loggalicious/backend/internal/database/migrations/registration.go

package migrations

import (
	"net/http"

	"git.icedream.tech/icedream/loggalicious/backend/internal/database"
	"github.com/blang/semver"
	"github.com/fjl/go-couchdb"
)

type MigrationFunc func(*database.DatabaseServer) error

var (
	orderedRegisteredVersions = []semver.Version{}
	registeredMigrations      = map[string][]MigrationFunc{}
)

func RegisteredVersions() []semver.Version {
	return orderedRegisteredVersions
}

func RegisteredMigrations(version semver.Version) []MigrationFunc {
	return registeredMigrations[version.String()]
}

func RegisterVersionIfNotRegistered(version semver.Version) {
	versionStr := version.String()
	if _, ok := registeredMigrations[versionStr]; !ok {
		registeredMigrations[versionStr] = []MigrationFunc{}
		injected := false
		for index, currentVersion := range orderedRegisteredVersions {
			if currentVersion.GT(version) /* first version to be newer than this version */ {
				newOrderedRegisteredVersions := append(orderedRegisteredVersions[0:index], version)
				newOrderedRegisteredVersions = append(newOrderedRegisteredVersions, orderedRegisteredVersions[index:]...)
				orderedRegisteredVersions = newOrderedRegisteredVersions
				injected = true
				break
			}
		}
		if !injected {
			orderedRegisteredVersions = append(orderedRegisteredVersions, version)
		}
	}
}

func RegisterMigration(versionStr string, cb MigrationFunc) {
	version := MustParseVersion(versionStr)
	RegisterVersionIfNotRegistered(version)

	registeredMigrations[versionStr] = append(registeredMigrations[versionStr], cb)
}

func MustParseVersion(version string) semver.Version {
	semverVersion, err := semver.Parse(version)
	if err != nil {
		panic(err)
	}
	return semverVersion
}

func Run(s *database.DatabaseServer) (err error) {
	// Fetch current version
	migrationDatabase := s.GetMigrationDatabase()
	version, rev, err := migrationDatabase.GetVersion()
	if err != nil {
		isActuallyAnError := true
		if cerr, ok := err.(*couchdb.Error); ok {
			// CouchDB error
			if cerr.StatusCode == http.StatusNotFound {
				isActuallyAnError = false
			}
		}
		if isActuallyAnError {
			return
		}
		version = semver.Version{
			Major: 0,
			Minor: 0,
			Patch: 0,
		}
		err = nil
	}

	for _, targetVersion := range orderedRegisteredVersions {
		// log.Println("Check if migration is needed:", targetVersion)
		if targetVersion.GT(version) {
			// log.Println("Migrating database:", version, "->", targetVersion)
			for _, cb := range registeredMigrations[targetVersion.String()] {
				err = cb(s)
				if err != nil {
					return
				}
			}
			version = targetVersion
			rev, err = migrationDatabase.PutVersion(version, rev)
			if err != nil {
				return
			}
		}
	}

	return
}