/*
   GoToSocial
   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org

   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 db

import (
	"context"
	"fmt"
	"strings"

	"github.com/go-fed/activity/pub"
	"github.com/gotosocial/gotosocial/internal/config"
	"github.com/gotosocial/gotosocial/internal/db/model"
	"github.com/gotosocial/gotosocial/pkg/mastotypes"
	"github.com/sirupsen/logrus"
)

const dbTypePostgres string = "POSTGRES"

// ErrNoEntries is to be returned from the DB interface when no entries are found for a given query.
type ErrNoEntries struct{}

func (e ErrNoEntries) Error() string {
	return "no entries"
}

// DB provides methods for interacting with an underlying database or other storage mechanism (for now, just postgres).
// Note that in all of the functions below, the passed interface should be a pointer or a slice, which will then be populated
// by whatever is returned from the database.
type DB interface {
	// Federation returns an interface that's compatible with go-fed, for performing federation storage/retrieval functions.
	// See: https://pkg.go.dev/github.com/go-fed/activity@v1.0.0/pub?utm_source=gopls#Database
	Federation() pub.Database

	/*
		BASIC DB FUNCTIONALITY
	*/

	// CreateTable creates a table for the given interface.
	// For implementations that don't use tables, this can just return nil.
	CreateTable(i interface{}) error

	// DropTable drops the table for the given interface.
	// For implementations that don't use tables, this can just return nil.
	DropTable(i interface{}) error

	// Stop should stop and close the database connection cleanly, returning an error if this is not possible.
	// If the database implementation doesn't need to be stopped, this can just return nil.
	Stop(ctx context.Context) error

	// IsHealthy should return nil if the database connection is healthy, or an error if not.
	IsHealthy(ctx context.Context) error

	// GetByID gets one entry by its id. In a database like postgres, this might be the 'id' field of the entry,
	// for other implementations (for example, in-memory) it might just be the key of a map.
	// The given interface i will be set to the result of the query, whatever it is. Use a pointer or a slice.
	// In case of no entries, a 'no entries' error will be returned
	GetByID(id string, i interface{}) error

	// GetWhere gets one entry where key = value. This is similar to GetByID but allows the caller to specify the
	// name of the key to select from.
	// The given interface i will be set to the result of the query, whatever it is. Use a pointer or a slice.
	// In case of no entries, a 'no entries' error will be returned
	GetWhere(key string, value interface{}, i interface{}) error

	// GetAll will try to get all entries of type i.
	// The given interface i will be set to the result of the query, whatever it is. Use a pointer or a slice.
	// In case of no entries, a 'no entries' error will be returned
	GetAll(i interface{}) error

	// Put simply stores i. It is up to the implementation to figure out how to store it, and using what key.
	// The given interface i will be set to the result of the query, whatever it is. Use a pointer or a slice.
	Put(i interface{}) error

	// UpdateByID updates i with id id.
	// The given interface i will be set to the result of the query, whatever it is. Use a pointer or a slice.
	UpdateByID(id string, i interface{}) error

	// DeleteByID removes i with id id.
	// If i didn't exist anyway, then no error should be returned.
	DeleteByID(id string, i interface{}) error

	// DeleteWhere deletes i where key = value
	// If i didn't exist anyway, then no error should be returned.
	DeleteWhere(key string, value interface{}, i interface{}) error

	/*
		HANDY SHORTCUTS
	*/

	// GetAccountByUserID is a shortcut for the common action of fetching an account corresponding to a user ID.
	// The given account pointer will be set to the result of the query, whatever it is.
	// In case of no entries, a 'no entries' error will be returned
	GetAccountByUserID(userID string, account *model.Account) error

	// GetFollowingByAccountID is a shortcut for the common action of fetching a list of accounts that accountID is following.
	// The given slice 'following' will be set to the result of the query, whatever it is.
	// In case of no entries, a 'no entries' error will be returned
	GetFollowingByAccountID(accountID string, following *[]model.Follow) error

	// GetFollowersByAccountID is a shortcut for the common action of fetching a list of accounts that accountID is followed by.
	// The given slice 'followers' will be set to the result of the query, whatever it is.
	// In case of no entries, a 'no entries' error will be returned
	GetFollowersByAccountID(accountID string, followers *[]model.Follow) error

	// GetStatusesByAccountID is a shortcut for the common action of fetching a list of statuses produced by accountID.
	// The given slice 'statuses' will be set to the result of the query, whatever it is.
	// In case of no entries, a 'no entries' error will be returned
	GetStatusesByAccountID(accountID string, statuses *[]model.Status) error

	// GetStatusesByTimeDescending is a shortcut for getting the most recent statuses. accountID is optional, if not provided
	// then all statuses will be returned. If limit is set to 0, the size of the returned slice will not be limited. This can
	// be very memory intensive so you probably shouldn't do this!
	// In case of no entries, a 'no entries' error will be returned
	GetStatusesByTimeDescending(accountID string, statuses *[]model.Status, limit int) error

	// GetLastStatusForAccountID simply gets the most recent status by the given account.
	// The given slice 'status' pointer will be set to the result of the query, whatever it is.
	// In case of no entries, a 'no entries' error will be returned
	GetLastStatusForAccountID(accountID string, status *model.Status) error

	// IsUsernameAvailable checks whether a given username is available on our domain.
	// Returns an error if the username is already taken, or something went wrong in the db.
	IsUsernameAvailable(username string) error

	// IsEmailAvailable checks whether a given email address for a user is available on our domain.
	// Returns an error if the email is already associated with an account, or something went wrong in the db.
	IsEmailAvailable(email string) error

	/*
		USEFUL CONVERSION FUNCTIONS
	*/

	// AccountToMastoSensitive takes a db model account as a param, and returns a populated mastotype account, or an error
	// if something goes wrong. The returned account should be ready to serialize on an API level, and may have sensitive fields,
	// so serve it only to an authorized user who should have permission to see it.
	AccountToMastoSensitive(account *model.Account) (*mastotypes.Account, error)
}

// New returns a new database service that satisfies the DB interface and, by extension,
// the go-fed database interface described here: https://github.com/go-fed/activity/blob/master/pub/database.go
func New(ctx context.Context, c *config.Config, log *logrus.Logger) (DB, error) {
	switch strings.ToUpper(c.DBConfig.Type) {
	case dbTypePostgres:
		return newPostgresService(ctx, c, log.WithField("service", "db"))
	default:
		return nil, fmt.Errorf("database type %s not supported", c.DBConfig.Type)
	}
}