package models

import (
	"bytes"
	"errors"
	"strings"
	"sync"
	"time"
)

const DateFormat = "January 02, 2006 at 03:04:05PM -0700"

type Entry struct {
	Title  string
	Date   time.Time
	Fields []Meta
}

type metaRes struct {
	out []byte
	err error
}

func (e Entry) getFieldMarshalChan() chan metaRes {
	size := len(e.Fields)
	ch := make(chan metaRes, size)
	var wg sync.WaitGroup

	// @todo figure out a way to handle json field
	for i := 0; i < size; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			o, er := e.Fields[i].MarshalText()
			ch <- metaRes{o, er}

		}(i)
	}

	go func() {
		wg.Wait()
		close(ch)
	}()
	return ch
}

func (e Entry) MarshalText() ([]byte, error) {
	e.Title = strings.TrimSpace(e.Title)
	if e.Title == "" {
		return []byte{}, errors.New("Empty title")
	}
	if e.Date == (time.Time{}) {
		return []byte{}, errors.New("Empty date")
	}
	ch := e.getFieldMarshalChan()
	buff := &bytes.Buffer{}
	buff.WriteString("@begin ")
	buff.WriteString(e.Date.Format(DateFormat))
	buff.WriteString(" - ")
	buff.WriteString(e.Title)

	for res := range ch {
		if res.err == nil && len(res.out) > 0 {
			buff.WriteString("\n")
			buff.Write(res.out)
		}
	}

	buff.WriteString(" @end")

	return buff.Bytes(), nil
}