package services

import (
	"context"
	"database/sql"
	"fmt"
	"strings"
	"time"

	_ "github.com/go-sql-driver/mysql"
	_ "github.com/lib/pq"
	_ "github.com/mattn/go-sqlite3"
	_ "github.com/microsoft/go-mssqldb"

	"github.com/sujit-baniya/fiber-boilerplate/pkg/models"
)

// connTimeout es el tiempo máximo para establecer una conexión a la DB externa.
const connTimeout = 8 * time.Second

// QueryResult contiene el resultado de una consulta SQL.
type QueryResult struct {
	Columns    []string         `json:"columns"`
	Rows       []map[string]any `json:"rows"`
	RowCount   int              `json:"row_count"`
	AffectedRows int64          `json:"affected_rows"`
	DurationMs int64            `json:"duration_ms"`
	IsSelect   bool             `json:"is_select"`
	Error      string           `json:"error,omitempty"`
}

// openDynamicDB abre una conexión a la base de datos indicada por ConxDb.
func openDynamicDB(c models.ConxDb) (*sql.DB, error) {
	driver := strings.ToLower(c.TipoDb.Nombre)
	host := c.Servidor.IpServidor
	port := c.Puerto
	user := c.Usuario
	pass := c.Password

	var dsn string
	var driverName string

	switch {
	case strings.Contains(driver, "postgres"):
		driverName = "postgres"
		dsn = fmt.Sprintf("host=%s port=%s user=%s password=%s sslmode=disable connect_timeout=8", host, port, user, pass)
	case strings.Contains(driver, "mysql") || strings.Contains(driver, "mariadb"):
		driverName = "mysql"
		dsn = fmt.Sprintf("%s:%s@tcp(%s:%s)/?timeout=8s&readTimeout=20s&writeTimeout=20s", user, pass, host, port)
	case strings.Contains(driver, "sqlite"):
		driverName = "sqlite3"
		dsn = host // para sqlite el host es la ruta del archivo
	case strings.Contains(driver, "sqlserver") || strings.Contains(driver, "mssql"):
		driverName = "sqlserver"
		dsn = fmt.Sprintf("sqlserver://%s:%s@%s:%s?dial+timeout=8", user, pass, host, port)
	default:
		return nil, fmt.Errorf("driver no soportado: %s", driver)
	}

	db, err := sql.Open(driverName, dsn)
	if err != nil {
		return nil, err
	}
	db.SetConnMaxLifetime(30 * time.Second)
	db.SetMaxOpenConns(2)
	// Verificar conectividad inmediatamente para fallar rápido en lugar de bloquear al hacer la primera query
	ctx, cancel := context.WithTimeout(context.Background(), connTimeout)
	defer cancel()
	if err := db.PingContext(ctx); err != nil {
		db.Close()
		return nil, fmt.Errorf("no se pudo conectar al servidor de base de datos: %w", err)
	}
	return db, nil
}

// ExecuteSQL ejecuta SQL arbitrario contra la conexión y devuelve QueryResult.
// También guarda en query_history.
func ExecuteSQL(conx models.ConxDb, database, sqlText string) QueryResult {
	start := time.Now()

	db, err := openDynamicDB(conx)
	if err != nil {
		saveHistory(conx.ID, sqlText, "error", err.Error(), 0, time.Since(start).Milliseconds())
		return QueryResult{Error: err.Error()}
	}
	defer db.Close()

	// Si se especifica una base de datos para seleccionar
	if database != "" {
		driver := strings.ToLower(conx.TipoDb.Nombre)
		if strings.Contains(driver, "postgres") {
			// En postgres se cambia con SET search_path o reconectando con dbname en DSN
			db2, err2 := openDynamicDBWithName(conx, database)
			if err2 == nil {
				db.Close()
				db = db2
			}
		} else {
			if _, err2 := db.Exec("USE " + quoteIdentifier(database, conx.TipoDb.Nombre)); err2 != nil {
				saveHistory(conx.ID, sqlText, "error", err2.Error(), 0, time.Since(start).Milliseconds())
				return QueryResult{Error: err2.Error()}
			}
		}
	}

	trimmed := strings.TrimSpace(sqlText)
	isSelect := isSelectStatement(trimmed)

	var result QueryResult
	result.IsSelect = isSelect

	if isSelect {
		rows, err := db.Query(trimmed)
		if err != nil {
			elapsed := time.Since(start).Milliseconds()
			saveHistory(conx.ID, sqlText, "error", err.Error(), 0, elapsed)
			return QueryResult{Error: err.Error(), IsSelect: true}
		}
		defer rows.Close()

		cols, _ := rows.Columns()
		result.Columns = cols

		for rows.Next() {
			vals := make([]any, len(cols))
			ptrs := make([]any, len(cols))
			for i := range vals {
				ptrs[i] = &vals[i]
			}
			rows.Scan(ptrs...)
			row := make(map[string]any, len(cols))
			for i, col := range cols {
				v := vals[i]
				if b, ok := v.([]byte); ok {
					row[col] = string(b)
				} else {
					row[col] = v
				}
			}
			result.Rows = append(result.Rows, row)
		}
		result.RowCount = len(result.Rows)
	} else {
		res, err := db.Exec(trimmed)
		elapsed := time.Since(start).Milliseconds()
		if err != nil {
			saveHistory(conx.ID, sqlText, "error", err.Error(), 0, elapsed)
			return QueryResult{Error: err.Error()}
		}
		affected, _ := res.RowsAffected()
		result.AffectedRows = affected
		result.DurationMs = elapsed
		saveHistory(conx.ID, sqlText, "ok", "", affected, elapsed)
		return result
	}

	result.DurationMs = time.Since(start).Milliseconds()
	saveHistory(conx.ID, sqlText, "ok", "", int64(result.RowCount), result.DurationMs)
	return result
}

// ListDatabases devuelve la lista de bases de datos del servidor.
func ListDatabases(conx models.ConxDb) ([]string, error) {
	db, err := openDynamicDB(conx)
	if err != nil {
		return nil, err
	}
	defer db.Close()

	driver := strings.ToLower(conx.TipoDb.Nombre)
	var query string
	switch {
	case strings.Contains(driver, "postgres"):
		query = "SELECT datname FROM pg_database WHERE datistemplate = false ORDER BY datname"
	case strings.Contains(driver, "mysql") || strings.Contains(driver, "mariadb"):
		query = "SHOW DATABASES"
	case strings.Contains(driver, "sqlserver") || strings.Contains(driver, "mssql"):
		query = "SELECT name FROM sys.databases ORDER BY name"
	default:
		return []string{"main"}, nil
	}

	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
	defer cancel()
	rows, err := db.QueryContext(ctx, query)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var dbs []string
	for rows.Next() {
		var name string
		rows.Scan(&name)
		dbs = append(dbs, name)
	}
	return dbs, nil
}

// ListTables devuelve las tablas de una base de datos.
func ListTables(conx models.ConxDb, database string) ([]string, error) {
	driver := strings.ToLower(conx.TipoDb.Nombre)

	var db *sql.DB
	var err error

	if strings.Contains(driver, "postgres") {
		db, err = openDynamicDBWithName(conx, database)
	} else {
		db, err = openDynamicDB(conx)
	}
	if err != nil {
		return nil, err
	}
	defer db.Close()

	var query string
	switch {
	case strings.Contains(driver, "postgres"):
		query = "SELECT tablename FROM pg_tables WHERE schemaname='public' ORDER BY tablename"
	case strings.Contains(driver, "mysql") || strings.Contains(driver, "mariadb"):
		if _, err := db.Exec("USE " + quoteIdentifier(database, conx.TipoDb.Nombre)); err != nil {
			return nil, err
		}
		query = "SHOW TABLES"
	case strings.Contains(driver, "sqlserver") || strings.Contains(driver, "mssql"):
		query = fmt.Sprintf("USE [%s]; SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE='BASE TABLE' ORDER BY TABLE_NAME", database)
	default:
		query = "SELECT name FROM sqlite_master WHERE type='table' ORDER BY name"
	}

	rows, err := db.Query(query)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var tables []string
	for rows.Next() {
		var name string
		rows.Scan(&name)
		tables = append(tables, name)
	}
	return tables, nil
}

// TestConnection verifica si la conexión es válida.
func TestDBConnection(conx models.ConxDb) error {
	db, err := openDynamicDB(conx)
	if err != nil {
		return err
	}
	defer db.Close()
	return db.Ping()
}

// ── helpers ──────────────────────────────────────────────────────────────────

func openDynamicDBWithName(c models.ConxDb, dbName string) (*sql.DB, error) {
	host := c.Servidor.IpServidor
	port := c.Puerto
	user := c.Usuario
	pass := c.Password
	driver := strings.ToLower(c.TipoDb.Nombre)

	var dsn string
	switch {
	case strings.Contains(driver, "postgres"):
		dsn = fmt.Sprintf("host=%s port=%s user=%s password=%s dbname=%s sslmode=disable connect_timeout=8", host, port, user, pass, dbName)
		db, err := sql.Open("postgres", dsn)
		if err != nil {
			return nil, err
		}
		db.SetConnMaxLifetime(30 * time.Second)
		db.SetMaxOpenConns(2)
		ctx, cancel := context.WithTimeout(context.Background(), connTimeout)
		defer cancel()
		if err := db.PingContext(ctx); err != nil {
			db.Close()
			return nil, fmt.Errorf("no se pudo conectar a la base de datos '%s': %w", dbName, err)
		}
		return db, nil
	default:
		return openDynamicDB(c)
	}
}

func isSelectStatement(sql string) bool {
	upper := strings.ToUpper(strings.TrimSpace(sql))
	keywords := []string{"SELECT ", "SHOW ", "DESCRIBE ", "EXPLAIN ", "WITH ", "PRAGMA "}
	for _, kw := range keywords {
		if strings.HasPrefix(upper, kw) {
			return true
		}
	}
	return false
}

func quoteIdentifier(name, driver string) string {
	d := strings.ToLower(driver)
	if strings.Contains(d, "postgres") {
		return `"` + strings.ReplaceAll(name, `"`, `""`) + `"`
	}
	return "`" + strings.ReplaceAll(name, "`", "``") + "`"
}

func saveHistory(conxID uint, sqlText, status, errMsg string, rows, durationMs int64) {
	models.SaveQueryHistory(models.QueryHistory{
		ConxDbID:   conxID,
		SQL:        sqlText,
		Status:     status,
		ErrorMsg:   errMsg,
		RowsAffect: rows,
		DurationMs: durationMs,
		ExecutedAt: time.Now(),
	})
}