package line

// LineProvider implements channelpkg.ChannelProvider for LINE Messaging API.
// Reference: gochat's WhatsAppProvider pattern — same interface, adapted for LINE.
//
// LINE channel lifecycle:
//   - OnCreate: validate channel_secret + channel_access_token, test API connectivity
//   - Incoming: webhook POST → validate X-Line-Signature → parse events → IncomingProcessor
//   - Outgoing: SendMessage → LINE Push Message API (or Reply Message API with reply token)
//   - OnDestroy: no cleanup needed (LINE doesn't have a webhook deletion API)

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

	channelpkg "github.com/gochat/gochat/internal/channel"
	"github.com/gochat/gochat/internal/model"
	applogger "github.com/gochat/gochat/pkg/logger"
)

// LineProvider implements channelpkg.ChannelProvider for LINE.
type LineProvider struct {
	service  *LineService
	repo     *Repository
	pipeline *IncomingProcessor
}

// NewLineProvider creates a LINE channel provider with required dependencies.
func NewLineProvider(service *LineService, repo *Repository, pipeline *IncomingProcessor) *LineProvider {
	return &LineProvider{
		service:  service,
		repo:     repo,
		pipeline: pipeline,
	}
}

// === Channel Identity ===

func (p *LineProvider) Type() channelpkg.ChannelType { return channelpkg.ChannelLine }
func (p *LineProvider) Name() string                 { return "LINE" }
func (p *LineProvider) Description() string {
	return "LINE Official Account messaging channel — supports text, image, video, audio, file, location, and sticker messages"
}

// === Configuration ===

func (p *LineProvider) ConfigSchema() *channelpkg.ConfigSchemaDefinition {
	return &channelpkg.ConfigSchemaDefinition{
		Type: "object",
		Properties: map[string]channelpkg.ConfigProperty{
			"channel_access_token": {
				Type:        "string",
				Description: "Long-lived channel access token for LINE Messaging API",
				Required:    true,
				Secret:      true,
			},
			"channel_secret": {
				Type:        "string",
				Description: "Channel secret for webhook signature verification (HMAC-SHA256)",
				Required:    true,
				Secret:      true,
			},
		},
		Required: []string{"channel_access_token", "channel_secret"},
	}
}

func (p *LineProvider) ValidateConfig(ctx context.Context, config channelpkg.ChannelConfig) error {
	token, _ := config["channel_access_token"].(string)
	secret, _ := config["channel_secret"].(string)

	if token == "" {
		return fmt.Errorf("channel_access_token is required")
	}
	if secret == "" {
		return fmt.Errorf("channel_secret is required")
	}
	return nil
}

func (p *LineProvider) DefaultConfig() channelpkg.ChannelConfig {
	return channelpkg.ChannelConfig{
		"channel_access_token": "",
		"channel_secret":       "",
	}
}

// === Lifecycle Hooks ===

func (p *LineProvider) OnCreate(ctx context.Context, inbox *model.Inbox, config channelpkg.ChannelConfig) (channelpkg.ChannelConfig, error) {
	// Validate access token by calling the LINE API
	token, _ := config["channel_access_token"].(string)
	if err := p.service.ValidateAccessToken(ctx, token); err != nil {
		applogger.L().Warnf("LINE OnCreate: access token validation failed: %v", err)
		// Don't fail creation — token may become valid later
	}
	return config, nil
}

func (p *LineProvider) OnDestroy(ctx context.Context, inbox *model.Inbox, config channelpkg.ChannelConfig) error {
	// LINE doesn't require cleanup when an inbox is destroyed
	return nil
}

// === Incoming ===

func (p *LineProvider) ProcessIncoming(ctx context.Context, inbox *model.Inbox, rawPayload []byte) (*channelpkg.IncomingMessage, error) {
	var webhookEvent WebhookEvent
	if err := json.Unmarshal(rawPayload, &webhookEvent); err != nil {
		return nil, fmt.Errorf("line ProcessIncoming: failed to parse payload: %w", err)
	}

	if len(webhookEvent.Events) == 0 {
		return nil, fmt.Errorf("line ProcessIncoming: no events in payload")
	}

	// Process the first event (typically one event per webhook call)
	return p.pipeline.ProcessEvent(ctx, inbox, webhookEvent.Events[0])
}

// ValidateWebhookRequest verifies LINE webhook authenticity using HMAC-SHA256.
func (p *LineProvider) ValidateWebhookRequest(ctx context.Context, inbox *model.Inbox, request *channelpkg.WebhookRequest) error {
	config := parseInboxConfig(inbox.ChannelConfig)
	secret := configStr(config, "channel_secret", "")

	if secret == "" {
		return fmt.Errorf("line ValidateWebhookRequest: channel_secret not configured")
	}

	// The signature comes from X-Line-Signature header
	signature := ""
	for k, v := range request.Headers {
		if k == "X-Line-Signature" {
			signature = v
			break
		}
	}

	if signature == "" {
		return fmt.Errorf("line ValidateWebhookRequest: missing X-Line-Signature header")
	}

	if !p.service.VerifySignature(secret, string(request.Body), signature) {
		return fmt.Errorf("line ValidateWebhookRequest: invalid HMAC signature")
	}

	return nil
}

// === Messaging: Outbound ===

// SendMessage sends an outgoing message via LINE Push Message API.
func (p *LineProvider) SendMessage(ctx context.Context, inbox *model.Inbox, message *model.Message, contact *model.Contact) (*channelpkg.SendResult, error) {
	config := parseInboxConfig(inbox.ChannelConfig)
	token := configStr(config, "channel_access_token", "")
	toUserID := contact.SourceID

	if toUserID == "" {
		return nil, fmt.Errorf("line SendMessage: contact has no source_id")
	}

	// Build outbound text message
	outboundMsg := OutboundMsg{
		Type: "text",
		Text: message.Content,
	}

	resp, err := p.service.PushMessage(ctx, token, toUserID, []OutboundMsg{outboundMsg})
	if err != nil {
		return nil, fmt.Errorf("line SendMessage: API call failed: %w", err)
	}

	result := &channelpkg.SendResult{
		DeliveredAt: time.Now(),
	}
	if resp != nil {
		result.Extra = channelpkg.ChannelConfig{
			"status": resp.Status,
		}
	}

	return result, nil
}

// === Contact Info ===

// GetContactProfile fetches a LINE user's profile.
func (p *LineProvider) GetContactProfile(ctx context.Context, inbox *model.Inbox, contactSource string) (*channelpkg.ContactProfile, error) {
	config := parseInboxConfig(inbox.ChannelConfig)
	token := configStr(config, "channel_access_token", "")

	profile, err := p.service.GetUserProfile(ctx, token, contactSource)
	if err != nil {
		return nil, fmt.Errorf("line GetContactProfile: failed: %w", err)
	}

	return &channelpkg.ContactProfile{
		Name:      profile.DisplayName,
		AvatarURL: profile.PictureURL,
		Extra: channelpkg.ChannelConfig{
			"status_message": profile.StatusMessage,
			"language":       profile.Language,
		},
	}, nil
}

// === Capabilities ===

func (p *LineProvider) Capabilities() channelpkg.ChannelCapabilities {
	return channelpkg.ChannelCapabilities{
		SupportsAttachments:     true,
		SupportsLocation:        true,
		SupportsTypingIndicator: false,
		SupportsDeliveryStatus:  false,
		SupportsReplies:         true,  // LINE supports reply-to specific messages
		SupportsEmojiReactions:  false,
		SupportsVoiceMessages:   true,
		SupportsVideoCalls:      false,
		SupportsCustomCards:     true,  // LINE Flex Messages
		SupportsTemplates:       true,  // LINE template messages
		SupportsEmailHeaders:    false,
		MaxAttachmentSize:       10 * 1024 * 1024, // 10MB
		MaxTextLength:           5000,
	}
}

// === Helpers ===

// parseInboxConfig converts the inbox's JSON string ChannelConfig into a ChannelConfig map.
func parseInboxConfig(configStr string) channelpkg.ChannelConfig {
	if configStr == "" {
		return channelpkg.ChannelConfig{}
	}
	var config channelpkg.ChannelConfig
	if err := json.Unmarshal([]byte(configStr), &config); err != nil {
		applogger.L().Warnf("LINE: failed to parse inbox channel_config JSON: %v", err)
		return channelpkg.ChannelConfig{}
	}
	return config
}

// configStr extracts a string value from ChannelConfig with a default fallback.
func configStr(config channelpkg.ChannelConfig, key, defaultVal string) string {
	if v, ok := config[key]; ok {
		if s, ok := v.(string); ok && s != "" {
			return s
		}
	}
	return defaultVal
}