package main

import (
	"bufio"
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"
)

const (
	cpuInfoPath  = "/proc/cpuinfo"
	procStatPath = "/proc/stat"
)

type cpuCollector struct {
	mu           sync.Mutex
	cpuInfoPath  string
	procStatPath string
	static       CPUStatic
	previous     cpuTimes
}

type CPUStatic struct {
	Model         string `json:"model"`
	Sockets       int    `json:"sockets"`
	PhysicalCores int    `json:"physicalCores"`
	LogicalCPUs   int    `json:"logicalCpus"`
}

type CPUMetrics struct {
	CPUStatic
	UsagePercent float64       `json:"usagePercent"`
	FrequencyMHz float64       `json:"frequencyMhz"`
	Load1        float64       `json:"load1"`
	Load5        float64       `json:"load5"`
	Load15       float64       `json:"load15"`
	Uptime       uint64        `json:"uptimeSeconds"`
	Temperatures []Temperature `json:"temperatures"`
	CollectedAt  time.Time     `json:"collectedAt"`
}

type Temperature struct {
	Label   string  `json:"label"`
	Celsius float64 `json:"celsius"`
}

type cpuTimes struct {
	total uint64
	idle  uint64
}

func newCPUCollector(infoPath, statPath string) (*cpuCollector, error) {
	static, err := readCPUStatic(infoPath)
	if err != nil {
		return nil, err
	}
	previous, err := readCPUTimes(statPath)
	if err != nil {
		return nil, err
	}
	return &cpuCollector{
		cpuInfoPath: infoPath, procStatPath: statPath,
		static: static, previous: previous,
	}, nil
}

func (c *cpuCollector) collect() (CPUMetrics, error) {
	c.mu.Lock()
	defer c.mu.Unlock()

	current, err := readCPUTimes(c.procStatPath)
	if err != nil {
		return CPUMetrics{}, err
	}

	var usage float64
	totalDelta := current.total - c.previous.total
	idleDelta := current.idle - c.previous.idle
	if totalDelta > 0 {
		usage = float64(totalDelta-idleDelta) / float64(totalDelta) * 100
	}
	c.previous = current

	frequency, _ := averageFrequencyMHz(c.cpuInfoPath)
	load1, load5, load15, _ := readLoadAverage()
	uptime, _ := readUptime()

	return CPUMetrics{
		CPUStatic: c.static, UsagePercent: usage, FrequencyMHz: frequency,
		Load1: load1, Load5: load5, Load15: load15, Uptime: uptime,
		Temperatures: readTemperatures(), CollectedAt: time.Now(),
	}, nil
}

func readCPUStatic(path string) (CPUStatic, error) {
	file, err := os.Open(path)
	if err != nil {
		return CPUStatic{}, err
	}
	defer file.Close()

	var model string
	logical := 0
	physicalIDs := map[string]struct{}{}
	cores := map[string]struct{}{}
	physicalID := "0"

	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		line := scanner.Text()
		if strings.TrimSpace(line) == "" {
			physicalID = "0"
			continue
		}
		key, value, found := strings.Cut(line, ":")
		if !found {
			continue
		}
		key, value = strings.TrimSpace(key), strings.TrimSpace(value)
		switch key {
		case "processor":
			logical++
		case "model name", "Hardware":
			if model == "" {
				model = value
			}
		case "physical id":
			physicalID = value
			physicalIDs[value] = struct{}{}
		case "core id":
			cores[physicalID+":"+value] = struct{}{}
		}
	}
	if err := scanner.Err(); err != nil {
		return CPUStatic{}, err
	}
	if model == "" {
		return CPUStatic{}, fmt.Errorf("модель CPU не найдена в %s", path)
	}
	if len(physicalIDs) == 0 {
		physicalIDs["0"] = struct{}{}
	}
	physicalCores := len(cores)
	if physicalCores == 0 {
		physicalCores = logical
	}
	return CPUStatic{
		Model: model, Sockets: len(physicalIDs),
		PhysicalCores: physicalCores, LogicalCPUs: logical,
	}, nil
}

func cpuModel(path string) (string, error) {
	info, err := readCPUStatic(path)
	return info.Model, err
}

func readCPUTimes(path string) (cpuTimes, error) {
	file, err := os.Open(path)
	if err != nil {
		return cpuTimes{}, err
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	if !scanner.Scan() {
		return cpuTimes{}, fmt.Errorf("пустой файл %s", path)
	}
	fields := strings.Fields(scanner.Text())
	if len(fields) < 5 || fields[0] != "cpu" {
		return cpuTimes{}, fmt.Errorf("неожиданный формат %s", path)
	}
	var values []uint64
	for _, field := range fields[1:] {
		value, err := strconv.ParseUint(field, 10, 64)
		if err != nil {
			return cpuTimes{}, err
		}
		values = append(values, value)
	}
	var total uint64
	for _, value := range values {
		total += value
	}
	idle := values[3]
	if len(values) > 4 {
		idle += values[4]
	}
	return cpuTimes{total: total, idle: idle}, nil
}

func averageFrequencyMHz(path string) (float64, error) {
	file, err := os.Open(path)
	if err != nil {
		return 0, err
	}
	defer file.Close()
	var sum float64
	var count int
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		key, value, found := strings.Cut(scanner.Text(), ":")
		if found && strings.TrimSpace(key) == "cpu MHz" {
			mhz, err := strconv.ParseFloat(strings.TrimSpace(value), 64)
			if err == nil {
				sum += mhz
				count++
			}
		}
	}
	if count == 0 {
		return 0, fmt.Errorf("частота CPU недоступна")
	}
	return sum / float64(count), scanner.Err()
}

func readLoadAverage() (float64, float64, float64, error) {
	data, err := os.ReadFile("/proc/loadavg")
	if err != nil {
		return 0, 0, 0, err
	}
	fields := strings.Fields(string(data))
	if len(fields) < 3 {
		return 0, 0, 0, fmt.Errorf("неожиданный формат /proc/loadavg")
	}
	one, err1 := strconv.ParseFloat(fields[0], 64)
	five, err2 := strconv.ParseFloat(fields[1], 64)
	fifteen, err3 := strconv.ParseFloat(fields[2], 64)
	if err1 != nil || err2 != nil || err3 != nil {
		return 0, 0, 0, fmt.Errorf("не удалось прочитать load average")
	}
	return one, five, fifteen, nil
}

func readUptime() (uint64, error) {
	data, err := os.ReadFile("/proc/uptime")
	if err != nil {
		return 0, err
	}
	seconds, err := strconv.ParseFloat(strings.Fields(string(data))[0], 64)
	return uint64(seconds), err
}

func readTemperatures() []Temperature {
	var result []Temperature
	paths, _ := filepath.Glob("/sys/class/hwmon/hwmon*/temp*_input")
	for _, path := range paths {
		hwmonDir := filepath.Dir(path)
		chipData, _ := os.ReadFile(filepath.Join(hwmonDir, "name"))
		chip := strings.TrimSpace(string(chipData))
		if !isCPUTemperatureChip(chip) {
			continue
		}
		data, err := os.ReadFile(path)
		if err != nil {
			continue
		}
		raw, err := strconv.ParseFloat(strings.TrimSpace(string(data)), 64)
		if err != nil || raw <= 0 {
			continue
		}
		label := filepath.Base(path)
		labelPath := strings.TrimSuffix(path, "_input") + "_label"
		if data, err := os.ReadFile(labelPath); err == nil {
			label = strings.TrimSpace(string(data))
		}
		if chip != "" {
			label = chip + " · " + label
		}
		result = append(result, Temperature{Label: label, Celsius: raw / 1000})
	}
	return result
}

func isCPUTemperatureChip(name string) bool {
	switch name {
	case "coretemp", "k10temp", "zenpower", "cpu_thermal", "soc_thermal":
		return true
	default:
		return false
	}
}