Model command alias prefix rewriting
This commit is contained in:
143
internal/alias/machine.go
Normal file
143
internal/alias/machine.go
Normal file
@@ -0,0 +1,143 @@
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package alias
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import (
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"sort"
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"gitea.maximumdirect.net/eric/CommandKit/internal/commandpath"
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)
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type symbolKind uint8
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const (
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literalSymbol symbolKind = iota
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otherSymbol
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endSymbol
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boundarySymbol
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)
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type symbol struct {
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kind symbolKind
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value string
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}
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type transitionKey struct {
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control int
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read symbol
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}
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type transition struct {
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next int
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push []symbol
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rule int
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}
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// Machine is a finite-control pushdown rewrite model compiled from a resolver.
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// Its transitions replace the stack's first symbol with zero to two symbols.
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type Machine struct {
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start int
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halt int
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transitions map[transitionKey]transition
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alphabet []symbol
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literals map[string]struct{}
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}
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// Compile builds a finite stack machine with explicit lookup, restoration,
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// and rewrite transitions for the mappings.
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func Compile(mappings []Mapping) (*Resolver, *Machine, error) {
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resolver, err := NewResolver(mappings)
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if err != nil {
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return nil, nil, err
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}
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return resolver, compileMachine(resolver), nil
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}
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func compileMachine(resolver *Resolver) *Machine {
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// Trie controls only move to child nodes. Helper controls prepend a fixed
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// number of saved symbols and then halt or return to the trie root after a
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// selected mapping has been completed.
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machine := &Machine{
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start: 0,
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halt: len(resolver.trie),
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transitions: make(map[transitionKey]transition),
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literals: make(map[string]struct{}),
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}
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for _, mapping := range resolver.mappings {
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for _, path := range []commandpath.Path{mapping.Source, mapping.Target} {
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for _, component := range path {
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machine.literals[component] = struct{}{}
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}
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}
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}
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for literal := range machine.literals {
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machine.alphabet = append(machine.alphabet, symbol{kind: literalSymbol, value: literal})
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}
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sort.Slice(machine.alphabet, func(i, j int) bool { return machine.alphabet[i].value < machine.alphabet[j].value })
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machine.alphabet = append(machine.alphabet, symbol{kind: otherSymbol}, symbol{kind: endSymbol}, symbol{kind: boundarySymbol})
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nextControl := machine.halt + 1
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for nodeIndex, node := range resolver.trie {
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for _, input := range machine.alphabet {
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if input.kind == literalSymbol {
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if childIndex, exists := node.children[input.value]; exists {
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machine.transitions[transitionKey{control: nodeIndex, read: input}] = transition{next: childIndex, rule: -1}
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continue
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}
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}
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word, next, rule := machine.lookupOutcome(resolver, nodeIndex, input)
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machine.addWordTransition(nodeIndex, input, word, next, rule, &nextControl)
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}
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}
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return machine
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}
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func (machine *Machine) lookupOutcome(resolver *Resolver, nodeIndex int, input symbol) ([]symbol, int, int) {
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node := resolver.trie[nodeIndex]
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word := make([]symbol, 0, len(node.path)+1)
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next := machine.halt
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rule := -1
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if node.best >= 0 {
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mapping := resolver.mappings[node.best]
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matchedLength := len(mapping.Source)
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for _, component := range mapping.Target {
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word = append(word, symbol{kind: literalSymbol, value: component})
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}
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for _, component := range node.path[matchedLength:] {
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word = append(word, symbol{kind: literalSymbol, value: component})
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}
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next = machine.start
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rule = node.best
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} else {
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for _, component := range node.path {
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word = append(word, symbol{kind: literalSymbol, value: component})
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}
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}
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word = append(word, input)
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return word, next, rule
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}
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func (machine *Machine) addWordTransition(control int, read symbol, word []symbol, next, rule int, nextControl *int) {
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key := transitionKey{control: control, read: read}
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if len(word) <= 2 {
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machine.transitions[key] = transition{next: next, push: append([]symbol(nil), word...), rule: rule}
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return
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}
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helper := *nextControl
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*nextControl = *nextControl + 1
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machine.transitions[key] = transition{next: helper, push: append([]symbol(nil), word[len(word)-2:]...), rule: rule}
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for index := len(word) - 3; index >= 0; index-- {
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following := next
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if index > 0 {
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following = *nextControl
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*nextControl = *nextControl + 1
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}
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expectedTop := word[index+1]
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machine.transitions[transitionKey{control: helper, read: expectedTop}] = transition{
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next: following,
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push: []symbol{word[index], expectedTop},
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rule: rule,
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}
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helper = following
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}
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}
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134
internal/alias/resolver.go
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134
internal/alias/resolver.go
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@@ -0,0 +1,134 @@
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// Package alias models application command-path rewriting independently of
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// command execution and the parsing backend.
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package alias
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import (
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"fmt"
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"gitea.maximumdirect.net/eric/CommandKit/internal/commandpath"
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)
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// Mapping replaces Source with Target when Source is the longest matching
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// prefix of an entered command path.
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type Mapping struct {
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Source commandpath.Path
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Target commandpath.Path
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}
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type trieNode struct {
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children map[string]int
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mapping int
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best int
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parent int
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path commandpath.Path
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}
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// Resolver selects longest matching command-path mappings.
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type Resolver struct {
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mappings []Mapping
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trie []trieNode
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}
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// NewResolver builds a resolver from normalized command-path mappings.
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func NewResolver(mappings []Mapping) (*Resolver, error) {
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resolver := &Resolver{trie: []trieNode{{mapping: -1, best: -1, parent: -1}}}
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for _, mapping := range mappings {
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if len(mapping.Source) == 0 {
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return nil, fmt.Errorf("command alias source path must not be empty")
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}
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if len(mapping.Target) == 0 {
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return nil, fmt.Errorf("command alias target path must not be empty")
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}
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for _, component := range append(mapping.Source.Clone(), mapping.Target...) {
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if err := commandpath.ValidateComponent(component); err != nil {
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return nil, err
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}
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}
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normalized := Mapping{Source: mapping.Source.Clone(), Target: mapping.Target.Clone()}
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index := len(resolver.mappings)
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resolver.mappings = append(resolver.mappings, normalized)
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nodeIndex := 0
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for _, component := range normalized.Source {
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node := &resolver.trie[nodeIndex]
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if node.children == nil {
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node.children = make(map[string]int)
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}
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childIndex, exists := node.children[component]
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if !exists {
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childIndex = len(resolver.trie)
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node.children[component] = childIndex
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childPath := append(resolver.trie[nodeIndex].path.Clone(), component)
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resolver.trie = append(resolver.trie, trieNode{mapping: -1, best: -1, parent: nodeIndex, path: childPath})
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}
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nodeIndex = childIndex
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}
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node := &resolver.trie[nodeIndex]
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if node.mapping >= 0 {
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previous := resolver.mappings[node.mapping]
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if previous.Target.Equal(normalized.Target) {
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resolver.mappings = resolver.mappings[:index]
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continue
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}
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return nil, fmt.Errorf("conflicting command aliases for %q", normalized.Source.String())
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}
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node.mapping = index
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node.path = normalized.Source.Clone()
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}
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resolver.setFallbacks()
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return resolver, nil
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}
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func (resolver *Resolver) setFallbacks() {
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for index := 0; index < len(resolver.trie); index++ {
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node := &resolver.trie[index]
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if index > 0 {
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node.best = resolver.trie[node.parent].best
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}
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if node.mapping >= 0 {
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node.best = node.mapping
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}
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}
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}
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// ResolveOnce applies at most one longest-prefix mapping. It returns the
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// original input unchanged when no mapping matches.
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func (resolver *Resolver) ResolveOnce(path commandpath.Path) (commandpath.Path, Mapping, bool) {
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if resolver == nil {
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return path.Clone(), Mapping{}, false
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}
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nodeIndex := 0
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matched := -1
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matchedLength := 0
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for index, component := range path {
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childIndex, exists := resolver.trie[nodeIndex].children[component]
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if !exists {
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break
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}
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nodeIndex = childIndex
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if mapping := resolver.trie[nodeIndex].mapping; mapping >= 0 {
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matched = mapping
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matchedLength = index + 1
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}
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}
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if matched < 0 {
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return path.Clone(), Mapping{}, false
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}
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mapping := resolver.mappings[matched]
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resolved := make(commandpath.Path, 0, len(mapping.Target)+len(path)-matchedLength)
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resolved = append(resolved, mapping.Target...)
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resolved = append(resolved, path[matchedLength:]...)
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return resolved, Mapping{Source: mapping.Source.Clone(), Target: mapping.Target.Clone()}, true
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}
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// Resolve applies mappings until no source matches. Installation validates
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// termination before a resolver is used for application input.
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func (resolver *Resolver) Resolve(path commandpath.Path) commandpath.Path {
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current := path.Clone()
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for {
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next, _, matched := resolver.ResolveOnce(current)
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if !matched {
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return current
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}
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current = next
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}
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}
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185
internal/alias/resolver_test.go
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185
internal/alias/resolver_test.go
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@@ -0,0 +1,185 @@
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package alias
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import (
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"reflect"
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"testing"
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"gitea.maximumdirect.net/eric/CommandKit/internal/commandpath"
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)
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func TestResolverUsesLongestTokenPrefixAndPreservesSuffix(t *testing.T) {
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resolver, err := NewResolver([]Mapping{
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{Source: commandpath.Path{"list"}, Target: commandpath.Path{"promptkit", "list"}},
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{Source: commandpath.Path{"list", "collections"}, Target: commandpath.Path{"app", "collections"}},
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})
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if err != nil {
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t.Fatal(err)
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}
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got := resolver.Resolve(commandpath.Path{"list", "collections", "extra"})
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want := commandpath.Path{"app", "collections", "extra"}
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if !got.Equal(want) {
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t.Fatalf("Resolve() = %#v, want %#v", got, want)
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}
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got = resolver.Resolve(commandpath.Path{"list", "prompts"})
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want = commandpath.Path{"promptkit", "list", "prompts"}
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if !got.Equal(want) {
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t.Fatalf("Resolve() = %#v, want %#v", got, want)
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}
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reversed, err := NewResolver([]Mapping{
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{Source: commandpath.Path{"list", "collections"}, Target: commandpath.Path{"app", "collections"}},
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{Source: commandpath.Path{"list"}, Target: commandpath.Path{"promptkit", "list"}},
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})
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if err != nil {
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t.Fatal(err)
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}
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if got := reversed.Resolve(commandpath.Path{"list", "collections", "extra"}); !got.Equal(commandpath.Path{"app", "collections", "extra"}) {
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t.Fatalf("reverse-order Resolve() = %#v", got)
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}
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}
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func TestResolverFallsBackAfterLongerTokenMatchFails(t *testing.T) {
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resolver, err := NewResolver([]Mapping{
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{Source: commandpath.Path{"a"}, Target: commandpath.Path{"short"}},
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{Source: commandpath.Path{"a", "b", "c"}, Target: commandpath.Path{"long"}},
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})
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if err != nil {
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t.Fatal(err)
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}
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got := resolver.Resolve(commandpath.Path{"a", "b", "x"})
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want := commandpath.Path{"short", "b", "x"}
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if !got.Equal(want) {
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t.Fatalf("Resolve() = %#v, want %#v", got, want)
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}
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}
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func TestResolverDoesNotMatchUnknownTokens(t *testing.T) {
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resolver, err := NewResolver([]Mapping{{Source: commandpath.Path{"list"}, Target: commandpath.Path{"promptkit", "list"}}})
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if err != nil {
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t.Fatal(err)
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}
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input := commandpath.Path{"listing", "collections"}
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got := resolver.Resolve(input)
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if !got.Equal(input) {
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t.Fatalf("Resolve() = %#v, want unchanged %#v", got, input)
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}
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}
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func TestCompiledMachineMatchesDirectResolver(t *testing.T) {
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mappings := []Mapping{
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{Source: commandpath.Path{"list"}, Target: commandpath.Path{"promptkit", "list"}},
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{Source: commandpath.Path{"list", "collections"}, Target: commandpath.Path{"promptkit", "list", "collections"}},
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{Source: commandpath.Path{"pk"}, Target: commandpath.Path{"promptkit"}},
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{Source: commandpath.Path{"promptkit", "list", "bundles"}, Target: commandpath.Path{"promptkit", "list", "collections"}},
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{Source: commandpath.Path{"short"}, Target: commandpath.Path{"promptkit", "list"}},
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{Source: commandpath.Path{"short", "b", "c"}, Target: commandpath.Path{"long"}},
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}
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resolver, machine, err := Compile(mappings)
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if err != nil {
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t.Fatal(err)
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}
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for key, operation := range machine.transitions {
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if len(operation.push) > 2 {
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t.Fatalf("transition %+v pushes %d symbols", key, len(operation.push))
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}
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}
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cases := []commandpath.Path{
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{"list"},
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{"list", "prompts"},
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{"list", "collections"},
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{"list", "collections", "extra"},
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{"pk", "list", "bundles", "tail"},
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{"short", "b", "x"},
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{"unknown", "operand"},
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{},
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}
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for _, marker := range []symbolKind{endSymbol, boundarySymbol} {
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for _, input := range cases {
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t.Run(input.String(), func(t *testing.T) {
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got, err := runMachineForTest(machine, input, marker)
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if err != nil {
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t.Fatal(err)
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}
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want := expectedSymbols(machine, resolver.Resolve(input), marker)
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if !reflect.DeepEqual(got, want) {
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t.Fatalf("machine result = %#v, want direct result %#v", got, want)
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}
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})
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}
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}
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}
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func TestResolverTreatsIdenticalMappingsAsIdempotent(t *testing.T) {
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mapping := Mapping{Source: commandpath.Path{"list"}, Target: commandpath.Path{"promptkit", "list"}}
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resolver, err := NewResolver([]Mapping{mapping, mapping})
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if err != nil {
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t.Fatal(err)
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}
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got := resolver.Resolve(commandpath.Path{"list", "prompts"})
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if want := (commandpath.Path{"promptkit", "list", "prompts"}); !got.Equal(want) {
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t.Fatalf("Resolve() = %#v, want %#v", got, want)
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}
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}
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func TestResolverRejectsInvalidAndConflictingMappings(t *testing.T) {
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for name, mappings := range map[string][]Mapping{
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"empty source": {{Target: commandpath.Path{"target"}}},
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"empty target": {{Source: commandpath.Path{"source"}}},
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"conflicting target": {
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{Source: commandpath.Path{"source"}, Target: commandpath.Path{"first"}},
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{Source: commandpath.Path{"source"}, Target: commandpath.Path{"second"}},
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},
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} {
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t.Run(name, func(t *testing.T) {
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if _, err := NewResolver(mappings); err == nil {
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t.Fatal("NewResolver() succeeded")
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}
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})
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}
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}
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func expectedSymbols(machine *Machine, path commandpath.Path, marker symbolKind) []symbol {
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result := make([]symbol, 0, len(path)+1)
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for _, token := range path {
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result = append(result, machine.classify(token))
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}
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result = append(result, symbol{kind: marker})
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return result
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}
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func runMachineForTest(machine *Machine, input commandpath.Path, marker symbolKind) ([]symbol, error) {
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stack := expectedSymbols(machine, input, marker)
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control := machine.start
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for steps := 0; steps < 10000; steps++ {
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if control == machine.halt {
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return stack, nil
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}
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if len(stack) == 0 {
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return nil, errMachineStackEmpty
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}
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operation, ok := machine.transitions[transitionKey{control: control, read: stack[0]}]
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if !ok {
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return nil, errMachineTransitionMissing
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}
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stack = append(append([]symbol(nil), operation.push...), stack[1:]...)
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control = operation.next
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}
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return nil, errMachineTestDidNotHalt
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}
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var (
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errMachineStackEmpty = testError("compiled machine emptied its stack")
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errMachineTransitionMissing = testError("compiled machine has no transition")
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errMachineTestDidNotHalt = testError("compiled machine did not halt in the test interpreter")
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)
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type testError string
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func (err testError) Error() string { return string(err) }
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func (machine *Machine) classify(token string) symbol {
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if _, exists := machine.literals[token]; exists {
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return symbol{kind: literalSymbol, value: token}
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}
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return symbol{kind: otherSymbol}
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}
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Reference in New Issue
Block a user