package main

import (
	"bufio"
	"os"
	"log"
	"fmt"
	"strconv"
	"math"
	"sort"
)

func getXcartesian(radius, angle float64) (coordinate float64){
	return radius * math.Cos(angle * (math.Pi / 180))
}
func getYcartesian(radius, angle float64) (coordinate float64){
	return radius * math.Sin(angle * (math.Pi / 180))
}

func getLines(filename string) ([]string) {
	lines := []string{}
	f, err := os.Open(filename)
	defer f.Close()
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	scanner := bufio.NewScanner(f)
	scanner.Split(bufio.ScanLines)
	inEntities := false
	 // extract all the lines of entities
	for scanner.Scan() {
		switch scanner.Text() {
		case "ENTITIES":
			inEntities = true
		case "ENDSEC":
			inEntities = false
		}
		if inEntities {
			lines = append(lines, scanner.Text())
		}
	}
	return lines
}

func getEnt(list []string, e []Ent) ([]Ent){
	// add error handling
	group := ""
	count := 0
	for i := range list {
		if len(group) > 0 {
			switch group {
			case "  0":
				if len(e) > 0 {count++}
				e = append(e, Ent{})
				e[count].G0 = list[i]
			case "  8":
				e[count].G8 = list[i]
			case " 10":
				e[count].G10, _ = strconv.ParseFloat(list[i],64)
			case " 11":
				e[count].G11, _ = strconv.ParseFloat(list[i],64)
			case " 20":
				e[count].G20, _ = strconv.ParseFloat(list[i],64)
			case " 21":
				e[count].G21, _ = strconv.ParseFloat(list[i],64)
			case " 30":
				e[count].G30, _ = strconv.ParseFloat(list[i],64)
			case " 31":
				e[count].G31, _ = strconv.ParseFloat(list[i],64)
			case " 40":
				e[count].G40, _ = strconv.ParseFloat(list[i],64)
			case " 50":
				e[count].G50, _ = strconv.ParseFloat(list[i],64)
			case " 51":
				e[count].G51, _ = strconv.ParseFloat(list[i],64)
			}
		group = ""
		}
		switch list[i] { // trigger when a group is found
		case "  0", "  8", " 10", " 11", " 20", " 21",
		 " 30", " 31", " 40", " 50", " 51":
			group = list[i]
		}
	}
	return e
}

func findEndPoints (e []Ent) ([]Ent){
	// add error handling
	for i := range e {
		switch e[i].G0 {
		case "ARC": // get the X and Y end points
			e[i].Xs = getXcartesian(e[i].G40, e[i].G50) + e[i].G10
			e[i].Xe = getXcartesian(e[i].G40, e[i].G51) + e[i].G10
			e[i].Ys = getYcartesian(e[i].G40, e[i].G50) + e[i].G20
			e[i].Ye = getYcartesian(e[i].G40, e[i].G51) + e[i].G20
		case "LINE":
			e[i].Xs = e[i].G10
			e[i].Ys = e[i].G20
			e[i].Zs = e[i].G30
			e[i].Xe = e[i].G11
			e[i].Ye = e[i].G21
			e[i].Zs = e[i].G31
		case "CIRCLE": // if it is a circle it must be the only entity on that layer
			fmt.Println("Circle")
		}
	}
	return e
}

// find the matching start points for each entity and assign index
func findIndex(s int, t float64, e []Ent) ([]Ent) {
	// add error handling
	xe := e[s].Xe
	ye := e[s].Ye
	index := 1
	for skip := range e {
		if skip != s {
			for i := range e {
				if math.Abs(e[i].Xs - xe) < t && math.Abs(e[i].Ys - ye) < t {
					e[i].Index = index
					index++
					xe = e[i].Xe
					ye = e[i].Ye
					break
				}
			}
		}
	}
	return e
}

type Ent struct {
	Index int
	G0, G8 string
	G10, G11, G20, G21, G30, G31, G40, G50, G51,
	Xs, Xe, Ys, Ye, Zs, Ze float64
}

type ByIndex []Ent

func (a ByIndex) Len() int { return len(a) }
func (a ByIndex) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func (a ByIndex) Less(i, j int) bool { return a[i].Index < a[j].Index }

func main(){
	var file = ""
	if len(os.Args) > 1 {
		file = os.Args[1]
	} else {
		file = "test.dxf"
	}
	var entities []Ent
	lines := getLines(file)
	entities = getEnt(lines, entities)
	entities = findEndPoints(entities)
	start := 3
	tolerance := 0.0000001
	entities = findIndex(start, tolerance, entities)
	sort.Sort(ByIndex(entities))

	for i := range(entities){
		fmt.Printf("%d %s %f %f %f %f\n",
		entities[i].Index, entities[i].G0, entities[i].Xs,
		entities[i].Ys, entities[i].Xe, entities[i].Ye)
	}
}