package gocsvtable

import (
	"encoding/csv"
	"fmt"
	"io"
	"os"
)

type GoCSVtable struct {
	file    *csv.Reader
	rows    int
	data    [][]string
	headers map[string]int

	Separator rune
	Comment   rune

	lastRow int

	// Row is the active CSV row, the data will start at 1
	Row int
}

func (gct *GoCSVtable) OpenCSV(filename string) error {
	osfile, err := os.Open(filename)
	if err != nil {
		return fmt.Errorf("Not possible to os.Open file: %s\n", err)
	}
	defer osfile.Close()

	// The default rune is 0
	if gct.Separator != 0 {
		gct.file.Comma = gct.Separator
	}

	// The default rune is 0
	if gct.Comment != 0 {
		gct.file.Comment = gct.Comment
	}

	gct.file = csv.NewReader(osfile)
	gct.data, err = gct.file.ReadAll()
	if err != nil {
		return fmt.Errorf("Not possible to csv.ReadAll file: %s\n", err)
	}

	gct.setHeaders()

	// First data row is 1
	gct.Row = 1

	// Last row number
	gct.lastRow = len(gct.data) - 1

	return nil
}

// setHeaders will associate the headers names with the correct column number
func (gct *GoCSVtable) setHeaders() {
	header := gct.data[0]
	columnsNumber := len(header)

	// Initiate Headers
	gct.headers = make(map[string]int)

	for field := 0; field < columnsNumber; field++ {
		name := header[field]
		gct.headers[name] = field
	}
}

// GetHeader return the col number from a field string
func (gct *GoCSVtable) GetHeader(field string) (int, error) {
	col, ok := gct.headers[field]
	if !ok {
		return 0, fmt.Errorf("Field '%s' does not exist", field)
	}

	return col, nil
}

// Next will jump to the next CSV row. If file is over, will return an io.EOF
func (gct *GoCSVtable) Next() error {

	if gct.Row >= gct.lastRow {
		return io.EOF
	}
	gct.Row++
	return nil
}

// GetNumberOfRows will return the number of data rows, not considering the
// header
func (gct *GoCSVtable) GetNumberOfRows() int {
	return gct.lastRow
}

// Read return a specific field from active row
func (gct *GoCSVtable) Read(field string) (string, error) {
	col, err := gct.GetHeader(field)
	if err != nil {
		return "", err
	}
	return gct.data[gct.Row][col], nil
}

// Read and return the entire row
func (gct *GoCSVtable) ReadRow(row int) ([]string, error) {
	if row > gct.lastRow {
		return []string{}, fmt.Errorf("Not possible to read row %v. Data has max of %v rows.\n", row, gct.lastRow)
	}
	return gct.data[row], nil
}

// ReadCol will return a slice with all row values from a single column (field)
func (gct *GoCSVtable) ReadCol(field string) ([]string, error) {
	data := []string{}
	fieldNumber, err := gct.GetHeader(field)
	if err != nil {
		return data, err
	}

	for row := 1; row <= gct.lastRow; row++ {
		data = append(data, gct.data[row][fieldNumber])
	}

	return data, nil
}