package models

import (
	"bufio"
	"bytes"
	"encoding/json"
	"errors"
	"regexp"
	"strings"
	"sync"
	"time"

	"codeberg.org/danjones000/my-log/tools"
)

const DateFormat = tools.DateFormat

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

func PartialEntry() Entry {
	return Entry{skipMissing: true}
}

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

	for i := 0; i < size; i++ {
		wg.Add(1)
		go func(m Meta) {
			defer wg.Done()
			if m.Key == "json" {
				if j, ok := m.Value.(json.RawMessage); ok {
					sub := Entry{skipMissing: true}
					json.Unmarshal(j, &sub)
					for _, subM := range sub.Fields {
						o, er := subM.MarshalText()
						ch <- metaRes{o, er}
					}
				}
			} else {
				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("\n@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

	for scan.Scan() {
		wg.Add(1)
		go func(field []byte) {
			defer wg.Done()
			m := new(Meta)
			err := m.UnmarshalText(field)
			if err == nil {
				if m.Key == "json" {
					if j, ok := m.Value.(json.RawMessage); ok {
						sub := Entry{skipMissing: true}
						json.Unmarshal(j, &sub)
						for _, subM := range sub.Fields {
							ch <- subM
						}
					}
				} else {
					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 {
			if f.Key == "json" {
				ob := map[string]any{}
				if j, ok := f.Value.(json.RawMessage); ok {
					json.Unmarshal(j, &ob)
				}
				// If we couldn't get valid data from there, this will just be empty
				for k, v := range ob {
					if k != "title" && k != "date" {
						out[k] = v
					}
				}
			} else {
				out[f.Key] = f.Value
				if vt, ok := f.Value.(time.Time); ok {
					out[f.Key] = vt.Format(time.RFC3339)
				}
			}
		}
	}
	return json.Marshal(out)
}

func (e *Entry) unmarshalJsonChanHelper(m map[string]any, ch chan Meta, wg *sync.WaitGroup) {
	for k, v := range m {
		wg.Add(1)
		go func(key string, value any) {
			defer wg.Done()
			if key != "json" {
				ch <- Meta{key, value}
				return
			}
			subM := map[string]any{}
			if s, ok := value.(string); ok {
				dec := json.NewDecoder(strings.NewReader(s))
				dec.UseNumber()
				dec.Decode(&subM)
			} else {
				subM = value.(map[string]any)
			}
			e.unmarshalJsonChanHelper(subM, ch, wg)
		}(k, v)
	}
}

func (e *Entry) getUnmarshalJsonChan(m map[string]any) chan Meta {
	ch := make(chan Meta, len(m))
	var wg sync.WaitGroup

	e.unmarshalJsonChanHelper(m, ch, &wg)
	go func() {
		wg.Wait()
		close(ch)
	}()

	return ch
}

func (e *Entry) UnmarshalJSON(in []byte) error {
	out := map[string]any{}
	dec := json.NewDecoder(bytes.NewReader(in))
	dec.UseNumber()
	err := dec.Decode(&out)
	if err != nil {
		return newParsingError(err)
	}
	title, ok := out["title"].(string)
	if (!ok || title == "") && !e.skipMissing {
		return ErrorMissingTitle
	}
	e.Title = title
	dates, ok := out["date"].(string)
	if (!ok || dates == "") && !e.skipMissing {
		return ErrorMissingDate
	}
	date, err := time.Parse(time.RFC3339, dates)
	if err != nil && !e.skipMissing {
		return newParsingError(err)
	}
	e.Date = date
	ch := e.getUnmarshalJsonChan(out)
	for m := range ch {
		if m.Key == "title" || m.Key == "date" {
			continue
		} else if vs, ok := m.Value.(string); ok {
			if vd, err := time.Parse(time.RFC3339, vs); err == nil {
				m.Value = vd
			} else {
				m.Value = vs
			}
		} else if n, ok := m.Value.(json.Number); ok {
			it, _ := n.Int64()
			fl, _ := n.Float64()
			if float64(it) == fl {
				m.Value = it
			} else {
				m.Value = fl
			}
		}
		e.Fields = append(e.Fields, m)
	}
	return nil
}