// Copyright (c) 2016 Mattermost, Inc. All Rights Reserved.
// See License.txt for license information.

package store

import (
	"github.com/mattermost/platform/einterfaces"
	"github.com/mattermost/platform/model"
	"github.com/mattermost/platform/utils"

	l4g "github.com/alecthomas/log4go"
	"github.com/go-gorp/gorp"
)

const (
	REACTION_CACHE_SIZE = 20000
	REACTION_CACHE_SEC  = 1800 // 30 minutes
)

var reactionCache *utils.Cache = utils.NewLru(REACTION_CACHE_SIZE)

type SqlReactionStore struct {
	*SqlStore
}

func NewSqlReactionStore(sqlStore *SqlStore) ReactionStore {
	s := &SqlReactionStore{sqlStore}

	for _, db := range sqlStore.GetAllConns() {
		table := db.AddTableWithName(model.Reaction{}, "Reactions").SetKeys(false, "UserId", "PostId", "EmojiName")
		table.ColMap("UserId").SetMaxSize(26)
		table.ColMap("PostId").SetMaxSize(26)
		table.ColMap("EmojiName").SetMaxSize(64)
	}

	return s
}

func (s SqlReactionStore) CreateIndexesIfNotExists() {
	s.CreateIndexIfNotExists("idx_reactions_post_id", "Reactions", "PostId")
	s.CreateIndexIfNotExists("idx_reactions_user_id", "Reactions", "UserId")
	s.CreateIndexIfNotExists("idx_reactions_emoji_name", "Reactions", "EmojiName")
}

func (s SqlReactionStore) Save(reaction *model.Reaction) StoreChannel {
	storeChannel := make(StoreChannel)

	go func() {
		result := StoreResult{}

		reaction.PreSave()
		if result.Err = reaction.IsValid(); result.Err != nil {
			storeChannel <- result
			close(storeChannel)
			return
		}

		if transaction, err := s.GetMaster().Begin(); err != nil {
			result.Err = model.NewLocAppError("SqlReactionStore.Save", "store.sql_reaction.save.begin.app_error", nil, err.Error())
		} else {
			err := saveReactionAndUpdatePost(transaction, reaction)

			if err != nil {
				transaction.Rollback()

				// We don't consider duplicated save calls as an error
				if !IsUniqueConstraintError(err.Error(), []string{"reactions_pkey", "PRIMARY"}) {
					result.Err = model.NewLocAppError("SqlPreferenceStore.Save", "store.sql_reaction.save.save.app_error", nil, err.Error())
				}
			} else {
				if err := transaction.Commit(); err != nil {
					// don't need to rollback here since the transaction is already closed
					result.Err = model.NewLocAppError("SqlPreferenceStore.Save", "store.sql_reaction.save.commit.app_error", nil, err.Error())
				}
			}

			if result.Err == nil {
				result.Data = reaction
			}
		}

		storeChannel <- result
		close(storeChannel)
	}()

	return storeChannel
}

func (s SqlReactionStore) Delete(reaction *model.Reaction) StoreChannel {
	storeChannel := make(StoreChannel)

	go func() {
		result := StoreResult{}

		if transaction, err := s.GetMaster().Begin(); err != nil {
			result.Err = model.NewLocAppError("SqlReactionStore.Delete", "store.sql_reaction.delete.begin.app_error", nil, err.Error())
		} else {
			err := deleteReactionAndUpdatePost(transaction, reaction)

			if err != nil {
				transaction.Rollback()

				result.Err = model.NewLocAppError("SqlPreferenceStore.Delete", "store.sql_reaction.delete.app_error", nil, err.Error())
			} else if err := transaction.Commit(); err != nil {
				// don't need to rollback here since the transaction is already closed
				result.Err = model.NewLocAppError("SqlPreferenceStore.Delete", "store.sql_reaction.delete.commit.app_error", nil, err.Error())
			} else {
				result.Data = reaction
			}
		}

		storeChannel <- result
		close(storeChannel)
	}()

	return storeChannel
}

func saveReactionAndUpdatePost(transaction *gorp.Transaction, reaction *model.Reaction) error {
	if err := transaction.Insert(reaction); err != nil {
		return err
	}

	return updatePostForReactions(transaction, reaction.PostId)
}

func deleteReactionAndUpdatePost(transaction *gorp.Transaction, reaction *model.Reaction) error {
	if _, err := transaction.Exec(
		`DELETE FROM
			Reactions
		WHERE
			PostId = :PostId AND
			UserId = :UserId AND
			EmojiName = :EmojiName`,
		map[string]interface{}{"PostId": reaction.PostId, "UserId": reaction.UserId, "EmojiName": reaction.EmojiName}); err != nil {
		return err
	}

	return updatePostForReactions(transaction, reaction.PostId)
}

const (
	// Set HasReactions = true if and only if the post has reactions, update UpdateAt only if HasReactions changes
	UPDATE_POST_HAS_REACTIONS_QUERY = `UPDATE
			Posts
		SET
			UpdateAt = (CASE
				WHEN HasReactions != (SELECT count(0) > 0 FROM Reactions WHERE PostId = :PostId) THEN :UpdateAt
				ELSE UpdateAt
			END),
			HasReactions = (SELECT count(0) > 0 FROM Reactions WHERE PostId = :PostId)
		WHERE
			Id = :PostId`
)

func updatePostForReactions(transaction *gorp.Transaction, postId string) error {
	_, err := transaction.Exec(UPDATE_POST_HAS_REACTIONS_QUERY, map[string]interface{}{"PostId": postId, "UpdateAt": model.GetMillis()})

	return err
}

func (s SqlReactionStore) InvalidateCacheForPost(postId string) {
	reactionCache.Remove(postId)
}

func (s SqlReactionStore) InvalidateCache() {
	reactionCache.Purge()
}

func (s SqlReactionStore) GetForPost(postId string, allowFromCache bool) StoreChannel {
	storeChannel := make(StoreChannel)

	go func() {
		result := StoreResult{}
		metrics := einterfaces.GetMetricsInterface()

		if allowFromCache {
			if cacheItem, ok := reactionCache.Get(postId); ok {
				if metrics != nil {
					metrics.IncrementMemCacheHitCounter("Reactions")
				}
				result.Data = cacheItem.([]*model.Reaction)
				storeChannel <- result
				close(storeChannel)
				return
			} else {
				if metrics != nil {
					metrics.IncrementMemCacheMissCounter("Reactions")
				}
			}
		} else {
			if metrics != nil {
				metrics.IncrementMemCacheMissCounter("Reactions")
			}
		}

		var reactions []*model.Reaction

		if _, err := s.GetReplica().Select(&reactions,
			`SELECT
				*
			FROM
				Reactions
			WHERE
				PostId = :PostId
			ORDER BY
				CreateAt`, map[string]interface{}{"PostId": postId}); err != nil {
			result.Err = model.NewLocAppError("SqlReactionStore.GetForPost", "store.sql_reaction.get_for_post.app_error", nil, "")
		} else {
			result.Data = reactions

			reactionCache.AddWithExpiresInSecs(postId, reactions, REACTION_CACHE_SEC)
		}

		storeChannel <- result
		close(storeChannel)
	}()

	return storeChannel
}

func (s SqlReactionStore) DeleteAllWithEmojiName(emojiName string) StoreChannel {
	storeChannel := make(StoreChannel)

	go func() {
		result := StoreResult{}

		// doesn't use a transaction since it's better for this to half-finish than to not commit anything
		var reactions []*model.Reaction

		if _, err := s.GetReplica().Select(&reactions,
			`SELECT
				*
			FROM
				Reactions
			WHERE
				EmojiName = :EmojiName`, map[string]interface{}{"EmojiName": emojiName}); err != nil {
			result.Err = model.NewLocAppError("SqlReactionStore.DeleteAllWithEmojiName",
				"store.sql_reaction.delete_all_with_emoji_name.get_reactions.app_error", nil,
				"emoji_name="+emojiName+", error="+err.Error())
			storeChannel <- result
			close(storeChannel)
			return
		}

		if _, err := s.GetMaster().Exec(
			`DELETE FROM
				Reactions
			WHERE
				EmojiName = :EmojiName`, map[string]interface{}{"EmojiName": emojiName}); err != nil {
			result.Err = model.NewLocAppError("SqlReactionStore.DeleteAllWithEmojiName",
				"store.sql_reaction.delete_all_with_emoji_name.delete_reactions.app_error", nil,
				"emoji_name="+emojiName+", error="+err.Error())
			storeChannel <- result
			close(storeChannel)
			return
		}

		for _, reaction := range reactions {
			if _, err := s.GetMaster().Exec(UPDATE_POST_HAS_REACTIONS_QUERY,
				map[string]interface{}{"PostId": reaction.PostId, "UpdateAt": model.GetMillis()}); err != nil {
				l4g.Warn(utils.T("store.sql_reaction.delete_all_with_emoji_name.update_post.warn"), reaction.PostId, err.Error())
			}
		}

		storeChannel <- result
		close(storeChannel)
	}()

	return storeChannel
}