71 lines
1.6 KiB
Go
71 lines
1.6 KiB
Go
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package main
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import (
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"errors"
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"fmt"
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)
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func NewMigrationGraph() MigrationGraph {
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return MigrationGraph{Migrations: map[string]Migration{}, parentage: map[string]*Migration{}}
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}
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// Adds a migration to the graph.
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//
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// This also adds the migration to the parentage mappings to link it
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// to its parent. If the migration added has no parent, then it's also
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// set to be the root of the graph.
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func (g *MigrationGraph) AddMigration(m Migration) {
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if m.Requires == "" {
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g.addRoot(m)
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}
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g.Migrations[m.Name] = m
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g.parentage[m.Requires] = &m
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}
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// Builds the linear history of migrations.
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func (g *MigrationGraph) GetLinearHistory() ([]Migration, error) {
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if g.Root == nil {
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return []Migration{}, errors.New("Cannot get linear history, the graph has no root.")
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}
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ordered := []Migration{}
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visited := map[string]bool{}
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unordered := []Migration{*g.Root}
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for len(unordered) > 0 {
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migration := unordered[0]
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unordered = unordered[1:]
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if _, hasVisited := visited[migration.Name]; hasVisited {
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return []Migration{}, errors.New("Cycle detected, cannot generate linear history.")
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}
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child, hasChildren := g.parentage[migration.Name]
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ordered = append(ordered, migration)
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if hasChildren {
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unordered = append(unordered, *child)
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}
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visited[migration.Name] = true
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}
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if len(ordered) != len(g.Migrations) {
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return ordered, errors.New("Not all migrations in the graph are part of the history.")
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}
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return ordered, nil
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}
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func (g *MigrationGraph) addRoot(m Migration) error {
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if g.Root != nil {
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return errors.New(fmt.Sprintf("Cannot have more than one root, tried to add %#v but already knew about %#v.", m, g.Root))
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}
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g.Root = &m
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return nil
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}
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