package chatclient

import (
	"context"
	"fmt"

	pb "git.be.kaien.ru/l-ai/l-ai-chat-client-go/proto/l-ai-chat-proto"
)

type HistoryRequest struct {
	TopicID        string
	BeforeSequence int64
	AfterSequence  int64
	Limit          int32
}

func (c *Client) History(ctx context.Context, req HistoryRequest) (*pb.HistoryResponse, error) {
	if err := c.checkOpen(); err != nil {
		return nil, err
	}
	if req.BeforeSequence > 0 && req.AfterSequence > 0 {
		return nil, fmt.Errorf("%w: before and after sequence are mutually exclusive", ErrInvalidConfig)
	}
	return c.api.History(ctx, &pb.HistoryRequest{
		TopicId:        req.TopicID,
		BeforeSequence: req.BeforeSequence,
		AfterSequence:  req.AfterSequence,
		Limit:          req.Limit,
	})
}

type HistoryPager struct {
	client  *Client
	req     HistoryRequest
	forward bool
	done    bool
}

func (c *Client) NewHistoryPager(req HistoryRequest) (*HistoryPager, error) {
	if req.BeforeSequence > 0 && req.AfterSequence > 0 {
		return nil, fmt.Errorf("%w: before and after sequence are mutually exclusive", ErrInvalidConfig)
	}
	return &HistoryPager{
		client:  c,
		req:     req,
		forward: req.AfterSequence > 0,
	}, nil
}

func (p *HistoryPager) Next(ctx context.Context) (*pb.HistoryResponse, error) {
	if p.done {
		return &pb.HistoryResponse{}, nil
	}
	resp, err := p.client.History(ctx, p.req)
	if err != nil {
		return nil, err
	}
	if len(resp.GetMessages()) == 0 || !resp.GetHasMore() {
		p.done = true
	}
	if len(resp.GetMessages()) > 0 {
		last := resp.GetMessages()[len(resp.GetMessages())-1].GetSequence()
		if p.forward {
			p.req.AfterSequence = last
		} else {
			p.req.BeforeSequence = last
		}
	}
	return resp, nil
}