package clouddetect

import (
	"bufio"
	"net"
	"os"
	"strings"
)

// LoadCIDRs reads the cloud_ranges.txt file and parses the CIDR blocks for each provider.
// The file format is simple: a provider name followed by a colon, then one CIDR per line.
// Blank lines and lines starting with '#' are ignored.
func LoadCIDRs(filePath string) (map[string][]*net.IPNet, error) {
	f, err := os.Open(filePath)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	cidrs := make(map[string][]*net.IPNet)
	var currentProvider string

	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		// Provider header, e.g., "Cloudflare:"
		if strings.HasSuffix(line, ":") {
			currentProvider = strings.TrimSuffix(line, ":")
			continue
		}
		// CIDR entry
		if currentProvider == "" {
			// Skip CIDR without a provider header.
			continue
		}
		_, ipnet, err := net.ParseCIDR(line)
		if err != nil {
			// Invalid CIDR – skip it.
			continue
		}
		cidrs[currentProvider] = append(cidrs[currentProvider], ipnet)
	}
	if err := scanner.Err(); err != nil {
		return nil, err
	}
	return cidrs, nil
}