basic frontend (#3)

Co-authored-by: aovantsev <aovantsev@avito.ru>
Reviewed-on: #3

database.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"database/sql"
+	"fmt"
+	"log"
+	"os"
+
+	_ "github.com/lib/pq"
+)
+
+var db *sql.DB
+
+// InitDB initializes the database connection (legacy function)
+func InitDB() error {
+	// Get database URL from environment variable
+	dbURL := os.Getenv("DATABASE_URL")
+	if dbURL == "" {
+		// Default for local development
+		dbURL = "postgres://postgres:password@localhost:5432/counter_db?sslmode=disable"
+	}
+	return initDBWithURL(dbURL)
+}
+
+// InitDBWithConfig initializes the database connection with configuration
+func InitDBWithConfig(config *Config) error {
+	return initDBWithURL(config.DatabaseURL)
+}
+
+// initDBWithURL initializes the database connection with a specific URL
+func initDBWithURL(dbURL string) error {
+
+	var err error
+	db, err = sql.Open("postgres", dbURL)
+	if err != nil {
+		return fmt.Errorf("failed to open database: %w", err)
+	}
+
+	// Test the connection
+	if err = db.Ping(); err != nil {
+		return fmt.Errorf("failed to ping database: %w", err)
+	}
+
+	log.Println("✅ Database connection established successfully")
+	return nil
+}
+
+// CreateTables creates the necessary database tables
+func CreateTables() error {
+	queries := []string{
+		`CREATE TABLE IF NOT EXISTS users (
+			id SERIAL PRIMARY KEY,
+			username VARCHAR(50) UNIQUE NOT NULL,
+			email VARCHAR(255) UNIQUE NOT NULL,
+			password VARCHAR(255) NOT NULL,
+			created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+			updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+		)`,
+		`CREATE TABLE IF NOT EXISTS counters (
+			id SERIAL PRIMARY KEY,
+			user_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
+			name VARCHAR(100) NOT NULL,
+			description TEXT,
+			created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+			updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+		)`,
+		`CREATE TABLE IF NOT EXISTS counter_entries (
+			id SERIAL PRIMARY KEY,
+			counter_id INTEGER REFERENCES counters(id) ON DELETE CASCADE,
+			value INTEGER NOT NULL,
+			date DATE NOT NULL,
+			created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+		)`,
+		`CREATE INDEX IF NOT EXISTS idx_counters_user_id ON counters(user_id)`,
+		`CREATE INDEX IF NOT EXISTS idx_counter_entries_counter_id ON counter_entries(counter_id)`,
+		`CREATE INDEX IF NOT EXISTS idx_counter_entries_date ON counter_entries(date)`,
+	}
+
+	for _, query := range queries {
+		if _, err := db.Exec(query); err != nil {
+			return fmt.Errorf("failed to execute query: %w", err)
+		}
+	}
+
+	log.Println("✅ Database tables created successfully")
+	return nil
+}
+
+// GetDB returns the database connection
+func GetDB() *sql.DB {
+	return db
+}