package dice

import (
	"encoding/json"
	"errors"
	"fmt"
	"math/rand"
	"regexp"
	"strconv"
	"strings"
)

type diceRequest struct {
	count    int
	diceType int
}

type DiceRoller interface {
	Roll(request string) ([]int, error)
	TableRoll() [2]int
}

type Roller struct {
	Rand *rand.Rand
	Seed int64
	DiceRoller
}

func NewRoller(seed int64) *Roller {
	return &Roller{
		Rand: rand.New(rand.NewSource(seed)),
		Seed: seed,
	}
}

// RollToJSON takes a []int and returns JSON with those ints in "results"
func RollToJSON(rolls []int) ([]byte, error) {
	result := struct {
		Results []int `json:"results"`
	}{
		Results: rolls,
	}

	jsonResults, err := json.Marshal(result)
	if err != nil {
		return []byte{}, err
	}

	return jsonResults, nil
}

// RollToText takes a []int and returns them a spaced separated string
func RollToText(rolls []int) string {
	results := []string{}
	for _, r := range rolls {
		results = append(results, strconv.Itoa(r))
	}
	response := strings.Join(results, " ")
	response = response + "\n"
	return response
}

// Roll takes a string in the format of "XdY" and returns []int for its results
func (r *Roller) Roll(request string) ([]int, error) {
	var result []int

	diceRequest, err := parseRoll(request)
	if err != nil {
		return result, err
	}

	for i := 1; i <= diceRequest.count; i++ {
		result = append(result, r.Rand.Intn(diceRequest.diceType)+1)
	}

	return result, nil
}

// TableRoll returns a roll used for selecting an item on a Maze Rats table
func (r *Roller) TableRoll() [2]int {
	result, _ := r.Roll("2d6")
	return [2]int{result[0], result[1]}
}

func parseRoll(request string) (diceRequest, error) {
	regexString := "[1-9][0-9]*d[1-9]+"
	diceRegEx := regexp.MustCompile(regexString)
	correctRequest := diceRegEx.Match([]byte(request))
	if !correctRequest {
		errMsg := fmt.Sprintf("Must pass string matching '%v' "+
			"you passed '%v'",
			regexString, request)
		return diceRequest{}, errors.New(errMsg)
	}

	var parsedRequest []string = strings.Split(request, "d")
	count, _ := strconv.Atoi(parsedRequest[0])
	diceType, _ := strconv.Atoi(parsedRequest[1])

	return diceRequest{
		count:    count,
		diceType: diceType,
	}, nil
}