package main

import (
	"fmt"
	"os"
	"path/filepath"
	"runtime"
	"strings"
)

// requiredGoVersion reads the Go version from the root go.mod file.
// Returns a version string like "1.25.7" for use in download URLs.
func requiredGoVersion() (string, error) {
	_, thisFile, _, _ := runtime.Caller(0)
	rootMod := filepath.Join(filepath.Dir(thisFile), "..", "..", "go.mod")

	data, err := os.ReadFile(rootMod)
	if err != nil {
		return "", fmt.Errorf("read root go.mod: %w", err)
	}

	for _, line := range strings.Split(string(data), "\n") {
		line = strings.TrimSpace(line)
		if strings.HasPrefix(line, "go ") {
			version := strings.TrimPrefix(line, "go ")
			version = strings.TrimSpace(version)
			// Validate it looks like a version
			if len(version) > 0 && version[0] >= '1' && version[0] <= '9' {
				return version, nil
			}
		}
	}

	return "", fmt.Errorf("no 'go X.Y.Z' directive found in %s", rootMod)
}