package sqlite

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"path/filepath"
	"sync"
	"time"

	"github.com/aarondl/opt/omit"
	migrate "github.com/rubenv/sql-migrate"
	"github.com/safing/portmaster/base/database/accessor"
	"github.com/safing/portmaster/base/database/iterator"
	"github.com/safing/portmaster/base/database/query"
	"github.com/safing/portmaster/base/database/record"
	"github.com/safing/portmaster/base/database/storage"
	"github.com/safing/portmaster/base/database/storage/sqlite/models"
	"github.com/safing/portmaster/base/log"
	"github.com/safing/structures/dsd"
	"github.com/stephenafamo/bob"
	"github.com/stephenafamo/bob/dialect/sqlite"
	"github.com/stephenafamo/bob/dialect/sqlite/im"
	"github.com/stephenafamo/bob/dialect/sqlite/um"

	_ "modernc.org/sqlite"
)

// SQLite storage.
type SQLite struct {
	name string

	db   *sql.DB
	bob  bob.DB
	lock sync.RWMutex

	ctx       context.Context
	cancelCtx context.CancelFunc
}

func init() {
	_ = storage.Register("sqlite", func(name, location string) (storage.Interface, error) {
		return NewSQLite(name, location)
	})
}

// NewSQLite creates a sqlite database.
func NewSQLite(name, location string) (*SQLite, error) {
	dbFile := filepath.Join(location, "db.sqlite")

	// Open database file.
	db, err := sql.Open("sqlite", dbFile)
	if err != nil {
		return nil, fmt.Errorf("open sqlite: %w", err)
	}

	// Run migrations on database.
	n, err := migrate.Exec(db, "sqlite3", getMigrations(), migrate.Up)
	if err != nil {
		return nil, fmt.Errorf("migrate sqlite: %w", err)
	}
	log.Debugf("database/sqlite: ran %d migrations on %s database", n, name)

	// Return as bob database.
	ctx, cancelCtx := context.WithCancel(context.Background())
	return &SQLite{
		name:      name,
		bob:       bob.NewDB(db),
		ctx:       ctx,
		cancelCtx: cancelCtx,
	}, nil
}

// Get returns a database record.
func (db *SQLite) Get(key string) (record.Record, error) {
	db.lock.RLock()
	defer db.lock.RUnlock()

	// Get record from database.
	r, err := models.FindRecord(db.ctx, db.bob, key)
	if err != nil {
		return nil, fmt.Errorf("%w: %s", storage.ErrNotFound, err)
	}

	// Return data in wrapper.
	return record.NewWrapperFromDatabase(db.name, key, getMeta(r), uint8(r.Format), r.Value)
}

// GetMeta returns the metadata of a database record.
func (db *SQLite) GetMeta(key string) (*record.Meta, error) {
	r, err := db.Get(key)
	if err != nil {
		return nil, err
	}

	return r.Meta(), nil
}

// Put stores a record in the database.
func (db *SQLite) Put(r record.Record) (record.Record, error) {
	return db.putRecord(r, nil)
}

func (db *SQLite) putRecord(r record.Record, tx *bob.Tx) (record.Record, error) {
	// Lock record if in a transaction.
	if tx != nil {
		r.Lock()
		defer r.Unlock()
	}

	// Serialize to JSON.
	data, err := r.MarshalDataOnly(r, dsd.JSON)
	if err != nil {
		return nil, err
	}

	// Create structure for insert.
	m := r.Meta()
	setter := models.RecordSetter{
		Key:        omit.From(r.DatabaseKey()),
		Format:     omit.From(int16(dsd.JSON)),
		Value:      omit.From(data),
		Created:    omit.From(m.Created),
		Modified:   omit.From(m.Modified),
		Expires:    omit.From(m.Expires),
		Deleted:    omit.From(m.Deleted),
		Secret:     omit.From(m.IsSecret()),
		Crownjewel: omit.From(m.IsCrownJewel()),
	}

	// Lock for writing.
	db.lock.Lock()
	defer db.lock.Unlock()

	// Simulate upsert with custom selection on conflict.
	dbQuery := models.Records.Insert(
		&setter,
		im.OnConflict("key").DoUpdate(
			im.SetExcluded("format", "value", "created", "modified", "expires", "deleted", "secret", "crownjewel"),
		),
	)

	// Execute in transaction or directly.
	if tx != nil {
		_, err = dbQuery.Exec(db.ctx, tx)
	} else {
		_, err = dbQuery.Exec(db.ctx, db.bob)
	}
	if err != nil {
		return nil, err
	}

	return r, nil
}

// PutMany stores many records in the database.
func (db *SQLite) PutMany(shadowDelete bool) (chan<- record.Record, <-chan error) {
	db.lock.Lock()
	defer db.lock.Unlock()
	// we could lock for every record, but we want to have the same behaviour
	// as the other storage backends, especially for testing.

	batch := make(chan record.Record, 100)
	errs := make(chan error, 1)

	tx, err := db.bob.BeginTx(db.ctx, nil)
	if err != nil {
		errs <- err
		return batch, errs
	}

	// start handler
	go func() {
		// Read all put records.
	writeBatch:
		for {
			select {
			case r := <-batch:
				if r != nil {
					// Write record.
					_, err := db.putRecord(r, &tx)
					if err != nil {
						errs <- err
						break writeBatch
					}
				} else {
					// Finalize transcation.
					errs <- tx.Commit()
					return
				}

			case <-db.ctx.Done():
				break writeBatch
			}
		}

		// Rollback transaction.
		errs <- tx.Rollback()
	}()

	return batch, errs
}

// Delete deletes a record from the database.
func (db *SQLite) Delete(key string) error {
	// Lock for writing.
	db.lock.Lock()
	defer db.lock.Unlock()

	toDelete := &models.Record{Key: key}
	return toDelete.Delete(db.ctx, db.bob)
}

// Query returns a an iterator for the supplied query.
func (db *SQLite) Query(q *query.Query, local, internal bool) (*iterator.Iterator, error) {
	_, err := q.Check()
	if err != nil {
		return nil, fmt.Errorf("invalid query: %w", err)
	}

	queryIter := iterator.New()

	go db.queryExecutor(queryIter, q, local, internal)
	return queryIter, nil
}

func (db *SQLite) queryExecutor(queryIter *iterator.Iterator, q *query.Query, local, internal bool) {
	// Build query.
	var recordQuery *sqlite.ViewQuery[*models.Record, models.RecordSlice]
	if q.DatabaseKeyPrefix() != "" {
		recordQuery = models.Records.View.Query(
			models.SelectWhere.Records.Key.Like(q.DatabaseKeyPrefix() + "%"),
		)
	} else {
		recordQuery = models.Records.View.Query()
	}

	// Get cursor to go over all records in the query.
	db.lock.RLock()
	cursor, err := models.RecordsQuery.Cursor(recordQuery, db.ctx, db.bob)
	db.lock.RUnlock()
	if err != nil {
		queryIter.Finish(err)
		return
	}
	defer cursor.Close()

recordsLoop:
	for cursor.Next() {
		// Get next record
		r, cErr := cursor.Get()
		if cErr != nil {
			err = fmt.Errorf("cursor error: %w", cErr)
			break recordsLoop
		}

		// Check if key matches.
		if !q.MatchesKey(r.Key) {
			continue recordsLoop
		}

		// Check Meta.
		m := getMeta(r)
		if !m.CheckValidity() ||
			!m.CheckPermission(local, internal) {
			continue recordsLoop
		}

		// Check Data.
		if q.HasWhereCondition() {
			jsonData := string(r.Value)
			jsonAccess := accessor.NewJSONAccessor(&jsonData)
			if !q.MatchesAccessor(jsonAccess) {
				continue recordsLoop
			}
		}

		// Build database record.
		matched, _ := record.NewWrapperFromDatabase(db.name, r.Key, m, uint8(r.Format), r.Value)

		select {
		case <-queryIter.Done:
			break recordsLoop
		case queryIter.Next <- matched:
		default:
			select {
			case <-queryIter.Done:
				break recordsLoop
			case queryIter.Next <- matched:
			case <-time.After(1 * time.Second):
				err = errors.New("query timeout")
				break recordsLoop
			}
		}

	}

	queryIter.Finish(err)
}

// Purge deletes all records that match the given query. It returns the number of successful deletes and an error.
func (db *SQLite) Purge(ctx context.Context, q *query.Query, local, internal, shadowDelete bool) (int, error) {
	// Optimize for local and internal queries without where clause.
	if local && internal && !shadowDelete && !q.HasWhereCondition() {
		db.lock.Lock()
		defer db.lock.Unlock()

		// First count entries (SQLite does not support affected rows)
		n, err := models.Records.Query(
			models.SelectWhere.Records.Key.Like(q.DatabaseKeyPrefix()+"%"),
		).Count(db.ctx, db.bob)
		if err != nil || n == 0 {
			return int(n), err
		}

		// Delete entries.
		_, err = models.Records.Delete(
			models.DeleteWhere.Records.Key.Like(q.DatabaseKeyPrefix()+"%"),
		).Exec(db.ctx, db.bob)
		return int(n), err
	}

	// Otherwise, iterate over all entries and delete matching ones.

	// Create iterator to check all matching records.
	queryIter := iterator.New()
	defer queryIter.Cancel()
	go db.queryExecutor(queryIter, q, local, internal)

	// Delete all matching records.
	var deleted int
	for r := range queryIter.Next {
		db.Delete(r.DatabaseKey())
		deleted++
	}

	return deleted, nil
}

// ReadOnly returns whether the database is read only.
func (db *SQLite) ReadOnly() bool {
	return false
}

// Injected returns whether the database is injected.
func (db *SQLite) Injected() bool {
	return false
}

// MaintainRecordStates maintains records states in the database.
func (db *SQLite) MaintainRecordStates(ctx context.Context, purgeDeletedBefore time.Time, shadowDelete bool) error {
	db.lock.Lock()
	defer db.lock.Unlock()

	now := time.Now().Unix()
	purgeThreshold := purgeDeletedBefore.Unix()

	// Option 1: Using shadow delete.
	if shadowDelete {
		// Mark expired records as deleted.
		models.Records.Update(
			um.SetCol("deleted").ToArg(now),
			models.UpdateWhere.Records.Deleted.EQ(0),
			models.UpdateWhere.Records.Expires.GT(0),
			models.UpdateWhere.Records.Expires.LT(now),
		).Exec(db.ctx, db.bob)

		// Purge deleted records before threshold.
		models.Records.Delete(
			models.DeleteWhere.Records.Deleted.GT(0),
			models.DeleteWhere.Records.Deleted.LT(purgeThreshold),
		).Exec(db.ctx, db.bob)
		return nil
	}

	// Option 2: Immediate delete.

	// Delete expired record.
	models.Records.Delete(
		models.DeleteWhere.Records.Expires.GT(0),
		models.DeleteWhere.Records.Expires.LT(now),
	).Exec(db.ctx, db.bob)
	// Delete shadow deleted records.
	models.Records.Delete(
		models.DeleteWhere.Records.Deleted.GT(0),
	).Exec(db.ctx, db.bob)

	return nil
}

func (db *SQLite) Maintain(ctx context.Context) error {
	db.lock.Lock()
	defer db.lock.Unlock()

	// Remove up to about 100KB of SQLite pages from the freelist on every run.
	// (Assuming 4KB page size.)
	_, err := db.db.ExecContext(ctx, "PRAGMA incremental_vacuum(25);")
	return err
}

func (db *SQLite) MaintainThorough(ctx context.Context) error {
	db.lock.Lock()
	defer db.lock.Unlock()

	// Remove all pages from the freelist.
	_, err := db.db.ExecContext(ctx, "PRAGMA incremental_vacuum;")
	return err
}

// Shutdown shuts down the database.
func (db *SQLite) Shutdown() error {
	db.lock.Lock()
	defer db.lock.Unlock()
	db.cancelCtx()

	return db.bob.Close()
}