package bash

import (
	"bufio"
	"io"
	"regexp"
	"strings"
)

// Decoder implements parser.Decoder
type Decoder struct{ reader io.Reader }

// Decode is the main function of the parser.Decoder interface
func (d *Decoder) Decode(v interface{}) error {

	// check 'v'
	if v == nil {
		return ErrNullReceiver
	}
	vcast, ok := v.(*File)
	if !ok {
		return ErrInvalidReceiver
	}
	vcast.Lines = make([]*Line, 0)

	r := bufio.NewReader(d.reader)
	n := -1 // line number

	// regexes
	reAssign := regexp.MustCompile(`(?m)^(\s*)([A-Za-z0-9_]+)=([^;]+);?\s*(#.+)?$`)
	eof := false

	for {
		n++
		if eof {
			break
		}

		l := &Line{Type: ANY}

		// 1. read line
		line, err := r.ReadString('\n')
		if err == io.EOF {
			if len(line) > 0 {
				eof = true
			} else {
				break
			}
		} else if err != nil {
			return &LineError{n, err}
		}
		line = strings.Trim(line, "\r\n")

		// 2. ignore empty
		if len(strings.Trim(line, " \t\r\n")) < 1 {
			continue
		}

		// 3. assignment
		match := reAssign.FindStringSubmatch(line)
		if match != nil {
			l.Type = ASSIGNMENT
			l.Components = match[1:]
		}

		// 4. add to file
		vcast.Lines = append(vcast.Lines, l)

	}

	return nil
}