my-log/models/entry.go

package models

import (
	"bufio"
	"bytes"
	"encoding/json"
	"errors"
	"regexp"
	"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(m Meta) {
			defer wg.Done()
			o, er := m.MarshalText()
			ch <- metaRes{o, er}

		}(e.Fields[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{}, ErrorMissingTitle
	}
	if e.Date == (time.Time{}) {
		return []byte{}, ErrorMissingDate
	}
	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
}

func (m *Entry) UnmarshalText(in []byte) error {
	re := regexp.MustCompile("(?s)^@begin (.+) - (.+?)[ \n]@")
	match := re.FindSubmatch(in)
	if len(match) == 0 {
		return newParsingError(errors.New("Failed to find title and date"))
	}

	ch := m.getFieldUnarshalChan(in)

	title := bytes.TrimSpace(match[2])
	if len(title) == 0 {
		return ErrorMissingTitle
	}
	m.Title = string(title)
	date := string(bytes.TrimSpace(match[1]))
	if date == "" {
		return ErrorMissingDate
	}
	d, e := time.Parse(time.RFC3339, date)
	if e != nil {
		d, e = time.Parse(DateFormat, date)
		if e != nil {
			return newParsingError(e)
		}
	}
	m.Date = d

	for meta := range ch {
		m.Fields = append(m.Fields, meta)
	}

	return nil
}

func scanEntry(data []byte, atEOF bool) (advance int, token []byte, err error) {
	if atEOF && len(data) == 0 {
		return 0, nil, nil
	}
	if i := bytes.Index(data, []byte{10, 64}); i > 0 {
		return i + 1, data[0:i], nil
	}
	if atEOF {
		end := []byte{32, 64, 101, 110, 100}
		token = data
		if i := bytes.Index(data, end); i >= 0 {
			token = data[0:i]
		}
		return len(data), token, nil
	}
	// Request more data.
	return 0, nil, nil
}

func (e *Entry) getFieldUnarshalChan(in []byte) chan Meta {
	size := len(in) / 3 // rough estimation
	ch := make(chan Meta, size)
	var wg sync.WaitGroup

	read := bytes.NewReader(in)
	scan := bufio.NewScanner(read)
	scan.Split(scanEntry)
	scan.Scan() // throw out first line

	// @todo figure out a way to handle json field
	for scan.Scan() {
		wg.Add(1)
		go func(field []byte) {
			defer wg.Done()
			m := new(Meta)
			err := m.UnmarshalText(field)
			if err == nil {
				ch <- *m
			}
		}(scan.Bytes())
	}

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

func (e Entry) MarshalJSON() ([]byte, error) {
	if e.Title == "" {
		return []byte{}, ErrorMissingTitle
	}
	if e.Date == (time.Time{}) {
		return []byte{}, ErrorMissingDate
	}

	out := map[string]any{}
	out["title"] = e.Title
	out["date"] = e.Date.Format(time.RFC3339)
	for _, f := range e.Fields {
		if _, ok := out[f.Key]; !ok {
			out[f.Key] = f.Value
			if vt, ok := f.Value.(time.Time); ok {
				out[f.Key] = vt.Format(time.RFC3339)
			}
		}
	}
	return json.Marshal(out)
}