package service

import (
	"bufio"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"metis/pkg/facts"
	"metis/pkg/inventory"
)

func (a *App) newJob(kind, node, host, device string) *Job {
	job := &Job{
		ID:          fmt.Sprintf("%d", time.Now().UTC().UnixNano()),
		Kind:        kind,
		Node:        node,
		Host:        host,
		Device:      device,
		Status:      JobQueued,
		ProgressPct: 0,
		StartedAt:   time.Now().UTC(),
		UpdatedAt:   time.Now().UTC(),
	}
	a.mu.Lock()
	a.jobs[job.ID] = job
	a.mu.Unlock()
	return job
}

type activeNodeJobError struct {
	Node  string
	Kind  string
	JobID string
}

// Error reports that a replacement-capable job is already active for the node.
func (e *activeNodeJobError) Error() string {
	if e == nil {
		return "node already has an active metis job"
	}
	return fmt.Sprintf("node %s already has an active %s job (%s)", e.Node, e.Kind, e.JobID)
}

func (a *App) activeJobForNode(node string) *Job {
	a.mu.RLock()
	defer a.mu.RUnlock()
	return a.activeJobForNodeLocked(node)
}

func (a *App) activeJobForNodeLocked(node string) *Job {
	node = strings.TrimSpace(node)
	if node == "" {
		return nil
	}
	var active *Job
	for _, job := range a.jobs {
		if job == nil || strings.TrimSpace(job.Node) != node {
			continue
		}
		if job.Status != JobQueued && job.Status != JobRunning {
			continue
		}
		switch job.Kind {
		case "build", "flash", "replace":
		default:
			continue
		}
		if active == nil || job.StartedAt.Before(active.StartedAt) {
			active = job
		}
	}
	if active == nil {
		return nil
	}
	copyJob := *active
	return &copyJob
}

func (a *App) reserveJob(kind, node, host, device string) (*Job, error) {
	a.mu.Lock()
	defer a.mu.Unlock()
	if active := a.activeJobForNodeLocked(node); active != nil {
		return nil, &activeNodeJobError{Node: node, Kind: active.Kind, JobID: active.ID}
	}
	now := time.Now().UTC()
	job := &Job{
		ID:          fmt.Sprintf("%d", now.UnixNano()),
		Kind:        kind,
		Node:        node,
		Host:        host,
		Device:      device,
		Status:      JobQueued,
		ProgressPct: 0,
		StartedAt:   now,
		UpdatedAt:   now,
	}
	a.jobs[job.ID] = job
	return job, nil
}

func (a *App) job(id string) *Job {
	a.mu.RLock()
	defer a.mu.RUnlock()
	return a.jobs[id]
}

func (a *App) setJob(id string, update func(*Job)) {
	a.mu.Lock()
	defer a.mu.Unlock()
	job := a.jobs[id]
	if job == nil {
		return
	}
	update(job)
	job.UpdatedAt = time.Now().UTC()
}

func (a *App) failJob(id string, err error) {
	a.completeJob(id, func(j *Job) {
		j.Status = JobError
		j.Error = err.Error()
		j.Message = err.Error()
	})
}

func (a *App) completeJob(id string, update func(*Job)) {
	a.mu.Lock()
	defer a.mu.Unlock()
	job := a.jobs[id]
	if job == nil {
		return
	}
	update(job)
	if job.Status != JobError {
		job.Status = JobDone
	}
	job.UpdatedAt = time.Now().UTC()
	job.FinishedAt = time.Now().UTC()
}

func (a *App) appendEvent(event Event) {
	line, err := json.Marshal(event)
	if err != nil {
		return
	}
	f, err := os.OpenFile(a.settings.HistoryPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0o644)
	if err != nil {
		return
	}
	defer f.Close()
	_, _ = f.Write(append(line, '\n'))
}

func (a *App) recentEvents(limit int) []Event {
	f, err := os.Open(a.settings.HistoryPath)
	if err != nil {
		return nil
	}
	defer f.Close()
	events := make([]Event, 0, limit)
	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		var event Event
		if err := json.Unmarshal(scanner.Bytes(), &event); err != nil {
			continue
		}
		events = append(events, event)
	}
	if len(events) > limit {
		events = events[len(events)-limit:]
	}
	for i, j := 0, len(events)-1; i < j; i, j = i+1, j-1 {
		events[i], events[j] = events[j], events[i]
	}
	return events
}

func cachedImageName(source string) string {
	return strings.TrimSuffix(filepath.Base(source), ".xz")
}

func (a *App) replacementNodes() []inventory.NodeSpec {
	nodes := make([]inventory.NodeSpec, 0, len(a.inventory.Nodes))
	for _, node := range a.inventory.Nodes {
		spec, class, err := a.inventory.FindNode(node.Name)
		if err != nil {
			continue
		}
		if replacementReady(spec, class) {
			nodes = append(nodes, node)
		}
	}
	sort.Slice(nodes, func(i, j int) bool {
		return nodes[i].Name < nodes[j].Name
	})
	return nodes
}

func (a *App) ensureReplacementReady(nodeName string) error {
	node, class, err := a.inventory.FindNode(nodeName)
	if err != nil {
		return err
	}
	if replacementReady(node, class) {
		return nil
	}
	return fmt.Errorf("node %s does not yet have a complete replacement definition", nodeName)
}

func replacementReady(node *inventory.NodeSpec, class *inventory.NodeClass) bool {
	if node == nil || class == nil {
		return false
	}
	if strings.TrimSpace(class.Image) == "" || strings.TrimSpace(class.Checksum) == "" {
		return false
	}
	if strings.TrimSpace(node.Name) == "" || strings.TrimSpace(node.Hostname) == "" || strings.TrimSpace(node.IP) == "" {
		return false
	}
	if strings.TrimSpace(node.K3sRole) == "" {
		return false
	}
	if strings.TrimSpace(node.K3sRole) != "server" && strings.TrimSpace(node.K3sURL) == "" {
		return false
	}
	if strings.TrimSpace(node.K3sToken) == "" {
		return false
	}
	if strings.TrimSpace(node.SSHUser) == "" || len(node.SSHAuthorized) == 0 {
		return false
	}
	return true
}

func (a *App) flashHosts() []string {
	hosts := map[string]struct{}{}
	for _, host := range a.settings.FlashHosts {
		if value := strings.TrimSpace(host); value != "" {
			hosts[value] = struct{}{}
		}
	}
	for _, host := range []string{a.settings.DefaultFlashHost, a.settings.LocalHost} {
		if value := strings.TrimSpace(host); value != "" {
			hosts[value] = struct{}{}
		}
	}
	for _, node := range clusterNodes() {
		if value := strings.TrimSpace(node.Name); value != "" {
			hosts[value] = struct{}{}
		}
	}
	out := make([]string, 0, len(hosts))
	for host := range hosts {
		out = append(out, host)
	}
	sort.Strings(out)
	if a.settings.DefaultFlashHost == "" {
		return out
	}
	return moveToFront(out, a.settings.DefaultFlashHost)
}

func (a *App) loadSnapshots() error {
	data, err := os.ReadFile(a.settings.SnapshotsPath)
	if err != nil {
		return err
	}
	var snapshots map[string]SnapshotRecord
	if err := json.Unmarshal(data, &snapshots); err != nil {
		return err
	}
	a.mu.Lock()
	a.snapshots = snapshots
	a.mu.Unlock()
	for _, snap := range snapshots {
		a.metrics.RecordSnapshot(snap.Node, "ok", snap.CollectedAt)
	}
	return nil
}

func (a *App) persistSnapshots() error {
	a.mu.RLock()
	data, err := json.MarshalIndent(a.snapshots, "", "  ")
	a.mu.RUnlock()
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(a.settings.SnapshotsPath), 0o755); err != nil {
		return err
	}
	return os.WriteFile(a.settings.SnapshotsPath, data, 0o644)
}

func (a *App) loadTargets() error {
	data, err := os.ReadFile(a.settings.TargetsPath)
	if err != nil {
		return err
	}
	var targets map[string]facts.Targets
	if err := json.Unmarshal(data, &targets); err != nil {
		return err
	}
	a.mu.Lock()
	a.targets = targets
	a.mu.Unlock()
	a.metrics.SetDriftTargets(targets, 0)
	return nil
}

func (a *App) persistTargets() error {
	a.mu.RLock()
	data, err := json.MarshalIndent(a.targets, "", "  ")
	a.mu.RUnlock()
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(a.settings.TargetsPath), 0o755); err != nil {
		return err
	}
	return os.WriteFile(a.settings.TargetsPath, data, 0o644)
}

func diffTargets(prev, next map[string]facts.Targets) []string {
	classes := map[string]struct{}{}
	for class := range prev {
		classes[class] = struct{}{}
	}
	for class := range next {
		classes[class] = struct{}{}
	}
	out := make([]string, 0)
	for class := range classes {
		if !targetsEqual(prev[class], next[class]) {
			out = append(out, class)
		}
	}
	sort.Strings(out)
	return out
}

func targetsEqual(a, b facts.Targets) bool {
	if a.Kernel != b.Kernel || a.OSImage != b.OSImage || a.Containerd != b.Containerd || a.K3sVersion != b.K3sVersion {
		return false
	}
	if len(a.Packages) != len(b.Packages) {
		return false
	}
	for key, value := range a.Packages {
		if b.Packages[key] != value {
			return false
		}
	}
	return true
}

func humanBytes(value int64) string {
	const unit = 1024
	if value < unit {
		return fmt.Sprintf("%d B", value)
	}
	div, exp := int64(unit), 0
	for n := value / unit; n >= unit; n /= unit {
		div *= unit
		exp++
	}
	return fmt.Sprintf("%.1f %ciB", float64(value)/float64(div), "KMGTPE"[exp])
}

func firstLine(value string) string {
	value = strings.TrimSpace(value)
	if idx := strings.IndexByte(value, '\n'); idx >= 0 {
		return strings.TrimSpace(value[:idx])
	}
	return value
}

func preferredDevice(devices []Device) string {
	if len(devices) == 0 {
		return ""
	}
	return devices[0].Path
}

func errorString(err error) string {
	if err == nil {
		return ""
	}
	return err.Error()
}

func cloneDevices(devices []Device) []Device {
	if len(devices) == 0 {
		return nil
	}
	out := make([]Device, len(devices))
	copy(out, devices)
	return out
}

func deleteNodeObject(node string) error {
	if err := deleteNodeObjectInCluster(node); err == nil {
		return nil
	}
	cmd := exec.Command("kubectl", "delete", "node", node, "--ignore-not-found")
	if out, err := cmd.CombinedOutput(); err != nil {
		return fmt.Errorf("delete node: %w: %s", err, strings.TrimSpace(string(out)))
	}
	return nil
}

func deleteNodeObjectInCluster(node string) error {
	kube, err := kubeClientFactory()
	if err != nil {
		return errors.New("not running in cluster")
	}
	return kube.deleteRequest(fmt.Sprintf("/api/v1/nodes/%s", node))
}