soumya92/barista

// Copyright 2017 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package weather provides an i3bar module that displays weather info.
package weather // import "barista.run/modules/weather"

import (
    "time"

    "barista.run/bar"
    "barista.run/base/notifier"
    "barista.run/base/value"
    l "barista.run/logging"
    "barista.run/outputs"
    "barista.run/timing"

    "github.com/martinlindhe/unit"
)

// Weather represents the current weather conditions.
type Weather struct {
    Location    string
    Condition   Condition
    Description string
    Temperature unit.Temperature
    Humidity    float64
    Pressure    unit.Pressure
    Wind        Wind
    CloudCover  float64
    Sunrise     time.Time
    Sunset      time.Time
    Updated     time.Time
    Attribution string
}

// Wind stores the wind speed and direction together.
type Wind struct {
    unit.Speed
    Direction
}

// Condition represents a weather condition.
type Condition int

// Possible weather conditions
const (
    ConditionUnknown Condition = iota
    Thunderstorm
    Drizzle
    Rain
    Snow
    Sleet
    Mist
    Smoke
    Whirls
    Haze
    Fog
    Clear
    Cloudy
    PartlyCloudy
    Overcast
    Tornado
    TropicalStorm
    Hurricane
    Cold
    Hot
    Windy
    Hail
)

// Direction represents a compass direction stored as degrees.
type Direction int

// Provider is an interface for weather providers,
// implemented by the various provider packages.
type Provider interface {
    GetWeather() (Weather, error)
}

// Module represents a bar.Module that displays weather information.
type Module struct {
    provider   Provider
    scheduler  *timing.Scheduler
    refreshFn  func()
    refreshCh  <-chan struct{}
    outputFunc value.Value // of func(Weather) bar.Output
}

// New constructs an instance of the weather module with the provided configuration.
func New(provider Provider) *Module {
    m := &Module{
        provider:  provider,
        scheduler: timing.NewScheduler(),
    }
    m.refreshFn, m.refreshCh = notifier.New()
    l.Register(m, "outputFunc", "clickHandler", "scheduler")
    // Default output is just the temperature and conditions.
    m.Output(func(w Weather) bar.Output {
        return outputs.Textf("%.1f℃ %s (%s)",
            w.Temperature.Celsius(), w.Description, w.Attribution)
    })
    m.RefreshInterval(10 * time.Minute)
    return m
}

// Output configures a module to display the output of a user-defined function.
func (m *Module) Output(outputFunc func(Weather) bar.Output) *Module {
    m.outputFunc.Set(outputFunc)
    return m
}

// RefreshInterval configures the polling frequency.
func (m *Module) RefreshInterval(interval time.Duration) *Module {
    m.scheduler.Every(interval)
    return m
}

// Refresh fetches updated weather information.
func (m *Module) Refresh() {
    m.refreshFn()
}

// Stream starts the module.
func (m *Module) Stream(s bar.Sink) {
    weather, err := m.provider.GetWeather()
    outputFunc := m.outputFunc.Get().(func(Weather) bar.Output)
    nextOutputFunc, done := m.outputFunc.Subscribe()
    defer done()
    for {
        if !s.Error(err) {
            s.Output(outputFunc(weather))
        }
        select {
        case <-nextOutputFunc:
            outputFunc = m.outputFunc.Get().(func(Weather) bar.Output)
        case <-m.scheduler.C:
            weather, err = m.provider.GetWeather()
        case <-m.refreshCh:
            if err != nil {
                s(nil)
            }
            weather, err = m.provider.GetWeather()
        }
    }
}