package finger

import (
	"bytes"
	"context"
	"errors"
	"os/exec"

	"tildegit.org/tjp/gus"
)

// ListingDenied is returned to reject online user listing requests.
var ListingDenied = errors.New("Finger online user list denied.")

// SystemFinger handles finger requests by invoking the finger(1) command-line utility.
func SystemFinger(allowListings bool) gus.Handler {
	return func(ctx context.Context, request *gus.Request) *gus.Response {
		fingerPath, err := exec.LookPath("finger")
		if err != nil {
			_ = request.Server.LogError(
				"msg", "handler failure",
				"ctx", "exec.LookPath(\"finger\")",
				"err", err,
			)
			return Error("Could not resolve request.")
		}

		path := request.Path[1:]

		if len(path) == 0 && !allowListings {
			return Error(ListingDenied.Error())
		}

		args := make([]string, 0, 1)
		if len(path) > 0 {
			args = append(args, path)
		}

		cmd := exec.CommandContext(ctx, fingerPath, args...)
		outbuf := &bytes.Buffer{}
		cmd.Stdout = outbuf

		if err := cmd.Run(); err != nil {
			return Error(err.Error())
		}
		return Success(outbuf)
	}
}