package log

import (
	"crypto/rand"
	"encoding/binary"
	"errors"
	"log"
	"strconv"
	"time"

	"git.aiterp.net/rpdata/api/internal/store"
	"github.com/globalsign/mgo"
	"github.com/globalsign/mgo/bson"
)

var postCollection *mgo.Collection

// A Post is a part of a log file.
type Post struct {
	ID       string    `bson:"_id"`
	LogID    string    `bson:"logId"`
	Time     time.Time `bson:"time"`
	Kind     string    `bson:"kind"`
	Nick     string    `bson:"nick"`
	Text     string    `bson:"text"`
	Position int       `bson:"position"`
}

// Edit the post
func (post *Post) Edit(time *time.Time, kind *string, nick *string, text *string) error {
	changes := bson.M{}
	changed := false
	postCopy := *post

	if time != nil && !time.IsZero() && !time.Equal(post.Time) {
		changes["time"] = *time
		changed = true
		postCopy.Time = *time
	}
	if kind != nil && *kind != "" && *kind != post.Kind {
		changes["kind"] = *kind
		changed = true
		postCopy.Kind = *kind
	}
	if nick != nil && *nick != "" && *nick != post.Nick {
		changes["nick"] = *nick
		changed = true
		postCopy.Nick = *nick
	}
	if text != nil && *text != "" && *text != post.Text {
		changes["text"] = *text
		changed = true
		postCopy.Text = *text
	}

	if !changed {
		return nil
	}

	err := postCollection.UpdateId(post.ID, bson.M{"$set": changes})
	if err != nil {
		return err
	}

	*post = postCopy
	return nil
}

// Move the post
func (post *Post) Move(toPosition int) error {
	if toPosition < 1 {
		return errors.New("Invalid position")
	}

	postMutex.Lock()
	defer postMutex.Unlock()

	// To avoid problems, only allow target indices that are allowed. If it's 1, then there is bound to
	// be a post at the position.
	if toPosition > 1 {
		existingPost := Post{}
		err := postCollection.Find(bson.M{"logId": post.LogID, "position": toPosition}).One(&existingPost)

		if err != nil || existingPost.Position != toPosition {
			return errors.New("No post found at the position")
		}
	}

	query := bson.M{"logId": post.LogID}
	operation := bson.M{"$inc": bson.M{"position": 1}}

	if toPosition < post.Position {
		query["$and"] = []bson.M{
			bson.M{"position": bson.M{"$gte": toPosition}},
			bson.M{"position": bson.M{"$lt": post.Position}},
		}
	} else {
		query["$and"] = []bson.M{
			bson.M{"position": bson.M{"$gt": post.Position}},
			bson.M{"position": bson.M{"$lte": toPosition}},
		}

		operation["$inc"] = bson.M{"position": -1}
	}

	_, err := postCollection.UpdateAll(query, operation)
	if err != nil {
		return errors.New("moving others: " + err.Error())
	}

	err = postCollection.UpdateId(post.ID, bson.M{"$set": bson.M{"position": toPosition}})
	if err != nil {
		return errors.New("moving: " + err.Error())
	}

	post.Position = toPosition

	return nil
}

// FindPostID finds a log post by ID.
func FindPostID(id string) (Post, error) {
	return findPost(bson.M{"_id": id})
}

// ListPostIDs lists log posts by ID
func ListPostIDs(ids ...string) ([]Post, error) {
	return listPosts(bson.M{"_id": bson.M{"$in": ids}})
}

// RemovePost removes a post, moving all subsequent post up one position
func RemovePost(id string) (Post, error) {
	postMutex.Lock()
	defer postMutex.Unlock()

	post, err := findPost(bson.M{"_id": id})
	if err != nil {
		return Post{}, err
	}

	err = postCollection.RemoveId(id)
	if err != nil {
		return Post{}, err
	}

	_, err = postCollection.UpdateAll(bson.M{"logId": post.LogID, "position": bson.M{"$gt": post.Position}}, bson.M{"$inc": bson.M{"position": -1}})
	if err != nil {
		return Post{}, err
	}

	return post, nil
}

func findPost(query interface{}) (Post, error) {
	post := Post{}
	err := postCollection.Find(query).One(&post)
	if err != nil {
		return Post{}, err
	}

	return post, nil
}

func listPosts(query interface{}) ([]Post, error) {
	posts := make([]Post, 0, 64)
	err := postCollection.Find(query).All(&posts)
	if err != nil {
		return nil, err
	}

	return posts, nil
}

// MakePostID makes a random post ID
func MakePostID(time time.Time) string {
	data := make([]byte, 4)
	rand.Read(data)

	return "P" + strconv.FormatInt(time.UnixNano(), 36) + strconv.FormatInt(int64(binary.LittleEndian.Uint32(data)), 36)
}

func init() {
	store.HandleInit(func(db *mgo.Database) {
		postCollection = db.C("logbot3.posts")

		postCollection.EnsureIndexKey("logId")
		postCollection.EnsureIndexKey("time")
		postCollection.EnsureIndexKey("kind")
		postCollection.EnsureIndexKey("position")

		err := postCollection.EnsureIndex(mgo.Index{
			Key: []string{"$text:text"},
		})
		if err != nil {
			log.Fatalln("init logbot3.logs:", err)
		}
	})
}