package main

import (
	"context"
	"database/sql"
	"encoding/csv"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"regexp"
	"strconv"
	"time"

	"github.com/go-sql-driver/mysql"
)

const (
	defaultUpdateDir   = "./update_data"
	defaultTable       = "user_program_info"
	defaultDB          = "user_program_info"
	defaultDumpTimeout = 5 * time.Minute
)

type config struct {
	host      string
	port      int
	user      string
	password  string
	database  string
	table     string
	updateDir string
	target    time.Time
}

func main() {
	logger := log.New(os.Stdout, "[dump] ", log.LstdFlags)

	cfg, err := loadConfig()
	if err != nil {
		log.Fatalf("config error: %v", err)
	}

	ctx, cancel := context.WithTimeout(context.Background(), defaultDumpTimeout)
	defer cancel()

	dsn := (&mysql.Config{
		User:                 cfg.user,
		Passwd:               cfg.password,
		Net:                  "tcp",
		Addr:                 netAddr(cfg.host, cfg.port),
		DBName:               cfg.database,
		Params:               map[string]string{"parseTime": "true", "loc": "UTC", "charset": "utf8mb4"},
		AllowNativePasswords: true,
	}).FormatDSN()

	db, err := sql.Open("mysql", dsn)
	if err != nil {
		log.Fatalf("failed to open mysql connection: %v", err)
	}
	defer db.Close()

	if err := db.PingContext(ctx); err != nil {
		log.Fatalf("failed to ping mysql: %v", err)
	}

	if _, err := db.ExecContext(ctx, "SET time_zone = '+00:00'"); err != nil {
		log.Fatalf("failed to set timezone: %v", err)
	}

	outPath, err := dumpToCSV(ctx, db, cfg)
	if err != nil {
		log.Fatalf("dump failed: %v", err)
	}

	logger.Printf("dumped %s to %s", cfg.target.Format("2006-01-02"), outPath)
}

func loadConfig() (config, error) {
	port, err := strconv.Atoi(env("USER_PROGRAM_INFO_PORT", "3306"))
	if err != nil {
		return config{}, fmt.Errorf("invalid USER_PROGRAM_INFO_PORT: %w", err)
	}

	target, err := resolveTargetDate(env("USER_PROGRAM_TARGET_DATE", ""))
	if err != nil {
		return config{}, err
	}

	table := env("USER_PROGRAM_INFO_TABLE", defaultTable)
	if !regexp.MustCompile(`^[a-zA-Z0-9_]+$`).MatchString(table) {
		return config{}, fmt.Errorf("invalid table name: %s", table)
	}

	updateDir := env("USER_PROGRAM_UPDATE_DIR", defaultUpdateDir)
	if updateDir == "" {
		updateDir = defaultUpdateDir
	}
	if err := os.MkdirAll(updateDir, 0o755); err != nil {
		return config{}, fmt.Errorf("creating update dir: %w", err)
	}

	return config{
		host:      envRequired("USER_PROGRAM_INFO_HOST"),
		port:      port,
		user:      envRequired("USER_PROGRAM_INFO_USERNAME"),
		password:  envRequired("USER_PROGRAM_INFO_PASSWORD"),
		database:  env("USER_PROGRAM_INFO_DB", defaultDB),
		table:     table,
		updateDir: updateDir,
		target:    target,
	}, nil
}

func dumpToCSV(ctx context.Context, db *sql.DB, cfg config) (string, error) {
	query := fmt.Sprintf(`
SELECT
  id,
  product_name,
  login_id,
  user_employee_id,
  login_version,
  login_public_ip,
  login_local_ip,
  user_company,
  user_department,
  user_position,
  user_login_time,
  created_at,
  user_family_flag
FROM %s
WHERE DATE(CONVERT_TZ(created_at, '+00:00', '+09:00')) = ?;`, cfg.table)

	rows, err := db.QueryContext(ctx, query, cfg.target.Format("2006-01-02"))
	if err != nil {
		return "", err
	}
	defer rows.Close()

	filename := fmt.Sprintf("user_program_info_%s.csv", cfg.target.Format("20060102"))
	outPath := filepath.Join(cfg.updateDir, filename)
	tmpPath := outPath + ".tmp"

	f, err := os.Create(tmpPath)
	if err != nil {
		return "", err
	}
	defer f.Close()

	writer := csv.NewWriter(f)
	defer writer.Flush()

	header := []string{
		"id",
		"product_name",
		"login_id",
		"user_employee_id",
		"login_version",
		"login_public_ip",
		"login_local_ip",
		"user_company",
		"user_department",
		"user_position",
		"user_login_time",
		"created_at",
		"user_family_flag",
	}
	if err := writer.Write(header); err != nil {
		return "", err
	}

	for rows.Next() {
		record, err := scanRow(rows)
		if err != nil {
			return "", err
		}
		if err := writer.Write(record); err != nil {
			return "", err
		}
	}
	if err := rows.Err(); err != nil {
		return "", err
	}
	writer.Flush()
	if err := writer.Error(); err != nil {
		return "", err
	}

	if err := os.Rename(tmpPath, outPath); err != nil {
		return "", err
	}
	return outPath, nil
}

func scanRow(rows *sql.Rows) ([]string, error) {
	var (
		id             sql.NullInt64
		productName    sql.NullString
		loginID        sql.NullString
		employeeID     sql.NullString
		loginVersion   sql.NullString
		loginPublicIP  sql.NullString
		loginLocalIP   sql.NullString
		userCompany    sql.NullString
		userDepartment sql.NullString
		userPosition   sql.NullString
		userLoginTime  sql.NullString
		createdAt      sql.NullString
		userFamilyFlag sql.NullString
	)

	if err := rows.Scan(
		&id,
		&productName,
		&loginID,
		&employeeID,
		&loginVersion,
		&loginPublicIP,
		&loginLocalIP,
		&userCompany,
		&userDepartment,
		&userPosition,
		&userLoginTime,
		&createdAt,
		&userFamilyFlag,
	); err != nil {
		return nil, err
	}
	if !id.Valid {
		return nil, fmt.Errorf("row missing id")
	}

	return []string{
		strconv.FormatInt(id.Int64, 10),
		nullToString(productName),
		nullToString(loginID),
		nullToString(employeeID),
		nullToString(loginVersion),
		nullToString(loginPublicIP),
		nullToString(loginLocalIP),
		nullToString(userCompany),
		nullToString(userDepartment),
		nullToString(userPosition),
		nullToString(userLoginTime),
		nullToString(createdAt),
		nullToString(userFamilyFlag),
	}, nil
}

func resolveTargetDate(raw string) (time.Time, error) {
	if raw == "" {
		now := time.Now().In(kst())
		yesterday := now.AddDate(0, 0, -1)
		return time.Date(yesterday.Year(), yesterday.Month(), yesterday.Day(), 0, 0, 0, 0, kst()), nil
	}
	t, err := time.ParseInLocation("2006-01-02", raw, kst())
	if err != nil {
		return time.Time{}, fmt.Errorf("invalid USER_PROGRAM_TARGET_DATE: %w", err)
	}
	return t, nil
}

func kst() *time.Location {
	loc, err := time.LoadLocation("Asia/Seoul")
	if err != nil {
		return time.FixedZone("KST", 9*60*60)
	}
	return loc
}

func env(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}

func envRequired(key string) string {
	v := os.Getenv(key)
	if v == "" {
		log.Fatalf("%s is required", key)
	}
	return v
}

func netAddr(host string, port int) string {
	return fmt.Sprintf("%s:%d", host, port)
}

func nullToString(v sql.NullString) string {
	if v.Valid {
		return v.String
	}
	return ""
}