feat(refactor): adding database package main code

cmd/api/database.go

@@ -0,0 +1,58 @@
+package database
+
+import (
+	"database/sql"
+	"fmt"
+
+	"forge.cadoles.com/LaCanne/realZ/internal/config"
+	_ "github.com/lib/pq" // Driver PostgreSQL
+)
+
+// Service holds the database connection pool.
+type Service struct {
+	db *sql.DB
+}
+
+// NewService initializes and returns a new database service.
+func NewService(cfg *config.DatabaseConfig) (*Service, error) {
+	connStr := fmt.Sprintf("user=%s password=%s dbname=%s host=%s port=%d sslmode=%s",
+		cfg.User, cfg.Password, cfg.Dbname,
+		cfg.Host, cfg.Port, cfg.Sslmode,
+	)
+
+	db, err := sql.Open("postgres", connStr)
+	if err != nil {
+		return nil, fmt.Errorf("could not open database connection: %w", err)
+	}
+
+	if err = db.Ping(); err != nil {
+		db.Close() // Close connection on ping failure
+		return nil, fmt.Errorf("could not ping database: %w", err)
+	}
+
+	return &Service{db: db}, nil
+}
+
+// Close closes the database connection.
+func (s *Service) Close() error {
+	return s.db.Close()
+}
+
+// QueryOrthometricCorrection queries the database for the orthometric correction for given coordinates.
+func (s *Service) QueryOrthometricCorrection(lat, lon float64, srcProj, dstProj int) (float64, error) {
+	var correction float64
+
+	query := `
+		SELECT ST_Value(rast, ST_Transform(ST_SetSRID(ST_MakePoint($2, $1), $3::integer), $4::integer)) AS pixel_value
+		FROM raf20lamber93
+		WHERE ST_Intersects(rast, ST_Transform(ST_SetSRID(ST_MakePoint($2, $1), $3::integer), $4::integer));
+	`
+
+	// QueryRow is ideal as we expect at most one row.
+	err := s.db.QueryRow(query, lat, lon, srcProj, dstProj).Scan(&correction)
+	if err != nil {
+		// If no rows are found, Scan will return sql.ErrNoRows.
+		return 0, err
+	}
+	return correction, nil
+}