package csvparser

import (
	"fmt"
	"strings"
	"unicode/utf8"
)

type CsvParser struct {
	enclosers []string
	delimiter rune
	fields    []string
}

func (p *CsvParser) Initialize(delimiter string, enclosers []string, lineFormat string) error {
	if utf8.RuneCountInString(delimiter) != 1 {
		return fmt.Errorf("delimiter shoud be one character")
	}
	p.enclosers = make([]string, 0)
	for _, encloser := range enclosers {
		if utf8.RuneCountInString(encloser) != 2 {
			return fmt.Errorf("encolser should have to characters")
		}
	}
	p.enclosers = enclosers
	p.delimiter = []rune(delimiter)[0]
	for _, pair := range enclosers {
		if utf8.RuneCountInString(pair) != 2 {
			return fmt.Errorf("encoloser should contain two characters: %s", pair)
		}
	}
	// line format is in the form of: field1 field2 ignore ...
	// if field name is ignore, it is parsed but not retained
	p.fields = strings.Split(lineFormat, " ")

	return nil
}

func (p *CsvParser) Parse(line string) (map[string]string, error) {
	inEnclosedField := false
	currentEncloserEnd := ' '
	escape := false
	currentFieldIndex := 0

	ret := make(map[string]string)
	valueStart := 0
	indexMax := len(line) - 1
	for index, r := range line {
		if index == indexMax {
			if currentFieldIndex < len(p.fields) && p.fields[currentFieldIndex] != "ignore" {
				if inEnclosedField && r == currentEncloserEnd {
					ret[p.fields[currentFieldIndex]] = line[valueStart:index]
				} else {
					ret[p.fields[currentFieldIndex]] = line[valueStart : index+1]
				}
			}
		}
		if r == '\\' {
			escape = !escape
		} else if inEnclosedField {
			if r == currentEncloserEnd && !escape {
				inEnclosedField = false
			}
		} else if r == p.delimiter {

			if currentFieldIndex < len(p.fields) && p.fields[currentFieldIndex] != "ignore" {
				ret[p.fields[currentFieldIndex]] = line[valueStart:index]
				valueStart = index + 1
			}
			currentFieldIndex++
		} else {
			for _, encloser := range p.enclosers {
				runes := []rune(encloser)
				if r == runes[0] {
					// opening encloser
					inEnclosedField = true
					currentEncloserEnd = runes[1]
					valueStart++
					break
				}
			}
		}
	}

	return ret, nil
}