package beego

//@todo add template funcs

import (
    "fmt"
	"errors"
	"github.com/russross/blackfriday"
	"html/template"
	"strings"
	"time"
)

var beegoTplFuncMap template.FuncMap

func init() {
	beegoTplFuncMap = make(template.FuncMap)
	beegoTplFuncMap["markdown"] = MarkDown
	beegoTplFuncMap["dateformat"] = DateFormat
	beegoTplFuncMap["date"] = Date
	beegoTplFuncMap["compare"] = Compare
}

// MarkDown parses a string in MarkDown format and returns HTML. Used by the template parser as "markdown"
func MarkDown(raw string) (output template.HTML) {
	input := []byte(raw)
	bOutput := blackfriday.MarkdownBasic(input)
	output = template.HTML(string(bOutput))
	return
}

// DateFormat takes a time and a layout string and returns a string with the formatted date. Used by the template parser as "dateformat"
func DateFormat(t time.Time, layout string) (datestring string) {
	datestring = t.Format(layout)
	return
}

// Date takes a PHP like date func to Go's time fomate
func Date(t time.Time, format string) (datestring string) {
	patterns := []string{
		// year
		"Y", "2006", // A full numeric representation of a year, 4 digits	Examples: 1999 or 2003
		"y", "06", //A two digit representation of a year	Examples: 99 or 03

		// month
		"m", "01", // Numeric representation of a month, with leading zeros	01 through 12
		"n", "1", // Numeric representation of a month, without leading zeros	1 through 12
		"M", "Jan", // A short textual representation of a month, three letters	Jan through Dec
		"F", "January", // A full textual representation of a month, such as January or March	January through December

		// day
		"d", "02", // Day of the month, 2 digits with leading zeros	01 to 31
		"j", "2", // Day of the month without leading zeros	1 to 31

		// week
		"D", "Mon", // A textual representation of a day, three letters	Mon through Sun
		"l", "Monday", // A full textual representation of the day of the week	Sunday through Saturday

		// time
		"g", "3", // 12-hour format of an hour without leading zeros	1 through 12
		"G", "15", // 24-hour format of an hour without leading zeros	0 through 23
		"h", "03", // 12-hour format of an hour with leading zeros	01 through 12
		"H", "15", // 24-hour format of an hour with leading zeros	00 through 23

		"a", "pm", // Lowercase Ante meridiem and Post meridiem	am or pm
		"A", "PM", // Uppercase Ante meridiem and Post meridiem	AM or PM

		"i", "04", // Minutes with leading zeros	00 to 59
		"s", "05", // Seconds, with leading zeros	00 through 59
	}
	replacer := strings.NewReplacer(patterns...)
	format = replacer.Replace(format)
	datestring = t.Format(format)
	return
}

// Compare is a quick and dirty comparison function. It will convert whatever you give it to strings and see if the two values are equal.
// Whitespace is trimmed. Used by the template parser as "eq"
func Compare(a, b interface{}) (equal bool) {
	equal = false
	if strings.TrimSpace(fmt.Sprintf("%v", a)) == strings.TrimSpace(fmt.Sprintf("%v", b)) {
		equal = true
	}
	return
}

// AddFuncMap let user to register a func in the template
func AddFuncMap(key string, funname interface{}) error {
	if _, ok := beegoTplFuncMap[key]; ok {
        return errors.New("funcmap already has the key")
	}
	beegoTplFuncMap[key] = funname
	return nil
}