package cluster

import (
	"encoding/json"
	"errors"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"
)

type RunbookStep struct {
	Title   string `json:"title"`
	Command string `json:"command,omitempty"`
	Note    string `json:"note,omitempty"`
}

type Runbook struct {
	ID          string        `json:"id"`
	Name        string        `json:"name"`
	Description string        `json:"description,omitempty"`
	Steps       []RunbookStep `json:"steps"`
	BuiltIn     bool          `json:"built_in,omitempty"`
	CreatedAt   time.Time     `json:"created_at,omitempty"`
	UpdatedAt   time.Time     `json:"updated_at,omitempty"`
}

func builtinRunbooks() []Runbook {
	return []Runbook{
		{
			ID:          "vm-health-check",
			Name:        "VM Health Check",
			Description: "Quick validation of agent, VM inventory and VM alert policy.",
			BuiltIn:     true,
			Steps: []RunbookStep{
				{Title: "Check agent status", Command: "cluster agent status"},
				{Title: "Check cluster drift", Command: "cluster drift"},
				{Title: "Check VM states", Command: "cluster alert-vm check"},
				{Title: "Inspect VM allocations", Command: "kvm top"},
			},
		},
		{
			ID:          "traffic-billing-audit",
			Name:        "Traffic Billing Audit",
			Description: "Collect interface P95 and graph evidence for billing period.",
			BuiltIn:     true,
			Steps: []RunbookStep{
				{Title: "List interfaces", Command: "cluster usage --range 1h"},
				{Title: "Compute P95 for target iface", Command: "cluster p95 --iface <iface> --range 30d --graph"},
				{Title: "Export report", Command: "cluster report export --format json --out ./report.json"},
			},
		},
	}
}

func (s *Service) runbookPath() string {
	return filepath.Join(s.DataDir(), "runbooks", "custom.json")
}

func (s *Service) loadCustomRunbooks() ([]Runbook, error) {
	path := s.runbookPath()
	raw, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			return []Runbook{}, nil
		}
		return nil, err
	}
	if len(strings.TrimSpace(string(raw))) == 0 {
		return []Runbook{}, nil
	}
	var items []Runbook
	if err := json.Unmarshal(raw, &items); err != nil {
		return nil, err
	}
	out := make([]Runbook, 0, len(items))
	for _, rb := range items {
		rb.ID = strings.TrimSpace(rb.ID)
		rb.Name = strings.TrimSpace(rb.Name)
		if rb.ID == "" || rb.Name == "" {
			continue
		}
		rb.BuiltIn = false
		out = append(out, rb)
	}
	return out, nil
}

func (s *Service) saveCustomRunbooks(items []Runbook) error {
	path := s.runbookPath()
	if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
		return err
	}
	b, err := json.MarshalIndent(items, "", "  ")
	if err != nil {
		return err
	}
	b = append(b, '\n')
	tmp := path + ".tmp"
	if err := os.WriteFile(tmp, b, 0o600); err != nil {
		return err
	}
	return os.Rename(tmp, path)
}

func (s *Service) ListRunbooks() ([]Runbook, error) {
	built := builtinRunbooks()
	custom, err := s.loadCustomRunbooks()
	if err != nil {
		return nil, err
	}
	all := append(append([]Runbook{}, built...), custom...)
	sort.Slice(all, func(i, j int) bool { return strings.ToLower(all[i].ID) < strings.ToLower(all[j].ID) })
	return all, nil
}

func (s *Service) GetRunbook(selector string) (Runbook, bool) {
	selector = strings.TrimSpace(selector)
	items, err := s.ListRunbooks()
	if err != nil {
		return Runbook{}, false
	}
	for _, rb := range items {
		if strings.EqualFold(rb.ID, selector) || strings.EqualFold(rb.Name, selector) {
			return rb, true
		}
	}
	return Runbook{}, false
}

func (s *Service) AddRunbook(rb Runbook) (Runbook, error) {
	rb.ID = strings.TrimSpace(rb.ID)
	rb.Name = strings.TrimSpace(rb.Name)
	if rb.ID == "" || rb.Name == "" {
		return Runbook{}, errors.New("runbook id and name are required")
	}
	if len(rb.Steps) == 0 {
		return Runbook{}, errors.New("runbook steps are required")
	}
	if b, ok := s.GetRunbook(rb.ID); ok && b.BuiltIn {
		return Runbook{}, errors.New("cannot overwrite built-in runbook")
	}
	custom, err := s.loadCustomRunbooks()
	if err != nil {
		return Runbook{}, err
	}
	for _, it := range custom {
		if strings.EqualFold(it.ID, rb.ID) {
			return Runbook{}, errors.New("runbook id already exists")
		}
	}
	now := s.now().UTC()
	rb.BuiltIn = false
	rb.CreatedAt = now
	rb.UpdatedAt = now
	custom = append(custom, rb)
	if err := s.saveCustomRunbooks(custom); err != nil {
		return Runbook{}, err
	}
	_ = s.AppendChange("runbook.add", rb.ID, rb.Name)
	return rb, nil
}

func (s *Service) RemoveRunbook(selector string) (Runbook, error) {
	custom, err := s.loadCustomRunbooks()
	if err != nil {
		return Runbook{}, err
	}
	idx := -1
	for i, rb := range custom {
		if strings.EqualFold(rb.ID, selector) || strings.EqualFold(rb.Name, selector) {
			idx = i
			break
		}
	}
	if idx < 0 {
		return Runbook{}, errors.New("custom runbook not found")
	}
	removed := custom[idx]
	custom = append(custom[:idx], custom[idx+1:]...)
	if err := s.saveCustomRunbooks(custom); err != nil {
		return Runbook{}, err
	}
	_ = s.AppendChange("runbook.remove", removed.ID, removed.Name)
	return removed, nil
}