package main

// TODO: allow free-text lookups of place names, rather than ids

import (
	"encoding/json"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
)

const metdefid = "310004"
const bbcdefid = "2654675"

const meturl = "https://www.metoffice.gov.uk/public/data/PWSCache/BestForecast/Forecast/%s.json?concise=true"
const bbcurl = "https://weather-broker-cdn.api.bbci.co.uk/en/forecast/aggregated/%s"

const mpsToMphMultiplier = 2.23693629

// BBC structures
type BBCResponse struct {
	Forecasts []struct {
		Detailed struct {
			Reports []Report
		}
	}
}

type Report struct {
	EnhancedWeatherDescription        string
	ExtendedWeatherType               int
	FeelsLikeTemperatureC             int
	FeelsLikeTemperatureF             int
	GustSpeedKph                      int
	GustSpeedMph                      int
	Humidity                          int
	LocalDate                         string
	PrecipitationProbabilityInPercent int
	PrecipitationProbabilityText      string
	Pressure                          int
	TemperatureC                      int
	TemperatureF                      int
	Timeslot                          string
	TimeslotLength                    int
	Visibility                        string
	WeatherType                       int
	WeatherTypeText                   string
	WindDescription                   string
	WindDirection                     string
	WindDirectionAbbreviation         string
	WindDirectionFull                 string
	WindSpeedKph                      int
	WindSpeedMph                      int
}

// Met Office structures
type MetResponse struct {
	BestFcst struct {
		Forecast struct {
			Location struct {
				Days []Day `json:"Day"`
			}
		}
	}
}

type Day struct {
	Date      string `json:"@date"`
	DayValues struct {
		WeatherParameters WeatherParams
	}
	NightValues struct {
		WeatherParameters WeatherParams
	}
	TimeSteps struct {
		TimeStep []struct {
			Time              string `json:"@time"`
			WeatherParameters WeatherParams
		}
	}
}

type WeatherParams struct {
	AQIndex int     // Air Quality
	F       float64 // Feels Like Temperature
	H       int     // Humidity
	P       int     // Pressure
	PP      int     // Precipitation Probability
	T       float64 // Temperature
	UV      int     // Max UV Index
	V       int     // Visibility
	WD      string  // Wind Direction
	WG      float64 // Wind Gust
	WS      float64 // Wind Speed
	WT      int     // Weather Type
}

var TypeDescription = map[int]string{
	0:  "Clear Sky",
	1:  "Sunny",
	2:  "Partly Cloudy",
	3:  "Sunny Intervals",
	4:  "Unknown",
	5:  "Mist",
	6:  "Fog",
	7:  "Light Cloud",
	8:  "Thick Cloud",
	9:  "Light Rain Showers",
	10: "Light Rain Showers",
	11: "Drizzle",
	12: "Light Rain",
	13: "Heavy Rain Showers",
	14: "Heavy Rain Showers",
	15: "Heavy Rain",
	16: "Sleet Showers",
	17: "Sleet Showers",
	18: "Sleet",
	19: "Hail Showers",
	20: "Hail Showers",
	21: "Hail",
	22: "Light Snow Showers",
	23: "Light Snow Showers",
	24: "Light Snow",
	25: "Heavy Snow Showers",
	26: "Heavy Snow Showers",
	27: "Heavy Snow",
	28: "Thundery Showers",
	29: "Thundery Showers",
	30: "Thunder",
}

// Our prefered struct
type Weather struct {
	date          string
	time          string
	temperature   float64
	precipitation int
	weathertype   int
	windspeed     float64
}

var (
	src     = flag.String("s", "bbc", "data source provider (valid options: 'bbc', 'metoffice')")
	numdays = flag.Int("n", 2, "number of days to show")
	verbose = flag.Bool("v", false, "verbose: show all weather details")
)

func processBBC(b []byte) []Weather {
	var r BBCResponse
	var weather []Weather
	var w Weather
	err := json.Unmarshal(b, &r)
	if err != nil {
		log.Fatal(err)
	}

	for _, f := range r.Forecasts {
		for _, report := range f.Detailed.Reports {
			w.date = report.LocalDate
			w.time = report.Timeslot
			w.temperature = float64(report.TemperatureC)
			w.precipitation = report.PrecipitationProbabilityInPercent
			w.weathertype = report.WeatherType
			w.windspeed = float64(report.WindSpeedMph)
			weather = append(weather, w)
		}
	}
	return weather
}

func processMet(b []byte) []Weather {
	var r MetResponse
	var weather []Weather
	var w Weather
	err := json.Unmarshal(b, &r)
	if err != nil {
		log.Fatal(err)
	}

	for _, d := range r.BestFcst.Forecast.Location.Days {
		w.date = d.Date
		w.time = "Day     "
		w.temperature = d.DayValues.WeatherParameters.T
		w.precipitation = d.DayValues.WeatherParameters.PP
		w.weathertype = d.DayValues.WeatherParameters.WT
		w.windspeed = d.DayValues.WeatherParameters.WS * mpsToMphMultiplier
		weather = append(weather, w)

		w.date = d.Date
		w.time = "Night   "
		w.temperature = d.DayValues.WeatherParameters.T
		w.precipitation = d.DayValues.WeatherParameters.PP
		w.weathertype = d.DayValues.WeatherParameters.WT
		w.windspeed = d.DayValues.WeatherParameters.WS * mpsToMphMultiplier
		weather = append(weather, w)

		for _, t := range d.TimeSteps.TimeStep {
			w.date = d.Date
			w.time = t.Time
			w.temperature = t.WeatherParameters.T
			w.precipitation = t.WeatherParameters.PP
			w.weathertype = t.WeatherParameters.WT
			w.windspeed = t.WeatherParameters.WS * mpsToMphMultiplier
			weather = append(weather, w)
		}
	}
	return weather
}

func main() {
	var err error
	var id string
	var url string
	var parsefunc func([]byte) []Weather
	var resp *http.Response
	var weather []Weather

	flag.Parse()

	switch *src {
	case "bbc":
		id = bbcdefid
		url = bbcurl
		parsefunc = processBBC
	case "metoffice":
		id = metdefid
		url = meturl
		parsefunc = processMet
	default:
		log.Fatalf("data source %s not supported; use either 'bbc' or 'metoffice'\n", *src)
	}

	if flag.NArg() > 0 {
		id = flag.Arg(0)
	}

	resp, err = http.Get(fmt.Sprintf(url, id))
	if err != nil {
		log.Fatal(err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		log.Fatalf("HTTP status code: %d\n", resp.StatusCode)
	}
	b, err := ioutil.ReadAll(resp.Body)

	weather = parsefunc(b)

	for _, w := range weather {
		fmt.Printf("%s %s  ", w.date, w.time)
		desc, ok := TypeDescription[w.weathertype]
		if !ok {
			desc = fmt.Sprintf("%d", w.weathertype)
		}
		fmt.Printf("%18s, Temp: %4.1f°C, ", desc, w.temperature)
		fmt.Printf("Rain: %2d%%, Wind: %4.1fmph\n", w.precipitation, w.windspeed)
		if *verbose {
			fmt.Printf("                  %+v\n", w)
		}
	}
}