"""MITRE ATT&CK reference endpoints.

Read access is open to any authenticated user (the catalogue is reference
data — not sensitive on its own). Sync is admin-only via `mitre.sync`.
"""

from __future__ import annotations

import logging

from flask import Blueprint, jsonify, request
from pydantic import BaseModel
from sqlalchemy import func, or_, select

from app.core.auth_decorators import require_auth, require_perm
from app.db.session import session_scope
from app.models.mitre import MitreSubtechnique, MitreTactic, MitreTechnique
from app.services import mitre_seed as mitre_seed_svc


class SyncResultOut(BaseModel):
    """Response schema for `POST /mitre/sync`. Mirrors `SeedResult.as_dict()`."""

    tactics_upserted: int
    techniques_upserted: int
    subtechniques_upserted: int
    subtechniques_skipped_orphan: int
    technique_tactic_links: int
    version: str | None
    source: str
    started_at: str
    finished_at: str
    duration_ms: int

bp = Blueprint("mitre", __name__, url_prefix="/mitre")
log = logging.getLogger("metamorph.api.mitre")


def _pagination_args() -> tuple[int, int] | tuple[None, tuple[int, str]]:
    """Returns (limit, offset) or (None, (status, error_payload))."""
    try:
        limit = int(request.args.get("limit", "100"))
        offset = int(request.args.get("offset", "0"))
    except ValueError:
        return None, (400, "invalid_pagination")
    limit = max(1, min(limit, 500))
    offset = max(0, offset)
    return limit, offset


def _search(stmt, model, q: str | None):
    if not q:
        return stmt
    like = f"%{q.lower()}%"
    return stmt.where(
        or_(
            func.lower(model.name).like(like),
            func.lower(model.external_id).like(like),
        )
    )


def _serialize_tactic(t: MitreTactic) -> dict:
    return {
        "id": str(t.id),
        "external_id": t.external_id,
        "short_name": t.short_name,
        "name": t.name,
        "description": t.description,
        "url": t.url,
    }


def _serialize_technique(t: MitreTechnique, *, include_tactics: bool = True) -> dict:
    out = {
        "id": str(t.id),
        "external_id": t.external_id,
        "name": t.name,
        "description": t.description,
        "url": t.url,
    }
    if include_tactics:
        out["tactics"] = sorted(
            ({"external_id": tac.external_id, "name": tac.name} for tac in t.tactics),
            key=lambda d: d["external_id"],
        )
    return out


def _serialize_subtechnique(sb: MitreSubtechnique) -> dict:
    return {
        "id": str(sb.id),
        "external_id": sb.external_id,
        "name": sb.name,
        "description": sb.description,
        "url": sb.url,
        "technique_id": str(sb.technique_id),
    }


@bp.get("/tactics")
@require_auth
def list_tactics():
    paging = _pagination_args()
    if paging[0] is None:
        return jsonify({"error": paging[1][1]}), paging[1][0]
    limit, offset = paging
    q = request.args.get("q") or None
    with session_scope() as s:
        stmt = select(MitreTactic).order_by(MitreTactic.external_id.asc())
        stmt = _search(stmt, MitreTactic, q)
        total = s.scalar(_search(select(func.count()).select_from(MitreTactic), MitreTactic, q)) or 0
        rows = s.scalars(stmt.limit(limit).offset(offset)).all()
        return jsonify(
            {
                "items": [_serialize_tactic(t) for t in rows],
                "total": int(total),
                "limit": limit,
                "offset": offset,
            }
        )


@bp.get("/techniques")
@require_auth
def list_techniques():
    paging = _pagination_args()
    if paging[0] is None:
        return jsonify({"error": paging[1][1]}), paging[1][0]
    limit, offset = paging
    q = request.args.get("q") or None
    tactic = request.args.get("tactic") or None
    with session_scope() as s:
        stmt = select(MitreTechnique).order_by(MitreTechnique.external_id.asc())
        count_stmt = select(func.count()).select_from(MitreTechnique)
        if tactic:
            tac = s.scalar(select(MitreTactic).where(MitreTactic.external_id == tactic))
            if tac is None:
                return jsonify({"items": [], "total": 0, "limit": limit, "offset": offset})
            stmt = stmt.join(MitreTechnique.tactics).where(MitreTactic.id == tac.id)
            count_stmt = (
                count_stmt.select_from(MitreTechnique)
                .join(MitreTechnique.tactics)
                .where(MitreTactic.id == tac.id)
            )
        stmt = _search(stmt, MitreTechnique, q)
        count_stmt = _search(count_stmt, MitreTechnique, q)
        total = s.scalar(count_stmt) or 0
        rows = s.scalars(stmt.limit(limit).offset(offset)).all()
        return jsonify(
            {
                "items": [_serialize_technique(t) for t in rows],
                "total": int(total),
                "limit": limit,
                "offset": offset,
            }
        )


@bp.get("/subtechniques")
@require_auth
def list_subtechniques():
    paging = _pagination_args()
    if paging[0] is None:
        return jsonify({"error": paging[1][1]}), paging[1][0]
    limit, offset = paging
    q = request.args.get("q") or None
    technique = request.args.get("technique") or None
    with session_scope() as s:
        stmt = select(MitreSubtechnique).order_by(MitreSubtechnique.external_id.asc())
        count_stmt = select(func.count()).select_from(MitreSubtechnique)
        if technique:
            tech = s.scalar(
                select(MitreTechnique).where(MitreTechnique.external_id == technique)
            )
            if tech is None:
                return jsonify({"items": [], "total": 0, "limit": limit, "offset": offset})
            stmt = stmt.where(MitreSubtechnique.technique_id == tech.id)
            count_stmt = count_stmt.where(MitreSubtechnique.technique_id == tech.id)
        stmt = _search(stmt, MitreSubtechnique, q)
        count_stmt = _search(count_stmt, MitreSubtechnique, q)
        total = s.scalar(count_stmt) or 0
        rows = s.scalars(stmt.limit(limit).offset(offset)).all()
        return jsonify(
            {
                "items": [_serialize_subtechnique(sb) for sb in rows],
                "total": int(total),
                "limit": limit,
                "offset": offset,
            }
        )


@bp.get("/matrix")
@require_auth
def matrix():
    """Return the full Enterprise matrix: tactics → techniques → sub-techniques.

    One-shot endpoint so the SPA can render the flat attack.mitre.org-style
    grid without firing 15 parallel queries. The payload is ~55 KB serialised
    against MITRE v19 (15 tactics × ~50 techniques × ~3 subs).
    """
    with session_scope() as s:
        # All techniques + their tactics (selectin-loaded by the relationship).
        techniques = s.scalars(
            select(MitreTechnique).order_by(MitreTechnique.external_id.asc())
        ).all()
        # Sub-techniques bucketed by parent.
        subs_by_parent: dict = {}
        for sb in s.scalars(
            select(MitreSubtechnique).order_by(MitreSubtechnique.external_id.asc())
        ).all():
            subs_by_parent.setdefault(sb.technique_id, []).append(
                {
                    "id": str(sb.id),
                    "external_id": sb.external_id,
                    "name": sb.name,
                }
            )
        # Tactics in canonical kill-chain order (matches attack.mitre.org).
        tactics = s.scalars(
            select(MitreTactic).order_by(MitreTactic.external_id.asc())
        ).all()

        # Group techniques by tactic short_name.
        techs_by_tactic: dict = {}
        for t in techniques:
            entry = {
                "id": str(t.id),
                "external_id": t.external_id,
                "name": t.name,
                "subtechniques": subs_by_parent.get(t.id, []),
            }
            for tac in t.tactics:
                techs_by_tactic.setdefault(tac.short_name, []).append(entry)

        return jsonify(
            {
                "tactics": [
                    {
                        "id": str(t.id),
                        "external_id": t.external_id,
                        "short_name": t.short_name,
                        "name": t.name,
                        "techniques": techs_by_tactic.get(t.short_name, []),
                    }
                    for t in tactics
                ]
            }
        )


@bp.get("/status")
@require_auth
def status():
    return jsonify(mitre_seed_svc.read_status())


@bp.post("/sync")
@require_auth
@require_perm("mitre.sync")
def sync():
    """Re-pull the configured (or default) STIX source and upsert.

    Custom `source` URLs MUST be paired with either `expected_sha256` (integrity
    guarantee) or `allow_unverified: true` (explicit opt-out) — the seed service
    will raise otherwise. The host is allowlisted (defaults to
    raw.githubusercontent.com, overridable via the MITRE_ALLOWED_HOSTS env).
    """
    payload = request.get_json(silent=True) or {}
    source = payload.get("source")  # optional URL override
    expected_sha256 = payload.get("expected_sha256")
    allow_unverified = bool(payload.get("allow_unverified", False))
    try:
        result = mitre_seed_svc.seed_mitre(
            source=source,
            expected_sha256=expected_sha256
            or (mitre_seed_svc.MITRE_DEFAULT_SHA256 if source is None else None),
            allow_unverified=allow_unverified,
        )
    except mitre_seed_svc.MitreSourceForbidden as e:
        return jsonify({"error": "source_forbidden", "message": str(e)}), 400
    except mitre_seed_svc.MitreChecksumMismatch as e:
        return jsonify({"error": "checksum_mismatch", "message": str(e)}), 502
    except mitre_seed_svc.MitreSeedError as e:
        return jsonify({"error": "seed_failed", "message": str(e)}), 502
    except Exception:  # noqa: BLE001
        # Do NOT leak the internal error string to the client (URLError stack,
        # DB driver text). The stack lands in our JSON logs.
        log.exception("metamorph.api.mitre.sync_failed")
        return jsonify({"error": "internal_error"}), 500
    # Validate via the Pydantic Out model so the response contract is
    # explicit (single source of truth shared with the TS interface).
    payload_out = SyncResultOut.model_validate(result.as_dict()).model_dump()
    log.info("metamorph.api.mitre.sync_done", extra=payload_out)
    return jsonify(payload_out)