package main

import (
	"fmt"
	"log"
	"math"
	"strings"
	"sync"
	"time"

	"go-weatherstation/internal/mqttingest"
	"go-weatherstation/internal/providers"
)

type ForecastCache struct {
	mu  sync.RWMutex
	res *providers.ForecastResult
}

func (c *ForecastCache) Set(res *providers.ForecastResult) {
	if c == nil {
		return
	}
	c.mu.Lock()
	c.res = copyForecast(res)
	c.mu.Unlock()
}

func (c *ForecastCache) Get() *providers.ForecastResult {
	if c == nil {
		return nil
	}
	c.mu.RLock()
	res := c.res
	c.mu.RUnlock()
	return res
}

func copyForecast(res *providers.ForecastResult) *providers.ForecastResult {
	if res == nil {
		return nil
	}
	out := &providers.ForecastResult{
		RetrievedAt: res.RetrievedAt,
		Model:       res.Model,
	}
	if len(res.Hourly) > 0 {
		out.Hourly = make([]providers.HourlyForecastPoint, len(res.Hourly))
		copy(out.Hourly, res.Hourly)
	}
	return out
}

func forecastSummary(res *providers.ForecastResult) string {
	if res == nil || len(res.Hourly) == 0 {
		return ""
	}

	start := res.Hourly[0].TS
	end := res.Hourly[len(res.Hourly)-1].TS
	parts := []string{
		fmt.Sprintf("range=%s..%s", start.Format(time.RFC3339), end.Format(time.RFC3339)),
	}

	var (
		minTemp, maxTemp float64
		hasTemp          bool
		maxWind          float64
		hasWind          bool
		maxGust          float64
		hasGust          bool
		totalPrecip      float64
		hasPrecip        bool
	)

	for _, pt := range res.Hourly {
		if pt.TempC != nil {
			if !hasTemp {
				minTemp, maxTemp = *pt.TempC, *pt.TempC
				hasTemp = true
			} else {
				if *pt.TempC < minTemp {
					minTemp = *pt.TempC
				}
				if *pt.TempC > maxTemp {
					maxTemp = *pt.TempC
				}
			}
		}

		if pt.WindMS != nil {
			if !hasWind || *pt.WindMS > maxWind {
				maxWind = *pt.WindMS
				hasWind = true
			}
		}

		if pt.WindGustMS != nil {
			if !hasGust || *pt.WindGustMS > maxGust {
				maxGust = *pt.WindGustMS
				hasGust = true
			}
		}

		if pt.PrecipMM != nil {
			totalPrecip += *pt.PrecipMM
			hasPrecip = true
		}
	}

	if hasTemp {
		parts = append(parts, fmt.Sprintf("temp_c(min=%.2f,max=%.2f)", minTemp, maxTemp))
	}
	if hasWind {
		parts = append(parts, fmt.Sprintf("wind_ms(max=%.2f)", maxWind))
	}
	if hasGust {
		parts = append(parts, fmt.Sprintf("gust_ms(max=%.2f)", maxGust))
	}
	if hasPrecip {
		parts = append(parts, fmt.Sprintf("precip_mm(total=%.2f)", totalPrecip))
	}

	return strings.Join(parts, " ")
}

func logForecastDeviation(cache *ForecastCache, snap mqttingest.Snapshot) {
	res := cache.Get()
	if res == nil || len(res.Hourly) == 0 {
		return
	}

	fc, diff := nearestForecastPoint(res.Hourly, snap.TS)
	if fc == nil || diff > 2*time.Hour {
		return
	}

	parts := []string{
		fmt.Sprintf("model=%s", res.Model),
		fmt.Sprintf("obs_ts=%s", snap.TS.Format(time.RFC3339)),
		fmt.Sprintf("fc_ts=%s", fc.TS.Format(time.RFC3339)),
		fmt.Sprintf("dt=%s", diff.Round(time.Minute)),
	}

	if fc.TempC != nil {
		parts = append(parts, fmt.Sprintf(
			"temp_c(obs=%.2f fc=%.2f d=%.2f)",
			snap.P.TemperatureC, *fc.TempC, snap.P.TemperatureC-*fc.TempC,
		))
	}

	if fc.WindMS != nil {
		parts = append(parts, fmt.Sprintf(
			"wind_ms(obs=%.2f fc=%.2f d=%.2f)",
			snap.P.WindAvgMS, *fc.WindMS, snap.P.WindAvgMS-*fc.WindMS,
		))
	}

	if fc.WindGustMS != nil {
		parts = append(parts, fmt.Sprintf(
			"gust_ms(obs=%.2f fc=%.2f d=%.2f)",
			snap.P.WindMaxMS, *fc.WindGustMS, snap.P.WindMaxMS-*fc.WindGustMS,
		))
	}

	if fc.WindDirDeg != nil {
		dirDelta := angularDiffDeg(snap.P.WindDirDeg, *fc.WindDirDeg)
		parts = append(parts, fmt.Sprintf(
			"wind_dir_deg(obs=%.0f fc=%.0f d=%.0f)",
			snap.P.WindDirDeg, *fc.WindDirDeg, dirDelta,
		))
	}

	if fc.PrecipMM != nil {
		parts = append(parts, fmt.Sprintf(
			"rain_mm(obs=%.2f fc=%.2f d=%.2f)",
			snap.RainLastHourMM, *fc.PrecipMM, snap.RainLastHourMM-*fc.PrecipMM,
		))
	}

	if len(parts) <= 4 {
		return
	}

	log.Printf("forecast deviation %s", strings.Join(parts, " "))
}

func nearestForecastPoint(hourly []providers.HourlyForecastPoint, ts time.Time) (*providers.HourlyForecastPoint, time.Duration) {
	if len(hourly) == 0 {
		return nil, 0
	}

	bestIdx := 0
	bestDiff := absDuration(ts.Sub(hourly[0].TS))
	for i := 1; i < len(hourly); i++ {
		diff := absDuration(ts.Sub(hourly[i].TS))
		if diff < bestDiff {
			bestIdx = i
			bestDiff = diff
		}
	}

	return &hourly[bestIdx], bestDiff
}

func absDuration(d time.Duration) time.Duration {
	if d < 0 {
		return -d
	}
	return d
}

func angularDiffDeg(a, b float64) float64 {
	diff := math.Mod(math.Abs(a-b), 360.0)
	if diff > 180.0 {
		diff = 360.0 - diff
	}
	return diff
}