package database

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

	"otpm/config"

	"github.com/jmoiron/sqlx"
)

// DB wraps sqlx.DB to provide additional functionality
type DB struct {
	*sqlx.DB
}

// New creates a new database connection
func New(cfg *config.DatabaseConfig) (*DB, error) {
	db, err := sqlx.Open(cfg.Driver, cfg.DSN)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to database: %w", err)
	}

	// Configure connection pool with optimized settings
	db.SetMaxOpenConns(cfg.MaxOpenConns)
	db.SetMaxIdleConns(max(1, cfg.MaxOpenConns/2)) // 50% of max open connections
	db.SetConnMaxLifetime(30 * time.Minute)        // Longer lifetime to reduce connection churn
	db.SetConnMaxIdleTime(5 * time.Minute)         // Close idle connections after 5 minutes

	// Verify connection with timeout
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	if err := db.PingContext(ctx); err != nil {
		return nil, fmt.Errorf("failed to ping database: %w", err)
	}

	log.Println("Successfully connected to database")
	return &DB{db}, nil
}

// WithTx executes a function within a transaction with retry logic
func (db *DB) WithTx(ctx context.Context, fn func(*sqlx.Tx) error) error {
	const maxRetries = 3
	var lastErr error

	// Default transaction options
	opts := &sql.TxOptions{
		Isolation: sql.LevelReadCommitted,
	}

	for attempt := 1; attempt <= maxRetries; attempt++ {
		start := time.Now()

		tx, err := db.BeginTxx(ctx, opts)
		if err != nil {
			if isRetryableError(err) && attempt < maxRetries {
				lastErr = err
				time.Sleep(time.Duration(attempt) * 100 * time.Millisecond) // exponential backoff
				continue
			}
			return fmt.Errorf("failed to begin transaction (attempt %d/%d): %w", attempt, maxRetries, err)
		}

		defer func() {
			if p := recover(); p != nil {
				tx.Rollback()
				panic(p)
			}
		}()

		if err := fn(tx); err != nil {
			if rbErr := tx.Rollback(); rbErr != nil {
				log.Printf("Transaction rollback error: %v (original error: %v)", rbErr, err)
			}

			if isRetryableError(err) && attempt < maxRetries {
				lastErr = err
				time.Sleep(time.Duration(attempt) * 100 * time.Millisecond)
				continue
			}
			return fmt.Errorf("transaction failed (attempt %d/%d): %w", attempt, maxRetries, err)
		}

		// Log long-running transactions
		if elapsed := time.Since(start); elapsed > 500*time.Millisecond {
			log.Printf("Transaction completed in %v", elapsed)
		}

		if err := tx.Commit(); err != nil {
			if isRetryableError(err) && attempt < maxRetries {
				lastErr = err
				time.Sleep(time.Duration(attempt) * 100 * time.Millisecond)
				continue
			}
			return fmt.Errorf("failed to commit transaction (attempt %d/%d): %w", attempt, maxRetries, err)
		}

		return nil
	}

	return lastErr
}

// isRetryableError checks if an error is likely to succeed on retry
func isRetryableError(err error) bool {
	if err == nil {
		return false
	}

	errStr := strings.ToLower(err.Error())
	return strings.Contains(errStr, "deadlock") ||
		strings.Contains(errStr, "timeout") ||
		strings.Contains(errStr, "try again") ||
		strings.Contains(errStr, "connection reset") ||
		strings.Contains(errStr, "busy") ||
		strings.Contains(errStr, "locked")
}

// ExecContext executes a query with adaptive timeout
func (db *DB) ExecContext(ctx context.Context, query string, args ...interface{}) error {
	// Set timeout based on query complexity
	timeout := 5 * time.Second
	if strings.Contains(strings.ToLower(query), "insert") ||
		strings.Contains(strings.ToLower(query), "update") ||
		strings.Contains(strings.ToLower(query), "delete") {
		timeout = 10 * time.Second
	}

	ctx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()

	start := time.Now()
	_, err := db.DB.ExecContext(ctx, query, args...)
	elapsed := time.Since(start)

	// Log slow queries
	if elapsed > timeout/2 {
		log.Printf("Slow query execution detected: %s (took %v)", query, elapsed)
	}

	if err != nil {
		return fmt.Errorf("failed to execute query [%s] with args %v: %w", query, args, err)
	}

	return nil
}

// QueryRowContext executes a query that returns a single row with timeout
func (db *DB) QueryRowContext(ctx context.Context, query string, args ...interface{}) *sqlx.Row {
	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()

	return db.DB.QueryRowxContext(ctx, query, args...)
}

// QueryContext executes a query that returns multiple rows with adaptive timeout
func (db *DB) QueryContext(ctx context.Context, query string, args ...interface{}) (*sqlx.Rows, error) {
	// Set timeout based on query complexity
	timeout := 5 * time.Second
	if strings.Contains(strings.ToLower(query), "join") ||
		strings.Contains(strings.ToLower(query), "group by") ||
		strings.Contains(strings.ToLower(query), "order by") {
		timeout = 15 * time.Second
	}

	ctx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()

	start := time.Now()
	rows, err := db.DB.QueryxContext(ctx, query, args...)
	elapsed := time.Since(start)

	// Log slow queries
	if elapsed > timeout/2 {
		log.Printf("Slow query detected: %s (took %v)", query, elapsed)
	}

	if err != nil {
		return nil, fmt.Errorf("failed to execute query [%s] with args %v: %w", query, args, err)
	}

	return rows, nil
}

// Close closes the database connection
func (db *DB) Close() error {
	if err := db.DB.Close(); err != nil {
		return fmt.Errorf("failed to close database connection: %w", err)
	}
	return nil
}