Initial commit

vendor/github.com/golang-migrate/migrate/v4/source/migration.go

@@ -0,0 +1,143 @@
+package source
+
+import (
+	"sort"
+)
+
+// Direction is either up or down.
+type Direction string
+
+const (
+	Down Direction = "down"
+	Up   Direction = "up"
+)
+
+// Migration is a helper struct for source drivers that need to
+// build the full directory tree in memory.
+// Migration is fully independent from migrate.Migration.
+type Migration struct {
+	// Version is the version of this migration.
+	Version uint
+
+	// Identifier can be any string that helps identifying
+	// this migration in the source.
+	Identifier string
+
+	// Direction is either Up or Down.
+	Direction Direction
+
+	// Raw holds the raw location path to this migration in source.
+	// ReadUp and ReadDown will use this.
+	Raw string
+}
+
+// Migrations wraps Migration and has an internal index
+// to keep track of Migration order.
+type Migrations struct {
+	index      uintSlice
+	migrations map[uint]map[Direction]*Migration
+}
+
+func NewMigrations() *Migrations {
+	return &Migrations{
+		index:      make(uintSlice, 0),
+		migrations: make(map[uint]map[Direction]*Migration),
+	}
+}
+
+func (i *Migrations) Append(m *Migration) (ok bool) {
+	if m == nil {
+		return false
+	}
+
+	if i.migrations[m.Version] == nil {
+		i.migrations[m.Version] = make(map[Direction]*Migration)
+	}
+
+	// reject duplicate versions
+	if _, dup := i.migrations[m.Version][m.Direction]; dup {
+		return false
+	}
+
+	i.migrations[m.Version][m.Direction] = m
+	i.buildIndex()
+
+	return true
+}
+
+func (i *Migrations) buildIndex() {
+	i.index = make(uintSlice, 0)
+	for version, _ := range i.migrations {
+		i.index = append(i.index, version)
+	}
+	sort.Sort(i.index)
+}
+
+func (i *Migrations) First() (version uint, ok bool) {
+	if len(i.index) == 0 {
+		return 0, false
+	}
+	return i.index[0], true
+}
+
+func (i *Migrations) Prev(version uint) (prevVersion uint, ok bool) {
+	pos := i.findPos(version)
+	if pos >= 1 && len(i.index) > pos-1 {
+		return i.index[pos-1], true
+	}
+	return 0, false
+}
+
+func (i *Migrations) Next(version uint) (nextVersion uint, ok bool) {
+	pos := i.findPos(version)
+	if pos >= 0 && len(i.index) > pos+1 {
+		return i.index[pos+1], true
+	}
+	return 0, false
+}
+
+func (i *Migrations) Up(version uint) (m *Migration, ok bool) {
+	if _, ok := i.migrations[version]; ok {
+		if mx, ok := i.migrations[version][Up]; ok {
+			return mx, true
+		}
+	}
+	return nil, false
+}
+
+func (i *Migrations) Down(version uint) (m *Migration, ok bool) {
+	if _, ok := i.migrations[version]; ok {
+		if mx, ok := i.migrations[version][Down]; ok {
+			return mx, true
+		}
+	}
+	return nil, false
+}
+
+func (i *Migrations) findPos(version uint) int {
+	if len(i.index) > 0 {
+		ix := i.index.Search(version)
+		if ix < len(i.index) && i.index[ix] == version {
+			return ix
+		}
+	}
+	return -1
+}
+
+type uintSlice []uint
+
+func (s uintSlice) Len() int {
+	return len(s)
+}
+
+func (s uintSlice) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+func (s uintSlice) Less(i, j int) bool {
+	return s[i] < s[j]
+}
+
+func (s uintSlice) Search(x uint) int {
+	return sort.Search(len(s), func(i int) bool { return s[i] >= x })
+}