package monitoring

import (
	"context"
	"fmt"
	"os"
	"strconv"
	"strings"
	"time"

	"github.com/example/storage-appliance/internal/infra/osexec"
	"github.com/example/storage-appliance/internal/service"
)

const (
	DefaultTimeout = 5 * time.Second
)

// MetricValue represents a single metric value
type MetricValue struct {
	Name   string
	Labels map[string]string
	Value  float64
	Type   string // "gauge" or "counter"
}

// MetricCollection represents a collection of metrics
type MetricCollection struct {
	Metrics []MetricValue
	Errors  []string
}

// Collector interface for different metric collectors
type Collector interface {
	Collect(ctx context.Context) MetricCollection
	Name() string
}

// ZFSCollector collects ZFS pool health and scrub status
type ZFSCollector struct {
	ZFSSvc service.ZFSService
	Runner osexec.Runner
}

func NewZFSCollector(zfsSvc service.ZFSService, runner osexec.Runner) *ZFSCollector {
	return &ZFSCollector{ZFSSvc: zfsSvc, Runner: runner}
}

func (c *ZFSCollector) Name() string {
	return "zfs"
}

func (c *ZFSCollector) Collect(ctx context.Context) MetricCollection {
	ctx, cancel := context.WithTimeout(ctx, DefaultTimeout)
	defer cancel()

	collection := MetricCollection{
		Metrics: []MetricValue{},
		Errors:  []string{},
	}

	// Get pool list
	pools, err := c.ZFSSvc.ListPools(ctx)
	if err != nil {
		collection.Errors = append(collection.Errors, fmt.Sprintf("failed to list pools: %v", err))
		return collection
	}

	for _, pool := range pools {
		// Pool health metric (1 = ONLINE, 0.5 = DEGRADED, 0 = FAULTED/OFFLINE)
		healthValue := 0.0
		switch strings.ToUpper(pool.Health) {
		case "ONLINE":
			healthValue = 1.0
		case "DEGRADED":
			healthValue = 0.5
		case "FAULTED", "OFFLINE", "UNAVAIL":
			healthValue = 0.0
		}

		collection.Metrics = append(collection.Metrics, MetricValue{
			Name:   "zfs_pool_health",
			Labels: map[string]string{"pool": pool.Name},
			Value:  healthValue,
			Type:   "gauge",
		})

		// Get scrub status
		scrubStatus, err := c.getScrubStatus(ctx, pool.Name)
		if err != nil {
			collection.Errors = append(collection.Errors, fmt.Sprintf("failed to get scrub status for %s: %v", pool.Name, err))
			continue
		}

		// Scrub in progress (1 = yes, 0 = no)
		scrubInProgress := 0.0
		if strings.Contains(scrubStatus, "scan: scrub in progress") {
			scrubInProgress = 1.0
		}

		collection.Metrics = append(collection.Metrics, MetricValue{
			Name:   "zfs_pool_scrub_in_progress",
			Labels: map[string]string{"pool": pool.Name},
			Value:  scrubInProgress,
			Type:   "gauge",
		})
	}

	return collection
}

func (c *ZFSCollector) getScrubStatus(ctx context.Context, pool string) (string, error) {
	out, _, _, err := osexec.ExecWithRunner(c.Runner, ctx, "zpool", "status", pool)
	if err != nil {
		return "", err
	}
	for _, line := range strings.Split(out, "\n") {
		if strings.Contains(line, "scan:") {
			return strings.TrimSpace(line), nil
		}
	}
	return "no-scan", nil
}

// SMARTCollector collects SMART health status
type SMARTCollector struct {
	Runner osexec.Runner
}

func NewSMARTCollector(runner osexec.Runner) *SMARTCollector {
	return &SMARTCollector{Runner: runner}
}

func (c *SMARTCollector) Name() string {
	return "smart"
}

func (c *SMARTCollector) Collect(ctx context.Context) MetricCollection {
	ctx, cancel := context.WithTimeout(ctx, DefaultTimeout)
	defer cancel()

	collection := MetricCollection{
		Metrics: []MetricValue{},
		Errors:  []string{},
	}

	// List all disks (simplified - try common devices)
	// In a real implementation, you'd scan /dev/ or use lsblk
	commonDisks := []string{"sda", "sdb", "sdc", "nvme0n1", "nvme1n1"}
	disks := []string{}
	for _, d := range commonDisks {
		disks = append(disks, fmt.Sprintf("/dev/%s", d))
	}

	// Check SMART health for each disk
	for _, disk := range disks {
		health, err := c.getSMARTHealth(ctx, disk)
		if err != nil {
			// Skip devices that don't exist or don't support SMART
			continue
		}

		// SMART health: 1 = PASSED, 0 = FAILED
		healthValue := 0.0
		if strings.Contains(strings.ToUpper(health), "PASSED") {
			healthValue = 1.0
		}

		collection.Metrics = append(collection.Metrics, MetricValue{
			Name:   "smart_health",
			Labels: map[string]string{"device": disk},
			Value:  healthValue,
			Type:   "gauge",
		})
	}

	return collection
}

func (c *SMARTCollector) getSMARTHealth(ctx context.Context, device string) (string, error) {
	// Use smartctl -H to get health status
	out, _, code, err := osexec.ExecWithRunner(c.Runner, ctx, "smartctl", "-H", device)
	if err != nil || code != 0 {
		return "", fmt.Errorf("smartctl failed: %v", err)
	}
	return out, nil
}

// ServiceCollector collects service states
type ServiceCollector struct {
	Runner osexec.Runner
}

func NewServiceCollector(runner osexec.Runner) *ServiceCollector {
	return &ServiceCollector{Runner: runner}
}

func (c *ServiceCollector) Name() string {
	return "services"
}

func (c *ServiceCollector) Collect(ctx context.Context) MetricCollection {
	ctx, cancel := context.WithTimeout(ctx, DefaultTimeout)
	defer cancel()

	collection := MetricCollection{
		Metrics: []MetricValue{},
		Errors:  []string{},
	}

	services := []string{"nfs-server", "smbd", "iscsid", "iscsi", "minio"}

	for _, svc := range services {
		status, err := c.getServiceStatus(ctx, svc)
		if err != nil {
			collection.Errors = append(collection.Errors, fmt.Sprintf("failed to check %s: %v", svc, err))
			continue
		}

		// Service state: 1 = active/running, 0 = inactive/stopped
		stateValue := 0.0
		if strings.Contains(strings.ToLower(status), "active") || strings.Contains(strings.ToLower(status), "running") {
			stateValue = 1.0
		}

		collection.Metrics = append(collection.Metrics, MetricValue{
			Name:   "service_state",
			Labels: map[string]string{"service": svc},
			Value:  stateValue,
			Type:   "gauge",
		})
	}

	return collection
}

func (c *ServiceCollector) getServiceStatus(ctx context.Context, service string) (string, error) {
	// Try systemctl first
	out, _, code, err := osexec.ExecWithRunner(c.Runner, ctx, "systemctl", "is-active", service)
	if err == nil && code == 0 {
		return out, nil
	}

	// Fallback to checking process
	out, _, code, err = osexec.ExecWithRunner(c.Runner, ctx, "pgrep", "-f", service)
	if err == nil && code == 0 && strings.TrimSpace(out) != "" {
		return "running", nil
	}

	return "inactive", nil
}

// HostCollector collects host metrics from /proc
type HostCollector struct{}

func NewHostCollector() *HostCollector {
	return &HostCollector{}
}

func (c *HostCollector) Name() string {
	return "host"
}

func (c *HostCollector) Collect(ctx context.Context) MetricCollection {
	ctx, cancel := context.WithTimeout(ctx, DefaultTimeout)
	defer cancel()

	collection := MetricCollection{
		Metrics: []MetricValue{},
		Errors:  []string{},
	}

	// Load average
	loadavg, err := c.readLoadAvg()
	if err != nil {
		collection.Errors = append(collection.Errors, fmt.Sprintf("failed to read loadavg: %v", err))
	} else {
		collection.Metrics = append(collection.Metrics, MetricValue{
			Name:   "host_load1",
			Labels: map[string]string{},
			Value:  loadavg.Load1,
			Type:   "gauge",
		})
		collection.Metrics = append(collection.Metrics, MetricValue{
			Name:   "host_load5",
			Labels: map[string]string{},
			Value:  loadavg.Load5,
			Type:   "gauge",
		})
		collection.Metrics = append(collection.Metrics, MetricValue{
			Name:   "host_load15",
			Labels: map[string]string{},
			Value:  loadavg.Load15,
			Type:   "gauge",
		})
	}

	// Memory info
	meminfo, err := c.readMemInfo()
	if err != nil {
		collection.Errors = append(collection.Errors, fmt.Sprintf("failed to read meminfo: %v", err))
	} else {
		collection.Metrics = append(collection.Metrics, MetricValue{
			Name:   "host_memory_total_bytes",
			Labels: map[string]string{},
			Value:  meminfo.MemTotal,
			Type:   "gauge",
		})
		collection.Metrics = append(collection.Metrics, MetricValue{
			Name:   "host_memory_free_bytes",
			Labels: map[string]string{},
			Value:  meminfo.MemFree,
			Type:   "gauge",
		})
		collection.Metrics = append(collection.Metrics, MetricValue{
			Name:   "host_memory_available_bytes",
			Labels: map[string]string{},
			Value:  meminfo.MemAvailable,
			Type:   "gauge",
		})
	}

	// Disk IO (simplified - read from /proc/diskstats)
	diskIO, err := c.readDiskIO()
	if err != nil {
		collection.Errors = append(collection.Errors, fmt.Sprintf("failed to read disk IO: %v", err))
	} else {
		for device, io := range diskIO {
			collection.Metrics = append(collection.Metrics, MetricValue{
				Name:   "host_disk_reads_completed",
				Labels: map[string]string{"device": device},
				Value:  io.ReadsCompleted,
				Type:   "counter",
			})
			collection.Metrics = append(collection.Metrics, MetricValue{
				Name:   "host_disk_writes_completed",
				Labels: map[string]string{"device": device},
				Value:  io.WritesCompleted,
				Type:   "counter",
			})
		}
	}

	return collection
}

type LoadAvg struct {
	Load1  float64
	Load5  float64
	Load15 float64
}

func (c *HostCollector) readLoadAvg() (LoadAvg, error) {
	data, err := os.ReadFile("/proc/loadavg")
	if err != nil {
		return LoadAvg{}, err
	}

	fields := strings.Fields(string(data))
	if len(fields) < 3 {
		return LoadAvg{}, fmt.Errorf("invalid loadavg format")
	}

	load1, _ := strconv.ParseFloat(fields[0], 64)
	load5, _ := strconv.ParseFloat(fields[1], 64)
	load15, _ := strconv.ParseFloat(fields[2], 64)

	return LoadAvg{Load1: load1, Load5: load5, Load15: load15}, nil
}

type MemInfo struct {
	MemTotal     float64
	MemFree      float64
	MemAvailable float64
}

func (c *HostCollector) readMemInfo() (MemInfo, error) {
	data, err := os.ReadFile("/proc/meminfo")
	if err != nil {
		return MemInfo{}, err
	}

	info := MemInfo{}
	lines := strings.Split(string(data), "\n")
	for _, line := range lines {
		fields := strings.Fields(line)
		if len(fields) < 2 {
			continue
		}
		key := strings.TrimSuffix(fields[0], ":")
		value, _ := strconv.ParseFloat(fields[1], 64)
		// Values are in KB, convert to bytes
		valueBytes := value * 1024

		switch key {
		case "MemTotal":
			info.MemTotal = valueBytes
		case "MemFree":
			info.MemFree = valueBytes
		case "MemAvailable":
			info.MemAvailable = valueBytes
		}
	}

	return info, nil
}

type DiskIO struct {
	ReadsCompleted  float64
	WritesCompleted float64
}

func (c *HostCollector) readDiskIO() (map[string]DiskIO, error) {
	data, err := os.ReadFile("/proc/diskstats")
	if err != nil {
		return nil, err
	}

	result := make(map[string]DiskIO)
	lines := strings.Split(string(data), "\n")
	for _, line := range lines {
		fields := strings.Fields(line)
		if len(fields) < 14 {
			continue
		}
		device := fields[2]
		reads, _ := strconv.ParseFloat(fields[3], 64)
		writes, _ := strconv.ParseFloat(fields[7], 64)

		result[device] = DiskIO{
			ReadsCompleted:  reads,
			WritesCompleted: writes,
		}
	}

	return result, nil
}