// modbot is a system information agregator
// 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 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

package readers

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

type CpuUsageInfo struct {
	InUse        uint64
	Total        uint64
	UsagePercent float64
}

func (cu CpuUsageInfo) String() string {
	return fmt.Sprintf("%d%%", uint(cu.UsagePercent))
}

func ReadCpuUsage() func() (interface{}, error) {
	return func() (interface{}, error) {
		file, err := os.Open("/proc/stat")
		if err != nil {
			return CpuUsageInfo{}, err
		}
		defer file.Close()

		var cpuInUse, cpuTotal uint64
		scanner := bufio.NewScanner(file)

		scanner.Scan()
		for scanner.Scan() {
			line := scanner.Text()

			if !strings.HasPrefix(line, "cpu") {
				break
			}

			var cpuN string
			var cpuUser, cpuNice, cpuSystem, cpuIdle, cpuIoWait, cpuIrq, cpuSoftIrq uint64

			_, err := fmt.Sscanf(line, "cpu%s %d %d %d %d %d %d %d",
				&cpuN, &cpuUser, &cpuNice, &cpuSystem, &cpuIdle, &cpuIoWait, &cpuIrq, &cpuSoftIrq)
			if err != nil {
				return CpuUsageInfo{}, fmt.Errorf("failed to parse CPU stats: %w", err)
			}

			inUse := cpuUser + cpuNice + cpuSystem
			total := inUse + cpuIdle + cpuIoWait + cpuIrq + cpuSoftIrq

			cpuInUse += inUse
			cpuTotal += total
		}

		if err := scanner.Err(); err != nil {
			return CpuUsageInfo{}, err
		}
		if cpuTotal == 0 {
			return CpuUsageInfo{}, errors.New("no CPU stats found")
		}

		return CpuUsageInfo{
			InUse:        cpuInUse,
			Total:        cpuTotal,
			UsagePercent: float64(cpuInUse) * 100 / float64(cpuTotal),
		}, nil
	}
}