package metrics

import (
	"strconv"
	"strings"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"lostak.dev/pve-exporter/proxmox"
)

// PveNodeZfsCollector collects ZFS pool and component health metrics.
type PveNodeZfsCollector struct {
	apiClient *proxmox.PveApiClient
	registry  *TTLRegistry

	state          *TTLGaugeVec
	readErrors     *TTLGaugeVec
	writeErrors    *TTLGaugeVec
	checksumErrors *TTLGaugeVec
}

// zfsMetricComponent is a flattened entry from the recursive ZFS topology.
type zfsMetricComponent struct {
	proxmox.PveZfsComponent
	Path string
}

var zfsStateValues = map[string]float64{
	"ONLINE":   1,
	"DEGRADED": 2,
	"FAULTED":  3,
	"OFFLINE":  4,
	"REMOVED":  5,
	"UNAVAIL":  6,
}

// NewPveNodeZfsCollector creates a ZFS metrics collector.
func NewPveNodeZfsCollector(apiClient *proxmox.PveApiClient, registry *TTLRegistry) *PveNodeZfsCollector {
	c := PveNodeZfsCollector{apiClient: apiClient, registry: registry}
	componentLabelNames := []string{"cluster", "node", "pool", "component", "path", "leaf"}

	c.state = NewTTLGaugeVec(
		prometheus.GaugeOpts{
			Name: "pve_node_zfs_state",
			Help: "ZFS pool component state (0 = UNKNOWN, 1 = ONLINE, 2 = DEGRADED, 3 = FAULTED, 4 = OFFLINE, 5 = REMOVED, 6 = UNAVAIL).",
		},
		componentLabelNames,
		5*time.Minute,
	)
	c.registry.Register(c.state)

	c.readErrors = NewTTLGaugeVec(
		prometheus.GaugeOpts{
			Name: "pve_node_zfs_read_errors",
			Help: "ZFS pool component read error count.",
		},
		componentLabelNames,
		5*time.Minute,
	)
	c.registry.Register(c.readErrors)

	c.writeErrors = NewTTLGaugeVec(
		prometheus.GaugeOpts{
			Name: "pve_node_zfs_write_errors",
			Help: "ZFS pool component write error count.",
		},
		componentLabelNames,
		5*time.Minute,
	)
	c.registry.Register(c.writeErrors)

	c.checksumErrors = NewTTLGaugeVec(
		prometheus.GaugeOpts{
			Name: "pve_node_zfs_checksum_errors",
			Help: "ZFS pool component checksum error count.",
		},
		componentLabelNames,
		5*time.Minute,
	)
	c.registry.Register(c.checksumErrors)

	return &c
}

// CollectMetrics implements PveMetricsCollector.
func (c *PveNodeZfsCollector) CollectMetrics() error {
	cluster, err := c.apiClient.GetClusterStatus()
	if err != nil {
		return err
	}

	for _, node := range cluster.NodeStatuses {
		pools, err := c.apiClient.GetNodeZfsPools(node.Name)
		if err != nil {
			return err
		}

		for _, pool := range *pools {
			status, err := c.apiClient.GetNodeZfsPoolStatus(node.Name, pool.Name)
			if err != nil {
				return err
			}

			for _, component := range flattenZfsComponents(status) {
				labels := prometheus.Labels{
					"cluster":   cluster.GetClusterName(),
					"node":      node.Name,
					"pool":      pool.Name,
					"component": component.Name,
					"path":      component.Path,
					"leaf":      strconv.FormatBool(component.Leaf == 1),
				}

				if component.State != "" {
					c.state.With(labels).Set(zfsStateNumeric(component.State))
				}
				if component.Read != nil {
					c.readErrors.With(labels).Set(float64(*component.Read))
				}
				if component.Write != nil {
					c.writeErrors.With(labels).Set(float64(*component.Write))
				}
				if component.Checksum != nil {
					c.checksumErrors.With(labels).Set(float64(*component.Checksum))
				}
			}
		}
	}

	return nil
}

// GetName implements PveMetricsCollector.
func (c *PveNodeZfsCollector) GetName() string {
	return "Node ZFS"
}

func flattenZfsComponents(status *proxmox.PveZfsPoolStatus) []zfsMetricComponent {
	components := make([]zfsMetricComponent, 0)
	appendZfsComponent(&components, status.PveZfsComponent, nil)
	return components
}

func appendZfsComponent(components *[]zfsMetricComponent, component proxmox.PveZfsComponent, parents []string) {
	pathParts := append(append([]string{}, parents...), component.Name)
	*components = append(*components, zfsMetricComponent{
		PveZfsComponent: component,
		Path:            strings.Join(pathParts, " > "),
	})

	for _, child := range component.Children {
		appendZfsComponent(components, child, pathParts)
	}
}

func zfsStateNumeric(state string) float64 {
	if value, ok := zfsStateValues[strings.ToUpper(state)]; ok {
		return value
	}
	return 0
}