123 lines
3.1 KiB
Go
123 lines
3.1 KiB
Go
package chroma
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import (
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"fmt"
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"strings"
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)
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// A Mutator modifies the behaviour of the lexer.
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type Mutator interface {
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// Mutate the lexer state machine as it is processing.
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Mutate(state *LexerState) error
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}
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// A LexerMutator is an additional interface that a Mutator can implement
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// to modify the lexer when it is compiled.
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type LexerMutator interface {
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// Rules are the lexer rules, state is the state key for the rule the mutator is associated with.
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MutateLexer(rules CompiledRules, state string, rule int) error
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}
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// A MutatorFunc is a Mutator that mutates the lexer state machine as it is processing.
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type MutatorFunc func(state *LexerState) error
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func (m MutatorFunc) Mutate(state *LexerState) error { return m(state) }
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// Mutators applies a set of Mutators in order.
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func Mutators(modifiers ...Mutator) MutatorFunc {
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return func(state *LexerState) error {
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for _, modifier := range modifiers {
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if err := modifier.Mutate(state); err != nil {
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return err
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}
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}
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return nil
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}
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}
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type includeMutator struct {
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state string
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}
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// Include the given state.
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func Include(state string) Rule {
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return Rule{Mutator: &includeMutator{state}}
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}
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func (i *includeMutator) Mutate(s *LexerState) error {
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return fmt.Errorf("should never reach here Include(%q)", i.state)
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}
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func (i *includeMutator) MutateLexer(rules CompiledRules, state string, rule int) error {
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includedRules, ok := rules[i.state]
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if !ok {
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return fmt.Errorf("invalid include state %q", i.state)
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}
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rules[state] = append(rules[state][:rule], append(includedRules, rules[state][rule+1:]...)...)
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return nil
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}
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type combinedMutator struct {
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states []string
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}
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// Combined creates a new anonymous state from the given states, and pushes that state.
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func Combined(states ...string) Mutator {
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return &combinedMutator{states}
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}
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func (c *combinedMutator) Mutate(s *LexerState) error {
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return fmt.Errorf("should never reach here Combined(%v)", c.states)
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}
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func (c *combinedMutator) MutateLexer(rules CompiledRules, state string, rule int) error {
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name := "__combined_" + strings.Join(c.states, "__")
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if _, ok := rules[name]; !ok {
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combined := []*CompiledRule{}
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for _, state := range c.states {
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rules, ok := rules[state]
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if !ok {
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return fmt.Errorf("invalid combine state %q", state)
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}
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combined = append(combined, rules...)
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}
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rules[name] = combined
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}
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rules[state][rule].Mutator = Push(name)
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return nil
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}
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// Push states onto the stack.
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func Push(states ...string) MutatorFunc {
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return func(s *LexerState) error {
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if len(states) == 0 {
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s.Stack = append(s.Stack, s.State)
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} else {
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for _, state := range states {
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if state == "#pop" {
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s.Stack = s.Stack[:len(s.Stack)-1]
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} else {
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s.Stack = append(s.Stack, state)
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}
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}
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}
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return nil
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}
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}
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// Pop state from the stack when rule matches.
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func Pop(n int) MutatorFunc {
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return func(state *LexerState) error {
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if len(state.Stack) == 0 {
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return fmt.Errorf("nothing to pop")
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}
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state.Stack = state.Stack[:len(state.Stack)-n]
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return nil
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}
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}
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// Default returns a Rule that applies a set of Mutators.
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func Default(mutators ...Mutator) Rule {
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return Rule{Mutator: Mutators(mutators...)}
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}
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