adrianolaselva / csvql

import (

	"adrianolaselva.github.io/csvql/pkg/filehandler"

	"adrianolaselva.github.io/csvql/pkg/storage"

	"bytes"

	"database/sql"

	"encoding/csv"

	"errors"

	"fmt"

	"github.com/schollz/progressbar/v3"

	"io"

	"os"

	"path/filepath"

	"strings"

	"sync"

)

const (

	bufferMaxLength = 32 * 1024

)

type csvHandler struct {

	mx          sync.Mutex

	bar         *progressbar.ProgressBar

	storage     storage.Storage

	files       []*os.File

	fileInputs  []string

	totalLines  int

	limitLines  int

	currentLine int

	delimiter   rune

}

func NewCsvHandler(fileInputs []string, delimiter rune, bar *progressbar.ProgressBar, storage storage.Storage, limitLines int) filehandler.FileHandler {

	return &csvHandler{fileInputs: fileInputs, delimiter: delimiter, storage: storage, bar: bar, limitLines: limitLines}

}

// Import import data

func (c *csvHandler) Import() error {

	if err := c.openFiles(); err != nil {

		return err

	}

	wg := new(sync.WaitGroup)

	wg.Add(len(c.fileInputs))

	errChannels := make(chan error, len(c.fileInputs))

	for _, file := range c.fileInputs {

		go func(wg *sync.WaitGroup, file string, errChan chan error) {

			defer wg.Done()

			err := c.loadTotalRows(file)

			errChan <- err

		}(wg, file, errChannels)

	}

	wg.Wait()

	if err := <-errChannels; err != nil {

		return err

	}

	if c.limitLines > 0 && c.totalLines > c.limitLines {

		c.totalLines = c.limitLines

	}

	wg.Add(len(c.files))

	errChannels = make(chan error, len(c.files))

	for _, file := range c.files {

		tableName := strings.ReplaceAll(strings.ToLower(filepath.Base(file.Name())), filepath.Ext(file.Name()), "")

		go func(wg *sync.WaitGroup, file *os.File, tableName string, errChan chan error) {

			defer wg.Done()

			errChan <- c.loadDataFromFile(tableName, file)

		}(wg, file, tableName, errChannels)

	}

	wg.Wait()

	if err := <-errChannels; err != nil {

		return err

	}

	return nil

}

// Query execute statements

func (c *csvHandler) Query(cmd string) (*sql.Rows, error) {

	rows, err := c.storage.Query(cmd)

	if err != nil {

		return nil, fmt.Errorf("failed to execute query: %w", err)

	}

	return rows, nil

}

// Lines return total lines

func (c *csvHandler) Lines() int {

	return c.totalLines

}

// Close execute in defer

// loadDataFromFile load data from file

func (c *csvHandler) loadDataFromFile(tableName string, file *os.File) error {

	c.mx.Lock()

	defer c.mx.Unlock()

	c.bar.ChangeMax(c.totalLines)

	r := csv.NewReader(file)

	r.Comma = c.delimiter

	columns, err := c.readHeader(tableName, r)

	if err != nil {

		return fmt.Errorf("failed to load headers and build structure: %w", err)

	}

	c.currentLine = 0

	for {

		err := c.readline(tableName, columns, r)

		if errors.Is(err, io.EOF) {

			break

		}

		if err != nil {

			return err

		}

	}

	return nil

}

// readHeader read header

func (c *csvHandler) readHeader(tableName string, r *csv.Reader) ([]string, error) {

	columns, err := r.Read()

	if err != nil {

		return nil, fmt.Errorf("failed to load headers: %w", err)

	}

	if err := c.storage.BuildStructure(tableName, columns); err != nil {

		return nil, fmt.Errorf("failed to load headers and build structure: %w", err)

	}

	return columns, nil

}

// readline read line

func (c *csvHandler) readline(tableName string, columns []string, r *csv.Reader) error {

	records, err := r.Read()

	if err != nil {

		return fmt.Errorf("failed to read line: %w", err)

	}

	if c.totalLines == c.currentLine {

		return io.EOF

	}

	_ = c.bar.Add(1)

	c.currentLine++

	if err := c.storage.InsertRow(tableName, columns, c.convertToAnyArray(records)); err != nil {

		return fmt.Errorf("failed to process row number %d: %w", c.currentLine, err)

	}

	return nil

}

// convertToAnyArray convert string array to any array

func (c *csvHandler) convertToAnyArray(records []string) []any {

	values := make([]any, 0, len(records))

	for _, r := range records {

		values = append(values, r)

	}

	return values

}

// openFile open file

func (c *csvHandler) openFiles() error {

	wg := new(sync.WaitGroup)

	wg.Add(len(c.fileInputs))

	errChannels := make(chan error, len(c.fileInputs))

	for _, file := range c.fileInputs {

		go func(wg *sync.WaitGroup, file string, errChan chan error) {

			defer wg.Done()

			f, err := os.Open(file)

			if err != nil {

				errChan <- fmt.Errorf("failed to open file: %w", err)

				return

			}

			c.files = append(c.files, f)

			errChan <- nil

		}(wg, file, errChannels)

	}

	wg.Wait()

	if err := <-errChannels; err != nil {

		return fmt.Errorf("failed to open file: %w", err)

	}

	return nil

}

// loadTotalRows load total rows in file

func (c *csvHandler) loadTotalRows(file string) error {

	r, err := os.Open(file)

	if err != nil {

		return fmt.Errorf("failed to open file %s: %w", file, err)

	}

	defer func(r *os.File) {

		_ = r.Close()

	}(r)

	buf := make([]byte, bufferMaxLength)

	c.totalLines = 0

	lineSep := []byte{'\n'}

	for {

		r, err := r.Read(buf)

		c.totalLines += bytes.Count(buf[:r], lineSep)

		switch {

		case err == io.EOF:

			return nil

		case err != nil:

			return fmt.Errorf("failed to totalize rows: %w", err)

		}

	}

}