package service

import (
	"context"
	"errors"
	"strings"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5/pgconn"
	"gitrepo.ru/neonxp/nquest/pkg/models"
	"gorm.io/gorm"
)

var (
	ErrGameNotStarted = errors.New("game not started")
	ErrInvalidCode    = errors.New("invalid code")
	ErrOldCode        = errors.New("old code")
	ErrGameFinished   = errors.New("game finished")
	ErrNextLevel      = errors.New("next level")
)

type Engine struct {
	DB *gorm.DB
}

func NewEngine(db *gorm.DB) *Engine {
	return &Engine{
		DB: db,
	}
}

func (e *Engine) GetState(ctx context.Context, game *models.Game, user *models.User) (*models.GameCursor, error) {
	db := e.DB.WithContext(ctx)

	// Пытаемся получить GameCursor
	cursor := &models.GameCursor{
		User:   user,
		Game:   game,
		Task:   game.Tasks[0],
		Status: models.TaskStarted,
		Codes:  make([]*models.Code, 0),
	}
	err := db.
		Where(`user_id = ? and game_id = ? and status = ?`, user.ID, game.ID, models.TaskStarted).
		Preload("Task").
		Preload("Task.Codes").
		Preload("Codes").
		FirstOrCreate(cursor).
		Error
	if err != nil {
		if err, ok := err.(*pgconn.PgError); ok {
			if err.Code == "23505" {
				return nil, ErrGameNotStarted
			}
		}

		return nil, err
	}

	return cursor, nil
}

func (e *Engine) EnterCode(ctx context.Context, game *models.Game, user *models.User, code string) (*models.GameCursor, error) {
	db := e.DB.WithContext(ctx)

	st, err := e.GetState(ctx, game, user)
	if err != nil {
		return nil, err
	}

	return st, db.Transaction(func(tx *gorm.DB) error {
		code = strings.Trim(code, " \n\t")
		code = strings.ToLower(code)
		var currentCode *models.Code
		for _, c := range st.Task.Codes {
			if c.Code == code {
				currentCode = c
				break
			}
		}
		if currentCode == nil {
			return ErrInvalidCode
		}
		for _, c := range st.Codes {
			if c.ID == currentCode.ID {
				return ErrOldCode
			}
		}

		if err := db.Model(st).Association("Codes").Append(currentCode); err != nil {
			return err
		}

		if len(st.Codes) != len(st.Task.Codes) {
			return nil
		}

		// Уровень пройден. Выдаем следующий

		if err := db.Model(st).UpdateColumn("Status", models.TaskFinished).Error; err != nil {
			return err
		}

		nextTask, err := e.GetNext(ctx, game.ID, st.Task.TaskOrder)
		if err != nil {
			return err
		}

		if nextTask == nil {
			user.Experience += st.Game.Points
			if err := db.Model(user).UpdateColumn("Experience", user.Experience).Error; err != nil {
				return err
			}
			if err := db.Model(st).UpdateColumn("Finish", true).Error; err != nil {
				return err
			}

			return ErrGameFinished
		}

		st = &models.GameCursor{
			User:   user,
			Game:   game,
			Task:   nextTask,
			Status: models.TaskStarted,
			Codes:  []*models.Code{},
		}
		if err := db.Create(st).Error; err != nil {
			return err
		}

		return ErrNextLevel
	})
}

func (e *Engine) GetNext(ctx context.Context, gameID uuid.UUID, currentOrder uint) (*models.Task, error) {
	var t models.Task
	err := e.DB.WithContext(ctx).
		Preload("Codes").
		Order("task_order ASC").
		First(&t, `game_id = ? AND task_order > ?`, gameID, currentOrder).
		Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, nil
		}

		return nil, err
	}
	return &t, nil
}