package db

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"sync"

	"gitlab.com/balki/ytui/pubsub"
)

type DownloadStatus string

var (
	NotStarted DownloadStatus = "NotStarted"
	InProgress DownloadStatus = "InProgress"
	Done       DownloadStatus = "Done"
	Error      DownloadStatus = "Error"
)

type Item struct {
	Id        int                    `json:"id"`
	Date      string                 `json:"date"`
	URL       string                 `json:"url"`
	Title     string                 `json:"title"`
	Status    DownloadStatus         `json:"status"`
	FileName  string                 `json:"file_name"`
	Pt        pubsub.ProgressTracker `json:"-"`
	TitleChan <-chan struct{}        `json:"-"`
}

type Jdb struct {
	Items []Item `json:"items"`
}

type Db struct {
	items  []Item
	mutex  sync.Mutex
	lastId int
	path   string
	index  map[string]int
}

func (d *Db) Add(i Item) (int, bool) {
	d.mutex.Lock()
	defer d.mutex.Unlock()
	if id, ok := d.index[i.URL]; ok {
		return id, false
	}
	i.Id = d.lastId
	d.lastId++
	d.items = append(d.items, i)
	d.save()
	d.index[i.URL] = i.Id
	return i.Id, true
}

func (d *Db) Transact(id int, persist bool, f func(*Item)) error {
	d.mutex.Lock()
	defer d.mutex.Unlock()
	for i, _ := range d.items {
		if d.items[i].Id == id {
			f(&d.items[i])
			if persist {
				d.save()
			}
			return nil
		}
	}
	return fmt.Errorf("Invalid id: %d", id)
}

func (d *Db) save() error {
	data, err := json.Marshal(Jdb{d.items})
	if err != nil {
		return err
	}
	return os.WriteFile(d.path, data, 0644)
}

func (d *Db) Run(f func(*Jdb)) {
	d.mutex.Lock()
	defer d.mutex.Unlock()
	f(&Jdb{d.items})
}

func (d *Db) Save() error {
	d.mutex.Lock()
	defer d.mutex.Unlock()
	return d.save()
}

func Load(path string) (*Db, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return &Db{
				path:   path,
				lastId: 0,
			}, nil
		}
		return nil, err
	}
	var jd Jdb
	err = json.Unmarshal(data, &jd)
	if err != nil {
		return nil, err
	}
	m := 0
	indexMap := map[string]int{}
	for _, item := range jd.Items {
		if item.Id > m {
			m = item.Id
		}
		indexMap[item.URL] = item.Id
	}
	return &Db{
		items:  jd.Items,
		path:   path,
		lastId: m + 1,
		index:  indexMap,
	}, nil
}