package store

import (
	"context"
	"errors"
	"strings"
	"time"

	"airlines/pkg/model"

	"gorm.io/driver/postgres"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
	"gorm.io/gorm/logger"
)

type Store struct {
	DB *gorm.DB
}

func NewStore(dsn string) (*Store, error) {
	db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{
		SkipDefaultTransaction:   true,
		PrepareStmt:              true,
		DisableNestedTransaction: true,
		Logger:                   logger.Default.LogMode(logger.Silent),
	})
	if err != nil {
		return nil, err
	}
	return &Store{DB: db}, nil
}

func (s *Store) AutoMigrate() error {
	return s.DB.AutoMigrate(&model.User{}, &model.Card{}, &model.Flight{})
}

func (s *Store) SaveUser(ctx context.Context, in *model.User) (*model.User, error) {
	if in == nil {
		return nil, errors.New("nil user")
	}
	in.Nick = strings.TrimSpace(in.Nick)
	in.Name = strings.TrimSpace(in.Name)
	in.Surname = strings.TrimSpace(in.Surname)
	in.Fathersname = strings.TrimSpace(in.Fathersname)
	if in.Birthday.IsZero() {
		in.Birthday = model.SentinelBirthday()
	}
	in.Birthday = in.Birthday.In(time.UTC)

	out := &model.User{}
	err := s.DB.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		// try by Nick
		if in.Nick != "" {
			if err := tx.Where("nick = ?", in.Nick).First(out).Error; err == nil {
				return nil
			} else if !errors.Is(err, gorm.ErrRecordNotFound) {
				return err
			}
		}
		// fallback by identity tuple
		q := tx.Where("name = ? AND surname = ?", in.Name, in.Surname)
		if in.Fathersname != "" {
			q = q.Where("fathersname = ?", in.Fathersname)
		} else {
			q = q.Where("(fathersname IS NULL OR fathersname = '')")
		}
		if in.Birthday.Year() != model.SentinelBirthday().Year() {
			q = q.Where("birthday = ?", in.Birthday)
		}
		if err := q.First(out).Error; err == nil {
			return nil
		} else if !errors.Is(err, gorm.ErrRecordNotFound) {
			return err
		}

		// create
		if err := tx.Create(in).Error; err != nil {
			return err
		}
		*out = *in
		return nil
	})
	return out, err
}

func (s *Store) SaveCard(ctx context.Context, in *model.Card) (*model.Card, error) {
	if in == nil {
		return nil, errors.New("nil card")
	}
	in.Prefix = strings.TrimSpace(in.Prefix)
	in.Bonusprogramm = strings.TrimSpace(in.Bonusprogramm)
	if in.Prefix == "" || in.Bonusprogramm == "" {
		return nil, errors.New("invalid card: empty prefix or bonusprogramm")
	}

	out := &model.Card{}
	err := s.DB.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		// find by unique triple
		if err := tx.Where("prefix = ? AND number = ? AND bonusprogramm = ?",
			in.Prefix, in.Number, in.Bonusprogramm).First(out).Error; err == nil {
			// link to user once if requested and not yet linked
			if in.UserID != 0 && out.UserID == 0 {
				if err := tx.Model(out).Update("user_id", in.UserID).Error; err != nil {
					return err
				}
				out.UserID = in.UserID
			}
			// refuse stealing
			if in.UserID != 0 && out.UserID != 0 && out.UserID != in.UserID {
				return errors.New("card already linked to another user")
			}
			return nil
		} else if !errors.Is(err, gorm.ErrRecordNotFound) {
			return err
		}

		// not found → create
		if err := tx.Create(in).Error; err != nil {
			return err
		}
		*out = *in
		return nil
	})
	return out, err
}

func (s *Store) SaveFlight(ctx context.Context, in *model.Flight) (*model.Flight, error) {
	if in == nil {
		return nil, errors.New("nil flight")
	}
	in.Date = in.Date.In(time.UTC)

	out := &model.Flight{}
	err := s.DB.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		// try to find existing
		if err := tx.Where(`"number" = ? AND "from" = ? AND "to" = ? AND "date" = ?`,
			in.Number, in.From, in.To, in.Date).First(out).Error; err == nil {
			// found
		} else if errors.Is(err, gorm.ErrRecordNotFound) {
			// not found → create
			cre := model.Flight{
				Number: in.Number,
				From:   in.From,
				To:     in.To,
				Date:   in.Date,
			}
			if err := tx.Clauses(clause.OnConflict{DoNothing: true}).Create(&cre).Error; err != nil {
				return err
			}
			// on conflict, fetch the existing one
			if cre.ID == 0 {
				if err := tx.Where(`"number" = ? AND "from" = ? AND "to" = ? AND "date" = ?`,
					in.Number, in.From, in.To, in.Date).First(&cre).Error; err != nil {
					return err
				}
			}
			*out = cre
		} else {
			return err
		}

		// many-to-many user-flight
		if in.UserID != 0 {
			u := model.User{ID: in.UserID}
			if err := tx.Model(out).Association("Users").Append(&u); err != nil {
				return err
			}
		}
		// many-to-many flight-card
		if in.CardID != 0 {
			c := model.Card{ID: in.CardID}
			if err := tx.Model(out).Association("Cards").Append(&c); err != nil {
				return err
			}
		}
		return nil
	})
	return out, err
}