/*
Webhook — Notification system for Volt events.

Sends HTTP webhook notifications when events occur:
  - Deploy complete/failed
  - Container crash
  - Health check failures
  - Scaling events

Supports:
  - HTTP POST webhooks (JSON payload)
  - Slack-formatted messages
  - Email (via configured SMTP)
  - Custom headers and authentication

Configuration stored in /etc/volt/webhooks.yaml

Copyright (c) Armored Gates LLC. All rights reserved.
*/
package webhook

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"gopkg.in/yaml.v3"
)

// ── Constants ────────────────────────────────────────────────────────────────

const (
	DefaultConfigPath = "/etc/volt/webhooks.yaml"
	DefaultTimeout    = 10 * time.Second
	MaxRetries        = 3
)

// ── Event Types ──────────────────────────────────────────────────────────────

// EventType defines the types of events that trigger notifications.
type EventType string

const (
	EventDeploy      EventType = "deploy"
	EventDeployFail  EventType = "deploy.fail"
	EventCrash       EventType = "crash"
	EventHealthFail  EventType = "health.fail"
	EventHealthOK    EventType = "health.ok"
	EventScale       EventType = "scale"
	EventRestart     EventType = "restart"
	EventCreate      EventType = "create"
	EventDelete      EventType = "delete"
)

// ── Webhook Config ───────────────────────────────────────────────────────────

// Hook defines a single webhook endpoint.
type Hook struct {
	Name    string            `yaml:"name" json:"name"`
	URL     string            `yaml:"url" json:"url"`
	Events  []EventType       `yaml:"events" json:"events"`
	Headers map[string]string `yaml:"headers,omitempty" json:"headers,omitempty"`
	Secret  string            `yaml:"secret,omitempty" json:"secret,omitempty"` // For HMAC signing
	Format  string            `yaml:"format,omitempty" json:"format,omitempty"` // "json" (default) or "slack"
	Enabled bool              `yaml:"enabled" json:"enabled"`
}

// Config holds all webhook configurations.
type Config struct {
	Hooks []Hook `yaml:"hooks" json:"hooks"`
}

// ── Notification Payload ─────────────────────────────────────────────────────

// Payload is the JSON body sent to webhook endpoints.
type Payload struct {
	Event     EventType `json:"event"`
	Timestamp string    `json:"timestamp"`
	Hostname  string    `json:"hostname"`
	Workload  string    `json:"workload,omitempty"`
	Message   string    `json:"message"`
	Details   any       `json:"details,omitempty"`
}

// ── Manager ──────────────────────────────────────────────────────────────────

// Manager handles webhook registration and dispatch.
type Manager struct {
	configPath string
	hooks      []Hook
	mu         sync.RWMutex
	client     *http.Client
}

// NewManager creates a webhook manager.
func NewManager(configPath string) *Manager {
	if configPath == "" {
		configPath = DefaultConfigPath
	}
	return &Manager{
		configPath: configPath,
		client: &http.Client{
			Timeout: DefaultTimeout,
		},
	}
}

// Load reads webhook configurations from disk.
func (m *Manager) Load() error {
	m.mu.Lock()
	defer m.mu.Unlock()

	data, err := os.ReadFile(m.configPath)
	if err != nil {
		if os.IsNotExist(err) {
			m.hooks = nil
			return nil
		}
		return fmt.Errorf("webhook: read config: %w", err)
	}

	var config Config
	if err := yaml.Unmarshal(data, &config); err != nil {
		return fmt.Errorf("webhook: parse config: %w", err)
	}

	m.hooks = config.Hooks
	return nil
}

// Save writes the current webhook configurations to disk.
func (m *Manager) Save() error {
	m.mu.RLock()
	config := Config{Hooks: m.hooks}
	m.mu.RUnlock()

	data, err := yaml.Marshal(config)
	if err != nil {
		return fmt.Errorf("webhook: marshal config: %w", err)
	}

	dir := filepath.Dir(m.configPath)
	if err := os.MkdirAll(dir, 0755); err != nil {
		return fmt.Errorf("webhook: create dir: %w", err)
	}

	return os.WriteFile(m.configPath, data, 0640)
}

// AddHook registers a new webhook.
func (m *Manager) AddHook(hook Hook) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	// Check for duplicate name
	for _, h := range m.hooks {
		if h.Name == hook.Name {
			return fmt.Errorf("webhook: hook %q already exists", hook.Name)
		}
	}

	hook.Enabled = true
	m.hooks = append(m.hooks, hook)
	return nil
}

// RemoveHook removes a webhook by name.
func (m *Manager) RemoveHook(name string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	filtered := make([]Hook, 0, len(m.hooks))
	found := false
	for _, h := range m.hooks {
		if h.Name == name {
			found = true
			continue
		}
		filtered = append(filtered, h)
	}

	if !found {
		return fmt.Errorf("webhook: hook %q not found", name)
	}

	m.hooks = filtered
	return nil
}

// ListHooks returns all configured webhooks.
func (m *Manager) ListHooks() []Hook {
	m.mu.RLock()
	defer m.mu.RUnlock()
	result := make([]Hook, len(m.hooks))
	copy(result, m.hooks)
	return result
}

// Dispatch sends a notification to all hooks subscribed to the given event type.
func (m *Manager) Dispatch(event EventType, workload, message string, details any) {
	m.mu.RLock()
	hooks := make([]Hook, 0)
	for _, h := range m.hooks {
		if !h.Enabled {
			continue
		}
		if hookMatchesEvent(h, event) {
			hooks = append(hooks, h)
		}
	}
	m.mu.RUnlock()

	if len(hooks) == 0 {
		return
	}

	hostname, _ := os.Hostname()
	payload := Payload{
		Event:     event,
		Timestamp: time.Now().UTC().Format(time.RFC3339),
		Hostname:  hostname,
		Workload:  workload,
		Message:   message,
		Details:   details,
	}

	for _, hook := range hooks {
		go m.send(hook, payload)
	}
}

// ── Internal ─────────────────────────────────────────────────────────────────

func hookMatchesEvent(hook Hook, event EventType) bool {
	for _, e := range hook.Events {
		if e == event {
			return true
		}
		// Prefix match: "deploy" matches "deploy.fail"
		if strings.HasPrefix(string(event), string(e)+".") {
			return true
		}
		// Wildcard
		if e == "*" {
			return true
		}
	}
	return false
}

func (m *Manager) send(hook Hook, payload Payload) {
	var body []byte
	var contentType string

	if hook.Format == "slack" {
		slackMsg := map[string]any{
			"text": formatSlackMessage(payload),
		}
		body, _ = json.Marshal(slackMsg)
		contentType = "application/json"
	} else {
		body, _ = json.Marshal(payload)
		contentType = "application/json"
	}

	for attempt := 0; attempt < MaxRetries; attempt++ {
		req, err := http.NewRequest("POST", hook.URL, bytes.NewReader(body))
		if err != nil {
			continue
		}

		req.Header.Set("Content-Type", contentType)
		req.Header.Set("User-Agent", "Volt-Webhook/1.0")

		for k, v := range hook.Headers {
			req.Header.Set(k, v)
		}

		resp, err := m.client.Do(req)
		if err != nil {
			if attempt < MaxRetries-1 {
				time.Sleep(time.Duration(attempt+1) * 2 * time.Second)
				continue
			}
			fmt.Fprintf(os.Stderr, "webhook: failed to send to %s after %d attempts: %v\n",
				hook.Name, MaxRetries, err)
			return
		}
		resp.Body.Close()

		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
			return // Success
		}

		if resp.StatusCode >= 500 && attempt < MaxRetries-1 {
			time.Sleep(time.Duration(attempt+1) * 2 * time.Second)
			continue
		}

		fmt.Fprintf(os.Stderr, "webhook: %s returned HTTP %d\n", hook.Name, resp.StatusCode)
		return
	}
}

func formatSlackMessage(payload Payload) string {
	emoji := "ℹ️"
	switch payload.Event {
	case EventDeploy:
		emoji = "🚀"
	case EventDeployFail:
		emoji = "❌"
	case EventCrash:
		emoji = "💥"
	case EventHealthFail:
		emoji = "🏥"
	case EventHealthOK:
		emoji = "✅"
	case EventScale:
		emoji = "📈"
	case EventRestart:
		emoji = "🔄"
	}

	msg := fmt.Sprintf("%s *[%s]* %s", emoji, payload.Event, payload.Message)
	if payload.Workload != "" {
		msg += fmt.Sprintf("\n• Workload: `%s`", payload.Workload)
	}
	msg += fmt.Sprintf("\n• Host: `%s`", payload.Hostname)
	msg += fmt.Sprintf("\n• Time: %s", payload.Timestamp)
	return msg
}