package keymgr

import (
	"fmt"
	"strings"
)

// RenderClientConfig produces an OpenSSH client config (works identically on
// Windows' built-in OpenSSH client, macOS, and Linux). It defines exactly
// one connection, "jump", carrying one LocalForward per allowed service —
// the user opens it once (see INSTRUCTIONS.txt) and every service becomes
// reachable at once on the listed local ports, for as long as that one
// connection stays open.
//
// This file is convenience only, not a security boundary: nothing stops a
// user from editing it or invoking ssh by hand. The actual restriction to
// these destinations is enforced server-side via authorized_keys
// permitopen= (see internal/sysadm/authorizedkeys.go) independent of what
// this file says.
func RenderClientConfig(jumpHost string, jumpPort int, username, keyFileName string, forwards []AllocatedForward) string {
	var b strings.Builder
	fmt.Fprintf(&b, "# ssh-access-tui client config for %s\n", username)
	fmt.Fprintf(&b, "# Generated %s. Regenerated whenever your allowed services change.\n\n", genTimestamp())

	fmt.Fprintf(&b, "Host jump\n")
	fmt.Fprintf(&b, "    HostName %s\n", jumpHost)
	fmt.Fprintf(&b, "    Port %d\n", jumpPort)
	fmt.Fprintf(&b, "    User %s\n", username)
	fmt.Fprintf(&b, "    IdentityFile ~/.ssh/%s\n", keyFileName)
	fmt.Fprintf(&b, "    IdentitiesOnly yes\n")
	for _, f := range forwards {
		comment := f.HostName + "/" + f.ServiceName
		if f.Description != "" {
			comment += ": " + f.Description
		}
		fmt.Fprintf(&b, "    LocalForward %d %s:%d  # %s\n", f.LocalPort, f.Address, f.Port, comment)
	}
	return b.String()
}