limoli/dbshift-core

package dbshiftcore

import (
    "errors"
    "fmt"
    "path/filepath"
    "strings"
)

type iDatabase interface {
    GetExtension() string
    GetStatus() (*Status, error)
    SetStatus(migration Migration, executionTimeInSeconds float64) error
    ExecuteMigration([]byte) error
}

// Status is a structure used to identify the current (latest) migration version and type executed on database.
type Status struct {
    Version string
    Type    migrationType
}

// Migration is a structure used to group the essential information regarding the database-schema migration.
type Migration struct {
    Version string
    Name    string
    Type    migrationType
}

// Migration type
type migrationType uint

const (
    migrationTypeDowngrade migrationType = iota
    migrationTypeUpgrade
)

func (m migrationType) String() string {
    if m == migrationTypeDowngrade {
        return "down"
    }
    return "up"
}

// Migrations sort

type upgradePerspective []Migration

func (s upgradePerspective) Len() int {
    return len(s)
}
func (s upgradePerspective) Swap(i, j int) {
    s[i], s[j] = s[j], s[i]
}
func (s upgradePerspective) Less(i, j int) bool {
    return s[i].Version < s[j].Version
}

type downgradePerspective []Migration

func (s downgradePerspective) Len() int {
    return len(s)
}
func (s downgradePerspective) Swap(i, j int) {
    s[i], s[j] = s[j], s[i]
}
func (s downgradePerspective) Less(i, j int) bool {
    return s[i].Version > s[j].Version
}

func newMigration(version string, migrationName string, migrationType migrationType, extension string) Migration {
    return Migration{
        Version: version,
        Name:    newMigrationFileName(version, migrationName, migrationType, extension),
        Type:    migrationType,
    }
}

func newMigrationFileName(version string, migrationName string, migrationType migrationType, extension string) string {
    return fmt.Sprintf("%s-%s.%s.%s", version, migrationName, migrationType.String(), extension)
}

func (m *Migration) getLocation(migrationsPath string) string {
    return filepath.Join(migrationsPath, m.Name)
}

func newMigrationTypeFromFileIndex(fileIndex uint) migrationType {
    if fileIndex%2 == 0 {
        return migrationTypeDowngrade
    }
    return migrationTypeUpgrade
}

func newMigrationFromFile(fileName string, fileIndex uint) (*Migration, error) {
    indexDelimiter, err := getDelimiterIndexFromFileName(fileName, '-')
    if err != nil {
        return nil, err
    }

    return &Migration{
        Version: fileName[:*indexDelimiter],
        Name:    fileName,
        Type:    newMigrationTypeFromFileIndex(fileIndex),
    }, nil
}

func getDelimiterIndexFromFileName(fileName string, delimiter rune) (*int, error) {
    indexDelimiter := strings.IndexRune(fileName, '-')
    if indexDelimiter == -1 {
        return nil, errors.New("bad migration file")
    }
    return &indexDelimiter, nil
}

type migrationFilterFn func(m Migration, status Status, toInclusiveVersion string) bool

func isUpgradable(m Migration, status Status, toInclusiveVersion string) bool {

    // Only upgrading migrations
    if m.Type != migrationTypeUpgrade {
        return false
    }

    // Only migrations with version greater or equal to the current version
    if m.Version < status.Version {
        return false
    }

    // Only migrations that are not already executed
    if status.Version == m.Version && status.Type == migrationTypeUpgrade {
        return false
    }

    // If inclusive version is set, only migration with a less/equal version
    if toInclusiveVersion != "" && m.Version > toInclusiveVersion {
        return false
    }

    return true
}

func isDowngradable(m Migration, status Status, toInclusiveVersion string) bool {

    // Only downgrading migrations
    if m.Type != migrationTypeDowngrade {
        return false
    }

    // Only migrations with version greater or equal to the current version
    if m.Version > status.Version {
        return false
    }

    // Only migrations that are not already executed
    if status.Version == m.Version && status.Type == migrationTypeDowngrade {
        return false
    }

    // If inclusive version is set, only migration with a less/equal version
    if toInclusiveVersion != "" && m.Version < toInclusiveVersion {
        return false
    }

    return true
}