// sysinfo queries information about your system
// Copyright (C) 2024 frosty <inthishouseofcards@gmail.com>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

package readers

import (
	"bufio"
	"errors"
	"fmt"
	"os"
	"strconv"
	"strings"
)

type MemoryInfo struct {
	Total     uint64
	Available uint64
	Used      uint64
}

func ReadMemory() (MemoryInfo, error) {
	file, err := os.Open("/proc/meminfo")
	if err != nil {
		return MemoryInfo{}, err
	}
	defer file.Close()

	var memTotal, memAvailable uint64
	scanner := bufio.NewScanner(file)

	for scanner.Scan() {
		line := scanner.Text()
		columns := strings.Fields(line)

		if len(columns) < 2 {
			continue
		}

		value, err := strconv.ParseUint(columns[1], 10, 64)
		if err != nil {
			return MemoryInfo{}, fmt.Errorf("failed to parse memory value: %w", err)
		}

		switch {
		case strings.HasPrefix(line, "MemTotal:"):
			memTotal = value
		case strings.HasPrefix(line, "MemAvailable:"):
			memAvailable = value
		}
	}

	if err := scanner.Err(); err != nil {
		return MemoryInfo{}, err
	}
	if memTotal == 0 {
		return MemoryInfo{}, errors.New("missing MemTotal")
	}
	if memAvailable == 0 {
		return MemoryInfo{}, errors.New("missing MemAvailable")
	}

	return MemoryInfo{
		Total:     memTotal,
		Available: memAvailable,
		Used:      memTotal - memAvailable,
	}, nil
}