package mongodb

import (
	"context"
	"errors"
	"git.aiterp.net/rpdata/api/internal/generate"
	"git.aiterp.net/rpdata/api/models"
	"git.aiterp.net/rpdata/api/repositories"
	"github.com/globalsign/mgo"
	"github.com/globalsign/mgo/bson"
	"log"
	"strings"
	"sync"
	"time"
)

type postRepository struct {
	restoreIDs bool
	logs       *mgo.Collection
	posts      *mgo.Collection

	orderMutex sync.Mutex
}

func newPostRepository(db *mgo.Database, restoreIDs bool) (*postRepository, error) {
	posts := db.C("logbot3.posts")

	err := posts.EnsureIndexKey("logId")
	if err != nil {
		return nil, err
	}
	err = posts.EnsureIndexKey("time")
	if err != nil {
		return nil, err
	}
	err = posts.EnsureIndexKey("kind")
	if err != nil {
		return nil, err
	}
	err = posts.EnsureIndexKey("position")
	if err != nil {
		return nil, err
	}

	err = posts.EnsureIndex(mgo.Index{
		Key: []string{"$text:text"},
	})
	if err != nil {
		return nil, err
	}

	return &postRepository{
		restoreIDs: restoreIDs,
		posts:      posts,
		logs:       db.C("logbot3.logs"),
	}, nil
}

func (r *postRepository) Find(ctx context.Context, id string) (*models.Post, error) {
	post := new(models.Post)
	err := r.posts.FindId(id).One(post)
	if err != nil {
		return nil, err
	}

	return post, nil
}

func (r *postRepository) List(ctx context.Context, filter models.PostFilter) ([]*models.Post, error) {
	query := bson.M{}
	if filter.LogID != nil && *filter.LogID != "" {
		logId := *filter.LogID
		if !strings.HasPrefix(logId, "L") {
			// Resolve long id to short id
			log := new(models.Log)
			err := r.logs.FindId(logId).Select(bson.M{"logId": 1, "_id": 1}).One(log)
			if err != nil {
				return nil, err
			}

			logId = log.ShortID
		}

		query["logId"] = logId
	}
	if len(filter.IDs) > 0 {
		query["_id"] = bson.M{"$in": filter.IDs}
	}
	if len(filter.Kinds) > 0 {
		query["kind"] = bson.M{"$in": filter.Kinds}
	}
	if filter.Search != nil {
		query["$text"] = bson.M{"$search": *filter.Search}
	}

	posts := make([]*models.Post, 0, 32)
	var err error
	if filter.LogID != nil {
		err = r.posts.Find(query).Sort("position").Limit(filter.Limit).All(&posts)
	} else {
		err = r.posts.Find(query).Limit(filter.Limit).All(&posts)
	}
	if err != nil {
		if err == mgo.ErrNotFound {
			return []*models.Post{}, nil
		}

		return nil, err
	}

	return posts, nil
}

func (r *postRepository) Insert(ctx context.Context, post models.Post) (*models.Post, error) {
	r.orderMutex.Lock()
	defer r.orderMutex.Unlock()

	lastPost := new(models.Post)
	err := r.posts.Find(bson.M{"logId": post.LogID}).Sort("-position").One(lastPost)
	if err != nil && err != mgo.ErrNotFound {
		return nil, err
	}

	if !r.restoreIDs {
		post.ID = generate.PostID()
	} else {
		if len(post.ID) != len(generate.PostID()) && strings.HasPrefix(post.ID, "P") {
			return nil, errors.New("invalid story id")
		}
	}

	post.Position = lastPost.Position + 1 // Position 1 is first position, so this is safe.

	err = r.posts.Insert(post)
	if err != nil {
		return nil, err
	}

	return &post, nil
}

func (r *postRepository) InsertMany(ctx context.Context, posts ...*models.Post) ([]*models.Post, error) {
	if len(posts) == 0 {
		return []*models.Post{}, nil
	}

	logId := posts[0].LogID
	for _, post := range posts {
		if post.LogID != logId {
			return nil, repositories.ErrParentMismatch
		}

		if !r.restoreIDs || post.ID == "" {
			post.ID = generate.PostID()
		}
	}

	r.orderMutex.Lock()
	defer r.orderMutex.Unlock()

	lastPost := new(models.Post)
	err := r.posts.Find(bson.M{"logId": posts[0].LogID}).Sort("-position").One(lastPost)
	if err != nil && err != mgo.ErrNotFound {
		return nil, err
	}

	docs := make([]interface{}, len(posts))
	for i := range posts {
		posts[i].Position = lastPost.Position + 1 + i
		docs[i] = posts[i]
	}

	err = r.posts.Insert(docs...)
	if err != nil && err != mgo.ErrNotFound {
		return nil, err
	}

	return posts, nil
}

func (r *postRepository) Update(ctx context.Context, post models.Post, update models.PostUpdate) (*models.Post, error) {
	updateBson := bson.M{}
	if update.Time != nil {
		updateBson["time"] = *update.Time
		post.Time = *update.Time
	}
	if update.Kind != nil {
		updateBson["kind"] = *update.Kind
		post.Kind = *update.Kind
	}
	if update.Nick != nil {
		updateBson["nick"] = *update.Nick
		post.Nick = *update.Nick
	}
	if update.Text != nil {
		updateBson["text"] = *update.Text
		post.Text = *update.Text
	}

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

	return &post, nil
}

func (r *postRepository) Move(ctx context.Context, post models.Post, position int) ([]*models.Post, error) {
	// If only MongoDB transactions weren't awful, this function would have been safe.
	// Since it isn't, then good luck.

	// Validate lower position bound.
	if position < 1 {
		return nil, repositories.ErrInvalidPosition
	}

	// Determine the operations on adjacent posts
	var resultFilter bson.M
	var pushFilter bson.M
	var increment int
	if post.Position > position {
		pushFilter = bson.M{"position": bson.M{
			"$gte": position,
			"$lt":  post.Position,
		}}
		increment = 1
		resultFilter = bson.M{"position": bson.M{
			"$lte": post.Position,
			"$gte": position,
		}}
	} else {
		pushFilter = bson.M{"position": bson.M{
			"$lte": position,
			"$gt":  post.Position,
		}}
		increment = -1
		resultFilter = bson.M{"position": bson.M{
			"$lte": position,
			"$gte": post.Position,
		}}
	}
	pushFilter["logId"] = post.LogID
	resultFilter["logId"] = post.LogID

	// From here on out, sync is required
	r.orderMutex.Lock()
	defer r.orderMutex.Unlock()

	// Detect ninja shenanigans
	post2 := new(models.Post)
	err := r.posts.FindId(post.ID).One(post2)
	if err != nil && post2.Position != post.Position {
		return nil, repositories.ErrNotFound
	}

	// Validate upper position bound
	lastPost := new(models.Post)
	err = r.posts.Find(bson.M{"logId": post.LogID}).Sort("-position").One(lastPost)
	if err != nil && err != mgo.ErrNotFound {
		return nil, err
	}
	if position > lastPost.Position {
		return nil, repositories.ErrInvalidPosition
	}

	// Move the posts
	changeInfo, err := r.posts.UpdateAll(pushFilter, bson.M{"$inc": bson.M{"position": increment}})
	if err != nil && err != mgo.ErrNotFound {
		return nil, err
	}
	err = r.posts.UpdateId(post.ID, bson.M{"$set": bson.M{"position": position}})
	if err != nil {
		// Try to undo it
		_, err := r.posts.UpdateAll(pushFilter, bson.M{"$inc": bson.M{"position": -increment}})
		if err != nil && err != mgo.ErrNotFound {
			return nil, err
		}

		return nil, err
	}

	results := make([]*models.Post, 0, changeInfo.Matched+1)
	err = r.posts.Find(resultFilter).All(&results)
	if err != nil {
		return nil, err
	}

	return results, nil
}

func (r *postRepository) Delete(ctx context.Context, post models.Post) error {
	r.orderMutex.Lock()
	defer r.orderMutex.Unlock()

	err := r.posts.RemoveId(post.ID)
	if err != nil {
		return err
	}

	_, _ = r.posts.UpdateAll(bson.M{"logId": post.LogID, "position": bson.M{"$gt": post.Position}}, bson.M{"$inc": bson.M{"position": -1}})

	return nil
}

func (r *postRepository) fixPositions(logRepo *logRepository) {
	disorders := make([]int, 0, 16)
	diffs := make([]int, 0, 16)
	startTime := time.Now()

	timeout, cancel := context.WithTimeout(context.Background(), time.Minute)
	defer cancel()

	logs, err := logRepo.List(timeout, models.LogFilter{})
	if err != nil {
		log.Println("Failed to get logs for position fix:", err)
	}

	log.Println("Starting log position fixing, this should not take longer than 10 seconds.")

	for _, l := range logs {
		r.orderMutex.Lock()

		posts, err := r.List(timeout, models.PostFilter{LogID: &l.ShortID})
		if err != nil {
			r.orderMutex.Unlock()
			continue
		}

		disorders = disorders[:0]
		diffs = diffs[:0]
		for i, post := range posts {
			if post.Position != (i + 1) {
				disorders = append(disorders, i)
				diffs = append(diffs, post.Position-(i+1))
			}
		}

		if len(disorders) > 0 {
			log.Println(len(disorders), "order errors detected in", l.ID)

			ops := 0

			for i, post := range posts {
				if (i + 1) != posts[i].Position {
					ops++

					err := r.posts.UpdateId(post.ID, bson.M{"$set": bson.M{"position": i + 1}})
					if err != nil {
						log.Println(l.ShortID, "fix failed after", ops, "ops:", err)
						break
					}
				}
			}

			log.Println(l.ShortID, "fixed after", ops, "ops.")
		}

		r.orderMutex.Unlock()
	}

	log.Println("Log position fixing finished in", time.Since(startTime))
}