path: root/main.go

// Copyright 2020 Nick White.
// Use of this source code is governed by the GPLv3
// license that can be found in the LICENSE file.
package main

// Note that this was the first Go I wrote. Look elsewhere for
// examples of best practise.

// BUG: need to allow choice of met-office source (-b 0 doesn't work how i thought it would)
// TODO: allow free-text lookups of place names, rather than ids
// TODO: convert metoffice windspeed to mph
// TODO: split output into days
// TODO: add -n flag to only output a certain number of days
// TODO: human friendly dates

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

const metdefid = "310118"
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"

// 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
}

// TODO: complete this mapping
var TypeDescription = map[int]string{
	0:  "Clear Sky",
	1:  "Sunny",
	2:  "Partly Cloudy",
	3:  "Sunny Intervals",
	5:  "Mist",
	7:  "Light Cloud",
	8:  "Thick Cloud",
	9:  "Light Rain Showers",
	10: "Light Rain Showers",
	11: "Drizzle",
	12: "Light Rain",
	14: "Heavy Rain Showers",
	15: "Heavy Rain",
	16: "Sleet Showers",
	17: "Sleet Showers",
	18: "Sleet",
	19: "Hail Showers",
	20: "Hail Showers",
	22: "Light Snow Showers",
	23: "Light Snow Showers",
	26: "Heavy Snow Showers",
	28: "Thundery Showers",
	29: "Thundery Showers",
}

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

var (
	bbc     = flag.Bool("b", true, "use bbc as data source")
	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
		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
		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
			weather = append(weather, w)
		}
	}
	return weather
}

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

	flag.Parse()
	if flag.NArg() > 0 {
		id = flag.Arg(0)
	} else {
		if *bbc {
			id = bbcdefid
		} else {
			id = metdefid
		}
	}

	if *bbc {
		resp, err = http.Get(fmt.Sprintf(bbcurl, id))
	} else {
		resp, err = http.Get(fmt.Sprintf(meturl, 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)

	if *bbc {
		weather = processBBC(b)
	} else {
		weather = processMet(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)
		}
	}
}