package storage

import (
	"fmt"
	"time"
	"strings"
	"encoding/json"
)

type ItemStatus int

const (
	UNREAD  ItemStatus = 0
	READ    ItemStatus = 1
	STARRED ItemStatus = 2
)

var StatusRepresentations = map[ItemStatus]string {
	UNREAD: "unread",
	READ: "read",
	STARRED: "starred",
}

var StatusValues = map[string]ItemStatus {
	"unread": UNREAD,
	"read": READ,
	"starred": STARRED,
}

func (s ItemStatus) MarshalJSON() ([]byte, error) {
	return json.Marshal(StatusRepresentations[s])
}

func (s *ItemStatus) UnmarshalJSON(b []byte) error {
	var str string
	if err := json.Unmarshal(b, &str); err != nil {
		return err
	}
	*s = StatusValues[str]
	return nil
}

type Item struct {
	Id int64 `json:"id"`
	GUID string `json:"guid"`
	FeedId int64 `json:"feed_id"`
	Title string `json:"title"`
	Link string `json:"link"`
	Description string `json:"description"`
	Content string `json:"content"`
	Author string `json:"author"`
	Date *time.Time `json:"date"`
	DateUpdated *time.Time `json:"date_updated"`
	Status ItemStatus `json:"status"`
	Image string `json:"image"`
}

type ItemFilter struct {
	FolderID *int64
	FeedID *int64
	Status *ItemStatus
}

func (s *Storage) CreateItems(items []Item) bool {
	tx, err := s.db.Begin()
	if err != nil {
		s.log.Print(err)
		return false
	}
	for _, item := range items {
		_, err = tx.Exec(`
			insert into items (
				guid, feed_id, title, link, description,
				content, author, date, date_updated, status, image
			)
			values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
			on conflict (guid) do update set date_updated=?`,
			item.GUID, item.FeedId, item.Title, item.Link, item.Description,
			item.Content, item.Author, item.Date, item.DateUpdated, UNREAD, item.Image,
			// upsert values
			item.DateUpdated,
		)
		if err != nil {
			s.log.Print(err)
			if err = tx.Rollback(); err != nil {
				s.log.Print(err)
				return false
			}
			return false
		}
	}
	if err = tx.Commit(); err != nil {
		s.log.Print(err)
		return false
	}
	return true
}

func listQueryPredicate(filter ItemFilter) (string, []interface{}) {
	cond := make([]string, 0)
	args := make([]interface{}, 0)
	if filter.FolderID != nil {
		cond = append(cond, "f.folder_id = ?")
		args = append(args, *filter.FolderID)
	}
	if filter.FeedID != nil {
		cond = append(cond, "i.feed_id = ?")
		args = append(args, *filter.FeedID)
	}
	if filter.Status != nil {
		cond = append(cond, "i.status = ?")
		args = append(args, *filter.Status)
	}

	predicate := "1"
	if len(cond) > 0 {
		predicate = strings.Join(cond, " and ")
	}
	return predicate, args
}

func (s *Storage) ListItems(filter ItemFilter, offset, limit int) []Item {
	predicate, args := listQueryPredicate(filter)
	result := make([]Item, 0, 0)
	query := fmt.Sprintf(`
		select
			i.id, i.guid, i.feed_id, i.title, i.link, i.description,
			i.content, i.author, i.date, i.date_updated, i.status, i.image
		from items i
		join feeds f on f.id = i.feed_id
		where %s
		order by i.date desc
		limit %d offset %d
		`, predicate, limit, offset)
	rows, err := s.db.Query(query, args...)
	if err != nil {
		s.log.Print(err)
		return result
	}
	for rows.Next() {
		var x Item
		err = rows.Scan(
			&x.Id,
			&x.GUID,
			&x.FeedId,
			&x.Title,
			&x.Link,
			&x.Description,
			&x.Content,
			&x.Author,
			&x.Date,
			&x.DateUpdated,
			&x.Status,
			&x.Image,
		)
		if err != nil {
			s.log.Print(err)
			return result
		}
		result = append(result, x)
	}
	return result
}

func (s *Storage) CountItems(filter ItemFilter) int64 {
	predicate, args := listQueryPredicate(filter)
	query := fmt.Sprintf(`
		select count(i.id)
		from items i
		join feeds f on f.id = i.feed_id
		where %s`, predicate)
	row := s.db.QueryRow(query, args...)
	if row != nil {
		var result int64
		row.Scan(&result)
		return result
	}
	return 0
}

func (s *Storage) UpdateItemStatus(item_id int64, status ItemStatus) bool {
	_, err := s.db.Exec(`update items set status = ? where id = ?`, status, item_id)
	return err == nil
}

func (s *Storage) MarkItemsRead(filter ItemFilter) bool {
	cond := make([]string, 0)
	args := make([]interface{}, 0)

	if filter.FolderID != nil {
		cond = append(cond, "f.folder_id = ?")
		args = append(args, *filter.FolderID)
	}
	if filter.FeedID != nil {
		cond = append(cond, "i.feed_id = ?")
		args = append(args, *filter.FeedID)
	}
	predicate := "1"
	if len(cond) > 0 {
		predicate = strings.Join(cond, " and ")
	}
	query := fmt.Sprintf(`
		update items set status = %d
		where id in (
			select i.id from items i
			join feeds f on f.id = i.feed_id
			where %s and i.status != %d
		)
		`, READ, predicate, STARRED)
	_, err := s.db.Exec(query, args...)
	if err != nil {
		s.log.Print(err)
	}
	return err == nil
}

type FeedStat struct {
	FeedId int64 `json:"feed_id"`
	UnreadCount int64 `json:"unread"`
	StarredCount int64 `json:"starred"`
}

func (s *Storage) FeedStats() []FeedStat {
	result := make([]FeedStat, 0)
	rows, err := s.db.Query(fmt.Sprintf(`
		select
			feed_id,
			sum(case status when %d then 1 else 0 end),
			sum(case status when %d then 1 else 0 end)
		from items
		group by feed_id
	`, UNREAD, STARRED))
	if err != nil {
		s.log.Print(err)
		return result
	}
	for rows.Next() {
		stat := FeedStat{}
		rows.Scan(&stat.FeedId, &stat.UnreadCount, &stat.StarredCount)
		result = append(result, stat)
	}
	return result
}