RETURNING id
            """,
            (edge_id, graph_id),
        )
        if not cur.fetchone():
            raise HTTPException(status_code=404, detail="Kante nicht gefunden")
        conn.commit()
    return {"ok": True}


@router.post("/exercise-progression-graphs/{graph_id}/edges/delete-batch")
def delete_progression_edges_batch(
    graph_id: int,
    body: EdgeIdsBatch,
    tenant: TenantContext = Depends(get_tenant_context),
):
    """Löscht mehrere Kanten (z. B. eine zusammenhängende Kette in einem Schritt)."""
    profile_id = tenant.profile_id
    role = tenant.global_role
    ids = body.edge_ids
    clean_ids = list(dict.fromkeys(ids))

    with get_db() as conn:
        cur = get_cursor(conn)
        _require_graph_write(cur, graph_id, profile_id, role)
        cur.execute(
            f"""
            DELETE FROM exercise_progression_edges
            WHERE graph_id = %s AND id IN ({",".join(["%s"] * len(clean_ids))})
            """,
            (graph_id, *clean_ids),
        )
        deleted = cur.rowcount
        conn.commit()
    return {"ok": True, "deleted": deleted}