// GoToSocial
// Copyright (C) GoToSocial Authors admin@gotosocial.org
// SPDX-License-Identifier: AGPL-3.0-or-later
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package bundb

import (
	"context"
	"errors"
	"slices"
	"time"

	"github.com/superseriousbusiness/gotosocial/internal/db"
	"github.com/superseriousbusiness/gotosocial/internal/gtscontext"
	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
	"github.com/superseriousbusiness/gotosocial/internal/id"
	"github.com/superseriousbusiness/gotosocial/internal/log"
	"github.com/superseriousbusiness/gotosocial/internal/paging"
	"github.com/superseriousbusiness/gotosocial/internal/state"
	"github.com/superseriousbusiness/gotosocial/internal/util/xslices"
	"github.com/uptrace/bun"
	"github.com/uptrace/bun/dialect"
)

type conversationDB struct {
	db    *bun.DB
	state *state.State
}

func (c *conversationDB) GetConversationByID(ctx context.Context, id string) (*gtsmodel.Conversation, error) {
	return c.getConversation(
		ctx,
		"ID",
		func(conversation *gtsmodel.Conversation) error {
			return c.db.
				NewSelect().
				Model(conversation).
				Where("? = ?", bun.Ident("id"), id).
				Scan(ctx)
		},
		id,
	)
}

func (c *conversationDB) GetConversationByThreadAndAccountIDs(ctx context.Context, threadID string, accountID string, otherAccountIDs []string) (*gtsmodel.Conversation, error) {
	otherAccountsKey := gtsmodel.ConversationOtherAccountsKey(otherAccountIDs)
	return c.getConversation(
		ctx,
		"ThreadID,AccountID,OtherAccountsKey",
		func(conversation *gtsmodel.Conversation) error {
			return c.db.
				NewSelect().
				Model(conversation).
				Where("? = ?", bun.Ident("thread_id"), threadID).
				Where("? = ?", bun.Ident("account_id"), accountID).
				Where("? = ?", bun.Ident("other_accounts_key"), otherAccountsKey).
				Scan(ctx)
		},
		threadID,
		accountID,
		otherAccountsKey,
	)
}

func (c *conversationDB) getConversation(
	ctx context.Context,
	lookup string,
	dbQuery func(conversation *gtsmodel.Conversation) error,
	keyParts ...any,
) (*gtsmodel.Conversation, error) {
	// Fetch conversation from cache with loader callback
	conversation, err := c.state.Caches.DB.Conversation.LoadOne(lookup, func() (*gtsmodel.Conversation, error) {
		var conversation gtsmodel.Conversation

		// Not cached! Perform database query
		if err := dbQuery(&conversation); err != nil {
			return nil, err
		}

		return &conversation, nil
	}, keyParts...)
	if err != nil {
		// already processe
		return nil, err
	}

	if gtscontext.Barebones(ctx) {
		// Only a barebones model was requested.
		return conversation, nil
	}

	if err := c.populateConversation(ctx, conversation); err != nil {
		return nil, err
	}

	return conversation, nil
}

func (c *conversationDB) populateConversation(ctx context.Context, conversation *gtsmodel.Conversation) error {
	var (
		errs gtserror.MultiError
		err  error
	)

	if conversation.Account == nil {
		conversation.Account, err = c.state.DB.GetAccountByID(
			gtscontext.SetBarebones(ctx),
			conversation.AccountID,
		)
		if err != nil {
			errs.Appendf("error populating conversation owner account: %w", err)
		}
	}

	if conversation.OtherAccounts == nil {
		conversation.OtherAccounts, err = c.state.DB.GetAccountsByIDs(
			gtscontext.SetBarebones(ctx),
			conversation.OtherAccountIDs,
		)
		if err != nil {
			errs.Appendf("error populating other conversation accounts: %w", err)
		}
	}

	if conversation.LastStatus == nil && conversation.LastStatusID != "" {
		conversation.LastStatus, err = c.state.DB.GetStatusByID(
			gtscontext.SetBarebones(ctx),
			conversation.LastStatusID,
		)
		if err != nil {
			errs.Appendf("error populating conversation last status: %w", err)
		}
	}

	return errs.Combine()
}

func (c *conversationDB) GetConversationsByOwnerAccountID(ctx context.Context, accountID string, page *paging.Page) ([]*gtsmodel.Conversation, error) {
	conversationLastStatusIDs, err := c.getAccountConversationLastStatusIDs(ctx, accountID, page)
	if err != nil {
		return nil, err
	}
	return c.getConversationsByLastStatusIDs(ctx, accountID, conversationLastStatusIDs)
}

func (c *conversationDB) getAccountConversationLastStatusIDs(ctx context.Context, accountID string, page *paging.Page) ([]string, error) {
	return loadPagedIDs(&c.state.Caches.DB.ConversationLastStatusIDs, accountID, page, func() ([]string, error) {
		var conversationLastStatusIDs []string

		// Conversation last status IDs not in cache. Perform DB query.
		if _, err := c.db.
			NewSelect().
			Model((*gtsmodel.Conversation)(nil)).
			Column("last_status_id").
			Where("? = ?", bun.Ident("account_id"), accountID).
			OrderExpr("? DESC", bun.Ident("last_status_id")).
			Exec(ctx, &conversationLastStatusIDs); // nocollapse
		err != nil && !errors.Is(err, db.ErrNoEntries) {
			return nil, err
		}

		return conversationLastStatusIDs, nil
	})
}

func (c *conversationDB) getConversationsByLastStatusIDs(
	ctx context.Context,
	accountID string,
	conversationLastStatusIDs []string,
) ([]*gtsmodel.Conversation, error) {
	// Load all conversation IDs via cache loader callbacks.
	conversations, err := c.state.Caches.DB.Conversation.LoadIDs2Part(
		"AccountID,LastStatusID",
		accountID,
		conversationLastStatusIDs,
		func(accountID string, uncached []string) ([]*gtsmodel.Conversation, error) {
			// Preallocate expected length of uncached conversations.
			conversations := make([]*gtsmodel.Conversation, 0, len(uncached))

			// Perform database query scanning the remaining (uncached) IDs.
			if err := c.db.NewSelect().
				Model(&conversations).
				Where("? = ?", bun.Ident("account_id"), accountID).
				Where("? IN (?)", bun.Ident("last_status_id"), bun.In(uncached)).
				Scan(ctx); err != nil {
				return nil, err
			}

			return conversations, nil
		},
	)
	if err != nil {
		return nil, err
	}

	// Reorder the conversations by their last status IDs to ensure correct order.
	getID := func(b *gtsmodel.Conversation) string { return b.ID }
	xslices.OrderBy(conversations, conversationLastStatusIDs, getID)

	if gtscontext.Barebones(ctx) {
		// no need to fully populate.
		return conversations, nil
	}

	// Populate all loaded conversations, removing those we fail to populate.
	conversations = slices.DeleteFunc(conversations, func(conversation *gtsmodel.Conversation) bool {
		if err := c.populateConversation(ctx, conversation); err != nil {
			log.Errorf(ctx, "error populating conversation %s: %v", conversation.ID, err)
			return true
		}
		return false
	})

	return conversations, nil
}

func (c *conversationDB) UpsertConversation(ctx context.Context, conversation *gtsmodel.Conversation, columns ...string) error {
	// If we're updating by column, ensure "updated_at" is included.
	if len(columns) > 0 {
		columns = append(columns, "updated_at")
	}

	return c.state.Caches.DB.Conversation.Store(conversation, func() error {
		_, err := NewUpsert(c.db).
			Model(conversation).
			Constraint("id").
			Column(columns...).
			Exec(ctx)
		return err
	})
}

func (c *conversationDB) LinkConversationToStatus(ctx context.Context, conversationID string, statusID string) error {
	conversationToStatus := &gtsmodel.ConversationToStatus{
		ConversationID: conversationID,
		StatusID:       statusID,
	}

	if _, err := c.db.NewInsert().
		Model(conversationToStatus).
		Exec(ctx); // nocollapse
	err != nil {
		return err
	}
	return nil
}

func (c *conversationDB) DeleteConversationByID(ctx context.Context, id string) error {
	// Gather necessary fields from
	// deleted for cache invaliation.
	var deleted gtsmodel.Conversation
	deleted.ID = id

	// Delete conversation from DB.
	if _, err := c.db.NewDelete().
		Model(&deleted).
		Where("? = ?", bun.Ident("id"), id).
		Returning("?", bun.Ident("account_id")).
		Exec(ctx); err != nil &&
		!errors.Is(err, db.ErrNoEntries) {
		return err
	}

	// Invalidate cached conversation by ID,
	// manually invalidate hook in case not cached.
	c.state.Caches.DB.Conversation.Invalidate("ID", id)
	c.state.Caches.OnInvalidateConversation(&deleted)

	return nil
}

func (c *conversationDB) DeleteConversationsByOwnerAccountID(ctx context.Context, accountID string) error {
	defer func() {
		// Invalidate any cached conversations and conversation IDs owned by this account on return.
		// Conversation invalidate hooks only invalidate the conversation ID cache,
		// so we don't need to load all conversations into the cache to run invalidation hooks,
		// as with some other object types (blocks, for example).
		c.state.Caches.DB.Conversation.Invalidate("AccountID", accountID)
		// In case there were no cached conversations,
		// explicitly invalidate the user's conversation last status ID cache.
		c.state.Caches.DB.ConversationLastStatusIDs.Invalidate(accountID)
	}()

	return c.db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
		// Delete conversations matching the account ID.
		deletedConversationIDs := []string{}
		if err := tx.NewDelete().
			Model((*gtsmodel.Conversation)(nil)).
			Where("? = ?", bun.Ident("account_id"), accountID).
			Returning("?", bun.Ident("id")).
			Scan(ctx, &deletedConversationIDs); // nocollapse
		err != nil {
			return gtserror.Newf("error deleting conversations for account %s: %w", accountID, err)
		}

		if len(deletedConversationIDs) == 0 {
			// Nothing
			// to delete.
			return nil
		}

		// Delete any conversation-to-status links
		// matching the deleted conversation IDs.
		if _, err := tx.NewDelete().
			Model((*gtsmodel.ConversationToStatus)(nil)).
			Where("? IN (?)", bun.Ident("conversation_id"), bun.In(deletedConversationIDs)).
			Exec(ctx); // nocollapse
		err != nil {
			return gtserror.Newf("error deleting conversation-to-status links for account %s: %w", accountID, err)
		}

		return nil
	})
}

func (c *conversationDB) DeleteStatusFromConversations(ctx context.Context, statusID string) error {
	var (
		updatedConversationIDs = []string{}
		deletedConversationIDs = []string{}

		// Method of creating + dropping temp
		// tables differs depending on driver.
		tmpQ string
	)

	if c.db.Dialect().Name() == dialect.PG {
		// On Postgres, we can instruct PG to clean
		// up temp tables on commit, so we can just
		// use any connection from the pool without
		// caring what happens to it when we're done.
		tmpQ = "CREATE TEMPORARY TABLE ? ON COMMIT DROP AS (?)"
	} else {
		// On SQLite, we can't instruct SQLite to drop
		// temp tables on commit, and we can't manually
		// drop temp tables without triggering a bug.
		// So we leave the temp tables alone, in the
		// knowledge they'll be cleaned up when this
		// connection gets recycled (in max 5min).
		tmpQ = "CREATE TEMPORARY TABLE ? AS ?"
	}

	if err := c.db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
		// First delete this status from
		// conversation-to-status links.
		_, err := tx.
			NewDelete().
			Table("conversation_to_statuses").
			Where("? = ?", bun.Ident("status_id"), statusID).
			Exec(ctx)
		if err != nil {
			return gtserror.Newf(
				"error deleting conversation-to-status links while deleting status %s: %w",
				statusID, err,
			)
		}

		// Note: Bun doesn't currently support `CREATE TABLE … AS SELECT …`
		// so we need to use raw queries to create temporary tables.

		// Create a temporary table containing all statuses other than
		// the deleted status, in each conversation for which the deleted
		// status is the last status, if there are such statuses.
		//
		// This will produce a query like:
		//
		//	CREATE TEMPORARY TABLE "conversation_statuses_01J78T2AR0YCZ4YR12WSCZ608S"
		//	  AS (
		//	    SELECT
		//	      "conversations"."id" AS "conversation_id",
		//	      "conversation_to_statuses"."status_id" AS "id",
		//	      "statuses"."created_at"
		//	    FROM
		//	      "conversations"
		//	      LEFT JOIN "conversation_to_statuses" ON (
		//	        "conversations"."id" = "conversation_to_statuses"."conversation_id"
		//	      )
		//	      AND (
		//	        "conversation_to_statuses"."status_id" != '01J78T2BQ4TN5S2XSC9VNQ5GBS'
		//	      )
		//	      LEFT JOIN "statuses" ON (
		//	        "conversation_to_statuses"."status_id" = "statuses"."id"
		//	      )
		//	    WHERE
		//	      (
		//	        "conversations"."last_status_id" = '01J78T2BQ4TN5S2XSC9VNQ5GBS'
		//	      )
		//	  )
		conversationStatusesTmp := "conversation_statuses_" + id.NewULID()
		conversationStatusesTmpQ := tx.NewRaw(
			tmpQ,
			bun.Ident(conversationStatusesTmp),
			tx.NewSelect().
				ColumnExpr(
					"? AS ?",
					bun.Ident("conversations.id"),
					bun.Ident("conversation_id"),
				).
				ColumnExpr(
					"? AS ?",
					bun.Ident("conversation_to_statuses.status_id"),
					bun.Ident("id"),
				).
				Column("statuses.created_at").
				Table("conversations").
				Join("LEFT JOIN ?", bun.Ident("conversation_to_statuses")).
				JoinOn(
					"? = ?",
					bun.Ident("conversations.id"),
					bun.Ident("conversation_to_statuses.conversation_id"),
				).
				JoinOn(
					"? != ?",
					bun.Ident("conversation_to_statuses.status_id"),
					statusID,
				).
				Join("LEFT JOIN ?", bun.Ident("statuses")).
				JoinOn(
					"? = ?",
					bun.Ident("conversation_to_statuses.status_id"),
					bun.Ident("statuses.id"),
				).
				Where(
					"? = ?",
					bun.Ident("conversations.last_status_id"),
					statusID,
				),
		)
		_, err = conversationStatusesTmpQ.Exec(ctx)
		if err != nil {
			return gtserror.Newf(
				"error creating temp table %s while deleting status %s: %w",
				conversationStatusesTmp, statusID, err,
			)
		}

		// Create a temporary table with the most recently created
		// status in each conversation for which the deleted status
		// is the last status, if there is such a status.
		//
		// This will produce a query like:
		//
		//	CREATE TEMPORARY TABLE "latest_conversation_statuses_01J78T2AR0E46SJSH6C7NRZ7MR"
		//	  AS (
		//	    SELECT
		//	      "conversation_statuses"."conversation_id",
		//	      "conversation_statuses"."id"
		//	    FROM
		//	      "conversation_statuses_01J78T2AR0YCZ4YR12WSCZ608S" AS "conversation_statuses"
		//	      LEFT JOIN "conversation_statuses_01J78T2AR0YCZ4YR12WSCZ608S" AS "later_statuses" ON (
		//	        "conversation_statuses"."conversation_id" = "later_statuses"."conversation_id"
		//	      )
		//	      AND (
		//	        "later_statuses"."created_at" > "conversation_statuses"."created_at"
		//	      )
		//	    WHERE
		//	      ("later_statuses"."id" IS NULL)
		//	  )
		latestConversationStatusesTmp := "latest_conversation_statuses_" + id.NewULID()
		latestConversationStatusesTmpQ := tx.NewRaw(
			tmpQ,
			bun.Ident(latestConversationStatusesTmp),
			tx.NewSelect().
				Column(
					"conversation_statuses.conversation_id",
					"conversation_statuses.id",
				).
				TableExpr(
					"? AS ?",
					bun.Ident(conversationStatusesTmp),
					bun.Ident("conversation_statuses"),
				).
				Join(
					"LEFT JOIN ? AS ?",
					bun.Ident(conversationStatusesTmp),
					bun.Ident("later_statuses"),
				).
				JoinOn(
					"? = ?",
					bun.Ident("conversation_statuses.conversation_id"),
					bun.Ident("later_statuses.conversation_id"),
				).
				JoinOn(
					"? > ?",
					bun.Ident("later_statuses.created_at"),
					bun.Ident("conversation_statuses.created_at"),
				).
				Where("? IS NULL", bun.Ident("later_statuses.id")),
		)
		_, err = latestConversationStatusesTmpQ.Exec(ctx)
		if err != nil {
			return gtserror.Newf(
				"error creating temp table %s while deleting status %s: %w",
				conversationStatusesTmp, statusID, err,
			)
		}

		// For every conversation where the given status was the last one,
		// reset its last status to the most recently created in the
		// conversation other than that one, if there is such a status.
		// Return conversation IDs for invalidation.
		updateQ := tx.NewUpdate().
			Table("conversations").
			TableExpr("? AS ?", bun.Ident(latestConversationStatusesTmp), bun.Ident("latest_conversation_statuses")).
			Set("? = ?", bun.Ident("last_status_id"), bun.Ident("latest_conversation_statuses.id")).
			Set("? = ?", bun.Ident("updated_at"), time.Now()).
			Where("? = ?", bun.Ident("conversations.id"), bun.Ident("latest_conversation_statuses.conversation_id")).
			Where("? IS NOT NULL", bun.Ident("latest_conversation_statuses.id")).
			Returning("?", bun.Ident("conversations.id"))
		_, err = updateQ.Exec(ctx, &updatedConversationIDs)
		if err != nil {
			return gtserror.Newf(
				"error rolling back last status for conversation while deleting status %s: %w",
				statusID, err,
			)
		}

		// If there is no such status,
		// just delete the conversation.
		// Return IDs for invalidation.
		_, err = tx.
			NewDelete().
			Table("conversations").
			Where(
				"? IN (?)",
				bun.Ident("id"),
				tx.NewSelect().
					Table(latestConversationStatusesTmp).
					Column("conversation_id").
					Where("? IS NULL", bun.Ident("id")),
			).
			Returning("?", bun.Ident("id")).
			Exec(ctx, &deletedConversationIDs)
		if err != nil {
			return gtserror.Newf(
				"error deleting conversation while deleting status %s: %w",
				statusID, err,
			)
		}

		return nil
	}); err != nil {
		return err
	}

	// Invalidate cache entries.
	updatedConversationIDs = append(updatedConversationIDs, deletedConversationIDs...)
	updatedConversationIDs = xslices.Deduplicate(updatedConversationIDs)
	c.state.Caches.DB.Conversation.InvalidateIDs("ID", updatedConversationIDs)

	return nil
}