package provider

import (
	"context"
	"encoding/json"
	"fmt"
	"strings"
	"time"

	"github.com/gochat/gochat/internal/channel"
	"github.com/gochat/gochat/internal/model"
)

// WebWidgetProvider implements ChannelProvider for the web widget channel.
// Reference: Chatwoot app/models/channel/web_widget.rb
// + app/controllers/api/v1/accounts/channels/web_widgets_controller.rb
// + app/services/web_widget/send_on_web_widget_service.rb
//
// The Web Widget is the primary self-hosted chat widget that embeds on customer websites.
// Messages flow via WebSocket (ActionCable in Chatwoot → Redis Pub/Sub in GoChat).
// Outbound messages are sent through the WebSocket hub, not HTTP API.
type WebWidgetProvider struct{}

func NewWebWidgetProvider() *WebWidgetProvider {
	return &WebWidgetProvider{}
}

func (p *WebWidgetProvider) Type() channel.ChannelType {
	return channel.ChannelWebWidget
}

func (p *WebWidgetProvider) Name() string {
	return "Web Widget"
}

func (p *WebWidgetProvider) Description() string {
	return "Embed a live chat widget on your website to connect with visitors"
}

// === Configuration ===

func (p *WebWidgetProvider) ConfigSchema() *channel.ConfigSchemaDefinition {
	return &channel.ConfigSchemaDefinition{
		Type: "object",
		Properties: map[string]channel.ConfigProperty{
			"website_url": {
				Type:        "string",
				Description: "The URL of the website where the widget will be embedded",
				Format:      "uri",
			},
			"widget_color": {
				Type:        "string",
				Description: "Primary color for the widget UI (hex format)",
				Pattern:     "^#[0-9a-fA-F]{6}$",
				Default:     "#1f93ff",
			},
		"welcome_title": {
				Type:        "string",
				Description: "Title shown on the widget welcome screen",
				Default:     "Hi there !",
			},
			"welcome_subtitle": {
				Type:        "string",
				Description: "Subtitle shown on the widget welcome screen",
				Default:     "We make it simple and seamless for businesses to be customer centric.",
			},
			"agent_away_message": {
				Type:        "string",
				Description: "Message shown when no agents are available",
				Default:     "We are away at the moment, please leave a message.",
			},
			"auto_resolve_duration": {
				Type:        "number",
				Description: "Auto-resolve conversation after N minutes of inactivity (0 = disabled)",
				Default:     0,
			},
			"continuity_via_email": {
				Type:        "boolean",
				Description: "Allow conversation continuity via email when widget is closed",
				Default:     false,
			},
			"hmac_token": {
				Type:        "string",
				Description: "HMAC verification token for widget identity verification",
				Secret:      true,
			},
			"reply_time": {
				Type:        "string",
				Description: "Estimated reply time displayed on widget",
				Enum:        []string{"in_a_few_minutes", "in_a_few_hours", "in_a_day"},
				Default:     "in_a_few_minutes",
			},
			"pre_chat_form_enabled": {
				Type:        "boolean",
				Description: "Require visitors to fill a pre-chat form before starting conversation",
				Default:     false,
			},
			"pre_chat_form_options": {
				Type:        "object",
				Description: "Pre-chat form field configuration (JSON)",
			},
			"business_hours_enabled": {
				Type:        "boolean",
				Description: "Show business availability hours on widget",
				Default:     false,
			},
			"offline_message_enabled": {
				Type:        "boolean",
				Description: "Allow visitors to submit messages when agents are offline or outside business hours",
				Default:     true,
			},
			"offline_message_title": {
				Type:        "string",
				Description: "Title shown on the offline message form",
				Default:     "Leave a message",
			},
			"offline_message_description": {
				Type:        "string",
				Description: "Description shown below the offline message form title",
				Default:     "We will get back to you as soon as possible.",
			},
		},
		Required: []string{"website_url"},
	}
}

func (p *WebWidgetProvider) ValidateConfig(ctx context.Context, config channel.ChannelConfig) error {
	websiteURL, ok := config["website_url"].(string)
	if !ok || websiteURL == "" {
		return fmt.Errorf("website_url is required")
	}
	if !strings.HasPrefix(websiteURL, "http://") && !strings.HasPrefix(websiteURL, "https://") {
		return fmt.Errorf("website_url must be a valid URL")
	}
	return nil
}

func (p *WebWidgetProvider) DefaultConfig() channel.ChannelConfig {
	return channel.ChannelConfig{
		"website_url":             "",
		"widget_color":            "#1f93ff",
		"welcome_title":           "Hi there !",
		"welcome_subtitle":        "We make it simple and seamless for businesses to be customer centric.",
		"agent_away_message":      "We are away at the moment, please leave a message.",
		"auto_resolve_duration":   0,
		"continuity_via_email":    false,
		"reply_time":              "in_a_few_minutes",
		"pre_chat_form_enabled":   false,
		"business_hours_enabled":  false,
		"offline_message_enabled":     true,
		"offline_message_title":       "Leave a message",
		"offline_message_description": "We will get back to you as soon as possible.",
	}
}

// === Lifecycle ===

func (p *WebWidgetProvider) OnCreate(ctx context.Context, inbox *model.Inbox, config channel.ChannelConfig) (channel.ChannelConfig, error) {
	// Generate HMAC token for widget identity verification
	// Reference: Chatwoot's Channel::WebWidget before_create :set_hmac_token
	hmacToken := generateHMACToken()
	config["hmac_token"] = hmacToken

	// Generate website token (identifier for widget embedding)
	// Reference: Chatwoot's Channel::WebWidget website_token
	websiteToken := generateWebsiteToken(inbox.ID)
	config["website_token"] = websiteToken
	config["identifier"] = websiteToken // used for webhook/WS routing

	return config, nil
}

func (p *WebWidgetProvider) OnDestroy(ctx context.Context, inbox *model.Inbox, config channel.ChannelConfig) error {
	// Web widget cleanup: just mark inbox as disabled
	// No external resources to clean up (no webhook, no API subscription)
	return nil
}

// === Inbound ===

func (p *WebWidgetProvider) ProcessIncoming(ctx context.Context, inbox *model.Inbox, rawPayload []byte) (*channel.IncomingMessage, error) {
	// Web widget messages come via WebSocket (not HTTP webhook)
	// The raw payload is the JSON sent from the widget client
	// Reference: Chatwoot's IncomingMessageService for WebWidget

	var widgetMsg WebWidgetMessage
	if err := json.Unmarshal(rawPayload, &widgetMsg); err != nil {
		return nil, fmt.Errorf("failed to parse web widget message: %w", err)
	}

	incoming := &channel.IncomingMessage{
		ChannelType:    channel.ChannelWebWidget,
		SourceID:       widgetMsg.MessageID, // client-generated or server-assigned
		ConversationID: widgetMsg.ConversationID,
		SenderID:       widgetMsg.ContactID, // widget contact identifier
		SenderName:     widgetMsg.ContactName,
		SenderType:     channel.SenderContact,
		InboxID:        inbox.ID,
		AccountID:      inbox.AccountID,
		ReceivedAt:     time.Now(),
		ContentType:    channel.ContentText,
		Content:        widgetMsg.Content,
		Extra: channel.ChannelConfig{
			"browser":     widgetMsg.BrowserInfo,
			"page_url":    widgetMsg.PageURL,
			"referer":     widgetMsg.Referer,
			"identifier":  widgetMsg.Identifier, // HMAC-verified contact identifier
		},
	}

	// Handle attachments (file uploads from widget)
	if len(widgetMsg.Attachments) > 0 {
		incoming.Attachments = make([]channel.Attachment, len(widgetMsg.Attachments))
		for i, att := range widgetMsg.Attachments {
			incoming.Attachments[i] = channel.Attachment{
				URL:         att.URL,
				ContentType: att.ContentType,
				Filename:    att.Filename,
				FileSize:    att.FileSize,
			}
		}
	}

	return incoming, nil
}

func (p *WebWidgetProvider) ValidateWebhookRequest(ctx context.Context, inbox *model.Inbox, request *channel.WebhookRequest) error {
	// Web widget doesn't use HTTP webhooks — messages come via WebSocket
	// But we still implement this for HMAC verification on the widget API endpoint
	// Reference: Chatwoot's widget API HMAC token verification

	hmacToken := request.Headers["X-Hmac-Token"]
	if hmacToken == "" {
		// First connection — no HMAC required for new visitors
		return nil
	}

	// Verify HMAC against stored token
	// Reference: Chatwoot's message_hmac_verification concern
	// TODO: implement actual HMAC verification using stored token (P6)
	return nil
}

// === Outbound ===

func (p *WebWidgetProvider) SendMessage(ctx context.Context, inbox *model.Inbox, message *model.Message, contact *model.Contact) (*channel.SendResult, error) {
	// Web widget outbound messages go via WebSocket hub, not HTTP API
	// Reference: Chatwoot's ActionCable broadcast → GoChat's Redis Pub/Sub
	// The actual sending is handled by the WebSocket hub (P9 implementation)
	//
	// This method is called by the message pipeline to prepare the outbound message,
	// then the WebSocket hub delivers it to connected widget clients.

	// For now, we return success — the actual WebSocket delivery happens via event bus
	return &channel.SendResult{
		ExternalID:  fmt.Sprintf("widget_%d_%d", inbox.ID, message.ID),
		DeliveredAt: time.Now(),
		Extra: channel.ChannelConfig{
			"delivery_method": "websocket",
			"website_token":   configFromWidgetInbox(inbox, "website_token"),
		},
	}, nil
}

// === Contact ===

func (p *WebWidgetProvider) GetContactProfile(ctx context.Context, inbox *model.Inbox, contactSource string) (*channel.ContactProfile, error) {
	// Web widget contacts don't have external profiles
	// Their info comes from the pre-chat form or browser metadata
	// Reference: Chatwoot's contact creation from widget identifier
	return &channel.ContactProfile{
		Name:  contactSource, // identifier-based name
		Extra: channel.ChannelConfig{
			"source": "web_widget",
		},
	}, nil
}

// === Capabilities ===

func (p *WebWidgetProvider) Capabilities() channel.ChannelCapabilities {
	return channel.ChannelCapabilities{
		SupportsAttachments:     true,  // file upload in widget
		SupportsLocation:        false,
		SupportsTypingIndicator: true,  // Chatwoot widget supports typing indicator
		SupportsDeliveryStatus:  false,
		SupportsReplies:         false,
		SupportsEmojiReactions:  false,
		SupportsVoiceMessages:   false,
		SupportsVideoCalls:      false,
		SupportsCustomCards:     false,
		SupportsTemplates:       false,
		SupportsEmailHeaders:    false,
		MaxAttachmentSize:       10 * 1024 * 1024, // 10MB
		MaxTextLength:           0,                  // unlimited (internal)
	}
}

// init registers WebWidgetProvider with the global channel registry.
func init() {
	channel.MustRegister(NewWebWidgetProvider())
}

// --- Web Widget Message Types ---

// WebWidgetMessage is the JSON payload sent from the widget client.
// Reference: Chatwoot's widget_api/messages_controller create action
type WebWidgetMessage struct {
	MessageID     string              `json:"message_id,omitempty"`
	ConversationID string             `json:"conversation_id,omitempty"`
	ContactID     string              `json:"contact_id,omitempty"`
	ContactName   string              `json:"contact_name,omitempty"`
	Content       string              `json:"content"`
	ContentType   string              `json:"content_type,omitempty"` // text, input_select, file
	Attachments   []WidgetAttachment  `json:"attachments,omitempty"`
	Identifier    string              `json:"identifier,omitempty"`   // HMAC-verified contact ID
	BrowserInfo   string              `json:"browser_info,omitempty"`
	PageURL       string              `json:"page_url,omitempty"`
	Referer       string              `json:"referer,omitempty"`
}

// WidgetAttachment is an attachment in a web widget message.
type WidgetAttachment struct {
	URL         string `json:"url"`
	ContentType string `json:"content_type"`
	Filename    string `json:"filename,omitempty"`
	FileSize    int64  `json:"file_size,omitempty"`
}

// --- Helper functions ---

func generateHMACToken() string {
	// Generate a random HMAC token for widget identity verification
	// Reference: Chatwoot's set_hmac_token callback
	// TODO: use crypto/rand for proper token generation (P6)
	return fmt.Sprintf("hmac_%d", time.Now().UnixNano())
}

func generateWebsiteToken(inboxID uint) string {
	// Generate a website token for widget embedding
	// Reference: Chatwoot's Channel::WebWidget website_token
	return fmt.Sprintf("wt_%d_%d", inboxID, time.Now().UnixNano())
}

func configFromWidgetInbox(inbox *model.Inbox, key string) string {
	// TODO: integrate with GORM repository for config lookup (P6)
	return ""
}