package dify

import (
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"strings"
)

// ChatStream sends a chat message and returns a reader for SSE events.
// Caller is responsible for closing the returned io.ReadCloser.
func (c *Client) ChatStream(ctx context.Context, apiKey string, req *ChatRequest) (io.ReadCloser, error) {
	req.ResponseMode = "streaming"

	resp, err := c.do(ctx, "POST", "/chat-messages", apiKey, req)
	if err != nil {
		return nil, err
	}
	return resp.Body, nil
}

// ChatBlocking sends a chat message and waits for the complete response.
func (c *Client) ChatBlocking(ctx context.Context, apiKey string, req *ChatRequest) (*ChatStreamEvent, error) {
	req.ResponseMode = "blocking"

	var result ChatStreamEvent
	if err := c.doJSON(ctx, "POST", "/chat-messages", apiKey, req, &result); err != nil {
		return nil, err
	}
	return &result, nil
}

// ParseSSEStream parses a Dify SSE stream and calls handler for each event.
func ParseSSEStream(reader io.Reader, handler func(event ChatStreamEvent) error) error {
	scanner := bufio.NewScanner(reader)
	scanner.Buffer(make([]byte, 64*1024), 256*1024)

	for scanner.Scan() {
		line := scanner.Text()

		if !strings.HasPrefix(line, "data: ") {
			continue
		}

		data := strings.TrimPrefix(line, "data: ")
		if data == "[DONE]" {
			break
		}

		var event ChatStreamEvent
		if err := json.Unmarshal([]byte(data), &event); err != nil {
			continue
		}

		if err := handler(event); err != nil {
			return err
		}
	}

	return scanner.Err()
}

// ListConversations returns the user's conversation list for an app.
func (c *Client) ListConversations(ctx context.Context, apiKey, user string, limit int, firstID string) (*ConversationListResponse, error) {
	path := fmt.Sprintf("/conversations?user=%s&limit=%d", user, limit)
	if firstID != "" {
		path += "&first_id=" + firstID
	}

	var result ConversationListResponse
	if err := c.doJSON(ctx, "GET", path, apiKey, nil, &result); err != nil {
		return nil, err
	}
	return &result, nil
}

// ListMessages returns messages in a conversation.
func (c *Client) ListMessages(ctx context.Context, apiKey, user, conversationID string, limit int, firstID string) (*MessageListResponse, error) {
	path := fmt.Sprintf("/messages?user=%s&conversation_id=%s&limit=%d", user, conversationID, limit)
	if firstID != "" {
		path += "&first_id=" + firstID
	}

	var result MessageListResponse
	if err := c.doJSON(ctx, "GET", path, apiKey, nil, &result); err != nil {
		return nil, err
	}
	return &result, nil
}

// DeleteConversation deletes a conversation.
func (c *Client) DeleteConversation(ctx context.Context, apiKey, user, conversationID string) error {
	body := map[string]string{"user": user}
	return c.doJSON(ctx, "DELETE", "/conversations/"+conversationID, apiKey, body, nil)
}

// SubmitFeedback submits feedback for a message.
func (c *Client) SubmitFeedback(ctx context.Context, apiKey, messageID string, req *FeedbackRequest) error {
	return c.doJSON(ctx, "POST", "/messages/"+messageID+"/feedbacks", apiKey, req, nil)
}