package db

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	_ "github.com/go-sql-driver/mysql"
	_ "modernc.org/sqlite"

	"ymhut-box/server/unified-management/internal/config"
)

type dialect struct {
	name   string
	driver string
}

func dialectFor(provider string) dialect {
	switch strings.ToLower(strings.TrimSpace(provider)) {
	case "mysql":
		return dialect{name: "mysql", driver: "mysql"}
	default:
		return dialect{name: "sqlite", driver: "sqlite"}
	}
}

func (d dialect) rebind(query string) string {
	return query
}

func (d dialect) idType() string {
	if d.name == "mysql" {
		return "BIGINT PRIMARY KEY AUTO_INCREMENT"
	}
	return "INTEGER PRIMARY KEY AUTOINCREMENT"
}

func (d dialect) keyTextType() string {
	if d.name == "mysql" {
		return "VARCHAR(191)"
	}
	return "TEXT"
}

func (d dialect) shortTextType() string {
	if d.name == "mysql" {
		return "VARCHAR(255)"
	}
	return "TEXT"
}

func (d dialect) mediumTextType() string {
	if d.name == "mysql" {
		return "VARCHAR(1024)"
	}
	return "TEXT"
}

func (d dialect) longTextType() string {
	if d.name == "mysql" {
		return "LONGTEXT"
	}
	return "TEXT"
}

func (d dialect) quoteIdent(identifier string) string {
	return "`" + strings.ReplaceAll(identifier, "`", "``") + "`"
}

func (d dialect) columnList(columns []string) string {
	quoted := make([]string, len(columns))
	for index, column := range columns {
		quoted[index] = d.quoteIdent(column)
	}
	return strings.Join(quoted, ", ")
}

func (d dialect) boolExpr(value bool) int {
	if value {
		return 1
	}
	return 0
}

func (d dialect) upsert(table string, columns, conflict []string) string {
	placeholders := make([]string, len(columns))
	for i := range placeholders {
		placeholders[i] = "?"
	}
	base := fmt.Sprintf("INSERT INTO %s (%s) VALUES (%s)", table, d.columnList(columns), strings.Join(placeholders, ", "))
	conflictSet := map[string]bool{}
	for _, column := range conflict {
		conflictSet[column] = true
	}
	updates := []string{}
	for _, column := range columns {
		if conflictSet[column] {
			continue
		}
		quoted := d.quoteIdent(column)
		if d.name == "mysql" {
			updates = append(updates, fmt.Sprintf("%s = VALUES(%s)", quoted, quoted))
		} else {
			updates = append(updates, fmt.Sprintf("%s = excluded.%s", quoted, quoted))
		}
	}
	if len(updates) == 0 {
		if d.name == "mysql" {
			return strings.Replace(base, "INSERT INTO", "INSERT IGNORE INTO", 1)
		}
		return strings.Replace(base, "INSERT INTO", "INSERT OR IGNORE INTO", 1)
	}
	if d.name == "mysql" {
		return base + " ON DUPLICATE KEY UPDATE " + strings.Join(updates, ", ")
	}
	return base + " ON CONFLICT (" + d.columnList(conflict) + ") DO UPDATE SET " + strings.Join(updates, ", ")
}

func (d dialect) limitOffset(limit, offset int) string {
	return fmt.Sprintf(" LIMIT %d OFFSET %d", limit, offset)
}

func openSQLDatabase(cfg config.DatabaseConfig) (*sql.DB, dialect, error) {
	d := dialectFor(cfg.Provider)
	dsn := strings.TrimSpace(cfg.SQLitePath)
	if d.name == "mysql" {
		dsn = strings.TrimSpace(cfg.MySQLDSN)
		if dsn == "" {
			return nil, d, errors.New("mysql_dsn is required")
		}
	} else {
		if dsn == "" {
			return nil, d, errors.New("sqlite path is required")
		}
		if !strings.HasPrefix(strings.ToLower(dsn), "file:") {
			if err := os.MkdirAll(filepath.Dir(dsn), 0o750); err != nil {
				return nil, d, err
			}
		}
	}
	conn, err := sql.Open(d.driver, dsn)
	if err != nil {
		return nil, d, err
	}
	conn.SetMaxOpenConns(cfg.MaxOpenConns)
	conn.SetMaxIdleConns(cfg.MaxIdleConns)
	conn.SetConnMaxLifetime(time.Duration(cfg.ConnMaxLifetimeSeconds) * time.Second)
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	if err := conn.PingContext(ctx); err != nil {
		_ = conn.Close()
		return nil, d, err
	}
	return conn, d, nil
}

func TestDatabase(cfg config.DatabaseConfig) error {
	if cfg.Provider == "" {
		cfg.Provider = "sqlite"
	}
	if cfg.MaxOpenConns <= 0 {
		cfg.MaxOpenConns = 1
	}
	if cfg.MaxIdleConns <= 0 {
		cfg.MaxIdleConns = 1
	}
	if cfg.ConnMaxLifetimeSeconds <= 0 {
		cfg.ConnMaxLifetimeSeconds = 60
	}
	conn, d, err := openSQLDatabase(cfg)
	if err != nil {
		return err
	}
	defer conn.Close()
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	if err := conn.PingContext(ctx); err != nil {
		return err
	}
	tx, err := conn.BeginTx(ctx, nil)
	if err != nil {
		return err
	}
	create := "CREATE TEMPORARY TABLE ymhut_unified_connection_test (id INTEGER)"
	if _, err := tx.ExecContext(ctx, d.rebind(create)); err != nil {
		_ = tx.Rollback()
		return err
	}
	_ = tx.Rollback()
	return nil
}

func placeholders(n int) string {
	items := make([]string, n)
	for i := range items {
		items[i] = "?"
	}
	return strings.Join(items, ", ")
}

func atoiDefault(value string, fallback int) int {
	parsed, err := strconv.Atoi(value)
	if err != nil {
		return fallback
	}
	return parsed
}