package model

import (
	"bufio"
	"database/sql"
	"fmt"
	"log"
	"os"
	"strings"
	"syscall"

	"github.com/go-sql-driver/mysql"
	"golang.org/x/term"
)

type DB struct {
	*sql.DB
}

type Tx struct {
	*sql.Tx
}

type Attribute struct {
	Value   interface{}
	Table   string
	AttName string
	ID      int64
}

func getUsername() (string, error) {
	user := os.Getenv("DB_USER")
	if user == "" {
		var err error
		fmt.Printf("DB Benutzer: ")
		user, err = bufio.NewReader(os.Stdin).ReadString('\n')
		if err != nil {
			return "", fmt.Errorf("error reading username: %v", err)
		}
	}
	return strings.TrimSpace(user), nil
}

func getPassword() (string, error) {
	pass := os.Getenv("DB_PASS")
	if pass == "" {
		fmt.Printf("DB Passwort: ")
		bytePass, err := term.ReadPassword(int(syscall.Stdin))
		if err != nil {
			return "", fmt.Errorf("error reading password: %v", err)
		}
		fmt.Println()
		pass = strings.TrimSpace(string(bytePass))
	}
	return pass, nil
}

func getCredentials() (string, string, error) {
	user, err := getUsername()
	if err != nil {
		return "", "", fmt.Errorf("error getting username: %v", err)
	}

	pass, err := getPassword()
	if err != nil {
		return "", "", fmt.Errorf("error getting password: %v", err)
	}

	return user, pass, nil
}

func OpenDB(dbName string) (*DB, error) {
	var err error
	db := DB{DB: &sql.DB{}}

	cfg := mysql.NewConfig()
	cfg.DBName = dbName
	cfg.User, cfg.Passwd, err = getCredentials()
	if err != nil {
		return nil, fmt.Errorf("error reading user credentials for DB: %v", err)
	}

	db.DB, err = sql.Open("mysql", cfg.FormatDSN())
	if err != nil {
		return nil, fmt.Errorf("error opening DB: %v", err)
	}
	if err = db.Ping(); err != nil {
		return nil, fmt.Errorf("error pinging DB: %v", err)
	}

	return &db, nil
}

func (db *DB) UpdateAttributes(a ...*Attribute) error {
	tx, err := db.Begin()
	if err != nil {
		return fmt.Errorf("error starting transaction: %v", err)
	}

	for _, attribute := range a {
		query := fmt.Sprintf(`
    UPDATE %s
    SET %s = ?
    WHERE id = ?
    `, attribute.Table, attribute.AttName)
		if _, err := tx.Exec(query, attribute.Value, attribute.ID); err != nil {
			if rollbackErr := tx.Rollback(); rollbackErr != nil {
				log.Fatalf("error: transaction error: %v, rollback error: %v", err, rollbackErr)
			}
			return fmt.Errorf("error updating article in DB: %v", err)
		}
	}

	if err = tx.Commit(); err != nil {
		return fmt.Errorf("error committing transaction: %v", err)
	}
	return nil
}

func (db *DB) CountEntries(table string) (int64, error) {
	var count int64

	query := fmt.Sprintf("SELECT COUNT(*) FROM %s", table)
	row := db.QueryRow(query)
	if err := row.Scan(&count); err != nil {
		return 0, fmt.Errorf("error counting rows in user DB: %v", err)
	}

	return count, nil
}

func (db *DB) StartTransaction() (*Tx, error) {
	tx := &Tx{Tx: new(sql.Tx)}
	var err error

	tx.Tx, err = db.Begin()
	if err != nil {
		return nil, fmt.Errorf("error starting transaction: %v", err)
	}

	return tx, nil
}

func (tx *Tx) CommitTransaction() error {
	if err := tx.Commit(); err != nil {
		return fmt.Errorf("error committing transaction: %v", err)
	}
	return nil
}

func (tx *Tx) RollbackTransaction() {
	if err := tx.Rollback(); err != nil {
		log.Fatalf("error rolling back transaction: %v", err)
	}
}

func (tx *Tx) UpdateAttributes(a ...*Attribute) error {
	for _, attribute := range a {
		query := fmt.Sprintf(`
            UPDATE %s
            SET %s = ?
            WHERE id = ?
            `, attribute.Table, attribute.AttName)
		if _, err := tx.Exec(query, attribute.Value, attribute.ID); err != nil {
			if rollbackErr := tx.Rollback(); rollbackErr != nil {
				log.Fatalf("error: transaction error: %v, rollback error: %v", err, rollbackErr)
			}
			return fmt.Errorf("error updating article in DB: %v", err)
		}
	}

	return nil
}