// Command mesh-checking-program is the checker's checking program (novox/hq ADR 0644, ADR 0656; design 47's bootstrap
// delivery): built from a check's heads and run in the build seat's sandbox through the seat node-build-go's ask run,
// with no network and no bus account, it reads the check's facts from the file MESH_RUN_INPUT names and answers the
// verdict the judging rules give them, as one JSON line on its standard output (rules.Answer).
//
//	mesh-checking-program -verdict
//	mesh-checking-program -seats
//
// Asked -seats, it answers the seat list of the heads laid in the directory MESH_RUN_HEADS names (rules.SeatsAnswer).
// It refuses facts of a version it does not read, naming it, with exit 2.
package main

import (
	"fmt"
	"io"
	"io/fs"
	"os"
	"slices"

	"mesh-delivery-checker/rules"

	"git.novox.be/novox/mesh-delivery/sdk/buildstep"
)

func main() {
	os.Exit(run(os.Args[1:], os.Getenv, os.Stdout, os.Stderr))
}

// run is the command over its arguments, environment and outputs, answering its exit.
func run(args []string, getenv func(string) string, stdout, stderr io.Writer) int {
	var heads fs.FS
	if dir := getenv(buildstep.RunHeadsEnv); dir != "" {
		heads = os.DirFS(dir)
	}
	input := func() ([]byte, error) {
		file := getenv(buildstep.RunInputEnv)
		if file == "" {
			return nil, fmt.Errorf("%s names no file", buildstep.RunInputEnv)
		}
		return os.ReadFile(file)
	}
	line, err := rules.Program(args, input, heads)
	if err != nil {
		if heads == nil && slices.Contains(args, "-seats") {
			err = fmt.Errorf("no heads: %s names no directory", buildstep.RunHeadsEnv)
		}
		fmt.Fprintf(stderr, "mesh-checking-program: %v\n", err)
		return 2
	}
	fmt.Fprintf(stdout, "%s\n", line)
	return 0
}