package drivers

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

type MemInfoDriver struct{}

func NewMemInfoDriver() (*MemInfoDriver, error) {
	r := MemInfoDriver{}
	_, err := r.Read()
	return &r, err
}

func (r *MemInfoDriver) Render(console *strings.Builder) error {
	u, err := r.Read()
	if err != nil {
		return err
	}

	usage := u.(MemoryUsage)

	fmt.Fprintf(console, "--- Usage ---\033[K\n")
	fmt.Fprintf(console, "%-16s | %.2f GiB\033[K\n", "Total", usage.TotalGB)
	fmt.Fprintf(console, "%-16s | %.2f GiB (%.2f%%) \033[K\n", "Used", usage.UsedGB, usage.UsedPercent)
	fmt.Fprintf(console, "%-16s | %.2f GiB\033[K\n", "Avail", usage.AvailableGB)

	return nil
}

// Read /proc/meminfo for active system memory statistics
func (r *MemInfoDriver) Read() (any, error) {
	usage := MemoryUsage{}
	file, err := os.Open("/proc/meminfo")
	if err != nil {
		return usage, err
	}
	defer file.Close()

	var memTotal, memAvailable float64
	scanner := bufio.NewScanner(file)

	for scanner.Scan() {
		line := scanner.Text()
		fields := strings.Fields(line)
		if len(fields) < 2 {
			continue
		}

		val, err := strconv.ParseFloat(fields[1], 64)
		if err != nil {
			continue
		}

		switch fields[0] {
		case "MemTotal:":
			memTotal = val // stored in kB
		case "MemAvailable:":
			memAvailable = val // stored in kB
		}
	}

	if err := scanner.Err(); err != nil {
		return usage, err
	}

	used := memTotal - memAvailable
	usedPct := (used / memTotal) * 100

	usage = MemoryUsage{
		TotalGB:     memTotal / (1024 * 1024),
		AvailableGB: memAvailable / (1024 * 1024),
		UsedGB:      used / (1024 * 1024),
		UsedPercent: usedPct,
	}

	return usage, nil
}