import time
import asyncio

from fastapi import APIRouter, HTTPException, BackgroundTasks
from typing import List, Optional
from pydantic import BaseModel
from app.services.coverage_service import (
    coverage_service,
    CoverageSettings,
    SiteParams,
    CoveragePoint,
    apply_preset,
    PRESETS,
)
from app.services.parallel_coverage_service import CancellationToken

router = APIRouter()


class CoverageRequest(BaseModel):
    """Request body for coverage calculation"""
    sites: List[SiteParams]
    settings: CoverageSettings = CoverageSettings()


class CoverageResponse(BaseModel):
    """Coverage calculation response"""
    points: List[CoveragePoint]
    count: int
    settings: CoverageSettings
    stats: dict
    computation_time: float  # seconds
    models_used: List[str]  # which models were active


@router.post("/calculate")
async def calculate_coverage(request: CoverageRequest) -> CoverageResponse:
    """
    Calculate RF coverage for one or more sites

    Returns grid of RSRP values with terrain and building effects.
    Supports propagation model presets: fast, standard, detailed, full.
    """
    if not request.sites:
        raise HTTPException(400, "At least one site required")

    if len(request.sites) > 10:
        raise HTTPException(400, "Maximum 10 sites per request")

    # Validate settings
    if request.settings.radius > 50000:
        raise HTTPException(400, "Maximum radius 50km")

    if request.settings.resolution < 50:
        raise HTTPException(400, "Minimum resolution 50m")

    # Apply preset and determine active models
    effective_settings = apply_preset(request.settings.model_copy())
    models_used = _get_active_models(effective_settings)

    # Time the calculation
    start_time = time.time()
    cancel_token = CancellationToken()

    try:
        # Calculate with 5-minute timeout
        if len(request.sites) == 1:
            points = await asyncio.wait_for(
                coverage_service.calculate_coverage(
                    request.sites[0],
                    request.settings,
                    cancel_token,
                ),
                timeout=300.0
            )
        else:
            points = await asyncio.wait_for(
                coverage_service.calculate_multi_site_coverage(
                    request.sites,
                    request.settings,
                    cancel_token,
                ),
                timeout=300.0
            )
    except asyncio.TimeoutError:
        cancel_token.cancel()
        raise HTTPException(408, "Calculation timeout (5 min) — try smaller radius or lower resolution")
    except asyncio.CancelledError:
        cancel_token.cancel()
        raise HTTPException(499, "Client disconnected")

    computation_time = time.time() - start_time

    # Calculate stats
    rsrp_values = [p.rsrp for p in points]
    los_count = sum(1 for p in points if p.has_los)

    stats = {
        "min_rsrp": min(rsrp_values) if rsrp_values else 0,
        "max_rsrp": max(rsrp_values) if rsrp_values else 0,
        "avg_rsrp": sum(rsrp_values) / len(rsrp_values) if rsrp_values else 0,
        "los_percentage": (los_count / len(points) * 100) if points else 0,
        "points_with_buildings": sum(1 for p in points if p.building_loss > 0),
        "points_with_terrain_loss": sum(1 for p in points if p.terrain_loss > 0),
        "points_with_reflection_gain": sum(1 for p in points if p.reflection_gain > 0),
        "points_with_vegetation_loss": sum(1 for p in points if p.vegetation_loss > 0),
        "points_with_rain_loss": sum(1 for p in points if p.rain_loss > 0),
        "points_with_indoor_loss": sum(1 for p in points if p.indoor_loss > 0),
        "points_with_atmospheric_loss": sum(1 for p in points if p.atmospheric_loss > 0),
    }

    return CoverageResponse(
        points=points,
        count=len(points),
        settings=effective_settings,
        stats=stats,
        computation_time=round(computation_time, 2),
        models_used=models_used
    )


@router.get("/presets")
async def get_presets():
    """Get available propagation model presets"""
    return {
        "presets": {
            "fast": {
                "description": "Quick calculation - terrain only",
                **PRESETS["fast"],
                "estimated_speed": "~5 seconds for 5km radius"
            },
            "standard": {
                "description": "Balanced - terrain + buildings with materials",
                **PRESETS["standard"],
                "estimated_speed": "~30 seconds for 5km radius"
            },
            "detailed": {
                "description": "Accurate - adds dominant path + vegetation",
                **PRESETS["detailed"],
                "estimated_speed": "~2 minutes for 5km radius"
            },
            "full": {
                "description": "Maximum realism - all models + water + vegetation",
                **PRESETS["full"],
                "estimated_speed": "~5 minutes for 5km radius"
            }
        }
    }


@router.get("/buildings")
async def get_buildings(
    min_lat: float,
    min_lon: float,
    max_lat: float,
    max_lon: float
):
    """
    Get buildings in bounding box (for debugging/visualization)
    """
    from app.services.buildings_service import buildings_service

    # Limit bbox size
    if (max_lat - min_lat) > 0.1 or (max_lon - min_lon) > 0.1:
        raise HTTPException(400, "Bbox too large (max 0.1 degrees)")

    buildings = await buildings_service.fetch_buildings(
        min_lat, min_lon, max_lat, max_lon
    )

    return {
        "count": len(buildings),
        "buildings": [b.model_dump() for b in buildings]
    }


def _get_active_models(settings: CoverageSettings) -> List[str]:
    """Determine which propagation models are active"""
    models = ["okumura_hata"]  # Always active as base model

    if settings.use_terrain:
        models.append("terrain_los")
    if settings.use_buildings:
        models.append("buildings")
    if settings.use_materials:
        models.append("materials")
    if settings.use_dominant_path:
        models.append("dominant_path")
    if settings.use_street_canyon:
        models.append("street_canyon")
    if settings.use_reflections:
        models.append("reflections")
    if settings.use_water_reflection:
        models.append("water_reflection")
    if settings.use_vegetation:
        models.append("vegetation")
    if settings.rain_rate > 0:
        models.append("rain_attenuation")
    if settings.indoor_loss_type != "none":
        models.append("indoor_penetration")
    if settings.use_atmospheric:
        models.append("atmospheric")

    return models