package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"os/exec"
	"strconv"
	"strings"

	tea "charm.land/bubbletea/v2"
)

type SysValue[T int | float64] struct {
	Val T
	Fmt string
	Inf bool
}

type Detail struct {
	Name      string
	Desc      string
	Memory    SysValue[float64]
	MemoryMax SysValue[float64]
	Tasks     SysValue[int]
	TasksMax  SysValue[int]
	Cpu       float64
	Active    string
	Load      string
	Sub       string
}

type DetailLoadedMsg struct {
	Detail Detail
	Err    error
}

func (m *model) LoadDetail() tea.Msg {
	d, err := m.loadDetail()

	if err != nil {
		return DetailLoadedMsg{Err: err}
	}

	if d == nil {
		return DetailLoadedMsg{}
	}

	cpu, _ := strconv.ParseFloat(d["CPUUsageNSec"], 64)

	return DetailLoadedMsg{Detail: Detail{
		Name:      m.filtered[m.cursor].Name,
		Desc:      m.filtered[m.cursor].Desc,
		Memory:    take[float64](d, "MemoryCurrent", "", "B", 2, 1000),
		MemoryMax: take[float64](d, "MemoryMax", "", "B", 2, 1000),
		Tasks:     take[int](d, "TasksCurrent", "", "", 1, 1000),
		TasksMax:  take[int](d, "TasksMax", "", "", 1, 1000),
		Cpu:       cpu / 1000000000,
		Active:    d["ActiveState"],
		Load:      d["LoadState"],
		Sub:       d["SubState"],
	}}
}

func take[T int | float64](d map[string]string, key string, start string, unit string, decimals int, step int) SysValue[T] {
	val, _ := takeVal[T](d, key, start)
	inf := normUnit(d, key, start) == ""
	fmt := formatUnit(d, key, start, unit, decimals, step)
	return SysValue[T]{Val: val, Inf: inf, Fmt: fmt}
}

func (v SysValue[T]) Alt(alt SysValue[T]) SysValue[T] {
	if v.Inf {
		return alt
	}
	return v
}

func (v SysValue[T]) Div(y SysValue[T]) float64 {
	return float64(v.Val) / float64(y.Val)
}

func takeVal[T int | float64](d map[string]string, key string, start string) (T, error) {
	x := normUnit(d, key, start)
	var zero T
	switch any(zero).(type) {
	case int:
		v, err := strconv.Atoi(x)
		return any(v).(T), err
	case float64:
		v, err := strconv.ParseFloat(x, 64)
		return any(v).(T), err
	default:
		return zero, fmt.Errorf("unsupported type")
	}
}

func (m *model) loadDetail() (map[string]string, error) {
	if len(m.filtered) == 0 {
		return nil, nil
	}

	detail := make(map[string]string)

	name := m.filtered[m.cursor].Name

	cmd := exec.Command(
		"systemctl", "show", name,
		"-p", "CPUUsageNSec",
		"-p", "CPUQuotaPerSecUSec",
		"-p", "MemoryCurrent",
		"-p", "MemoryMax",
		"-p", "TasksCurrent",
		"-p", "TasksMax",
		"-p", "ActiveState",
		"-p", "LoadState",
		"-p", "SubState",
	)

	out, err := cmd.Output()
	if err != nil {
		return nil, err
	}

	lines := strings.SplitSeq(string(out), "\n")

	for line := range lines {
		if parts := strings.SplitN(line, "=", 2); len(parts) == 2 {
			detail[parts[0]] = parts[1]
		}
	}

	return detail, nil
}

type System struct {
	Memory SysValue[float64]
	Tasks  SysValue[int]
}

type SystemLoadedMsg struct {
	System System
	Err    error
}

func LoadSystem() tea.Msg {
	d, err := loadMemSystem()

	if err != nil {
		return SystemLoadedMsg{Err: err}
	}

	if d == nil {
		return SystemLoadedMsg{}
	}

	return SystemLoadedMsg{System: System{
		Memory: take[float64](d, "MemTotal", "K", "B", 2, 1000),
		Tasks:  take[int](d, "TasksMax", "", "", 1, 1000),
	}}
}

func loadMemSystem() (map[string]string, error) {
	f, err := os.Open("/proc/meminfo")
	if err != nil {
		return nil, err
	}
	defer f.Close()

	l := make(map[string]string)

	scanner := bufio.NewScanner(f)

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

		key := strings.TrimSuffix(parts[0], ":")
		val, err := strconv.ParseUint(parts[1], 10, 64)
		if err != nil {
			continue
		}

		l[key] = strconv.FormatUint(val, 10)
	}

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

	return l, nil
}

func normUnit(dic map[string]string, key string, start string) string {
	start = strings.ToUpper(start)

	st := dic[key]

	if st == "infinity" || st == "" {
		return ""
	}

	sizes := []string{"", "K", "M", "G", "T", "P", "E", "Z", "Y"}

	n := 0
	for i, s := range sizes {
		if s == start {
			n = i
			break
		}
	}

	return fmt.Sprintf("%s%s", dic[key], strings.Repeat("0", n*3))
}

func formatUnit(dic map[string]string, key string, start string, unit string, decimals int, step int) string {
	start = strings.ToUpper(start)
	fstep := float64(step)

	st := dic[key]

	if st == "infinity" || st == "" {
		return fmt.Sprintf("∞ %s", unit)
	}

	value, _ := strconv.ParseFloat(st, 64)

	if value == 0 {
		return fmt.Sprintf("0 %s%s", start, unit)
	}

	sizes := []string{"", "K", "M", "G", "T", "P", "E", "Z", "Y"}

	n := 0
	for i, s := range sizes {
		if s == start {
			n = i
			break
		}
	}

	i := n + int(math.Floor(math.Log(value)/math.Log(fstep)))
	if i < 0 {
		i = 0
	}
	if i >= len(sizes) {
		i = len(sizes) - 1
	}

	value = value / math.Pow(fstep, float64(i-n))

	if math.Abs(value-math.Round(value)) < 0.05 {
		value = math.Round(value)
	}

	var formatted string
	if math.Mod(value, 1) == 0 {
		formatted = fmt.Sprintf("%.0f", value)
	} else {
		format := fmt.Sprintf("%%.%df", decimals)
		formatted = fmt.Sprintf(format, value)
	}

	return fmt.Sprintf("%s %s%s", formatted, sizes[i], unit)
}