package migrator

import (
	"encoding/xml"
	"fmt"
	"io"
	"strings"
	"time"

	log "github.com/go-pkgz/lgr"

	"github.com/umputun/remark42/backend/app/store"
)

// Disqus implements Importer from disqus xml
type Disqus struct {
	DataStore Store
}

type disqusThread struct {
	UID         string    `xml:"id,attr"`
	Forum       string    `xml:"forum"`
	Link        string    `xml:"link"`
	Title       string    `xml:"title"`
	Message     string    `xml:"message"`
	CreateAt    time.Time `xml:"createdAt"`
	AuthorName  string    `xml:"author>name"`
	AuthorEmail string    `xml:"author>email"`
	IP          string    `xml:"ipAddress"`
	Anonymous   bool      `xml:"author>isAnonymous"`
	Closed      bool      `xml:"isClosed"`
	Deleted     bool      `xml:"isDeleted"`
}

type disqusComment struct {
	UID            string    `xml:"id,attr"`
	ID             string    `xml:"id"`
	Message        string    `xml:"message"`
	CreatedAt      time.Time `xml:"createdAt"`
	AuthorEmail    string    `xml:"author>email"`
	AuthorName     string    `xml:"author>name"`
	AuthorUserName string    `xml:"author>username"`
	IP             string    `xml:"ipAddress"`
	Tid            uid       `xml:"thread"`
	Pid            uid       `xml:"parent"`
	IsSpam         bool      `xml:"isSpam"`
	Deleted        bool      `xml:"isDeleted"`
}

type uid struct {
	Val string `xml:"id,attr"`
}

// Import from disqus and save to store
func (d *Disqus) Import(r io.Reader, siteID string) (size int, err error) {
	if e := d.DataStore.DeleteAll(siteID); e != nil {
		return 0, e
	}

	commentsCh := d.convert(r, siteID)
	failed, passed := 0, 0
	for c := range commentsCh {
		if _, err = d.DataStore.Create(c); err != nil {
			failed++
			continue
		}
		passed++
	}

	if failed > 0 {
		err = fmt.Errorf("failed to save %d comments", failed)
		if passed == 0 {
			err = fmt.Errorf("import failed")
		}
	}

	log.Printf("[DEBUG] imported %d comments to site %s", passed, siteID)

	return passed, err
}

// convert disqus stream (xml) from reader and fill channel of comments.
// runs async and closes channel on completion.
func (d *Disqus) convert(r io.Reader, siteID string) (ch chan store.Comment) {
	postsMap := map[string]string{} // tid:url
	decoder := xml.NewDecoder(r)
	commentsCh := make(chan store.Comment)

	stats := struct {
		inpThreads, inpComments          int
		commentsCount, spamComments      int
		failedThreads, failedPosts       int
		deletedComments, skippedComments int
	}{}

	go func() {
		for {
			t, err := decoder.Token()
			if t == nil || err != nil {
				break
			}

			if se, ok := t.(xml.StartElement); ok {
				if se.Name.Local == "thread" {
					stats.inpThreads++
					thread := disqusThread{}
					if err = decoder.DecodeElement(&thread, &se); err != nil {
						log.Printf("[WARN] can't decode disqus thread, %s", err)
						stats.failedThreads++
						continue
					}
					if thread.Deleted {
						continue
					}
					postsMap[thread.UID] = thread.Link
					continue
				}

				if se.Name.Local == "post" {
					stats.inpComments++
					comment := disqusComment{}
					if err = decoder.DecodeElement(&comment, &se); err != nil {
						log.Printf("[WARN] can't decode disqus comment, %s", err)
						stats.failedPosts++
						continue
					}
					if comment.Deleted {
						stats.deletedComments++
						continue
					}
					if comment.IsSpam {
						stats.spamComments++
						continue
					}

					url, ok := postsMap[comment.Tid.Val]
					if !ok {
						stats.skippedComments++
						continue
					}

					c := store.Comment{
						ID:      comment.UID,
						Locator: store.Locator{URL: url, SiteID: siteID},
						User: store.User{
							ID:   "disqus_" + store.EncodeID(comment.AuthorUserName),
							Name: comment.AuthorName,
							IP:   comment.IP,
						},
						Text:      d.cleanText(comment.Message),
						Timestamp: comment.CreatedAt,
						ParentID:  comment.Pid.Val,
						Imported:  true,
					}
					if comment.AuthorUserName == "" { // empty comment.AuthorUserName from disqus
						c.User.ID = "disqus_" + store.EncodeID(c.User.Name)
					}
					if c.ID == "" { // no comment.UID
						c.ID = comment.ID
					}
					commentsCh <- c
					stats.commentsCount++
					if stats.commentsCount%1000 == 0 {
						log.Printf("[DEBUG] processed %d comments", stats.commentsCount)
					}
				}
			}
		}
		close(commentsCh)
		log.Printf("[INFO] converted %d posts, %+v", len(postsMap), stats)
	}()

	return commentsCh
}

func (*Disqus) cleanText(text string) string {
	text = strings.TrimSpace(text)
	text = strings.ReplaceAll(text, "\n", "")
	text = strings.ReplaceAll(text, "\t", "")
	return text
}