package services

import (
	"bytes"
	"encoding/base64"
	"errors"
	"html/template"
	"image/png"
	"math"
	"strconv"

	"git.odit.services/lfk/document-server/models"
	"github.com/boombuler/barcode"
	"github.com/boombuler/barcode/ean"
)

type Templater interface {
	Execute(template *template.Template, data interface{}) (string, error)
	StringToTemplate(templateString string) (*template.Template, error)
}

type DefaultTemplater struct {
}

type ContractTemplateOptions struct {
	Runners              []models.Runner `json:"runners"`
	CurrencySymbol       string          `json:"currency_symbol"`
	Disclaimer           string          `json:"disclaimer"`
	ReceiptMinimumAmount int             `json:"receipt_minimum_amount"`
	EventName            string          `json:"event_name"`
	SponsoringHeader     string          `json:"base_url"`
}

func idToEan13(id int) (string, error) {
	multiply := [2]int{1, 3}
	idStr := strconv.Itoa(id)

	if len(idStr) > 12 {
		return "", errors.New("id too long")
	}
	for len(idStr) < 12 {
		idStr = "0" + idStr
	}

	total := 0
	for i, char := range idStr {
		num, err := strconv.Atoi(string(char))
		if err != nil {
			return "", err
		}
		total += num * multiply[i%2]
	}
	checkSum := (int(math.Ceil(float64(total)/10)) * 10) - total
	return idStr + strconv.Itoa(checkSum), nil
}

func (t *DefaultTemplater) GenerateBarcode(code int) (string, error) {
	encodedEan, err := idToEan13(code)
	eanCode, err := ean.Encode(encodedEan)
	if err != nil {
		return "", err
	}
	scaledCode, err := barcode.Scale(eanCode, 100, 50)
	if err != nil {
		return "", err
	}

	var buf bytes.Buffer
	err = png.Encode(&buf, scaledCode)
	if err != nil {
		return "", err
	}

	return base64.StdEncoding.EncodeToString(buf.Bytes()), nil
}

func (t *DefaultTemplater) StringToTemplate(templateString string) (*template.Template, error) {
	return template.New("template").Funcs(template.FuncMap{
		"barcode": t.GenerateBarcode,
	}).Parse(templateString)
}

func (t *DefaultTemplater) Execute(baseTemplate *template.Template, data interface{}) (string, error) {
	resultBuffer := new(bytes.Buffer)

	err := baseTemplate.Execute(resultBuffer, data)
	if err != nil {
		return "", err
	}

	return resultBuffer.String(), nil
}