/*
   GoToSocial
   Copyright (C) 2021-2022 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 oauth

import (
	"context"
	"errors"
	"fmt"
	"time"

	"github.com/superseriousbusiness/gotosocial/internal/db"
	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
	"github.com/superseriousbusiness/gotosocial/internal/id"
	"github.com/superseriousbusiness/gotosocial/internal/log"
	"github.com/superseriousbusiness/oauth2/v4"
	"github.com/superseriousbusiness/oauth2/v4/models"
)

// tokenStore is an implementation of oauth2.TokenStore, which uses our db interface as a storage backend.
type tokenStore struct {
	oauth2.TokenStore
	db db.Basic
}

// newTokenStore returns a token store that satisfies the oauth2.TokenStore interface.
//
// In order to allow tokens to 'expire', it will also set off a goroutine that iterates through
// the tokens in the DB once per minute and deletes any that have expired.
func newTokenStore(ctx context.Context, db db.Basic) oauth2.TokenStore {
	ts := &tokenStore{
		db: db,
	}

	// set the token store to clean out expired tokens once per minute, or return if we're done
	go func(ctx context.Context, ts *tokenStore) {
	cleanloop:
		for {
			select {
			case <-ctx.Done():
				log.Info("breaking cleanloop")
				break cleanloop
			case <-time.After(1 * time.Minute):
				log.Trace("sweeping out old oauth entries broom broom")
				if err := ts.sweep(ctx); err != nil {
					log.Errorf("error while sweeping oauth entries: %s", err)
				}
			}
		}
	}(ctx, ts)
	return ts
}

// sweep clears out old tokens that have expired; it should be run on a loop about once per minute or so.
func (ts *tokenStore) sweep(ctx context.Context) error {
	// select *all* tokens from the db
	// todo: if this becomes expensive (ie., there are fucking LOADS of tokens) then figure out a better way.
	tokens := new([]*gtsmodel.Token)
	if err := ts.db.GetAll(ctx, tokens); err != nil {
		return err
	}

	// iterate through and remove expired tokens
	now := time.Now()
	for _, dbt := range *tokens {
		// The zero value of a time.Time is 00:00 january 1 1970, which will always be before now. So:
		// we only want to check if a token expired before now if the expiry time is *not zero*;
		// ie., if it's been explicity set.
		if !dbt.CodeExpiresAt.IsZero() && dbt.CodeExpiresAt.Before(now) || !dbt.RefreshExpiresAt.IsZero() && dbt.RefreshExpiresAt.Before(now) || !dbt.AccessExpiresAt.IsZero() && dbt.AccessExpiresAt.Before(now) {
			if err := ts.db.DeleteByID(ctx, dbt.ID, dbt); err != nil {
				return err
			}
		}
	}

	return nil
}

// Create creates and store the new token information.
// For the original implementation, see https://github.com/superseriousbusiness/oauth2/blob/master/store/token.go#L34
func (ts *tokenStore) Create(ctx context.Context, info oauth2.TokenInfo) error {
	t, ok := info.(*models.Token)
	if !ok {
		return errors.New("info param was not a models.Token")
	}

	dbt := TokenToDBToken(t)
	if dbt.ID == "" {
		dbtID, err := id.NewRandomULID()
		if err != nil {
			return err
		}
		dbt.ID = dbtID
	}

	if err := ts.db.Put(ctx, dbt); err != nil {
		return fmt.Errorf("error in tokenstore create: %s", err)
	}
	return nil
}

// RemoveByCode deletes a token from the DB based on the Code field
func (ts *tokenStore) RemoveByCode(ctx context.Context, code string) error {
	return ts.db.DeleteWhere(ctx, []db.Where{{Key: "code", Value: code}}, &gtsmodel.Token{})
}

// RemoveByAccess deletes a token from the DB based on the Access field
func (ts *tokenStore) RemoveByAccess(ctx context.Context, access string) error {
	return ts.db.DeleteWhere(ctx, []db.Where{{Key: "access", Value: access}}, &gtsmodel.Token{})
}

// RemoveByRefresh deletes a token from the DB based on the Refresh field
func (ts *tokenStore) RemoveByRefresh(ctx context.Context, refresh string) error {
	return ts.db.DeleteWhere(ctx, []db.Where{{Key: "refresh", Value: refresh}}, &gtsmodel.Token{})
}

// GetByCode selects a token from the DB based on the Code field
func (ts *tokenStore) GetByCode(ctx context.Context, code string) (oauth2.TokenInfo, error) {
	if code == "" {
		return nil, nil
	}
	dbt := &gtsmodel.Token{
		Code: code,
	}
	if err := ts.db.GetWhere(ctx, []db.Where{{Key: "code", Value: code}}, dbt); err != nil {
		return nil, err
	}
	return DBTokenToToken(dbt), nil
}

// GetByAccess selects a token from the DB based on the Access field
func (ts *tokenStore) GetByAccess(ctx context.Context, access string) (oauth2.TokenInfo, error) {
	if access == "" {
		return nil, nil
	}
	dbt := &gtsmodel.Token{
		Access: access,
	}
	if err := ts.db.GetWhere(ctx, []db.Where{{Key: "access", Value: access}}, dbt); err != nil {
		return nil, err
	}
	return DBTokenToToken(dbt), nil
}

// GetByRefresh selects a token from the DB based on the Refresh field
func (ts *tokenStore) GetByRefresh(ctx context.Context, refresh string) (oauth2.TokenInfo, error) {
	if refresh == "" {
		return nil, nil
	}
	dbt := &gtsmodel.Token{
		Refresh: refresh,
	}
	if err := ts.db.GetWhere(ctx, []db.Where{{Key: "refresh", Value: refresh}}, dbt); err != nil {
		return nil, err
	}
	return DBTokenToToken(dbt), nil
}

/*
	The following models are basically helpers for the token store implementation, they should only be used internally.
*/

// TokenToDBToken is a lil util function that takes a gotosocial token and gives back a token for inserting into a database.
func TokenToDBToken(tkn *models.Token) *gtsmodel.Token {
	now := time.Now()

	// For the following, we want to make sure we're not adding a time.Now() to an *empty* ExpiresIn, otherwise that's
	// going to cause all sorts of interesting problems. So check first to make sure that the ExpiresIn is not equal
	// to the zero value of a time.Duration, which is 0s. If it *is* empty/nil, just leave the ExpiresAt at nil as well.

	cea := time.Time{}
	if tkn.CodeExpiresIn != 0*time.Second {
		cea = now.Add(tkn.CodeExpiresIn)
	}

	aea := time.Time{}
	if tkn.AccessExpiresIn != 0*time.Second {
		aea = now.Add(tkn.AccessExpiresIn)
	}

	rea := time.Time{}
	if tkn.RefreshExpiresIn != 0*time.Second {
		rea = now.Add(tkn.RefreshExpiresIn)
	}

	return &gtsmodel.Token{
		ClientID:            tkn.ClientID,
		UserID:              tkn.UserID,
		RedirectURI:         tkn.RedirectURI,
		Scope:               tkn.Scope,
		Code:                tkn.Code,
		CodeChallenge:       tkn.CodeChallenge,
		CodeChallengeMethod: tkn.CodeChallengeMethod,
		CodeCreateAt:        tkn.CodeCreateAt,
		CodeExpiresAt:       cea,
		Access:              tkn.Access,
		AccessCreateAt:      tkn.AccessCreateAt,
		AccessExpiresAt:     aea,
		Refresh:             tkn.Refresh,
		RefreshCreateAt:     tkn.RefreshCreateAt,
		RefreshExpiresAt:    rea,
	}
}

// DBTokenToToken is a lil util function that takes a database token and gives back a gotosocial token
func DBTokenToToken(dbt *gtsmodel.Token) *models.Token {
	now := time.Now()

	var codeExpiresIn time.Duration
	if !dbt.CodeExpiresAt.IsZero() {
		codeExpiresIn = dbt.CodeExpiresAt.Sub(now)
	}

	var accessExpiresIn time.Duration
	if !dbt.AccessExpiresAt.IsZero() {
		accessExpiresIn = dbt.AccessExpiresAt.Sub(now)
	}

	var refreshExpiresIn time.Duration
	if !dbt.RefreshExpiresAt.IsZero() {
		refreshExpiresIn = dbt.RefreshExpiresAt.Sub(now)
	}

	return &models.Token{
		ClientID:            dbt.ClientID,
		UserID:              dbt.UserID,
		RedirectURI:         dbt.RedirectURI,
		Scope:               dbt.Scope,
		Code:                dbt.Code,
		CodeChallenge:       dbt.CodeChallenge,
		CodeChallengeMethod: dbt.CodeChallengeMethod,
		CodeCreateAt:        dbt.CodeCreateAt,
		CodeExpiresIn:       codeExpiresIn,
		Access:              dbt.Access,
		AccessCreateAt:      dbt.AccessCreateAt,
		AccessExpiresIn:     accessExpiresIn,
		Refresh:             dbt.Refresh,
		RefreshCreateAt:     dbt.RefreshCreateAt,
		RefreshExpiresIn:    refreshExpiresIn,
	}
}