package models

import (
	"context"
	"crypto/rand"
	"errors"
	"fmt"
	"log/slog"
	"time"

	"github.com/ncruces/go-sqlite3"
	_ "github.com/ncruces/go-sqlite3/embed"
	"github.com/ncruces/go-sqlite3/gormlite"
	"github.com/oklog/ulid/v2"
	slogGorm "github.com/orandin/slog-gorm"
	"gorm.io/gorm"
	gormPrometheus "gorm.io/plugin/prometheus"
)

var (
	ErrCantSwitchToYourself = errors.New("models: you can't switch to yourself")
)

type DAO struct {
	db          *gorm.DB
	backupDBLoc string
}

func (d *DAO) DB() *gorm.DB {
	return d.db
}

func (d *DAO) Ping(ctx context.Context) error {
	if err := d.db.WithContext(ctx).Exec("select 1+1").Error; err != nil {
		return err
	}

	return nil
}

func New(dbLoc, backupDBLoc string) (*DAO, error) {
	db, err := gorm.Open(gormlite.Open(dbLoc), &gorm.Config{
		Logger: slogGorm.New(
			slogGorm.WithErrorField("err"),
			slogGorm.WithRecordNotFoundError(),
		),
	})
	if err != nil {
		return nil, fmt.Errorf("failed to connect to database: %w", err)
	}

	if err := db.AutoMigrate(
		&Member{},
		&Switch{},
		&Blogpost{},
		&Event{},
	); err != nil {
		return nil, fmt.Errorf("failed to migrate schema: %w", err)
	}

	db.Use(gormPrometheus.New(gormPrometheus.Config{
		DBName: "mi",
	}))

	return &DAO{db: db, backupDBLoc: backupDBLoc}, nil
}

func (d *DAO) Members(ctx context.Context) ([]Member, error) {
	var result []Member
	if err := d.db.WithContext(ctx).Find(&result).Error; err != nil {
		return nil, err
	}

	return result, nil
}

func (d *DAO) WhoIsFront(ctx context.Context) (*Switch, error) {
	var sw Switch
	if err := d.db.Joins("Member").Order("created_at DESC").First(&sw).Error; err != nil {
		return nil, err
	}

	return &sw, nil
}

func (d *DAO) SwitchFront(ctx context.Context, memberName string) (*Switch, *Switch, error) {
	var old Switch
	tx := d.db.Begin()

	if err := tx.WithContext(ctx).Joins("Member").Where("ended_at IS NULL").First(&old).Error; err != nil {
		tx.Rollback()
		return nil, nil, err
	}

	if old.Member.Name == memberName {
		tx.WithContext(ctx).Rollback()
		return nil, nil, ErrCantSwitchToYourself
	}

	now := time.Now()
	old.EndedAt = &now
	if err := tx.WithContext(ctx).Save(&old).Error; err != nil {
		tx.Rollback()
		return nil, nil, err
	}

	var newMember Member
	if err := tx.WithContext(ctx).Where("name = ?", memberName).First(&newMember).Error; err != nil {
		tx.Rollback()
		return nil, nil, err
	}

	new := Switch{
		ID:       ulid.MustNew(ulid.Now(), rand.Reader).String(),
		MemberID: newMember.ID,
	}

	if err := tx.WithContext(ctx).Create(&new).Error; err != nil {
		tx.Rollback()
		return nil, nil, err
	}

	if err := tx.WithContext(ctx).Commit().Error; err != nil {
		tx.Rollback()
		return nil, nil, err
	}

	return &old, &new, nil
}

func (d *DAO) GetSwitch(ctx context.Context, id string) (*Switch, error) {
	var sw Switch
	if err := d.db.WithContext(ctx).
		Joins("Member").
		Where("switches.id = ?", id).
		First(&sw).Error; err != nil {
		return nil, err
	}

	return &sw, nil
}

func (d *DAO) ListSwitches(ctx context.Context, count, page int) ([]Switch, error) {
	var switches []Switch
	if err := d.db.WithContext(ctx).
		Joins("Member").
		Order("created_at DESC").
		Limit(count).
		Offset(count * page).
		Find(&switches).Error; err != nil {
		return nil, err
	}

	return switches, nil
}

func (d *DAO) Backup() {
	slog.Info("starting backup")
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
	defer cancel()
	err := d.backup(ctx, d.backupDBLoc)
	if err != nil {
		slog.Error("failed to backup database", "err", err)
	}
	slog.Info("backup done")
}

func (d *DAO) backup(ctx context.Context, to string) error {
	db, err := d.db.DB()
	if err != nil {
		return fmt.Errorf("failed to get database connection: %w", err)
	}

	if err := db.Ping(); err != nil {
		return fmt.Errorf("failed to ping database: %w", err)
	}

	conn, err := db.Conn(ctx)
	if err != nil {
		return fmt.Errorf("failed to get database connection: %w", err)
	}

	defer conn.Close()

	if err := conn.Raw(func(dca any) error {
		conn, ok := dca.(sqlite3.DriverConn)
		if !ok {
			return fmt.Errorf("db connection is not a sqlite3 connection, it is %T", dca)
		}

		bu, err := conn.Raw().BackupInit("main", to)
		if err != nil {
			return fmt.Errorf("failed to initialize backup: %w", err)
		}
		defer bu.Close()

		var done bool
		for !done {
			done, err = bu.Step(bu.Remaining())
			if err != nil {
				return fmt.Errorf("failed to backup database: %w", err)
			}
		}

		if err := bu.Close(); err != nil {
			return fmt.Errorf("failed to close backup: %w", err)
		}

		return nil
	}); err != nil {
		return fmt.Errorf("failed to backup database: %w", err)
	}

	return nil
}