package source

import (
	"fmt"
	"io/ioutil"
	"path/filepath"
	"regexp"
	"strconv"

	yaml "github.com/ghodss/yaml"
	"github.com/pkg/errors"
)

var (
	ErrParse = fmt.Errorf("no match")
)

var (
	DefaultParse = Parse
	DefaultRegex = Regex
)

// Regex matches the following pattern:
//  123_name.up.ext
//  123_name.down.ext
var Regex = regexp.MustCompile(`^([0-9]+)_(.*)\.(` + string(Down) + `|` + string(Up) + `)\.(.*)$`)

// Parse returns Migration for matching Regex pattern.
func Parse(raw string) (*Migration, error) {
	var direction Direction
	m := Regex.FindStringSubmatch(raw)
	if len(m) == 5 {
		versionUint64, err := strconv.ParseUint(m[1], 10, 64)
		if err != nil {
			return nil, err
		}

		// Have different direction type for yaml and sql
		if m[4] == "yaml" {
			if m[3] == "up" {
				direction = MetaUp
			} else if m[3] == "down" {
				direction = MetaDown
			} else {
				return nil, errors.New("Invalid Direction type")
			}
		} else if m[4] == "sql" {
			if m[3] == "up" {
				direction = Up
			} else if m[3] == "down" {
				direction = Down
			} else {
				return nil, errors.New("Invalid Direction type")
			}
		}

		return &Migration{
			Version:    versionUint64,
			Identifier: m[2],
			Direction:  direction,
		}, nil
	}
	return nil, ErrParse
}

// Validate file to check for empty sql or yaml content.
func IsEmptyFile(m *Migration, directory string) (bool, error) {
	data, err := ioutil.ReadFile(filepath.Join(directory, m.Raw))
	if err != nil {
		return false, errors.Wrapf(err, "cannot read file %s", m.Raw)
	}
	switch direction := m.Direction; direction {
	case MetaUp, MetaDown:
		var t []interface{}
		err = yaml.Unmarshal(data, &t)
		if err != nil {
			return false, errors.Wrapf(err, "invalid yaml file: %s", m.Raw)
		}
		if len(t) == 0 {
			return false, nil
		}
	case Up, Down:
		if string(data[:]) == "" {
			return false, nil
		}
	}
	return true, nil
}