package db

import (
	"context"
	"database/sql"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"ymhut-box/server/unified-management/internal/config"
)

type Store struct {
	mu            sync.RWMutex
	cfg           *config.Config
	path          string
	db            *sql.DB
	dialect       dialect
	localDB       *sql.DB
	localDialect  dialect
	remoteDB      *sql.DB
	remoteDialect dialect
	status        DatabaseStatus
	stop          chan struct{}
}

func Open(cfg *config.Config) (*Store, error) {
	path := cfg.Database.SQLitePath
	if strings.TrimSpace(path) == "" {
		path = filepath.Join(cfg.StorageDir, "unified.sqlite")
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o750); err != nil {
		return nil, err
	}
	if err := os.MkdirAll(cfg.StorageDir, 0o750); err != nil {
		return nil, err
	}
	prototype, err := readPrototypeState(path)
	if err != nil {
		return nil, err
	}
	if prototype != nil {
		if err := backupPrototypeFile(path); err != nil {
			return nil, err
		}
	}
	localCfg := cfg.Database
	localCfg.Provider = "sqlite"
	localCfg.SQLitePath = path
	local, localDialect, err := openSQLDatabase(localCfg)
	if err != nil {
		return nil, err
	}
	local.SetMaxOpenConns(1)
	store := &Store{
		cfg:          cfg,
		path:         path,
		db:           local,
		dialect:      localDialect,
		localDB:      local,
		localDialect: localDialect,
		stop:         make(chan struct{}),
		status: DatabaseStatus{
			ActiveProvider:  "sqlite",
			ConfigProvider:  cfg.Database.Provider,
			SQLiteReady:     true,
			LastRecoveredAt: Now(),
		},
	}
	if err := store.migrate(local, localDialect); err != nil {
		_ = local.Close()
		return nil, err
	}
	if prototype != nil {
		if err := store.importPrototype(*prototype); err != nil {
			_ = local.Close()
			return nil, err
		}
	}
	if strings.EqualFold(cfg.Database.Provider, "mysql") {
		if err := store.openRemote(); err != nil {
			store.markFailover(err)
		}
	}
	go store.maintain()
	return store, nil
}

func (s *Store) Close() error {
	close(s.stop)
	s.mu.Lock()
	defer s.mu.Unlock()
	var err error
	if s.remoteDB != nil && s.remoteDB != s.localDB {
		err = s.remoteDB.Close()
	}
	if s.localDB != nil {
		if closeErr := s.localDB.Close(); err == nil {
			err = closeErr
		}
	}
	return err
}

func (s *Store) Status() DatabaseStatus {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.status
}

func (s *Store) Path() string {
	return s.path
}

func (s *Store) active() (*sql.DB, dialect) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.db, s.dialect
}

func (s *Store) exec(query string, args ...any) (sql.Result, error) {
	conn, d := s.active()
	result, err := conn.Exec(d.rebind(query), args...)
	if err != nil {
		s.markFailover(err)
		conn, d = s.active()
		if conn != nil {
			result, err = conn.Exec(d.rebind(query), args...)
		}
	}
	return result, err
}

func (s *Store) query(query string, args ...any) (*sql.Rows, error) {
	conn, d := s.active()
	rows, err := conn.Query(d.rebind(query), args...)
	if err != nil {
		s.markFailover(err)
		conn, d = s.active()
		if conn != nil {
			rows, err = conn.Query(d.rebind(query), args...)
		}
	}
	return rows, err
}

func (s *Store) queryRow(query string, args ...any) *sql.Row {
	conn, d := s.active()
	return conn.QueryRow(d.rebind(query), args...)
}

func (s *Store) insertID(query string, args ...any) (int64, error) {
	result, err := s.exec(query, args...)
	if err != nil {
		return 0, err
	}
	return result.LastInsertId()
}

func (s *Store) maintain() {
	ticker := time.NewTicker(time.Duration(s.cfg.Database.HealthIntervalSec) * time.Second)
	defer ticker.Stop()
	for {
		select {
		case <-ticker.C:
			s.checkRemote()
		case <-s.stop:
			return
		}
	}
}

func (s *Store) openRemote() error {
	if !strings.EqualFold(s.cfg.Database.Provider, "mysql") {
		return nil
	}
	remote, remoteDialect, err := openSQLDatabase(s.cfg.Database)
	if err != nil {
		return err
	}
	if err := s.migrate(remote, remoteDialect); err != nil {
		_ = remote.Close()
		return err
	}
	s.mu.Lock()
	if s.remoteDB != nil && s.remoteDB != s.localDB && s.remoteDB != remote {
		_ = s.remoteDB.Close()
	}
	s.remoteDB = remote
	s.remoteDialect = remoteDialect
	s.db = remote
	s.dialect = remoteDialect
	s.status.ActiveProvider = "mysql"
	s.status.ConfigProvider = "mysql"
	s.status.RemoteReady = true
	s.status.FailoverActive = false
	s.status.LastError = ""
	s.status.LastRecoveredAt = Now()
	s.mu.Unlock()
	return nil
}

func (s *Store) checkRemote() {
	if !strings.EqualFold(s.cfg.Database.Provider, "mysql") {
		return
	}
	s.mu.RLock()
	remote := s.remoteDB
	s.mu.RUnlock()
	if remote == nil {
		if err := s.openRemote(); err != nil {
			s.markFailover(err)
		}
		return
	}
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	err := remote.PingContext(ctx)
	cancel()
	if err != nil {
		s.markFailover(err)
		return
	}
	s.mu.Lock()
	if s.db == s.localDB {
		s.db = s.remoteDB
		s.dialect = s.remoteDialect
	}
	s.status.ActiveProvider = "mysql"
	s.status.RemoteReady = true
	s.status.FailoverActive = false
	s.status.LastError = ""
	s.status.LastRecoveredAt = Now()
	s.mu.Unlock()
}

func (s *Store) markFailover(err error) {
	if err == nil || !s.cfg.Database.FailoverEnabled {
		return
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	s.db = s.localDB
	s.dialect = s.localDialect
	s.status.ActiveProvider = "sqlite"
	s.status.ConfigProvider = s.cfg.Database.Provider
	s.status.RemoteReady = false
	s.status.FailoverActive = !strings.EqualFold(s.cfg.Database.Provider, "sqlite")
	s.status.LastError = err.Error()
	s.status.LastFailoverAt = Now()
}