Bnei-Baruch/mdb

// This file takes Rambler parser to our project as Rambler is binary and
// cannot be imported.
// Copied from https://github.com/elwinar/rambler/raw/master/migration.go (0dcaf6b)
package migrations

import (
    "bufio"
    "fmt"
    "io"
    "os"
    "path/filepath"
    "strings"
)

const prefix = `-- rambler`

// Migration represent a migration file, composed of up and down sections containing
// one or more statements each.
type Migration struct {
    Name   string
    reader io.Reader
}

// NewMigration generate a migration from the given file
func NewMigration(path string) (*Migration, error) {
    file, err := os.Open(path)
    if err != nil {
        return nil, fmt.Errorf("Unable to open file %s: %s", path, err.Error())
    }

    m := &Migration{
        Name:   filepath.Base(path),
        reader: file,
    }

    return m, nil
}

// Scan retrieve all sections of the file with the given section marker.
func (m Migration) scan(section string) []string {
    var scanner = bufio.NewScanner(m.reader)
    var statements []string
    var buffer string

    recording := false
    for scanner.Scan() {
        line := scanner.Text()

        if strings.HasPrefix(line, prefix) {
            if len(strings.TrimSpace(buffer)) != 0 {
                statements = append(statements, strings.TrimSpace(buffer))
            }

            buffer = ""
            cmd := strings.TrimSpace(line[len(prefix):])

            switch cmd {
            case section:
                recording = true
            default:
                recording = false
            }

            continue
        }

        if recording {
            buffer = buffer + "\n" + line
        }
    }

    if len(strings.TrimSpace(buffer)) != 0 {
        statements = append(statements, strings.TrimSpace(buffer))
    }

    return statements
}

// Up return the up statements of the migration
func (m Migration) Up() []string {
    return m.scan(`up`)
}

// Down return the down statements of the migration
func (m Migration) Down() []string {
    raw := m.scan(`down`)
    var stmt []string
    for i := len(raw) - 1; i >= 0; i-- {
        stmt = append(stmt, raw[i])
    }
    return stmt
}