package main

import (
	"encoding/json"
	"fmt"
	"os"
)

func readJSON(path string, v any) error {
	body, err := os.ReadFile(path)
	if err != nil {
		return err
	}
	return json.Unmarshal(body, v)
}

// writeJSON replaces the file atomically: a half-written state file would look
// like a corrupt install on the next run.
func writeJSON(path string, v any) error {
	body, err := json.MarshalIndent(v, "", "   ")
	if err != nil {
		return err
	}
	tmp := fmt.Sprintf("%s.%d", path, os.Getpid())
	addTemp(tmp)
	defer dropTemp(tmp)

	if err := os.WriteFile(tmp, append(body, '\n'), 0o644); err != nil {
		return fmt.Errorf("cannot write %s: %w", tmp, err)
	}
	if err := os.Rename(tmp, path); err != nil {
		os.Remove(tmp)
		return fmt.Errorf("cannot update %s: %w", path, err)
	}
	return nil
}

func humanSize(n int64) string {
	switch {
	case n >= 1024*1024:
		return fmt.Sprintf("%.1f MB", float64(n)/1024/1024)
	case n >= 1024:
		return fmt.Sprintf("%.1f kB", float64(n)/1024)
	}
	return fmt.Sprintf("%d B", n)
}