from datetime import datetime
from uuid import uuid4

import asyncpg
from fastapi import APIRouter, Depends, HTTPException, Query, status
from sqlalchemy import and_, delete, desc, select
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.db import get_db
from app.core.deps import get_current_user, require_roles
from app.core.errors import api_error
from app.models.models import Metric, QueryStat, Target, TargetOwner, User
from app.schemas.metric import MetricOut, QueryStatOut
from app.schemas.overview import DatabaseOverviewOut
from app.schemas.target import (
    TargetConnectionTestRequest,
    TargetCreate,
    TargetOut,
    TargetOwnerOut,
    TargetOwnersUpdate,
    TargetUpdate,
)
from app.services.audit import write_audit_log
from app.services.collector import build_target_dsn
from app.services.crypto import encrypt_secret
from app.services.overview_service import get_target_overview

router = APIRouter()


async def _owners_by_target_ids(db: AsyncSession, target_ids: list[int]) -> dict[int, list[int]]:
    if not target_ids:
        return {}
    rows = (
        await db.execute(select(TargetOwner.target_id, TargetOwner.user_id).where(TargetOwner.target_id.in_(target_ids)))
    ).all()
    mapping: dict[int, list[int]] = {target_id: [] for target_id in target_ids}
    for target_id, user_id in rows:
        mapping.setdefault(target_id, []).append(user_id)
    return mapping


def _target_out_with_owners(target: Target, owner_user_ids: list[int]) -> TargetOut:
    return TargetOut(
        id=target.id,
        name=target.name,
        host=target.host,
        port=target.port,
        dbname=target.dbname,
        username=target.username,
        sslmode=target.sslmode,
        use_pg_stat_statements=target.use_pg_stat_statements,
        owner_user_ids=owner_user_ids,
        tags=target.tags or {},
        created_at=target.created_at,
    )


async def _set_target_owners(db: AsyncSession, target_id: int, user_ids: list[int], assigned_by_user_id: int | None) -> None:
    await db.execute(delete(TargetOwner).where(TargetOwner.target_id == target_id))
    for user_id in sorted(set(user_ids)):
        db.add(TargetOwner(target_id=target_id, user_id=user_id, assigned_by_user_id=assigned_by_user_id))


async def _discover_databases(payload: TargetCreate) -> list[str]:
    ssl = False if payload.sslmode == "disable" else True
    conn = None
    try:
        conn = await asyncpg.connect(
            host=payload.host,
            port=payload.port,
            database=payload.dbname,
            user=payload.username,
            password=payload.password,
            ssl=ssl,
            timeout=8,
        )
        rows = await conn.fetch(
            """
            SELECT datname
            FROM pg_database
            WHERE datallowconn
              AND NOT datistemplate
            ORDER BY datname
            """
        )
        return [row["datname"] for row in rows if row["datname"]]
    except Exception as exc:
        raise HTTPException(
            status_code=400,
            detail=api_error("database_discovery_failed", "Database discovery failed", {"error": str(exc)}),
        )
    finally:
        if conn:
            await conn.close()


async def _next_unique_target_name(db: AsyncSession, base_name: str) -> str:
    candidate = base_name.strip()
    suffix = 2
    while True:
        exists = await db.scalar(select(Target.id).where(Target.name == candidate))
        if exists is None:
            return candidate
        candidate = f"{base_name} ({suffix})"
        suffix += 1


@router.get("", response_model=list[TargetOut])
async def list_targets(user: User = Depends(get_current_user), db: AsyncSession = Depends(get_db)) -> list[TargetOut]:
    _ = user
    targets = (await db.scalars(select(Target).order_by(Target.id.desc()))).all()
    owner_map = await _owners_by_target_ids(db, [item.id for item in targets])
    return [_target_out_with_owners(item, owner_map.get(item.id, [])) for item in targets]


@router.post("/test-connection")
async def test_target_connection(
    payload: TargetConnectionTestRequest,
    user: User = Depends(require_roles("admin", "operator")),
) -> dict:
    _ = user
    ssl = False if payload.sslmode == "disable" else True
    conn = None
    try:
        conn = await asyncpg.connect(
            host=payload.host,
            port=payload.port,
            database=payload.dbname,
            user=payload.username,
            password=payload.password,
            ssl=ssl,
            timeout=8,
        )
        version = await conn.fetchval("SHOW server_version")
        return {"ok": True, "message": "Connection successful", "server_version": version}
    except Exception as exc:
        raise HTTPException(
            status_code=400,
            detail=api_error("connection_test_failed", "Connection test failed", {"error": str(exc)}),
        )
    finally:
        if conn:
            await conn.close()


@router.post("", response_model=TargetOut, status_code=status.HTTP_201_CREATED)
async def create_target(
    payload: TargetCreate,
    user: User = Depends(require_roles("admin", "operator")),
    db: AsyncSession = Depends(get_db),
) -> TargetOut:
    owner_ids = sorted(set(payload.owner_user_ids or []))
    if owner_ids:
        owners_exist = (await db.scalars(select(User.id).where(User.id.in_(owner_ids)))).all()
        if len(set(owners_exist)) != len(owner_ids):
            raise HTTPException(
                status_code=400,
                detail=api_error("owner_users_not_found", "One or more owner users were not found"),
            )

    encrypted_password = encrypt_secret(payload.password)
    created_targets: list[Target] = []

    if payload.discover_all_databases:
        databases = await _discover_databases(payload)
        if not databases:
            raise HTTPException(
                status_code=400,
                detail=api_error("no_databases_discovered", "No databases discovered on target"),
            )
        group_id = str(uuid4())
        base_tags = payload.tags or {}
        for dbname in databases:
            duplicate = await db.scalar(
                select(Target.id).where(
                    Target.host == payload.host,
                    Target.port == payload.port,
                    Target.dbname == dbname,
                    Target.username == payload.username,
                )
            )
            if duplicate is not None:
                continue
            target_name = await _next_unique_target_name(db, f"{payload.name} / {dbname}")
            tags = {
                **base_tags,
                "monitor_mode": "all_databases",
                "monitor_group_id": group_id,
                "monitor_group_name": payload.name,
            }
            target = Target(
                name=target_name,
                host=payload.host,
                port=payload.port,
                dbname=dbname,
                username=payload.username,
                encrypted_password=encrypted_password,
                sslmode=payload.sslmode,
                use_pg_stat_statements=payload.use_pg_stat_statements,
                tags=tags,
            )
            db.add(target)
            await db.flush()
            created_targets.append(target)
            if owner_ids:
                await _set_target_owners(db, target.id, owner_ids, user.id)

        if not created_targets:
            raise HTTPException(
                status_code=400,
                detail=api_error("all_discovered_databases_exist", "All discovered databases already exist as targets"),
            )
        await db.commit()
        for item in created_targets:
            await db.refresh(item)
        await write_audit_log(
            db,
            "target.create.all_databases",
            user.id,
            {"base_name": payload.name, "created_count": len(created_targets), "host": payload.host, "port": payload.port},
        )
        owner_map = await _owners_by_target_ids(db, [created_targets[0].id])
        return _target_out_with_owners(created_targets[0], owner_map.get(created_targets[0].id, []))

    target_name = await _next_unique_target_name(db, payload.name)
    target = Target(
        name=target_name,
        host=payload.host,
        port=payload.port,
        dbname=payload.dbname,
        username=payload.username,
        encrypted_password=encrypted_password,
        sslmode=payload.sslmode,
        use_pg_stat_statements=payload.use_pg_stat_statements,
        tags=payload.tags,
    )
    db.add(target)
    await db.commit()
    await db.refresh(target)

    if owner_ids:
        await _set_target_owners(db, target.id, owner_ids, user.id)
        await db.commit()

    await write_audit_log(db, "target.create", user.id, {"target_id": target.id, "name": target.name})
    owner_map = await _owners_by_target_ids(db, [target.id])
    return _target_out_with_owners(target, owner_map.get(target.id, []))


@router.get("/owner-candidates", response_model=list[TargetOwnerOut])
async def list_owner_candidates(
    user: User = Depends(require_roles("admin", "operator")),
    db: AsyncSession = Depends(get_db),
) -> list[TargetOwnerOut]:
    _ = user
    users = (await db.scalars(select(User).order_by(User.email.asc()))).all()
    return [TargetOwnerOut(user_id=item.id, email=item.email, role=item.role) for item in users]


@router.get("/{target_id}", response_model=TargetOut)
async def get_target(target_id: int, user: User = Depends(get_current_user), db: AsyncSession = Depends(get_db)) -> TargetOut:
    _ = user
    target = await db.scalar(select(Target).where(Target.id == target_id))
    if not target:
        raise HTTPException(status_code=404, detail=api_error("target_not_found", "Target not found"))
    owner_map = await _owners_by_target_ids(db, [target.id])
    return _target_out_with_owners(target, owner_map.get(target.id, []))


@router.put("/{target_id}", response_model=TargetOut)
async def update_target(
    target_id: int,
    payload: TargetUpdate,
    user: User = Depends(require_roles("admin", "operator")),
    db: AsyncSession = Depends(get_db),
) -> TargetOut:
    target = await db.scalar(select(Target).where(Target.id == target_id))
    if not target:
        raise HTTPException(status_code=404, detail=api_error("target_not_found", "Target not found"))

    updates = payload.model_dump(exclude_unset=True)
    owner_user_ids = updates.pop("owner_user_ids", None)
    if "password" in updates:
        target.encrypted_password = encrypt_secret(updates.pop("password"))
    for key, value in updates.items():
        setattr(target, key, value)

    if owner_user_ids is not None:
        owners_exist = (await db.scalars(select(User.id).where(User.id.in_(owner_user_ids)))).all()
        if len(set(owners_exist)) != len(set(owner_user_ids)):
            raise HTTPException(
                status_code=400,
                detail=api_error("owner_users_not_found", "One or more owner users were not found"),
            )
        await _set_target_owners(db, target.id, owner_user_ids, user.id)

    await db.commit()
    await db.refresh(target)
    await write_audit_log(db, "target.update", user.id, {"target_id": target.id})
    owner_map = await _owners_by_target_ids(db, [target.id])
    return _target_out_with_owners(target, owner_map.get(target.id, []))


@router.put("/{target_id}/owners", response_model=list[TargetOwnerOut])
async def set_target_owners(
    target_id: int,
    payload: TargetOwnersUpdate,
    user: User = Depends(require_roles("admin", "operator")),
    db: AsyncSession = Depends(get_db),
) -> list[TargetOwnerOut]:
    target = await db.scalar(select(Target).where(Target.id == target_id))
    if not target:
        raise HTTPException(status_code=404, detail=api_error("target_not_found", "Target not found"))
    owner_user_ids = sorted(set(payload.user_ids))
    if owner_user_ids:
        owners_exist = (await db.scalars(select(User.id).where(User.id.in_(owner_user_ids)))).all()
        if len(set(owners_exist)) != len(set(owner_user_ids)):
            raise HTTPException(
                status_code=400,
                detail=api_error("owner_users_not_found", "One or more owner users were not found"),
            )
    await _set_target_owners(db, target_id, owner_user_ids, user.id)
    await db.commit()
    await write_audit_log(db, "target.owners.update", user.id, {"target_id": target_id, "owner_user_ids": owner_user_ids})
    rows = (
        await db.execute(
            select(User.id, User.email, User.role)
            .join(TargetOwner, TargetOwner.user_id == User.id)
            .where(TargetOwner.target_id == target_id)
            .order_by(User.email.asc())
        )
    ).all()
    return [TargetOwnerOut(user_id=row.id, email=row.email, role=row.role) for row in rows]


@router.get("/{target_id}/owners", response_model=list[TargetOwnerOut])
async def get_target_owners(
    target_id: int,
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
) -> list[TargetOwnerOut]:
    _ = user
    target = await db.scalar(select(Target).where(Target.id == target_id))
    if not target:
        raise HTTPException(status_code=404, detail=api_error("target_not_found", "Target not found"))
    rows = (
        await db.execute(
            select(User.id, User.email, User.role)
            .join(TargetOwner, TargetOwner.user_id == User.id)
            .where(TargetOwner.target_id == target_id)
            .order_by(User.email.asc())
        )
    ).all()
    return [TargetOwnerOut(user_id=row.id, email=row.email, role=row.role) for row in rows]


@router.delete("/{target_id}")
async def delete_target(
    target_id: int,
    user: User = Depends(require_roles("admin", "operator")),
    db: AsyncSession = Depends(get_db),
) -> dict:
    target = await db.scalar(select(Target).where(Target.id == target_id))
    if not target:
        raise HTTPException(status_code=404, detail=api_error("target_not_found", "Target not found"))
    await db.delete(target)
    await db.commit()
    await write_audit_log(db, "target.delete", user.id, {"target_id": target_id})
    return {"status": "deleted"}


@router.get("/{target_id}/metrics", response_model=list[MetricOut])
async def get_metrics(
    target_id: int,
    metric: str = Query(...),
    from_ts: datetime = Query(alias="from"),
    to_ts: datetime = Query(alias="to"),
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
) -> list[MetricOut]:
    _ = user
    rows = (
        await db.scalars(
            select(Metric).where(
                and_(Metric.target_id == target_id, Metric.metric_name == metric, Metric.ts >= from_ts, Metric.ts <= to_ts)
            ).order_by(Metric.ts.asc())
        )
    ).all()
    return [MetricOut(ts=r.ts, metric_name=r.metric_name, value=r.value, labels=r.labels) for r in rows]


async def _live_conn(target: Target) -> asyncpg.Connection:
    try:
        return await asyncpg.connect(dsn=build_target_dsn(target))
    except (OSError, asyncpg.PostgresError) as exc:
        raise HTTPException(
            status_code=503,
            detail=api_error(
                "target_unreachable",
                "Target database is not reachable",
                {
                    "target_id": target.id,
                    "host": target.host,
                    "port": target.port,
                    "error": str(exc),
                },
            ),
        ) from exc


@router.get("/{target_id}/locks")
async def get_locks(target_id: int, user: User = Depends(get_current_user), db: AsyncSession = Depends(get_db)) -> list[dict]:
    _ = user
    target = await db.scalar(select(Target).where(Target.id == target_id))
    if not target:
        raise HTTPException(status_code=404, detail=api_error("target_not_found", "Target not found"))
    conn = await _live_conn(target)
    try:
        rows = await conn.fetch(
            """
            SELECT locktype, mode, granted, relation::regclass::text AS relation, pid
            FROM pg_locks
            ORDER BY granted ASC, mode
            LIMIT 500
            """
        )
        return [dict(r) for r in rows]
    finally:
        await conn.close()


@router.get("/{target_id}/activity")
async def get_activity(target_id: int, user: User = Depends(get_current_user), db: AsyncSession = Depends(get_db)) -> list[dict]:
    _ = user
    target = await db.scalar(select(Target).where(Target.id == target_id))
    if not target:
        raise HTTPException(status_code=404, detail=api_error("target_not_found", "Target not found"))
    conn = await _live_conn(target)
    try:
        rows = await conn.fetch(
            """
            SELECT pid, usename, application_name, client_addr::text, state, wait_event_type, wait_event, now() - query_start AS running_for, left(query, 300) AS query
            FROM pg_stat_activity
            WHERE datname = current_database()
            ORDER BY query_start NULLS LAST
            LIMIT 200
            """
        )
        return [dict(r) for r in rows]
    finally:
        await conn.close()


@router.get("/{target_id}/top-queries", response_model=list[QueryStatOut])
async def get_top_queries(target_id: int, user: User = Depends(get_current_user), db: AsyncSession = Depends(get_db)) -> list[QueryStatOut]:
    _ = user
    target = await db.scalar(select(Target).where(Target.id == target_id))
    if not target:
        raise HTTPException(status_code=404, detail=api_error("target_not_found", "Target not found"))
    if not target.use_pg_stat_statements:
        return []
    rows = (
        await db.scalars(
            select(QueryStat)
            .where(QueryStat.target_id == target_id)
            .order_by(desc(QueryStat.ts))
            .limit(100)
        )
    ).all()
    return [
        QueryStatOut(
            ts=r.ts,
            queryid=r.queryid,
            calls=r.calls,
            total_time=r.total_time,
            mean_time=r.mean_time,
            rows=r.rows,
            query_text=r.query_text,
        )
        for r in rows
    ]


@router.get("/{target_id}/overview", response_model=DatabaseOverviewOut)
async def get_overview(target_id: int, user: User = Depends(get_current_user), db: AsyncSession = Depends(get_db)) -> DatabaseOverviewOut:
    _ = user
    target = await db.scalar(select(Target).where(Target.id == target_id))
    if not target:
        raise HTTPException(status_code=404, detail=api_error("target_not_found", "Target not found"))
    try:
        return await get_target_overview(target)
    except (OSError, asyncpg.PostgresError) as exc:
        raise HTTPException(
            status_code=503,
            detail=api_error(
                "target_unreachable",
                "Target database is not reachable",
                {
                    "target_id": target.id,
                    "host": target.host,
                    "port": target.port,
                    "error": str(exc),
                },
            ),
        ) from exc