from fastapi import APIRouter, Depends, Query
from sqlalchemy import text
from sqlalchemy.ext.asyncio import AsyncSession
from core.database import get_session

router = APIRouter()

ROOMS = {
    "sg-01": [
        {"room_id": "hall-a", "racks": [f"SG1A01.{i:02d}" for i in range(1, 21)] + [f"SG1A02.{i:02d}" for i in range(1, 21)], "crac_id": "crac-01"},
        {"room_id": "hall-b", "racks": [f"SG1B01.{i:02d}" for i in range(1, 21)] + [f"SG1B02.{i:02d}" for i in range(1, 21)], "crac_id": "crac-02"},
    ]
}

# Rated capacity config — would be per-asset configurable in production
RACK_POWER_CAPACITY_KW  = 10.0   # max kW per rack
ROOM_POWER_CAPACITY_KW  = 400.0  # 40 racks × 10 kW
CRAC_COOLING_CAPACITY_KW = 160.0  # rated cooling per CRAC
RACK_U_TOTAL             = 42


@router.get("/summary")
async def capacity_summary(
    site_id: str = Query(...),
    session: AsyncSession = Depends(get_session),
):
    """Per-rack and per-room capacity: power used vs rated, cooling load vs rated, rack space."""
    result = await session.execute(text("""
        SELECT DISTINCT ON (sensor_id)
            rack_id, room_id, sensor_type, value
        FROM readings
        WHERE site_id     = :site_id
          AND sensor_type IN ('power_kw', 'temperature')
          AND rack_id    IS NOT NULL
          AND recorded_at > NOW() - INTERVAL '10 minutes'
        ORDER BY sensor_id, recorded_at DESC
    """), {"site_id": site_id})
    rows = result.mappings().all()

    # Index: rack_id → {power_kw, temperature, room_id}
    rack_idx: dict[str, dict] = {}
    for row in rows:
        rid = row["rack_id"]
        if rid not in rack_idx:
            rack_idx[rid] = {"room_id": row["room_id"]}
        if row["sensor_type"] == "power_kw":
            rack_idx[rid]["power_kw"] = round(float(row["value"]), 2)
        elif row["sensor_type"] == "temperature":
            rack_idx[rid]["temperature"] = round(float(row["value"]), 1)

    rooms_out = []
    racks_out = []

    for room in ROOMS.get(site_id, []):
        room_id = room["room_id"]
        room_power = 0.0
        populated = 0

        for rack_id in room["racks"]:
            d = rack_idx.get(rack_id, {})
            power = d.get("power_kw")
            temp  = d.get("temperature")

            if power is not None:
                room_power += power
                populated += 1

            power_pct = round((power / RACK_POWER_CAPACITY_KW) * 100, 1) if power is not None else None
            racks_out.append({
                "rack_id":            rack_id,
                "room_id":            room_id,
                "power_kw":           power,
                "power_capacity_kw":  RACK_POWER_CAPACITY_KW,
                "power_pct":          power_pct,
                "temp":               temp,
            })

        room_power = round(room_power, 2)
        rooms_out.append({
            "room_id": room_id,
            "power": {
                "used_kw":     room_power,
                "capacity_kw": ROOM_POWER_CAPACITY_KW,
                "pct":         round((room_power / ROOM_POWER_CAPACITY_KW) * 100, 1),
                "headroom_kw": round(ROOM_POWER_CAPACITY_KW - room_power, 2),
            },
            "cooling": {
                "load_kw":     room_power,  # IT power ≈ heat generated
                "capacity_kw": CRAC_COOLING_CAPACITY_KW,
                "pct":         round(min(100.0, (room_power / CRAC_COOLING_CAPACITY_KW) * 100), 1),
                "headroom_kw": round(max(0.0, CRAC_COOLING_CAPACITY_KW - room_power), 2),
            },
            "space": {
                "racks_total":     len(room["racks"]),
                "racks_populated": populated,
                "pct":             round((populated / len(room["racks"])) * 100, 1),
            },
        })

    return {
        "site_id": site_id,
        "config": {
            "rack_power_kw":   RACK_POWER_CAPACITY_KW,
            "room_power_kw":   ROOM_POWER_CAPACITY_KW,
            "crac_cooling_kw": CRAC_COOLING_CAPACITY_KW,
            "rack_u_total":    RACK_U_TOTAL,
        },
        "rooms": rooms_out,
        "racks": racks_out,
    }