package mrktplaats

import (
	"context"
	"encoding/json"
	"fmt"
	"net/url"
	"time"
)

// MessagingService handles conversations and messages.
type MessagingService struct {
	t *transport
}

// Conversation represents a messaging thread.
type Conversation struct {
	ID                  string            `json:"id"`
	ItemID              string            `json:"itemId"`
	SellerID            int               `json:"sellerId"`
	OtherParticipant    Participant       `json:"otherParticipant"`
	UnreadMessagesCount int               `json:"unreadMessagesCount"`
	Title               string            `json:"title"`
	ImageURL            string            `json:"imageUrl"`
	Embedded            conversationEmbed `json:"_embedded"`
}

// LatestMessage returns the latest message in the conversation.
func (c *Conversation) LatestMessage() *Message {
	return c.Embedded.LatestMessage
}

type conversationEmbed struct {
	LatestMessage *Message `json:"mc:latest-message"`
}

// Participant is the other user in a conversation.
type Participant struct {
	ID           int    `json:"id"`
	Name         string `json:"name"`
	IsReviewable bool   `json:"isReviewable"`
}

// Message represents a single message in a conversation.
type Message struct {
	ID              string    `json:"id"`
	SenderID        int       `json:"senderId"`
	Text            string    `json:"text"`
	ReceivedDate    time.Time `json:"receivedDate"`
	IsRead          bool      `json:"isRead"`
	MessageType     string    `json:"messageType"`
	IsMarkedAsFraud bool      `json:"isMarkedAsFraud"`
	Actions         []any     `json:"actions"`
}

// ConversationsResponse is the response from listing conversations.
type ConversationsResponse struct {
	ConversationsWithUnreadMessagesCount int `json:"conversationsWithUnreadMessagesCount"`
	Limit                                int `json:"limit"`
	Offset                               int `json:"offset"`
	TotalCount                           int `json:"totalCount"`
	UnreadMessagesCount                  int `json:"unreadMessagesCount"`
	Conversations                        []Conversation
}

// UnmarshalJSON handles the HAL _embedded format for conversations.
func (r *ConversationsResponse) UnmarshalJSON(data []byte) error {
	type plain struct {
		ConversationsWithUnreadMessagesCount int `json:"conversationsWithUnreadMessagesCount"`
		Limit                                int `json:"limit"`
		Offset                               int `json:"offset"`
		TotalCount                           int `json:"totalCount"`
		UnreadMessagesCount                  int `json:"unreadMessagesCount"`
		Embedded                             struct {
			Conversations []Conversation `json:"mc:conversations"`
		} `json:"_embedded"`
	}
	var p plain
	if err := json.Unmarshal(data, &p); err != nil {
		return err
	}
	r.ConversationsWithUnreadMessagesCount = p.ConversationsWithUnreadMessagesCount
	r.Limit = p.Limit
	r.Offset = p.Offset
	r.TotalCount = p.TotalCount
	r.UnreadMessagesCount = p.UnreadMessagesCount
	r.Conversations = p.Embedded.Conversations
	return nil
}

// MessagesResponse is the response from fetching a conversation's messages.
type MessagesResponse struct {
	Offset     int       `json:"offset"`
	Limit      int       `json:"limit"`
	TotalCount int       `json:"totalCount"`
	Messages   []Message
}

// UnmarshalJSON handles the deeply nested HAL format for messages.
func (r *MessagesResponse) UnmarshalJSON(data []byte) error {
	var raw struct {
		Embedded struct {
			Messages struct {
				Offset     int `json:"offset"`
				Limit      int `json:"limit"`
				TotalCount int `json:"totalCount"`
				Embedded   struct {
					Message []Message `json:"mc:message"`
				} `json:"_embedded"`
			} `json:"mc:messages"`
		} `json:"_embedded"`
	}
	if err := json.Unmarshal(data, &raw); err != nil {
		return err
	}
	r.Offset = raw.Embedded.Messages.Offset
	r.Limit = raw.Embedded.Messages.Limit
	r.TotalCount = raw.Embedded.Messages.TotalCount
	r.Messages = raw.Embedded.Messages.Embedded.Message
	return nil
}

// ServerTime returns the current server datetime.
func (s *MessagingService) ServerTime(ctx context.Context) (time.Time, error) {
	var resp struct {
		DateTime time.Time `json:"dateTime"`
	}
	if err := s.t.get(ctx, "/app/messaging/v1/datetime", nil, &resp); err != nil {
		return time.Time{}, err
	}
	return resp.DateTime, nil
}

// ConversationsOptions configures a conversations list request.
type ConversationsOptions struct {
	Offset    int
	Limit     int
	Latitude  float64
	Longitude float64
}

// Conversations lists the authenticated user's conversations.
func (s *MessagingService) Conversations(ctx context.Context, opts *ConversationsOptions) (*ConversationsResponse, error) {
	params := url.Values{}
	if opts != nil {
		if opts.Offset > 0 {
			params.Set("offset", fmt.Sprintf("%d", opts.Offset))
		}
		if opts.Limit > 0 {
			params.Set("limit", fmt.Sprintf("%d", opts.Limit))
		}
		if opts.Latitude != 0 {
			params.Set("latitude", fmt.Sprintf("%f", opts.Latitude))
		}
		if opts.Longitude != 0 {
			params.Set("longitude", fmt.Sprintf("%f", opts.Longitude))
		}
	}
	var resp ConversationsResponse
	if err := s.t.get(ctx, "/app/messaging/v1/conversations/android", params, &resp); err != nil {
		return nil, err
	}
	return &resp, nil
}

// Messages retrieves the messages in a conversation.
func (s *MessagingService) Messages(ctx context.Context, conversationID string, offset, limit int) (*MessagesResponse, error) {
	path := fmt.Sprintf("/app/messaging/v1/conversations/android/%s/messages", conversationID)
	params := url.Values{
		"offset": {fmt.Sprintf("%d", offset)},
		"limit":  {fmt.Sprintf("%d", limit)},
	}
	var resp MessagesResponse
	if err := s.t.get(ctx, path, params, &resp); err != nil {
		return nil, err
	}
	return &resp, nil
}

// StartConversation sends an initial message to the seller of a listing
// using the ASQ (Ask Seller a Question) enquiry endpoint.
// sellerID is the numeric seller ID from ListingDetail.SellerInformation.ID.
// Returns nil on success (the API responds with 204 No Content).
func (s *MessagingService) StartConversation(ctx context.Context, itemID, sellerID, text string) error {
	body := AskQuestionBody{
		AdURN:       itemID,
		BidValue:    -1.0,
		Body:        text,
		RecipientID: sellerID,
	}
	return s.t.postJSON(ctx, "/app/enquiry/v1/question", nil, nil, body, nil)
}

// SendMessage sends a text message in an existing conversation.
func (s *MessagingService) SendMessage(ctx context.Context, conversationID, text string) (string, error) {
	path := fmt.Sprintf("/app/messaging/v1/conversations/android/%s/text", conversationID)
	body := struct {
		Text    string `json:"text"`
		Actions any    `json:"actions"`
	}{
		Text: text,
	}
	var resp struct {
		ID string `json:"id"`
	}
	if err := s.t.postJSON(ctx, path, nil, nil, body, &resp); err != nil {
		return "", err
	}
	return resp.ID, nil
}

// EmailSubscriptions returns the user's messaging email notification settings.
func (s *MessagingService) EmailSubscriptions(ctx context.Context) (json.RawMessage, error) {
	var resp json.RawMessage
	if err := s.t.get(ctx, "/app/messaging/v1/subscriptions/email", nil, &resp); err != nil {
		return nil, err
	}
	return resp, nil
}