package elastic

import (
	"context"
	"fmt"

	"elasticstream/opencdc"
)

func (c *Client) Read(context.Context) (*opencdc.Data, error) {

	data, ok := <-c.ch
	if !ok {
		return nil, fmt.Errorf("error reading data from channel")
	}

	index := data.Header.Index
	if !ok {
		return nil, fmt.Errorf("error index not found in data header")
	}

	offset, ok := c.offsets[index]
	if !ok {
		return nil, fmt.Errorf("error offset index not found")
	}

	c.offsets[index] = offset + 1

	err := setOffset(c.db, index, c.offsets[index])
	if err != nil {
		return nil, err
	}

	return &data, nil
}