// 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
//
// It refuses facts of a version it does not read, naming it, with exit 2.
package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"os"

	"git.novox.be/novox/mesh-sdk/go/delivery"
	"mesh-delivery-checker/rules"
)

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 {
	fs := flag.NewFlagSet("mesh-checking-program", flag.ContinueOnError)
	fs.SetOutput(stderr)
	verdict := fs.Bool("verdict", false, "answer the verdict of the facts in the input")
	if err := fs.Parse(args); err != nil {
		return 2
	}
	refuse := func(format string, a ...any) int {
		fmt.Fprintf(stderr, "mesh-checking-program: "+format+"\n", a...)
		return 2
	}
	if !*verdict {
		return refuse("nothing asked: give -verdict")
	}
	file := getenv(delivery.RunInputEnv)
	if file == "" {
		return refuse("no input: %s names no file", delivery.RunInputEnv)
	}
	data, err := os.ReadFile(file)
	if err != nil {
		return refuse("the input cannot be read: %v", err)
	}
	facts, err := rules.DecodeFacts(data)
	if err != nil {
		return refuse("%v", err)
	}
	line, err := json.Marshal(rules.Judged(facts))
	if err != nil {
		return refuse("the verdict cannot be written: %v", err)
	}
	fmt.Fprintf(stdout, "%s\n", line)
	return 0
}