package main

import (
	"errors"
	"flag"
	"fmt"
	"math"
	"os"
	"strconv"
	"strings"
	"time"

	"git.fireandbrimst.one/aw/go-chart"
	"git.fireandbrimst.one/aw/go-chart/drawing"
	util "git.fireandbrimst.one/aw/go-chart/util"
	goutil "git.fireandbrimst.one/aw/goutil/misc"
)

const (
	initflag   = ".hdiet"
	logfile    = "weight.txt"
	dietfile   = "diet.txt"
	dateLayout = "2006-01-02"
	imgfile    = "weightplot.png"
	width      = 1600
	height     = 900
)

type DateFlag struct {
	date *time.Time
}

func (d DateFlag) String() string {
	if d.date == nil {
		return ""
	} else {
		return time.Time(*d.date).Format(dateLayout)
	}
}

func (d *DateFlag) Set(s string) error {
	if d == nil {
		return errors.New("func (d *DateFlag) Set(s string): d is nil")
	}
	val, err := time.Parse(dateLayout, s)
	if err == nil {
		d.date = &val
	}
	return err
}

func isInitialized() bool {
	return goutil.PathExists(initflag)
}

func errNotInitialized() error {
	dir, err := os.Getwd()
	if err == nil {
		err = errors.New(dir + ": " + "is not an initialized hdiet directory")
	}
	return err
}

func initHdiet(args []string) error {
	if !isInitialized() {
		return goutil.WriteFile(initflag, "")
	}
	return nil
}

func log(args []string) error {
	if !isInitialized() {
		return errNotInitialized()
	}
	if len(args) != 1 {
		return errors.New("log: Please provide weight as argument (floating point number)")
	}
	weight, err := strconv.ParseFloat(args[0], 64)
	if err != nil {
		return errors.New("log: " + err.Error())
	}
	date := time.Now().Format(dateLayout)
	err = goutil.AppendToFile(logfile, fmt.Sprintf("%s\t%.1f\n", date, weight))
	if err != nil {
		return err
	}
	return show(showFlags{})
}

type point struct {
	date   time.Time
	weight float64
	trend  float64
}

type dateInterval struct {
	min time.Time
	max time.Time
}

type yRange struct {
	min float64
	max float64
}

func readFile(file string) (map[time.Time]float64, time.Time, time.Time) {
	optPanic := func(err error) {
		if err != nil {
			panic("process:" + err.Error())
		}
	}
	weights, err := goutil.ReadFile(file)
	if err != nil {
		return nil, time.Time{}, time.Time{}
	}
	lines := strings.Split(weights, "\n")
	var firstDay time.Time
	firstDayIsSet := false
	var lastDay time.Time
	dateToWeight := make(map[time.Time]float64)
	for _, line := range lines {
		line = strings.TrimSpace(line)
		if len(line) == 0 {
			continue
		}
		splitline := strings.Split(line, "\t")
		if len(splitline) < 2 {
			optPanic(errors.New("invalid line in weight file " + file + ": " + line))
		}
		date, err := time.Parse(dateLayout, splitline[0])
		optPanic(err)
		weight, err := strconv.ParseFloat(splitline[1], 64)
		optPanic(err)
		if !firstDayIsSet {
			firstDay = date
			firstDayIsSet = true
		}
		lastDay = date
		dateToWeight[date] = weight
	}
	return dateToWeight, firstDay, lastDay
}

func process(file string) []point {
	dateToWeight, firstDay, lastDay := readFile(file)
	if dateToWeight == nil {
		return []point{}
	}
	trend := 0.0
	points := []point{}
	for d := firstDay; d.Before(lastDay) || d == lastDay; d = d.AddDate(0, 0, 1) {
		var weight float64
		if w, ok := dateToWeight[d]; ok {
			weight = w
		} else {
			prevPoint := points[len(points)-1]
			prevDay := prevPoint.date
			prevWeight := prevPoint.weight
			var nextWeight float64
			var nextDay time.Time
			for nextDay = d.AddDate(0, 0, 1); nextDay.Before(lastDay) || nextDay == lastDay; nextDay = nextDay.AddDate(0, 0, 1) {
				if w, ok := dateToWeight[nextDay]; ok {
					nextWeight = w
					break
				}
			}
			days := nextDay.Sub(prevDay).Hours() / 24
			changePerDay := (nextWeight - prevWeight) / days
			weight = prevWeight + changePerDay
		}
		if trend == 0.0 {
			trend = weight
		} else {
			trend = math.Floor((trend+0.1*(weight-trend))*100) / 100
		}
		points = append(points, point{d, weight, trend})

	}
	return points
}

type showFlags struct {
	from      DateFlag
	to        DateFlag
	nodisplay bool
}

func show(args showFlags) error {
	points := process(logfile)
	dietpoints := process(dietfile)
	var to time.Time
	var from time.Time
	if args.to.date != nil {
		to = *args.to.date
	} else {
		to = time.Now()
	}
	if args.from.date != nil {
		from = *args.from.date
	} else {
		from = to.AddDate(0, 0, -31)
	}

	fromTo := dateInterval{from, to}
	s1 := timeSeries("weight", chart.ColorCyan)
	xRange, yRange1 := addPointsGetRange(&s1, points, fromTo, func(p point) float64 { return p.weight })
	s2 := timeSeries("trend", drawing.Color{R: 255, A: 255})
	_, yRange2 := addPointsGetRange(&s2, points, xRange, func(p point) float64 { return p.trend })
	s3 := timeSeries("diet", drawing.Color{R: 255, G: 211, A: 255})
	yRange3 := yRange2
	if dietpoints != nil {
		_, yRange3 = addPointsGetRange(&s3, dietpoints, xRange, func(p point) float64 { return p.weight })
	}
	YRange := yRange{math.Min(math.Min(yRange1.min, yRange2.min), yRange3.min), math.Max(math.Max(yRange1.max, yRange2.max), yRange3.max)}
	YRange.min = math.Floor(YRange.min) - 1.0
	YRange.max = math.Ceil(YRange.max) + 1.0
	graph := graph(xticks(xRange), s1, s2, s3, YRange)
	err := writeGraphToFile(graph)
	if err != nil {
		return err
	}
	if args.nodisplay {
		return nil
	} else {
		return openGraphFile()
	}
}

func showCommand() (goutil.CommandFlagsInit, goutil.CommandFunc) {
	sf := showFlags{}
	flagsInit := func(s *flag.FlagSet) {
		s.Var(&sf.from, "from", "YYYY-MM-DD (optional)")
		s.Var(&sf.to, "to", "YYYY-MM-DD (optional)")
		s.BoolVar(&sf.nodisplay, "nodisplay", false, "don't display graph image")
	}
	return flagsInit, func([]string) error { return show(sf) }
}

func writeDietFile(from time.Time, initial float64, goal float64, change float64) error {
	date := from
	weight := initial
	s := ""
	s += fmt.Sprintf("%s\t%.1f\n", date.Format(dateLayout), weight)
	for weight > goal {
		date = date.AddDate(0, 0, 1)
		weight += change / 7.0
		s += fmt.Sprintf("%s\t%.3f\n", date.Format(dateLayout), weight)
	}
	err := goutil.WriteFile(dietfile, s)
	if err == nil {
		fmt.Println("Wrote to " + dietfile)
	}
	return err
}

func diet([]string) error {
	if !isInitialized() {
		return errNotInitialized()
	}
	fromStr, err := goutil.AskFor("From? (YYYY-MM-DD) [today]")
	var from time.Time
	if fromStr == "" {
		from = time.Now()
	} else {
		from, err = time.Parse(dateLayout, fromStr)
	}
	initial, err := parseFloat(askFor(err, "Initial weight?"))
	goal, err := parseFloat(askFor(err, "Goal weight?"))
	change, err := parseFloat(askFor(err, "Change per week?"))
	if err != nil {
		return err
	}
	if change == 0 {
		return errors.New("change is zero")
	}
	if (initial >= goal && change > 0) || (initial <= goal && change < 0) {
		change *= -1
	}
	return writeDietFile(from, initial, goal, change)
}

func main() {
	commands := []goutil.Command{
		goutil.NewCommand("init", initHdiet, "init an hdiet folder"),
		goutil.NewCommand("log", log, "log today's weight (given as argument)"),
		goutil.NewCommandWithFlags("show", showCommand, "show the trend curve (today's or [from] [to])"),
		goutil.NewCommand("calcdiet", diet, "calculate a diet curve"),
	}
	err := goutil.Execute(commands)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(-1)
	}
}

/*****************************/

func xticks(d dateInterval) []chart.Tick {
	ticks := []chart.Tick{}
	start := d.min
	end := d.max
	stepDays := int(end.Sub(start).Hours() / 24 / 10)
	if stepDays < 1 {
		stepDays = 1
	}
	for i := 0; start.AddDate(0, 0, i).Before(end.AddDate(0, 0, stepDays)); i += stepDays {
		val := start.AddDate(0, 0, i)
		label := val.Format(dateLayout)
		ticks = append(ticks, chart.Tick{util.Time.ToFloat64(val), label})
	}
	return ticks
}

func addPointsGetRange(s *chart.TimeSeries, points []point, di dateInterval, project func(point) float64) (dateInterval, yRange) {
	XRange := dateInterval{time.Now().AddDate(10000, 0, 0), time.Now().AddDate(-10000, 0, 0)}
	YRange := yRange{math.MaxFloat64, -math.MaxFloat64}
	for _, p := range points {
		if (p.date.After(di.min) || p.date.Equal(di.min)) && (p.date.Before(di.max) || p.date.Equal(di.max)) && !math.IsNaN(project(p)) {
			xVal := p.date
			s.XValues = append(s.XValues, xVal)
			if xVal.Before(XRange.min) {
				XRange.min = xVal
			}
			if xVal.After(XRange.max) {
				XRange.max = xVal
			}
			yVal := project(p)
			s.YValues = append(s.YValues, yVal)
			if yVal < YRange.min {
				YRange.min = yVal
			}
			if yVal > YRange.max {
				YRange.max = yVal
			}
		}
	}
	return XRange, YRange
}

func timeSeries(name string, color drawing.Color) chart.TimeSeries {
	return chart.TimeSeries{Name: name, Style: chart.Style{Show: true, StrokeColor: color}}
}

func graph(xticks []chart.Tick, s1 chart.TimeSeries, s2 chart.TimeSeries, s3 chart.TimeSeries, YRange yRange) chart.Chart {
	graph := chart.Chart{
		Width:  width,
		Height: height,
		XAxis: chart.XAxis{
			Name:           "date",
			NameStyle:      chart.StyleShow(),
			Style:          chart.StyleShow(),
			ValueFormatter: chart.TimeDateValueFormatter,
			Ticks:          xticks,
		},
		YAxis: chart.YAxis{
			Name:      "kg",
			NameStyle: chart.StyleShow(),
			Style:     chart.StyleShow(),
			Range: &chart.ContinuousRange{
				Min: YRange.min,
				Max: YRange.max,
			},
		},
		Background: chart.Style{
			Padding: chart.Box{
				Top:  20,
				Left: 80,
			},
		},
		Series: []chart.Series{s1, s2, s3},
	}
	graph.Elements = []chart.Renderable{chart.LegendLeft(&graph)}
	return graph
}

func writeGraphToFile(graph chart.Chart) error {
	f, err := os.OpenFile(imgfile, os.O_WRONLY|os.O_CREATE, 0644)
	if err != nil {
		return err
	}
	err = graph.Render(chart.PNG, f)
	f.Close()
	return err
}

func openGraphFile() error {
	return goutil.OpenInDefaultApp(imgfile, false)
}

func askFor(err error, q string) (string, error) {
	if err == nil {
		return goutil.AskFor(q)
	} else {
		return "", err
	}
}

func parseFloat(s string, err error) (float64, error) {
	if err == nil {
		return strconv.ParseFloat(s, 64)
	} else {
		return 0, err
	}
}